Electrical Exterior Facilities Specification
Electrical Exterior Facilities Specification
Electrical Exterior Facilities Specification
FACILITIES ENGINEERING
ELECTRICAL EXTERIOR FACILITIES
REPRODUCTION AUTHORIZATION/RESTRICTIONS
This manual has been prepared by and for the Government and,
except to the extent indicated below, is public property and not subject to copyright.
Copyrighted material included in the manual has been used with the
knowledge and permission of the proprietors and is acknowledged as
such at point of use. Anyone wishing to make further use of any
copyrighted material, by itself and apart from this text, should seek
necessary permission directly from the proprietors.
Reprints or republication of this manual should include a credit substantially as follows: Joint Departments of the Army, the Navy and
the Air Force, TM 5-864/NAVFAC MO-200/AFJMAN 32-1082.
If the reprint or republication includes copyrighted material, the
credit should also state: Anyone wishing to make further use of
copyrighted material, by itself and apart from this text, should seek
necessary permission directly from the proprietor.
Tables 13-l and 16-1 are reprinted from table 2 of IEEE Std 18-1992
and table 11.1 of IEEE Std 519-1992 respectively.
Copyright 0 1993 by the Institute of Electrical and Electronics Engineers, Inc. The IEEE disclaims any responsibility or liability resulting
from the placement and use in this publication. Information is reprinted with the permission of the IEEE.
>
HEADQUARTERS
DEPARTMENTS OF THE ARMY,
THE NAVY, AND THE AIR FORCE
WASHINGTON , D.C. 29 November 1996
Page
1. INTRODUCTION
CHAPTER
SECTION I-PRIMARY CONSIDERATIONS
Purpose and scop
ee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Application of codes and publications. .....................................................
Standardsofmaintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Maintenance responsibilities. .............................................................
Maintenance records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Priority and scheduling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
l-l
l-2
l-3
l-4
l-5
l-6
l-7
l-l
l-l
l-l
l-l
l-l
l-2
l-2
S ECTION II-SAFETY
Minimizinghazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Qualification of electric workers. ..........................................................
Certification of electric workers ...........................................................
Publicsafety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Personnel safety
y .........................................................................
Live-linemaintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
l-8
l-9
l-10
l-11
1-12
1-13
l-3
l-3
l-3
l-3
l-3
l-3
1-14
1-15
1-16
l-4
l-4
l-4
2-l
2-2
2-3
2-l
2-l
2-l
S ECTION II-REQUIREMENTS
Electric workers, instruments, and reports
Frequencyofinspection.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-4
2-5
2-2
2-2
3-l
3-2
3-3
3-4
3-5
3-6
3-7
3-l
3-l
3-l
3-l
3-l
3-l
3-l
3-8
3-9
3-10
3-11
3-12
3-13
3-14
3-2
3-2
3-3
3-3
3-3
3-3
3-3
3-15
3-16
3-17
3-18
3-3
3-3
3-3
3-3
Page
S ECTION IV-INSULATORS
Function of insulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Testsofinsulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inspection and repair of insulators ........................................................
Cleaningofinsulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3-19
3-20
3-21
3-22
3-4
3-4
3-4
3-5
3-23
3-24
3-25
3-26
3-7
3-7
3-7
3-7
3-27
3-28
3-29
3-30
3-7
3-7
3-7
3-8
S ECTION VII-BUSHINGS
Definition of bushing
s ....................................................................
Type of bushings covered . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Maintenanceofbushings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bushingpowerfactortests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bushing insulation resistance test. ........................................................
3-31
3-32
3-33
3-34
3-35
3-8
3-8
3-8
3-10
3-12
4. OVERHEAD DISTRIBUTION
CHAPTER
SECTION I-ASSOCIATED OVERHEAD DISTRIBUTION GUIDANCE
Relevant overhead distribution guidance. ..................................................
General construction guidance
e ............................................................
4-1
4-2
4-3
4-4
4-5
4-6
4-7
4-8
4-9
4-4
4-4
4-10
4-11
4-12
4-13
4-14
4-15
4-16
4-17
4-18
4-4
4-4
4-4
4-6
4-6
4-7
4-9
4-10
4-10
4-19
4-20
4-2 1
4-11
4-12
4-12
4-22
4-23
4-24
4-13
4-13
4-13
4-25
4-26
4-27
4-28
4-29
4-14
4-15
4-15
4-15
4-15
,-
Page
4-30
4-31
4-15
4-15
4-32
4-33
4-34
4-35
4-36
4-37
4-16
4-16
4-16
4-16
4-17
4-18
4-38
4-39
4-18
4-18
4-40
4-41
4-42
4-43
4-18
4-19
4-20
4-22
4-44
4-45
4-46
4-47
4-22
4-22
4-22
4-24
S ECTION XIII-GUYS
Guy functional requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Guy strand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Anchor assemblies.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Guy attachments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Guystraininsulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-48
4-49
4-50
4-51
4-52
4-25
4-25
4-25
4-26
4-27
4-53
4-54
4-55
4-56
4-57
4-58
4-59
4-60
4-61
4-29
4-30
4-31
4-31
4-32
4-32
4-32
4-33
4-33
4-62
4-63
4-64
4-65
4-33
4-33
4-34
4-34
4-66
4-67
4-35
4-35
5-l
5-2
5-l
5-l
5-3
5-4
5-2
5-2
S ECTION III-INSPECTION
Frequency of underground system inspections. .............................................
Structureinspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cableinspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Underground equipment inspections ......................................................
5-5
5-6
5-7
5-8
5-3
5-3
5-3
5-3
...
111
Page
5-9
5-10
5-11
5-12
5-13
5-14
5-15
5-16
5-17
5-18
5-19
5-20
5-2 1
5-22
5-23
5-24
5-25
5-10
5-10
5-11
5-11
5-12
5-12
5-13
5-26
5-27
5-28
5-29
5-30
5-31
5-14
5-14
5-15
5-16
5-17
5-17
5-32
5-33
5-34
5-18
5-18
5-18
6. OUTDOOR LIGHTING
CHAPTER
S ECTION I-LIGHTING AND CIRCUIT TYPES
Outdoorlightinguse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Types of lighting circuits ..................................................................
6-1
6-2
6-l
6-l
6-3
6-4
6-5
6-6
6-7
6-8
6-l
6-l
6-l
6-2
6-2
6-3
6-9
6-10
6-11
6-12
6-13
6-14
6-15
6-16
7-1
7-2
7-3
6-6
6-6
6-7
7-l
7-l
7-l
iv
Page
S ECTION II-MAINTENANCE
Transformer inspection and maintenance frequencies. ......................................
Transformer inspectionss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Transformer testing guidance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Solid (winding) insulation tests ...........................................................
Transformer insulation liquids. ...........................................................
7-4
7-5
7-6
7-7
7-8
7-2
7-3
7-6
7-6
7-7
8-l
8-2
8-3
8-4
8-1
8-1
8-1
8-1
8-5
8-1
8-2
8-2
8-3
S ECTION II-FUSES
Fuseusage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuse operating safety considerations ......................................................
Fuse replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuse maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
..
8-7
8-8
S ECTION III-SWITCHES
Switchusage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operationofswitches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Switch maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-9
8-10
8-11
8-3
8-12
8-13
8-l4
8-l5
8-16
8-l7
8-6
8-6
8-7
8-10
8-12
8-12
8-18
8-l9
8-14
8-14
CHAPTER
9. OVERVOLTAGE PROTECTION
S ECTION I-CONSIDERATIONS
Overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lightning-induced voltage surges .........................................................
System operating voltage disturbances ....................................................
Surge limiting protective device requirements. .............................................
9-l
9-2
9-3
9-4
9-l
9-1
9-l
9-l
9-5
9-7
9-8
9-l
9-l
9-2
9-2
9-9
9-10
9-11
9-12
9-2
9-3
9-3
9-3
C HAPTER
10. GROUNDING
S ECTION I-CONSIDERATIONS
Basic principles of grounding .............................................................
Groundingprovisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10-l
10-2
10-l
10-l
S ECTION II-MAINTENANCE
Groundingmaintenancesafety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Visual inspection of grounds ..............................................................
Galvanic corrosion of grounds. ............................................................
10-3
10-4
10-5
10-l
10-l
10-2
S ECTION III-TESTING
Ground resistance tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Groundvaluemeasurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10-6
10-7
10-2
10-2
Page
10-2
10-4
11-l
11-2
11-3
11-4.
11-5
11-6
11-7
11-8
11-9
11-l
11-l
11-l
11-2
11-2
11-3
11-3
11-4
11-5
S ECTION II-CONTROLS
Control functions.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Preventive maintenance and inspections of controls ........................................
Troubleshootingcontrols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11-10
11-11
11-12
11-6
11-7
11-8
12-l
12-2
12-3
12-4
12-5
12-6
12-7
12-1
12-1
12-1
12-1
12-1
12-1
12-1
12-8
12-9
12-10
12-2
12-2
12-2
12-11
12-12
12-2
12-2
S ECTION IV-REPAIRS
Field repairs of instruments and meters
Shop repairs of instruments and meters
...................................................
...................................................
12-13
12-14
12-4
12-4
S ECTION V-TROUBLESHOOTING
Temperature influence on instruments and meters .........................................
Stray-field influence on instruments and meters ...........................................
Calibration of instruments and meters ....................................................
Other instrument and meter considerations ................................................
12-15
12-16
12-17
12-18
12-5
12-5
12-6
12-6
13-l
13-2
13-3
13-4
13-1
13-1
13-1
13-1
13-5
13-6
13-7
13-8
13-9
13-10
13-11
13-1
13-1
13-1
13-2
13-2
13-2
13-2
S ECTION III-TESTS
Field tests for power capacitors ...........................................................
Terminal tests of power capacitors ........................................................
Leak tests of power capacitors ............................................................
13-12
13-13
13-14
13-2
13-3
13-3
_-
Page
14-1
14-2
14-3
14-4
14-1
14-1
14-3
14-4
14-5
14-6
14-7
14-8
14-4
14-6
14-7
14-8
14-9
14-10
14-11
14-12
14-9
14-9
14- 10
14-10
14-13
14-14
14-15
14-11
14-11
14-11
14-16
14-17
14- 12
14-12
14-18
14-19
14-14
14- 14
14-20
14-21
14-22
14-23
14-14
14-15
14-15
14-15
14-24
14-25
14-26
14-16
14-16
14-16
14-27
14-28
14-17
14-17
14-29
14-30
14-17
14-17
15-1
15-2
15-3
15-1
15-1
15-1
15-4
15-5
15-6
15-7
15-8
15-1
15-1
15-2
15-2
15-2
15-9
15-10
15-11
15-12
15-13
15-2
15-3
15-3
15-3
15-3
Page
15- 14
15-15
15-16
15-4
15-5
15-5
15-17
15- 18
15-19
15-6
15-6
15-7
15-20
15-21
15-22
15-7
15-7
15-7
S ECTION VII-ROPE
Careofrope.............................................................................
Splicingrope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15-23
15-24
15-8
15-8
15-25
15-26
15-10
15-10
15-27
15-28
15-11
15-11
16-l
16-2
16-3
16-1
16-1
16-1
16-4
16-5
16-6
16-7
16-8
16-9
16-1
16-1
16-3
16-3
16-3
16-4
16-10
16-11
16-12
16-13
16-4
16-4
16-4
16-5
CHAPTER
17. MAINTENANCE SCHEDULES
S ECTION I-CONSIDERATIONS
Maintenance
planning....................................................................
Maintenance priorities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17-l
17-2
17-l
17-l
S ECTION II-SCHEDULES
Maintenance frequency guides . . . . . . .
Revisions to maintenance frequencies
17-3
17-4
17-l
17-l
........................................
........................................
...,.................
.....................
...............................
...............................
APPENDIX A-REFERENCES
APPENDIX B-BIBLIOGRAPI-IY
APPENDIX C-ADDITIONAL WOOD POLE DATA
INDEX
LIST OF FIGURES
Figure 3-l.
3-2.
4-l.
4-2.
4-3.
v i. i. i.
Page
3-12
3-12
4-2
4-3
4-5
Page
4-6
4-8
4-8
4-11
4-12
4-14
4-17
4-17
4-19
4-19
4-20
4-20
4-21
4-23
4-25
4-26
4-27
4-28
4-29
4-30
4-30
4-3 1
4-32
5-8
5-9
5-16
6-5
10-3
10-3
10-4
10-5
10-6
11-3
11-4
11-4
11-5
11-6
12-3
12-3
13-3
13-4
14-2
15-8
15-8
15-9
15-9
c-3
c-3
c-4
LIST OF TABLES
Page
Table
3-l.
3-2.
3-3.
3-4.
4-l.
4-2.
4-3.
4-4.
4-5.
5-l.
6-1.
7-1.
3-2
3-6
3-11
3-13
4-8
4-10
4-24
4-24
4-30
5-17
6-5
7-3
ix
Page
7-6
7-8
8-12
8-13
11-6
11-8
12-6
12-6
13-2
13-3
14-2
14-9
14-11
14-13
15-11
16-5
17-l
_.--.-I
CHAPTER 1
INTRODUCTION
Section I - PRIMARY CONSIDERATIONS
1-1. Purpose and scope.
This manual provides guidance for the maintenance
and repair of exterior electrical distribution systems. New construction of exterior electrical facilities, even when funded from maintenance appropriations, should comply with the appropriate
design criteria. These systems include substations,
overhead and underground electrical distribution
systems, exterior lighting systems, and electrical
apparatus and components. Guidance for generators and interior electrical systems (600 volts and
less) are covered in the following publications:
5-683/NAVFAC
MO-ll6/AFJMAN
a. TM
32-1083.
b. TM 5-685/NAVFAC MO-912.
c. MIL-HDBK-1003A/ll.
1-2. References.
Appendix A contains a list of references used in this
manual.
1-3. Application of codes and publications.
The information in this manual should not supersede equipment manufacturers instructions and requirements. When conflicts exist the most rigorous
requirement should be followed. A11 maintenance
and repair of electrical systems should be performed
in such a manner that the completed work will
conform to the publications listed below to the degree indicated.
a. Codes. The listed codes and standard contain
rules (both mandatory and advisory) for the safe
installation, maintenance, and operation of electrical systems and equipment.
(1) The National Electrical Code (NEC), NFPA
70.
(2) The National Electrical Safety Code
(NESC), ANSI C2.
(3) Occupational Safety and Health (OSHA),
General Industry Standards, 29 CFR 1910.
b. Nongovernment publications. Other nongovernment publications referenced in this manual expand guidance in line with recognized industry
standards. The most extended coverage on recommended practices for electrical equipment maintenance, and one that should be used in conjunction
with both the NEC and the NESC, is NFPA 70B.
Publication NFPA 70B is recommended as a useful
1-1
practices, part designations, and ordering procedures. Spare parts lists are a vital part of these
records.
(2) Installation drawings. Maintenance is often
affected by the manner in which the equipment is
installed. For convenience, and as a means of expediting maintenance, as-built installation drawings
should be readily accessible to maintenance and
inspection personnel.
(3) Wiring diagrams. Adequate and up-to-date
wiring diagrams are important for proper maintenance. Diagrams facilitate locating troubles, which
otherwise may require extensive probing and testing procedures. Such diagrams should be readily
available to maintenance personnel.
(4) Distribution maps. Maps showing locations
of distribution lines, wire sizes, transformer sizes,
pole numbers, voltage classes, and sectionalizing
devices are vital. Up-to-date distribution maps
mounted on the maintenance or electrical shop wall
are very useful.
b. Service records. Service records constitute a
history of all work performed on each item of equipment and are helpful in determining the overall
condition and reliability of the electrical facilities.
Service records should show type of work (visual
inspection, routine maintenance, tests, repair), test
results (load, voltage, amperes, temperature), and
any other remarks deemed suitable. It is highly
recommended that service records should include a
log of incidents and emergency operating procedures.
(1) Logs of incidents. Logs of incidents, such as
power failures, surges, low voltage, or other system
disturbances are very useful in planning and justifying corrective action.
(2) Emergency operating instructions. Emergency work on electrical facilities is safer and
quicker when instructions are prepared and posted
in advance. Instructions should be prepared for
each general type of anticipated emergency, stating
what each employee will do, setting up alternatives
for key personnel, and establishing follow-up procedures. Instructions should be posted in the electrical shop, security guard office, substations, operating areas, and such other locations as the
responsible supervisor deems advisable. Employees
should be 1isted by name, title, and official telephone number. These instructions should emphasize safety under conditions of stress, power interruptions, and similar emergencies.
1-7. Priority and scheduling.
a. Priority. In regard to the support of the installation physical plant, it is the policy of the military
manders to meet local requirements. Service intervals may be lengthened only when justified by
extenuating circumstances. Whenever service intervals or other guidance in this manual differs from
information supplied by the manufacturer, the more
stringent procedure should be followed.
Section II - SAFETY
1-8. Minimizing hazards.
Material specifications, construction criteria, installation standards, and safe working procedures have
been developed to minimize hazards. All work and
materials should conform to the latest accepted procedures and standards, as defined in publications
listed or referred to in this manual.
1-9. Qualification of electrical workers.
Due to the inherent hazards encountered in the
maintenance of electrical distribution systems and
equipment, it is essential that all electrical workers
be thoroughly trained and be familiar with the
equipment and procedures to be followed.
l-3
l-4
--
CHAPTER 2
INSPECTION AND TESTS
Section I - PERFORMANCE
2-1. Determining equipment condition.
The ability of equipment to perform its function, or
to continue its function for its normal life cycle,
must be determined if the distribution system is to
operate dependably and economically. The condition
of equipment can be determined by two methods:
inspection and tests. Such things as broken insulators or oil leaks can easily be determined by inspections, but other details such as the condition of
transformer oil or a trip setting for a circuit breaker
can be determined only by tests. The scope of inspection and tests is dependent on the type and
complexity of the equipment, and the results desired. Inspections are normally visual, but hearing,
touching, and smelling can also indicate problem
areas. Tests can be electrical, physical, or chemical,
or combinations of these. The selection of the test to
be made may be at least partially determined by the
availability of test equipment and of personnel capable of using it.
2-2. Reasons for inspections and tests.
Inspections and tests are performed for several reasons.
a. Preventive maintenance. This includes routine
testing of operating equipment and periodic testing
of nonoperating components to anticipate and correct possible equipment failure before it occurs.
b. Maintenance proof testing. This is testing to
ensure that maintenance/repair was done properly.
This should be done when maintenance and/or repair are complete, and to show whether the equipment is operable and properly connected.
2-3. Associated test guidance and records.
Tests are ordinarily used in the field to determine
the condition of various elements of an electrical
power-distribution system. The data obtained in
these tests provide information that is used to determine whether any corrective maintenance or replacement is necessary or desirable. The ability of
the element to continue to perform its design function adequately can be ascertained. Also the gradual
deterioration of the equipment over its service life
can be charted. Records must include factory test
data provided with shop drawing submittals, acceptance testing data, and each routine maintenance
test, so that the history of the equipment may be
2-l
._
2-2
CHAPTER 3
-
This chapter includes a transmission and distribution substation which is an assemblage of equipment for purposes other than generation or utilization, through which electrical energy in bulk is
passed for the purpose of switching or modifying its
characteristics.
In addition to the personnel safety hazards mentioned above, an electrical substation presents an
attraction to would-be vandals, dissidents, or other
belligerents. For these reasons, good security is a
basic requirement. All means of access to substations, including buildings and yards, will be kept
locked when unoccupied and secure when occupied
by authorized personnel.
3-l
-.-
Deficiency
Possible
Probable
Major
Action
Investigate
Repair as time permits
Repair immediately
1
Consider providing photographs an&or thermograms as seen on
the imaging system in reports where appropriate to the size and
criticality of the equipment examined.
3-2
Structures of aluminum alloy normally need no surface protection. Painting of aluminum alloy members is not recommended except where esthetics is
of prime importance.
3-12. Wood structures.
Permanent wood structures should be inspected
and treated as described in chapter 4, section IV.
Temporary wood structures may or may not be
treated, depending on the local climate and expected life of the structure.
3-13. Concrete for structure foundations.
Concrete is used extensively as a foundation for
metal structures and for equipment. Concrete
should be visually checked during the course of
other maintenance and repair. Cracks wider than
about 1/16 of an inch (0.16 millimeters) should be
repaired with a sand-cement grout. Badly deteriorated concrete should be replaced.
3-14. Structure connections and joints.
Regardless of material, all connections and joints
should be checked periodically for tightness of fastening hardware. Loose, broken, or missing parts
should be tightened or replaced as required to maintain a rigid structure.
3-3
Section IV - INSULATORS
3-19. Function of insulators.
The function of an insulator is to support a conductor or conducting device safely. An insulator, being
of a nonconductive material, physically and electrically separates the supported item from any
grounded or energized conductors or devices.
a. Composition and problems. Insulators are
composed of porcelain, glass, fiberglass, or a composite compound. Maintenance is necessary to preserve their insulating ability which can be degraded
by contamination or other damaging actions. Most
insulator damage will result from gun shots; lightning, surge, or contamination flashovers; and wind
damage. Defective insulators can also cause visible
corona or interference voltage propagation.
b. Related material. Apparatus type insulators
are provided in substations to support devices and
heavy lines. See chapter 4, section XII, which provides a discussion of insulation levels.
3-20. Tests of insulators.
Radio interference conditions may be detected by
using instruments designed for this purpose. Otherwise, maintenance tests on insulators are normally
limited to occasional power factor measurements at
the more important installations, where the loss of
the facilities must be kept to an absolute minimum.
Bus and switch insulators should be power-factor
tested in conjunction with similar testing of other
apparatus within the substation. Power factor tests
are described in section VII.
3-21. Inspection and repair of insulators.
Switch-and-bus apparatus type insulators are the
most intricate type and require the highest degree
of reliability in service. This is because the several
pieces of porcelain and hardware, assembled in a
single unit, are usually located at key positions in
the systems, where failure is extremely serious.
Switch-and-bus insulator failures occur when porcelain is thrown in tension by any thermal movement
between nested parts, which can cause cracking and
allow the entrance of moisture. An accumulation of
3-4
foreign deposits, and mechanical damage from external sources also cause deterioration. Evidence of
such impairments may cause a flashover puncture
accompanied by a destruction of insulator parts.
Workers should be CAUTIONED that equipment
must be de-energized unless the procedure in chapter 4, section XV is authorized.
a. Ceramic insulators. Ceramic insulators are
made of wet-process porcelain or toughened glass.
(1) Construction.
(a) Porcelain insulators. Porcelain insulators
are manufactured from special clays to produce a
plastic-like compound which is molded, oven dried,
dipped in a colored glazing solution, and fired in a
kiln. The glossy surface of the glaze makes the insulator surface self-cleaning. Large porcelain insulators are made up of several shapes cemented together. A chemical reaction on the metal parts from
improper cementing can result in a cement growth
which can be sufficiently stressful to crack the porcelain.
(b) Glass i nsulators.. Glass insulators are
made from a mixture of sand, soda ash, and lime
which is mixed and melted in an oven, then molded,
cooled, and annealed.
(2) Inspection.
(a) Look for fractures, chips, deposits of dirt,
salt, cement dust, acid fumes, or foreign matter,
which under moist conditions may cause a flashover.
(b) Check fo r cracks in insulators by tapping
gently with a small metal object ONLY WHEN DEENERGIZED, about the size of a 6-inch (15 centimeter) wrench. Insulators free of cracks emit a ringing sound when tapped; cracked ones sound dull
and hollow. To avoid damaging good insulators, tap
them; do not hit them hard.
(3) Repair.
(a) If the main body of a pin type or post
insulator is cracked, replace it immediately.
(b) Hone small chips from shells or skirts,
and paint with an insulating paint or varnish to
3-5
Cement dust.
...... ........
....................
F l y ash..........................
Gummy soil, dirt and oil.
Iron ore . . . . . . . . . . . . . . . .
Leather dust . . . . . . . . . . . . . . . . . . .
Lime............................
Oil soot
t ..................
Red lead .................
Salt. .....................
Smoke..........................
Sulfur.
..........................
..................
Type of cleaner
How applied
Rag. ............................
Brush . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hot bath ........................
Brush. ..........................
Rag. ............................
Satisfactory
Fair
Satisfactory
Satisfactory
Satisfactory
Wash ...........................
Cloth ...........................
Rub . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Brush. ..........................
Brush. ..........................
Steel wool, rags, and salvasol .....
Steel wool, rags, and salvasol .....
Rag. ............................
Wash ...........................
Satisfactory
Satisfactory
Good
Satisfactory
Satisfactory
Requires annual cleanup
Used below 32F (00
Used below 32F (0C)
Satisfactory
Brush. ..........................
Dip or wipe. .....................
Hand ...........................
Wipe. ...........................
Rag. ............................
Rag. ............................
Water and rags, steel wool, rags,
and water. ......................
Satisfactory
Satisfactory
Satisfactory
Satisfactory
Satisfactory
Satisfactory
Lockbrite2. ......................
Larkin cleaner2 ..................
Oakite2 .........................
Standard Oil solvent2 ............
Lockbrite2 .......................
Windex glass cleaner2 ............
Vinegar and bicarbonate of soda
paste . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Brush . . . . . . . . . . . . . . . . . . . . . . . . . . .
Results
Satisfactory
Satisfactory
Steel wool, rags, and water ....... Satisfactory
Rags. ........................... Satisfactory
Cloth ........................... Satisfactory
Cloth ........................... Satisfactory
Atomizer and wipe with dry rags. . Fair
Rag-coat porcelain, rub off, and
finish with steel wool. ............ Fair
Brush. .......................... Satisfactory
The insulating qualities of ceramic insulators and bushings and their ability to prevent flashovers depend largely on the glass-like glaze
of the surface. During cleaning operations, therefore, care must be taken to preserve this smooth surface and prevent its being scratched
or dulled.
2
The use of brand names is to identify the type of material recommended and does not imply superiority over other brands of similar
material.
3
This chemical gives off irritating fumes which are dangerous in high concentration. Do not use without respiratory protection.
4
Some paint thinners are highly flammable. When use of a thinner having a flash point under 100F (38C) is necessary, it will be
handled in accordance with applicable safety regulations.
3-6
3-7
thing that may result in an operating hazard. Fractures or chips may be caused by the following actions.
(a) Rigid bus connections that do not allow
for thermal expansion or contraction.
(b) Thrust from breaker operation, which
may fracture either the top or bottom porcelain if
the bottom member is loose.
(c) Uneven or excessive tightening of
clamping-ring bolts.
(d) Improper cementing onto the clamping
ring.
(e) Mechanical shock caused by blows or projectiles.
(2) Contamination. Check for foreign deposits,
such as dirt, salt, cement dust, rust, carbon, acid oil
sludge, filler compound, copper sulfate, or other material that may cause flashover under moist conditions.
(3) Loose porcelain. Check for loose or improper
seating of the lower porcelain.
(4) Evidence of flashover. Flashover may be
caused by an operating voltage above the bushing
rating, excessive transient voltage, or semiconductive foreign particles contaminating the porcelain.
d. Porcelain repair. In addition to the upper or
main body porcelain, some bushings have a lower
porcelain member to give added strength against
mechanical shock. Porcelain repairs generally are
made in either of the following ways:
(1) Fractures. When the main section of either
the lower or upper porcelain is fractured, replace
the bushing. When the cause appears to be a too
rigid connection, install a flexible connector or expansion joint made from a flat strap, in addition to
replacing the bushing.
(2) Chips. When the main body of the porcelain
is intact, but a crack is about to detach a large chip
of skirt, protect adjacent skirt and remove the chip
with a hammer. Smooth the sharp edges with an
abrasive stone to prevent injury to workmen, and
paint the exposed surfaces with a weather-resisting
material to provide a glossy finish that keeps out
dirt and grit.
(3) Contam ination. Remove deposits of foreign
materials. Clean as recommended.
(4) Tracking. When there is evidence of flashover, check the bushing voltage rating and surge
protection. Clean the bushings. Bushings experiencing frequent flashovers should be reported to the
operating department, as this may require a review
of the application and associated surge.
e. Metal parts inspection. Metal parts of bushings, including the mounting flange and hardware,
should be inspected for fractures, cracks, blowholes
3-9
pf at 20C = pf at TC x K
3-11
(3) Connect the high-voltage lead of the power factor test set to the top terminal of the bushing and the
low-voltage lead to the bushing support.
(4) Ground the test set to the apparatus tank, and
measure the power factor
(5) Record temperature of the bushing.
h. High-voltage cold-guard circuit test. When
bushings to be tested have detachable cable conductors, they may be tested in the following manner:
(1) Remove the bushing terminal and insulate
the conductor from the bushing tube by stuffing a
small amount of insulation into the space between
them. If bushing is equipped with an insulating
head, it is only necessary to remove the connector
between the upper and lower rings.
(2) Clean the porcelain ring of the insulating
head.
(3) Connect the guard circuit to the cable lead
and the high-voltage lead of the test set to the bushing tube.
(4) Ground the mounting flange of the bushing.
i. Collar tests. The overall power factor test on
bushings may be performed by placing a flexible
3-12
--
-.
CONOUCTINC
HOT-COLLAR TEST
,L ,##ri--10-W
I
N
E
CONOUCTlNC
COLD-COLLAR TEST
Figure 3-2. Connections for hot- and cold-collar tests
Table 3-4. Insulation resistance tests on electrical apparatus
and systems1
Maximum voltage
Minimum test
rating of equipment
voltage, dc
250 volts . . . . . . .
500 Volts . . . . . . .
600 volts . . . . . . .
1,000 Volts . . . . . . .
2,500 Volts . . . . . . .
5,000 volts . . . . . . .
8,000 volts . . . . . . .
2,500 Volts . . . . . . .
15,000 volts . . . . . . .
2,500 Volts . . . . . . .
25,000 volts . . . . . . .
5,000 Volts . . . . . . .
35,000 volts . . . . . . . 15,000 Volts . . . . . . .
46,000 volts . . . . . . . 15,000 Volts . . . . . . .
69,000 volts . . . . . . . 15,000 Volts . . , . . . .
1This
Recommended
minimum
insulation
resistance in
megohms
25
100
1,000
2,000
5,000
20,000
100,000
100,000
100,000
3-13
CHAPTER 4
OVERHEAD DISTRIBUTION
Section I - ASSOCIATED OVERHEAD DISTRIBUTION GUIDANCE
4-1. Relevant overhead distribution guidance.
_-
Maintenance work involving aerial line changes requires an understanding of the basic design premises of overhead construction requirements.
a. Location of electric circuits on poles. Where
more than one electric circuit is carried on a pole,
the highest voltage is at the top down to the lowest
voltage above any communication circuits. Through
wires of the same voltage level should be carried
above local wires (those which are tapped frequently). The two or more wires of a circuit should
always be carried in adjacent positions. To facilitate
troubleshooting, wires of a circuit should always
take the same positions on all poles, except where
long lines have been provided with a transposition
(change of line positions) to reduce electrostatic and
electromagnetic unbalance.
b. Joint electric supply and communications circuits on poles. Electrical supply wires must be carried above communication circuits. Minimum clearances between supply wires and communication
wires are specified in the NESC.
4-2. General construction guidance.
Rights-of-way for navigable water crossings and
structure identification and climbing space free of
obstructions must meet the following requirements.
a. Rights-of-way requirements. When the system
is being extended across navigable waters within
mission system is used for high and ultra-high voltage systems; subtransmission system for 46- to 69kilovolt systems; and distribution system is used for
35 kilovolt down to and including low-voltage systems. Utilization voltage is also used to describe the
voltage from which the equipment directly operates,
which may in some cases be a medium-voltage input.
4-6. Voltage origination point.
Input to a device which transforms voltage from one
level to another is called a primary circuit, while the
devices output is called a secondary circuit. While
most transformers are used to step down voltages,
there are cases of step-up systems; so a primary
circuit could have a lower voltage than a secondary
circuit.
4-l
OIMENSIONS
X - - - - - B i n (200mm)
Y-----24in ( 6 0 O m m )
z -----3Oin (75Omm)
TRIANGULAR
T A N G E N T AND MINOR ANGLE
ailWING
SPACE
VERflCAL
MINOR ANGLE
INTERMEDIATE ANGLE
TANGENT AND
ri
CLIMBING
SPACE
46 la
-L-
X CONNECTION
T- CORNER
CORNER
ILLUSTRATION OF
WAFT OF CLlU8lNC
S P A C E COLUUN
ARMLESS CONNECTION
NOTE: UNLESS OTHERWISE INDICATED ALL CLIMBING SPACE IS 2 BY 2 MINIMUM
AlM8lNC
I-SPACE
alumwc
SPACE -7
IF THIS IS WITHIN
PRIYARICS. aIU8INC SPA
must BE 2 SOUARE
DETAIL-
DETAIL- 2
DETAIL- 4
DETAIL- 3
A
DETAIL- 5
+LlMBlNC SPACE
CONOUCTW
DETAIL-6
SECONDARY RACK
BUILDING LINE
ml
L CLIMBING SPACE
OETAIL- 8
DETAIL- 7
CROSSARM CONSTRUCTION
Figure 4-l. Details showing various horizontal dimensions necessary to provide recommended climbing space
4-2
Y---24in(60bnm)
L---3Oii75Onm)
bmnca
TANQNT
AN0 UINOR
ANCLE
TANCENT
INWtUEOIATE
A N GL E
CLUSmAnON C6
SHAf 1 of CLlYBlNG
w&a COLUMN
r-l
'1'
CmNER
I-
CCSNER
X CCMNER
*RyEss CawwcnoN
OCTAL- 11
bf:RfKAL OIMENSWS
OF QIUWG SPACE
COLUUN
I
I
II
I
I
I
I
I
II
NOTES
PguE&D ARR*nQuEMl
n+c (*YMR Q uNoauPE0
F1)coOllONSlSlWwuC
mR 1Owm) Ams (DETAILS
i n a on mamf 4-1)
OETAJL-14
Figure 4-2. Details showing various vertical dimensions necessary to provide recommended climbing space
work, is the one used in this manual, unless otherwise stated. Therefore, primary circuits have a
medium-voltage rating; secondary circuits have a
low-voltage rating.
_-
TM 5-684/NAVFAC MO-200/AFJMAN32-1082
POLE INSPECTION AND MAINTENANCE RECORD
Other Yelotenaoco/CommoeL
for Trpe
of . s.
Preeeure t r e a t e d - - r e c o r d pounda
Full-leo2lh non-pmmrum l r e a t e d
But1 treated
epplled.
Yoderalel
l dvanced decA but pole well above mlnlmum permlael lo r o u n d l i n e c r c u m f e m n c e . Croundllne tmatmeat
applied.
Relnepect I n 5 - 5 yearn.
Extenelve decay. No groundline treatment
r e p l a c e o r slub rllhln 1 y e a r :
FallurO. Replace or l
l
applied. Relnepect.
lub prOmplly.*
Figure 4-3. Sample format for recording pole inspection and maintenance data
4-5
+
ABC0
D
60
SPC
7-30
Suppliers Brand
Plant Designation
Year of treatment
Species of Timber and
Preservative Treatment
Retentions
Class and length in feet
e. Inspection equipment. For convenience, the following list shows the minimum amount of equipment usually needed. It may be added to according
to type of soil, terrain, or extent of work to be undertaken.
(1) A shovel for digging around the pole and a
tamper for use when the soil is backfilled.
(2) A flat-bladed spade, a suitable scraper, and
a chipper to remove decayed wood.
(3) A wire brush for removing dirt and decayed
wood.
(4) A pole prod or a small blunt tool for probing
the pole for decay below ground line, such as a
dulled ice pick or a screwdriver.
(5) An increment borer and wood plugs.
(6) A l- to 2- pound (0.5 to l-kilogram) hammer
for sounding poles and for driving wood plugs.
(7) A tape for measuring the groundline circumference of the pole and a 6-inch (150-millimeter)
rule.
(8) A flashlight and a binocular (6 x 30) for
observing the upper portion of the pole above the
inspectors groundline vision.
(9) Previous records and blank forms for recording all details of work.
(10) Dating nails to indicate year of inspection
or groundline treatment and tags to indicate rejected poles and dangerous poles.
(11) Preservative and application equipment
for groundline treatment.
(12) A first-aid kit to handle minor injuries.
f. Recommended time of year: If possible, inspect
during the summer months when preservatives
need not be heated, digging is easier, and the pole is
drier. A dry pole makes examination for decay more
positive, and ensures better penetration of preservatives.
--
___
3a
r
and must be approved for use. None of the preservative should be exposed when backfilling is completed. Personnel applying pesticides must be certified in accordance with applicable directives.
(3) Backfilling. R ep1ace with sufficient resterilized soil tamped to avoid any water-collecting depressions.
f. Internal inspection. One or two borings should
be taken above or below the ground line when
sounding or other inspection methods cause a doubt
as to the sturdiness of the interior pole condition.
g. Accuracy. When a reasonable accurate determination as to the condition of poles cannot be made
by spot inspection methods, the more thorough procedures described for the pole-by-pole inspection
should be followed. For these cases, the excavated
poles should be groundline treated and so recorded.
4-15. Wood pole-by-pole inspection procedure.
Before any extensive inspection or maintenance
work is begun, it should be known or ascertained
that the line (or individual pole) can be expected to
remain in the same position for several years without relocation. Before proceeding with the inspection, the upper portion of the pole should be observed from the ground to make sure it has not been
badly damaged by woodpeckers, lightning, or other
causes that would require replacement regardless of
the groundline condition. Nondestructive pole testing may be used where PoleTest equipment is
available. (See para 4-14.) Otherwise sounding and
test boring may be necessary.
a. Sounding. If the pole condition appears good,
then the pole should be sounded. This is a method of
checking for interior decay above the ground line. It
is not an infallible test and requires considerable
practice to attune the ear to meaningful sounds. It
should not be relied upon until considerable experience has been acquired.
(1) Method. With a l- or 2-pound (0.5 to
l-kilogram) hammer, strike the pole squarely and
firmly all around the pole from the ground line to as
high as can be conveniently reached, while listening
to the sound. A good pole has a solid ring, whereas
one containing decay may give a hollow sound or
dull thud. Often, however, such things as checks,
separations, shakes (separation along the grain of
the wood, usually occurring between the annual
rings due to causes other than drying), loose slivers,
loose molding, guys, load carried, wood density,
moisture content, and the pole loading will affect or
alter the resonance.
(2) Purpose. This method avoids needless excavation of poles found badly decayed internally above
ground and assists in detecting the most likely
4-7
C-km
of
borer.
Sapwood thickness
(inches)
0.5
0.75
0.5
0.75
2.0
to
to
to
to
to
1.25
2.5
1.5
2.0
4.0
Sapwood thickness
(millimeters)
13
19
13
19
51
to
to
to
to
to
4-8
32
64
38
51
102
Natural heartwood
decay resistance
High
Moderate
Moderate
Moderate
Moderate
__
Sapwood thickness
(inches)
2.0
0.5
2.0
to
to
to
4.25
2.0
3.5
Sapwood thickness
(millimeters)
51
13
51
to
to
t0
108
51
200
Natural heartwood
decay resistance
Low to moderate
Low
Low
4-9
4-10
Setting depths
Straight lines
Feet
30 ........
35 ........
40 ........
45 ........
50 ........
55 ........
60 ........
70 ........
Meters
. . . . 9.0
. . . , 9.0
. . . . 9.0
. . . . 9.0
. . . . 9.0
. . . . 9.0
. . . . 9.0
. . . . 9.0
Feet
Meters
5.5 ........... 1.7
6.0 ........... 1.8
6.0 ........... 1.8
6.5 ........... 2.0
7.0.. ........ .2.1
7.5 ........... 2.3
8.0 ........... 2.4
9.0 ........... 2.8
Curves, corners
and points of
extra strain
Feet
Meters
5.5 . . . . . . . . . . . . . 1.7
6.0 . .. . . . . . . . . . . 1.8
6.5.. . . . . . . . . . . .2.0
7.0.. . . . . . . . . . . .2.1
77.5 . . . . . . . . . . .2.3
8.0 . . . . . . . . . . .2.4
8.5 . . . . . . . . . . .2.6
9.5 . . . . . . . . . . .2.9
W I R E CLAMP
OF LEAD
STAPLE
T E N S I O N S T R A N D WITH
DOU6LE ARMING DOLT
( C U T OfF AFTCR I N S T A L L A T I O N )
360 Kc
3OM)
ments should be kept tight. If preservative treatment is applied to the pole, the crossarms should
also be treated. Crossarms should be inspected visually from the ground whenever a pole is inspected. If the pole inspection indicates the pole
may be climbed, a closer inspection should be made.
a. Decay. Crossarm decay usually starts at pinholes and can best be detected with a probe, if warranted by visual inspection. Probe the arm enough
to determine the extent of the decay.
4-11
T M 5-684/NAVFAC
MO-200/AFJMAN 32-1082
---
-c
SHAPED STEEL
TREATING
-GROUND LINE
4-12
d. Treatment of exposed surfaces. Preservative solutions may be applied to exposed surfaces of wood
poles and fixtures by either brush or powered equipment. Starting at the top and working down, the
surface should be flooded with as much preservative
as it will absorb. Special care should be taken to
thoroughly flood all holes, splits, and check separations.
e. Brushing. A brush, a bucket, and a handline
with snatch blocks are required for brush treatment. The brush should be as large as can be conveniently handled to minimize the number of dips.
Care should be exercised to prevent splashing, spattering, or dripping the solution on nearby structures, vehicles, or pedestrians below.
f. Treatment of hollow heart. When hollow heart
exists, locate the top of the damaged area and flood
the cavity completely from this point. If no splits,
checks, separations, or other openings from the surfaces to the cavity exist, apply the solution under
pressure through the inspection hole. If other openings do exist, apply paste or gel under pressure.
g. Contact treatment. The above-ground portion
of a pole is not subjected to the same conditions that
promote decay at the ground line. Nevertheless, decay above-ground will develop sooner or later in all
poles. In recent years, there has been increased use
of spray, run-on, or brush treatments to the upper
portion of poles.
(1) Treatment U se an approved remedial preservative. The pole surface should be dry, with the
pole moisture content below 30 percent as determined with a moisture meter. The treatment should
be applied in accordance with the preservative
treatment manufacturers recommendation, starting at the top of the pole. Immediately after the first
treatment, a second application should be given the
top 10 feet (3 meters) of the pole to ensure maximum absorption in the upper section and at points
of attachments.
(2) Safety. Safety precautions must be carefully
observed, especially when applying this treatment
to poles in energized electric lines. Caution should
also be used to avoid damage to freshly treated
poles by grass fires.
4-24. Wood pole treatment at or below the
ground line.
Groundline treatment should be provided whenever
a pole is excavated during an inspection or resetting, and it has been determined the excavated pole
need not be replaced. It is also required whenever a
pole over 5 years old is moved. Such treatment involves excavation, cleaning of the surface, applica-
4-13
___
4-14
4-15
nealed or soft-drawn copper wire where it is necessary to bend and shape the conductor, such as for
ground wires. Medium-hard-drawn copper is used
for distribution, especially where wire sizes smaller
than No. 2 AWG are needed.
b. Aluminum. An aluminum conductor has about
61 percent of the conductivity of copper of the same
cross section but is lighter. Aluminum is relatively
soft and, although low in tensile strength, is very
durable. Some alloys are available with greater
strength but less conductivity. Various combinations
of steel and aluminum strands are available for use
where both strength and good conductivity are required. Standard aluminum conductor steelreinforced (ACSR) conductors should not be used in
areas of severe corrosion. There are a variety of
special aluminum alloy conductors some with special steel reinforcing, for use under conditions of
corrosion, for greater strength requirements, and
for self-damping to limit aeolian vibration. When
replacing aluminum conductors, check to be sure
the selection meets the requirements of the original
design. Connectors used will conform to section XI.
c. Copper-clad steel. High-strength steel may be
covered with copper to yield a conductor having 30
to 40 percent of the conductivity of pure copper. It is
corrosion resistant and may be stranded in various
combinations with copper to give various combinations of strength and conductivity. Its chief application is for use as an overhead ground wire.
__
4-16
_..,
Aeolian vibration, galloping, sway oscillation, unbalanced loading, lightning discharges, and shortcircuit effects can be damaging to conductors in
service. Poor connections cannot only cause damage, but are also possible sources of radio or television interference. An infrared scanning system is
recommended over visual inspection. Equipment
can be operated from the air or from the ground
using aircraft or aerial equipment or vehicularmounted or hand-held devices.
a. Damage signs. The following signs indicate
that the conductor is probably being damaged.
\- SIGHTING
Showing
position
of
sighting
markers.
I
e
mode.
a. AdlustIng t h e m a r k e r s .
A
B
C
b.
4-17
weather shielding, taping, or spreading single conductors. Permanent repairs should be as extensive
as necessary, from patching to replacement of the
damaged length.
c. Messenger. The supporting messenger is usually of stranded galvanized steel or copper-clad
steel. The initial design will provide adequate
strength to support the cable under the maximum
loading of ice and wind, and the temporary loads
involved in installation and maintenance. Wear or
rusting can reduce the messengers strength. When
it reaches the minimum safe value, then a messenger replacement should be made. Under these conditions, it is probable that other parts of the cable
assembly will also require replacement.
d. Lashing. Metal rings are used with metallicsheathed cables for field-assembled aerial cable.
The disadvantage of this combination is the relatively rapid wear of the sheath at point of contact
with the ring. Moving the rings periodically will
alleviate this. When excessive wear occurs, lashing
with a spiral wrap of metallic band or tape is recommended. This is the method used for factoryassembled cables, and it can also be used for field
assembly, with little or no relative movement between conductors, messenger, and band.
e. Splices and taps. When making splices and
taps on aerial cables, procedures specified elsewhere in this manual for overhead open wires in
section XI or underground cables in chapter 5, section VI, as appropriate, should be followed.
4-18
CONDUCTOR
SLEEVE
STEEL SUPPORT
STRAND
NUM
UCTOR
81+-STEEL SLEEVE
ALUMINUM
SLEEVE
01
1 D D 1 D
1 D 1) 11)
I I
4-19
c
LSpring
/
Cartridge Assembly
/-
Normal
Duly Type
4-20
(1) Burning of the main conductor at the contact due to looseness and high resistance;
(2) Difficulty of removal due to freezing of the
bolt in the body. The clamp should be located where
vibration and flexing of the tap wire will be a minimum. To prevent burning from damaging and possibly dropping the main conductor, a hot line clamp
should not be attached directly to the main conductor except in a nontension loop. The best method is
to attach a suitable stirrup, either clamp or compression type, and apply the hot line clamp to the
stirrup. In this way, any burning at contact or arcing during removal will burn the stirrup and not
damage the main conductor. Hot line clamps can be
applied over armor, if the contact between conductor and armor is thoroughly cleaned first. The problem of freezing threads is a matter of design, and
the more modern hot line clamps are much less
likely to have this trouble. Any hot line clamp that
is not in good condition should be discarded.
e. Internally-fired taps. Internally-fired taps are
used for a tee connection on transmission and distribution conductors of both copper and aluminum.
The tap housing is made of a suitable alloy, tapered
at the ends where the conductors enter. The application tool as shown in figure 4-16 contains a highstrength steel powder chamber that is loaded with a
fast-burning propellant charge contained in a polyethylene cartridge. A simple hammer blow detonates the cartridge. Igniting the charge creates instantaneous high pressure in the chamber. This
pressure drives cylindrical sets of wedge-shaped
serrated aluminum jaws (into which the conductor
ends have been inserted) at high velocity into the
tapered ends of the housing. The jaws clamp and
lock the conductor ends in position, providing the
required holding strength and establishing a lowresistant current path across the housing. If correctly operated, a locking tab will verify the wedge
Wedge
fits In nouslng
Locot~on of wedoe
to be dr,ven Into
Powaer
chamoer---
Appkct
on
tool-
4-21
--
i
r)
G U Y S T RA I N, CLASS 54-l
SUSPENSION, CLASS 52 - 2
---
Y
\
col
SUSPENSION. CLASS 52- 3
IO
a-3/4
(17lmuJ~lo :
3-3/4lO
(P3mm)
L
SPOOL CLASS 53-2
4lO(
IoommMl~
\ / i_
Chap-top for
mououn#
v.r(lc~l
- I /4lr
m4mm)
la.2
-chap-top ror
borisomkat
rnmuOll~
PIN, C L A S S 5 6 - 4
LINE POST
SIMILAR TO CLASS 57-14
4-23
Conductor
Copper AWG. . . . . . . . . . . . . . . . . . . . . . .
6 .................................
4 and 2 . . . . . . . . . . . . . . . . . . . . . . . . . . .
1 through 3/O. . . . . . . . . . . . . . . . . . . . . .
4/O and larger . . . . . . . . . . . . . . . . . . . . .
AAC,AAAC,orACSRAWG . . . . . . . . .
Any size. . . . . . . . . . . . . . . . . . . . . . . . . . .
relate directly to insulator classes. An understanding of the relations between insulator classes and
insulation level requirements is helpful in understanding why each facility should have a recognized
insulation level (class) for its various on-site distribution levels if they vary from requirements given
in table 4-4.
a. Code requirements. The NESC spells out dry
flashover requirements up to 230 kV These should
be considered a minimum, even though a qualified
engineering study could permit lower insulation
levels. The NESC requires the use of insulators
with higher dry flashover levels where severe lightning, high atmospheric contamination, or other unfavorable conditions exist. The NESC preparers recognized that dry flashover may not be the best test,
but it has been used for many years with reasonable
success. The desirability of using wet flashover as a
basis has been recognized, but no consensus agreement has been reached.
Table 4-4. Relation of the NESC voltage levels to ANSI C29 class ratings
NESC (ANSI C2) requirement
Nominal
voltage
(between
phases)(kV)
6.9 . . . . . . . . . . . . .
13.2 .............
23.0 .............
34.5 .............
Rated dry
flashover voltage
of insulators
&VI
Rated dry
flashover
voltage of
Area
No. of
insulators (kV)
designation 2
insulators
ANSI C29.2--Suspension Insulators
60.. . . . . . . . . . . . . A . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . .
39 . . . . . . . . . . . . . .
115.. ........... B . . . . . . . . . . . . . . . 2 ...............
130 ............. A . . . . . . . . . . . . . . . 2 ...............
55 .............. 155
............. B ............... 2 ...............
A . . . . . . . . . . . . . . . 2 ...............
75.. ............ ;;;"""**'**'* B
39 . . . . . . . . . . . . . .
13.2 .............
55 ..............
23.0 .............
75 ..............
34.5 .............
13.2.............
23.0.............
34.5.............
52-l............
52-12.. .........
52-2 ............
523/4 .............
523A .............
.............
............... 3 ............... 523A .............
A . . . . . . . . . . . . . . . 3 ............... 52% .............
100 ............. ;;;***"*+* B
.............
............... 4 ............... 52% .............
6.9. . . . . . . . . . . . . .
6.9. .............
ANSI class
Facility
voltage
level (kV)
up to 5
6 to 15
16 to 25
26 to 35
Insulators
1 . . . . . . . . . . . . . . . 55 . . . . . . . . . . . . . .
...........
80.. ............
125 .............
125 .............
1 ............... 140 .............
1 ............... 140 .............
1 ............... 175 .............
1 . . . . . . . . . . . . . . . 80 . . .
1 ...............
1 ...............
1 ...............
...............
80.. ............
80.. ............
80 ..............
110.. ...........
110.. . . . . . . . . . . .
125 .............
125 .............
150 .............
up to 5
6 to 15
16 to 25
26 to 35
up to 5
6 to 15
16 to 25
26 to 35
The rated dry flashover voltage is based on manufacturers tests where more than one insulator is required.
2 Use the A value in areas where the atmosphere is dry (desert) or where fog occurs only to a limited degree and there is not more than
moderate industry contamination. Use the B value in areas where medium-to-heavy fog is common occurrence and there is medium
industrial contamination along a salt-water coast line.
4-24
_-
15
4-25
KEY ANCHORS
CONE ANCHORS
EXPANOING
ANCHORS
ROCK ANCHORS
PLATE ANCHORS
4-26
__
LOCATION STAKE T
\
! /
DEADMAN
8 In BY 3 In MINIUUM -J
(200UU b y 8OUM)
/ LOG
SLOPE
DCPTH
u
L/H
0.5 . . . .
1 . . . . .
1.S . . . .
Sft (l.Sm)
(1.2m)
(0.9m)
. 4tt
. 3ft
LINE OF GUY
DISTANCE
K
30 UlNlMUM
. . . 2.Sft (0.7Sm)
. . . 411 (1.2m)
. . . 4.Sft (l.JSm)
Figure 4-20. Log anchor
4-27
PUSH BRACE
(USE LINE POLE)
lin(25mm)
have been set according to the need to bypass lightning strokes around the wood. The insulator should
be replaced if deterioration or damage affects its
strength. When a wood insulator replacement is
needed, provide a fiberglass insulator instead.
c. Fiberglass. Fiberglass insulators should be
used for guys in lieu of wood. Advantages are their
indefinitely long life; their imperviousness to moisture; and their ability to withstand a direct stroke of
lightning without bursting. They do not require arcing horns to bypass the lightning stroke. Fiberglass
insulators are shorter than wood insulators, so they
take up less space. Corrosion or rusting of the metal
and fittings will ultimately be the reason for their
replacement.
4-28
TM 5-684/NAVFAC MO-200/AFJMAN32-1082
GUY ATTACHMENT
ON EACH END OF
5/8 i n (16mm)
BOLT
-7
l/4 in ( 6 m m ) E X T R A
HIGH -STRENGTH STRAND
DEADEND W I T H l/4 in
(6mm) CLAMPS
ZZ
-&
B L- PREFERRED
ANGLE
EXPANDING ANCHOR1
Figure 4-22. Side anchor
Dirzction of pull
angle b o l t with
Strain plote
A
4
Pounds
4,000
6,000
10,000
16,000
square wosher
'Guy
clomp
Stroin insulator
\ l%;;e pole
A=three
equal spaces
-Log screws
y Eye bolt
wtth square
washer
10 ft (3m)
opproxtmote Concrete qt
least 8 In
( 2 0 0 m m ) thick
around pole
\
Set pole 111
(O.Sm) deeper
thon stondord -
Type of clamp
Kilograms
1,800 . . . . . . . . 1 . . . . . . . . . . . .
2,700 . . . . . . . . 1 . . . . . . . . . . . .
4,500 . . . . . . . . 2 . . . . . . . . . . . .
7,200 . . . . . . . . 3 . . . . . . . . . . .
Two-bolt
Three-bolt
Three-bolt
Three-bolt
\ Golvonized
turnbuckle
eye and eye
I
Number of
clamps
Breaking strength of
guy stand
- Guyeye
-Guy quord
Minimum clearances to be maintained between conductors and any part of a tree are shown in figure
4-24. These distances may be increased as desired.
Note that distances A and B are measured from the
normal sagged position of the conductor, and that
distance C, D, and E must be increased by the sag
at that point. For tree trimming purposes, the 30inch (750-millimeter) climbing space dimensions
shown in figure 4-l should be increased to 40
inches (1,000 millimeters), and distances in figure
4-24 should be increased as required to maintain a
40-inch (l,000-millimeter) minimum climbing
space.
Anchor rod
;i Stroin plote
0 to
750 v
ond I32
Neutrol
311(0.9m)
lSft(1.5m)
750 lo
8700 V
Sft(
1.5m)
13.2 Phase
lo 4 0
120
KV
Kv
811(2.5m)
AVOIO
lOft(3m)
I5ft(4 5m)
Avao
S A G O f LINE PLUS
.
UUN lRUNU
211(0.6m)
0
UAIN LIUB
411(1.2m)
.E .
ERANCMS
5ft( 1.5m)
6ft(
1.h)
Avao
4ft(1.2m)
7ft(2.1 m)
*MB0
5ft( 1.5m)
EIft(2.5m)
211(0.6m)
4-30
12ft(3.7m)
BEFORE
of clearance and shaping. Tree-trimming jobs usually come under one of the following classifications,
as shown in figure 4-25.
a. Center trimming. Center trimming, when necessary, requires that the limbs he cut away to leave
a clear space around the wires. The cuts should be
made at tree crotches to encourage the direction of
limb growth away from the wires, thus avoiding the
need for frequent trimming in the future.
b. Side trimming. Side trimming is necessary
when the ends of the limbs on the side of a tree
extend into or over the wires. In these cases, the
limbs are cut off at a crotch so the limb can continue
to grow, but in a direction parallel to or away from
the line wires. The amount of trimming needed depends on the size and location of the limbs. Side
trimming usually results in notches or an unbalanced tree that looks unsightly. When this is the
case, branches or limbs not interfering with wires
should be trimmed from the other side so that the
tree is balanced.
c. Top trimming. Top trimming is necessary when
a tree is growing into the wires. The ends of the
C e n t e r Yrtmmlnq
BEfORE
AFTER
BEFORE
AFTE R
S i d e Trlmmlnq
AFTER
c . T o p TrimmIng
4-31
0.
Method
no.
b. M e t h o d
4-32
no.
--
4-34
(a) Water resistiuity. Water having a resistivity greater than 1500 ohm-centimeters can usually
be obtained from city water system hydrants. This
is an acceptable low-level resistivity. Water resistivity changes inversely with temperature and must be
measured periodically during washing operations,
especially in hot weather. In no case should water
be used having a resistivity of below 1,000 ohmcentimeters. No soap, detergents, anti-freeze, or alcohol should be added.
(b) Nozzle type. A jet nozzle is more suited to
transmission (high-voltage) systems because wind
effects the spray less and the spray range is greater.
The spray nozzle is suited for distribution (mediumvoltage) systems.
(c) Apparatus. Consult manufacturers when
washing nonceramic insulators. Bushings made of
porcelain must be treated with great care and the
effects of water pressure and volume and the mechanical support provided the bushing must be considered. Energized washing of surge arresters may
impose severe electrical stresses on the arresters
due to voltage imbalance and should not be done
without the consent of the arrester manufacturer.
(4) Safety. Follow facility rules and general industry practices as covered in ANSI/IEEE 957. The
OSHA safe working distance (from Table V-l of
Subpart V, Section 1926.950) is the minimum distance recommended for personnel adjacent to energized objects at any time. This distance applies to
the phase-to-phase voltage and is 2 feet (0.6 meters)
for 2.1- to 15-kilovolt energized parts and 2.33 feet
(0.71 meters) for 15.1- to 35-kilovolt energized
parts.
e. Other procedures. Cutting out and replacing
live conductors requires supporting the conductors
and providing a temporary jumper to bypass the
current while the splice is completed. The bypass
uses hot-line clamps as does tapping a conductor.
Installation of hot-line clamps, armor rods, and vibration dampers should follow manufacturers hotline instructions. Phasing-out requires a phasetester, which should be connected in accordance
with the manufacturers instructions.
4-35
4-36
CHAPTER 5
UNDERGROUND AND SUBMARINE CABLES
Section 1 - ASSOCIATED GUIDANCE
5-1. Relevant cable guidance.
Maintenance work involving underground or submarine cable changes requires an understanding of
the basic design premises of such cables.
a. Types of installations. Underground cables
may be installed in conduit, in duct banks, or by
direct burial in the earth; submarine cables are
usually submerged directly in the water and lie on
the bed of the waterway. The terminal ends of both
underground and submarine cables are often aboveground. The burial depth of raceways or cables
should never be less than the depths permitted by
the NEC or the NESC and, in most cases, will be
more to conform to facility design practice.
(1) Cable in conduit removal freplacement. Although it is easy enough to install several cables in
one conduit and mechanically easy to withdraw
them, the removal usually ruins the cable. Cables
become impacted in a conduit, and, when one is
drawn out, the sheath may be stripped either from
the withdrawn cable or from one of the other cables.
Therefore, when one cable of a set in a conduit fails,
all cables must be replaced.
(2) Direct-burial cable reinstallation. Directburial cables being replaced must be installed below
the frost line.
b. Joint electric supply and communication circuits. Unlike aerial lines, joint structure use is not
allowed for electric supply and communication circuits. Communication cables are installed to be
completely isolated from electric power cables and
require separate ducts and structures. Economy
may dictate contiguous structures and duct lines
having a common trench excavation. Direct-burial
power and communication lines should be separated
at least the minimum required distance, usually set
by the local communication agency. Control, alarm
signalling, and other low-current and low-voltage
circuits may be installed in electric manholes, dependent upon facility requirements, but require
special shielding or increased insulation levels.
5-2. General construction guidance.
Rights-of-way for navigable waters and identification must meet the following requirements. The influence of conditions which can generate cable failures in the following discussion should be checked
for their impacts.
a. Rights-of-way requirements. When the system
is being extended across navigable waters within
5-l
important at these points. Where recabling is required do not use T splices in manholes, except
where the facilitys engineering staff concur that
avoiding their use is uneconomical.
e. Lightning protection and grounding. Lightning
protection for aerial to underground primary cable
connections, and grounding and bonding of underground cables, contribute to the protection of the
cables and to the safety of the system.
(1) Surge arresters. When a transition is made
between overhead conductors and underground or
submarine primary cables, facility practice requires
that a surge arrester be installed at the termination
connecting insulated underground cables to aerial
bare conductors. A ground rod should be installed
and the metallic sheath or armor of the cable
bonded to that ground installation. The surge arrester then protects the primary cable from switching or lightning surge overvoltages which could
overstress the cable insulation. Secondary cables
are usually protected from these over-voltages by
primary surge arresters located at pole or groundmounted transformer installations.
(2) Grounding and bonding. All noncurrentcarrying conductive materials in the structure and
any neutrals must be grounded. Most standard
structures are provided with a driven ground rod.
Bonding includes the metallic sheath or armor of all
cables, cable shields, manhole hardware, the tanks
of all equipment and apparatus, and the secondary
neutral of transformer installations. Where
nonmetallic-sheathed cable having a ground wire is
used, the ground wire is usually brought out at the
joint. These ground wires should be grounded to the
neutral and the driven ground The resistance of
ground connections must meet the requirements
given in chapter 10, section III.
Subsurface structures such as manholes, handholes, equipment vaults, and splicing boxes are subject to accumulation of dangerous gases that may be
combustible and/or explosive, toxic, or deficient in
oxygen. Before entering any manhole or vault, it
must be checked for these conditions.
a. Combustible gases. Combustible gases may be
detected by means of a test instrument or safety
lamp. When using this equipment, the precautions
and instructions provided by the manufacturer
should be followed. If it is determined that combustible gases are present, it will be necessary to ventilate the manhole or vault before any work is done.
5-2
---
intended. Look for signs of traction on cable terminations or direct-burial cable which may be a result
of expansion and contraction of the cable.
a. Cable supports. Check mountings and supports to ensure they are secure. Remove rust and
corrosion and clean and repaint supports with
corrosion-resistant paint.
b. Duct entrances. End bells are usually used to
prevent cable damage at duct entrances. If they
were not installed, or are damaged, strips of hard
rubber or similar material should be used to protect
the cable at the duct entrance.
c. Testing. Cable insulation integrity cannot be
visually checked; it requires some type of insulation
testing to determine whether the cable is reaching
an insulation breakdown that will lead to a cable
fault. Testing is described in section VII.
d. Cable faults. Inspection alone may reveal the
location of a cable fault or it may be a more complicated process requiring test equipment. Visual and
test procedures are covered in section V.
5-8. Underground equipment inspections.
Special maintenance for such distribution equipment in underground locations includes the following:
a. Keep items clean and protected from corrosion.
b. Check equipment covers to be sure that their
gasketing is water-tight.
c. Keep nuts and bolts free from rust by applications of paint or heavy grease.
--
Most damage to duct systems results from new unrelated construction and settling of ducts. Too often,
the new construction fails to locate an adjacent duct
line accurately and damages the line. Ducts sometimes settle where they cross older understructures,
whose overlay was completed without adequate
backfilling and tamping. Duct settling is often not
apparent unless cable failure results or an empty
duct is rodded in preparation for pulling in new
cable. In either event, the condition must be investigated and repaired. A new structure at the point of
settlement may possibly be the quickest and cheapest repair.
intended to prevent extended outages due to transient disturbances on aerial lines. But repeated
reclosing on an underground cable fault tends to
create unusually high fault resistances. Reclosing
serves to aggravate an underground cable fault
which may then stress upstream circuitry.
b. Aerial-to-underground line connections. Fuse
protection is required to be provided at or near riser
poles where such connections are made. When any
aerial lines feeding underground cable systems are
provided with automatic reclosing, that feature
should be designed so that any permanent fault on
5-5
(4) Open circuit. The continuity of the conductors is determined by grounding the conductors at
the far end and then testing between each conductor and ground. If the conductors are continuous,
the resistance reads low; and, if an open circuit
exists, the tester will indicate a very high resistance.
5-14. Cable fault locating test methods.
The methods generally used may be separated into
two major classifications: terminal measurement
methods and tracer methods. Except in the case of
faults on series lighting circuits (which usually result in considerable carbonization because of the
constant-current system involved) the resistances of
faults are often quite high, ranging from several
hundred ohms to megohms when measured at a
low-voltage level.
a. Terminal measurement methods. Terminal
measurement methods involve determining the chosen electrical value of the faulted conductor from
one of the cable terminations to the fault, and comparing this value with the same electrical value on
unfaulted cable. The proportions of the electrical
values in regard to the length of the unfaulted cable
provides the fault distance. The effectiveness of all
terminal measurement methods is dependent upon
the accuracy of installation records. While most of
the work is done at one terminal, access to the other
terminal may be necessary to connect or disconnect
conductors as required. Terminal methods include
the Murray loop, the capacitance bridge measurement method, the quarter-wave or half-wave resonance methods, and the pulse (time domain
reflectometer) method.
b. Tracer methods. These methods require test
equipment at the cable terminal but rely on checks
along the cable tracer to locate the fault. Tracer
methods include the modulated direct-current
method, the modulated alternating-current method,
the impulse (thumper) method, the audio frequency
(tone tracing) method, and the earth gradient
method.
(1) Tracer method warning. Some of the tracer
methods of fault locating can ignite residual gas in
the vicinity of a fault and cause explosions. The
likelihood of such an occurrence, while extremely
remote, cannot be ignored.
(2) Structure testing. Normal gas tests with
combustible gas detectors should be made prior to
entering structures during all fault-locating operations, regardless of the urgency of the situation or
the type of fault-locating equipment being used. It is
also advisable to use a carbon monoxide (CO) tester
to check the atmosphere in structures where fault
repairs are to be made, particularly in cases where
the closed loop to be used for fault-locating measurements and comparing this measurement to
known circuit constants. Conductor continuity generally will have no effect on the operation of tracertype fault-locating equipment. Faults exhibiting
both high series resistance (open conductor) and
high parallel resistance (ungrounded conductor) can
be located by using a capacitance-type terminal
measurement device.
5-16. Cable fault locating equipment.
Cable fault locating equipment is available from
test equipment rental companies. Member companies of the InterNational Electrical Testing Association (NETA) can be hired to test and to provide the
test equipment. As with all techniques used infrequently, the skill of trained outside personnel may
well be worth the additional cost,. Electrical Equipment Testing and Maintenance covers terminal
and tracer cable-fault locating methods in more detail for those who wish an explanation of testing
technique principles. Three of the methods using
less complex methods of measuring some electrical
characteristics of faulted cable are shown in figure
5-1. Another method uses a time domain reflectometer tester.
a. Murray loop resistance bridge method. To use
this method, the grounded conductor must be continuous at the fault and a continuous ungrounded
conductor in the faulted cable must be available.
The accuracy of this method is directly related to
the accuracy of the plans showing cable routing.
The fault is located in terms of its distance from its
cable terminal by measuring and comparing electrical characteristics of the cables faulted and
unfaulted conductors. It is essentially a Wheatstone
bridge of the slide-wire type. When the bridge is
balanced, the fault distance is found as indicated in
figure 5-1. A number of slide-wire bridges designed
for fault location are available commercially. They
range from inexpensive units with limited accuracy
to more expensive units which can locate a fault
within one foot per mile (0.2 meters per kilometer)
of cable length. Instructions for use, including applicable mathematical formulas, should be supplied
with the instrument.
b. Capacitance bridge measurement method. The
capacitance bridge measurement method is effective where both the parallel and series fault resistances are high enough to treat an unfaulted and
the faulted conductor as capacitances to a metallic
shield or sheath. This technique is simply the measurement of capacitance from one end of the faulted
cable to ground and comparing it in terms of distance with the capacitance of an unfaulted conductor in the same cable. Almost any alternating-
5-7
Point of
fault
120 v
60 Hz
(eq. 5-1)
5-8
TM 5-684/NAVFAC MO-200/AFJMAN
N 32-1082
da
d,,,Ac
l??;Eted
Open In the
cable
Transmitted pulse
Short in
the cable
\IA
\
/
\ /
1
T
\ Reflected
pulse
__
5-12
More ebooks : http://artikel-software.com/blog
.-
_-
-_
5-15
POWER FACTOR=
WATTS
R
.
V O L T A M P E R E S = VI,
= C O S I N E ++
Figure 5-3. Insulation power factor equivalent circuit and vector diagram
5-16
At 20 degrees centigrade
f. Temperature correction. Temperature has an
influence on the power factor values. However, at
the operating temperature normally encountered in
the field, this influence is minimal for modern insulation systems. Older forms of insulation may require a temperature-correction factor. It is difficult
to obtain accurate field cable temperature measurements; hence, most utilities evaluate the condition
of the insulation of their cables based on test data,
uncorrected for temperature. If it appears that high
cable temperature may have influenced the results
it is recommended that a cable having a high power
factor be retested at a time when a lower cable
temperature will occur.
5-17
5-18
CHAPTER 6
OUTDOOR LIGHTING
Section I--LIGHTING AND CIRCUIT TYPES
6-1. Outdoor lighting use.
Outdoor lighting includes public way, recreational,
airfield, and security or protective lighting, whether
installed on buildings or detached supports. The
primary purpose of outdoor lighting is to provide
lighting for exterior facilities, which require some
degree of lighting during times of reduced visibility
for safety or for observation. Poles which support
outdoor lighting should be maintained as described
in chapter 4, sections VII and VIII. Outside
building-mounted lighting is considered interior
lighting, if its sole purpose is to facilitate entrance
into that building.
6-2. Types of lighting circuits.
- -
6-l
--
.-
6-3
0.5 milliampere, it should be returned to the manufacturer for rehabilitation, or replaced with a photoconductive cell. The relay for a phototronic cell is
very delicate because of the small amount of energy
needed to operate it. Misoperation is most often the
result of sticking contacts and damaged bearings.
Sticking contacts should be carefully cleaned with
crocus cloth. Damaged bearings are usually caused
by severe continuous vibration or knocks. Any
maintenance on the relay panel, other than the
cleaning of contacts mentioned above, should be
done by the manufacturer. Careful handling is essential.
(2) Phototube photocell. A periodic checkup
should be made every 6 months. The windows
should be cleaned and all tubes replaced. Replaced
tubes should be checked by a competent tester and
discarded if poor. Any extensive maintenance work
should be considered justification for replacing with
a solid-state type.
(3) Solid-stat e pho t ocell.. Failure of this type is
denoted by lights being on during daylight. If cleaning the window does not correct the malfunction,
the unit should be replaced. The high repair labor
cost usually exceeds the replacement cost.
__
TYPE I
0
TYPE I
4 WAY
b
T Y P E II
TYPE II
4 WAY
TYPE Ill
TYPE V
TYPE IV
f
g
Figure 6-l. Light distribution patterns for roadway lighting
.........
.........
.......,.
5 .........
6 .........
7 . . . . . . . . .
1This
Beam spread
degrees range
Projection distance
10 to 18. . . . . . . 240 ft and greater (73 m and
greater)
18 up to 29. . . . 200 to 240 ft (61 to 73 m)
29 up to 46. . . . 175 to 200 ft (53 to 61 m)
46 up to 70. . . . 145 to 175 ft (44 to 53 m)
7oup to loo... 105 to 145 ft (32 to 44 m)
100 up to 130. . 80 to 105 ft (24 to 32 m)
130 and up . . . . Under 80 ft (under 24 m)
6-5
6-6
socket before inserting the socket into the receptacle. If the socket is replaced before putting the
lamp in it, the film cutout will puncture. Never
re-use a punctured film disk. Paper, cardboard, or
other insulation should never be used as a substitute for the film cutout.
6-15. Series type lighting power supply
equipment.
The main item of power supply equipment is the
constant-current transformer to supply the series
circuit power. The other item is the insulating
transformer, whose main purpose is to isolate each
luminaire to prevent an open circuit when a lamp
burns out.
a. Constant-current transformers. The transformer (usually called a regulator) has a movable
secondary winding that automatically changes position to provide a constant-current output for any
varying load impedance, within its rating, when
supplied from an approximately constant-voltage
source. The balance point between coil weight and
magnetic force may be adjusted to provide the desired output current. Most existing constantcurrent transformers are oil-insulated; but dry type
units, which are not much larger, are available and
should be considered for replacement of failed oilinsulated units whenever possible.
(1) Loading. Constant-current regulators
should be loaded as near to 100 percent as possible.
It is generally accepted that overheating will not be
caused by any load between 50 percent and 100
percent of rated kW. Regulators, unlike transformers, are rated in kW, not kVA.
(2) Operation. A constant-current regulator
must never be operated with an open-circuit secondary. However, a short circuit, even a bolted short, on
a secondary will have no immediate adverse effects
if a reasonable percentage of the load remains energized.
b. Insulating transformers. Insulating transformers isolate the medium-voltage of a series
circuit from the wiring and fixtures. In addition,
they are sometimes used to obtain higher or lower current for lamps having a different ampere rating, or constant voltage for multiple lamps connected to a series circuit. They are sometimes
referred to as isolating transformers. Unless the
case and one secondary conductor are grounded, the
secondary must be treated as a medium-voltage circuit:
__
.-
Use the recommended guidelines for the maintenance of airport visual aid facilities given in FAA
AC 150/5340-26 which covers the various types of
lighting systems, the airfield lighting vault equipment, and associated control tower equipment. It
also includes troubleshooting procedures for series
lighting circuits.
6-7
CHAPTER 7
TRANSFORMERS AND REGULATORS
Section I-CONSIDERATIONS
7-1. Voltage provisions covered.
This chapter provides maintenance and repair requirements for transformers used in the transmission and distribution of electrical energy and for
voltage regulators. Requirements apply to units
having at least one medium-voltage winding and
generally providing three-phase service, although
single-phase units may be found for housing or
other small loads.
7-2. Defining transformer and regulator characteristics.
A transformer utilizes electromagnetic induction between circuits of the same frequency, usually with
changed values of voltage and current. All transformers covered in this chapter are constant-voltage
type. That is, they maintain an approximately constant voltage ratio over loads from zero to the rated
output. Constant-current transformers are described in chapter 6, section IV Transformers can be
classified in various ways, but their basic construction consists of windings, magnetic cores on which
windings are coiled, insulation, and any special connections applying to the type of load.
a. Winding terminology. Winding terminology
given below is based on the voltage flow, rating, or
winding provisions.
(1) A primary winding has input from the
power source and a secondary winding supplies input to the loads.
(2) A high-tension winding has a higher voltage than a low-tension winding. Most transformers
have high-tension primary windings and are therefore step-down transformers. If the same transformer utilized the low-tension winding as the primary winding it would be a step-up transformer.
(3) Most transformers have two windings,
which are electrically insulated from each other.
High-voltage power transformers found in
transmission-to-distribution substations may have
a single winding (autotransformers) or a tertiary
winding to eliminate voltage problems and/or to
supply a second load voltage economically.
b. Regulation. Transformers can maintain an acceptable voltage ratio of about a 2 percent voltage
drop from zero to rated output in most cases. Most
distribution transformers and smaller power transformers have tapped windings, which permit adjusting the output voltage to broaden the range of
Section II-MAINTENANCE
7-4. Transformer inspection and maintenance
frequencies.
Transformers are simple rugged devices which will
give many years of trouble-free operation if provided with periodic inspections and maintenance.
Inspections of transformers should be made regu7-2
larly and permanent records kept of all observations and tests for both scheduled and unscheduled
inspections. The frequency of inspection should be
based on the importance of the transformer, the
operating environment, and the severity of the loading conditions. In addition to the inspection recom-
__
_-
mendations listed herein, it is good practice to develop a habit of visual inspection whenever a
transformer area is visited. In this way leaks,
cracked insulators, loose connections, and similar
problems may be noticed before serious problems
develop that might affect the continuity of service.
When working around a transformer, particular
care must be taken in handling all tools and other
loose articles, since material dropped into the windings and allowed to remain can cause a breakdown.
a. Power transformers. For maintenance purposes consider the impact that the loss of a power
transformer will have on the facilities operation.
Utility-facility interconnection transformers and
transformers with medium-voltage secondary lines
can be defined as significant impact transformers,
while other power transformers can be considered
as less significant impact transformers. There may
be slightly different maintenance techniques for liquid and dry-type transformers, but the general approach is the same.
(1) Significant impact transformers. Table 7-l
is a recommended inspection and maintenance
checklist based on input from NFPA, NETA, and
manufacturers published guides. For transformers
having a less significant impact, checking should be
decreased as covered later.
(2) Less significant impact transformers.
Transformer readings should include load current
at peak load, voltage readings during both peakload and low-load periods, temperature, liquid level,
and pressure/vacuum recordings. These readings
should be taken not less than every 6 months along
with general inspection tests from table 7-l that
are not annual or 3-to-6 year tests. Other tests of
table 7-l may be needed dependent upon the results of the 6-months tests.
b. Distribution transformers. Porcelain bushings
should be kept clean and the transformers inspected annually. Check for broken porcelain, loose
power connections, blown fuses, and defective surge
arresters. Check for leaks, hardened bushing gaskets, corroded or broken ground connections, rusting of tanks, and signs of corrosion on terminals,
bushing studs, and connectors. If the transformer is
excessively noisy or has a ruptured gasket, then the
unit should be opened, internally inspected, and
tested.
(1) Load test. A load test should be made annually on transformers which supply a load that is
known to be increasing. Transformers which supply
a steady connected load should be load tested every
5 years. Load tests should be made with portable
ammeters (dial-indicating or recording-chart type),
installed for at least 24 hours on a peak loading
period day as determined by spot checking with a
Frequency
Weekly or monthly
Weekly or monthly
Weekly or monthly
Weekly or monthly
Annually
Monthly
Every 6 months
Every 6 months
Every 3 months
Monthly
Annually
Annually
Every 6 months
From 3 to 6 years
...
...
...
...
..
..
..
..
..
..
Annually
Annually
From 3 to 6 years
From 3 to 6 years
From 3 to 6 years
Annually
Insulating liquid
Gas analysis. .....................
Dielectric strength ................
Color . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Acidity (neutralization number). ...
Interfacial tension (IFT) ...........
General inspection items
Power factor test. .................
..
..
..
..
..
.
.
.
.
.
...
Annually
Annually
Annually
Annually
From 3 to 6 years
Frequency
From 3 to 6 years
clamp-on ammeter. Reasonable accuracy and complete safety should be of the greatest importance in
making transformer load surveys. Readings should
be taken on the secondary side of the transformer
whenever possible. Testing all transformers may
not be necessary, because similar areas and buildings may have quite similar loads.
(2) Dielectric tests. Dielectric tests of liquid immersed transformers need not be made on distribution transformers of less than l00-kVA capacity.
Liquid samples should be taken at 5-year intervals
from each liquid-immersed distribution transformer
of 100-kVA and greater capacity. These samples
should be given a dielectric test. If a liquidimmersed transformer has been out of service for
one year or more, dielectrically test a liquid sample
from that unit before re-energizing the transformer.
When a liquid sample fails to meet the dielectric
standard, filter the liquid until it meets the standard or replace with new liquid of a type and grade
recommended by the transformer manufacturer.
7-3
-_
.-
7-5
a. Insulation resistance test. Routine insulation resistance tests on transformers are normally
made at voltages given in table 3-4. Insulation
resistance usually decreases somewhat with an
increase in applied voltage. However, for a variation of two to one or three to one in the usual test
voltage ranges, there is no appreciable effect on
insulation resistance for equipment that is in
good condition. Marked variations in insulation
resistance for different values of voltage are usually
due to the effects of dirt or moisture. The insulation resistance values for oil-filled transformers
will vary due to humidity, size and type of transformer, temperature, and the value the test voltage
applied.
(1) Records. A record should be made of all
factors for comparison with previous and future test
results. Temperature correction factors are indicated in table 7-2. To obtain the equivalent insulation resistance at 20 degrees C, multiply the insulation resistance reading in megohms by the
appropriate correction factor. Values of winding insulation resistance may be affected by residual
charges that are retained in the winding. For this
reason, windings should be discharged to the frame
until the discharge current reaches a negligible
value. Ten minutes or more may be required to
complete the discharge.
(2) Insulation testers. Resistance testers are
available that indicate directly in ohms the resistance being measured. The power source necessary
for operation of the tester may be a hand cranked
generator, motor operated generator, or rectifier
supplying a direct-current voltage for test purposes.
For best results, the detailed instructions furnished
with each of these instruments should be followed.
Table 7-2. Insulation resistance conversion factors to 20C
Temperature
(C)
0 . . .
5 . . *
10 . . .
15 . . .
20 . . .
25 . . .
30 . . .
35 . . .
40 . . .
45 . . .
50 . . .
55 . . .
60 . . .
65 . . .
70 . . .
75 . . .
80 . . .
7-6
Transformer
Oil
...........
...........
...........
...........
...........
...........
...........
Dry
0.40
0.45
0.50
0.75
1.00
1.30
1.60
2.05
2.50
3.25
4.00
5.20
6.40
8.70
10.00
13.00
16.00
.-
(3) Test voltage. An insulation test is not intended to be a destructive test. The test voltage
used must be restricted to a value commensurate
with apparatus voltage rating and condition of insulation being tested. This is particularly important in
the case of small, low-voltage transformers or those
units containing an excessive amount of moisture.
b. Polarization index (PI) test. A PI test or dielectric absorption test is a continuation of the insulation resistance test in which the voltage is applied
for a longer period of time. For good insulation, the
resistance values will increase with time. The polarization index is the ratio of the lo-minute to the
l-minute readings. An index below 1 indicates poor
insulation. An index between 1 and 2 indicates that
the insulation is questionable. An index of a 2 and
higher indicates good insulation.
c. Power factor test. The power factor of an insulation is a measure of the energy components of the
charging current. The test indicates the power loss
caused by leakage current through the insulation.
The equipment to be tested should be disconnected
and all bushings should be cleaned and dried. The
test should be conducted when the relative humidity is below 70 percent and the temperature is above
32 degrees F (0 degrees C). On transformer tests,
the power factor of each winding with respect to
ground, and each winding with respect to its other
winding, should be measured. Evaluation of the
data obtained should be based on comparison of
data with any previous tests on the same transformer or on test data from similar units.
d. High-potential test. A high potential test is a
voltage applied across an insulation, at or above the
direct-current equivalent of the 60-hertz operating
crest voltage. The maximum direct-current test
voltage for periodic testing between windings, and
from winding to ground, should not exceed the original factory alternating-current test voltage. Good
insulation will exhibit a gradually rising leakage
current with an increase in test voltage. If the leakage current increases rapidly, the test should be
halted because a breakdown of the insulation is
indicated.
7-7
7-8
RTemp Silicone
. . 0.005 . . . . . . 0.005
. . 0.01. . . . . . . . 0.0 1
0.005
0.005
CHAPTER 8
-..-
Section II-FUSES
8-5. Fuse usage.
Fuses provide relatively inexpensive protection by
opening an electric line when a short circuit or overload occurs on the load side of the fuse. Always
remember that a fuse is a single-phase device.
a. Construction. A fuse is designed to be an
intentionally-weakened link in an electric circuit
and to be the first point of failure.
(1) Fuse link. A fuse link uses a metal such as
silver, tin, lead, copper or any alloy, which will melt
when a predetermined current is maintained for a
predetermined time period. The fuses melting current (rating) is selected to permit severing the circuit before the same current could damage the electrical system.
(2) Fuse tube. A fuse tube is provided to prevent damage from the melting fuse link, which otherwise might start a fire from possible flying metal,
and to aid in quenching the arc developed by sever-
8-1
__
.-
(4) Check fo r any missing or damaged hardware, such as nuts, bolts, washers, and pins.
(5) Clean and polish contact surfaces of clips
and ferrules that are corroded or oxidized.
(6) Tighten all 1 oose connections and check to
see if the fuse clips exert sufficient pressure to
maintain good contact.
(7) Fuses that show signs of deterioration, such
as loose connections, discoloration, or damaged casing should normally be replaced.
b. Periodic inspection of fuse links in distribution
cutouts. These fuse links may require periodic inspections, since corrosion of the lower terminal of
the fuse link (generally a flexible cable) at the lower
open-end of the fuse holder may cause breakage or
melting at this point, rather than in the currentresponsive element. Link-break cutouts are particularly susceptible since their link-break mechanisms
impose a mechanical strain on fuses.
c. Inspection of distribution oil fuse cutouts. In
addition to applicable general inspection requirements, the following items should be included:
(1) Sample insulating oil periodically and test
for dielectric breakdown strength. Cutouts that experience regular load-break or fuse-interrupting
duty should have their oil tested on a more frequent
basis.
(2) Nonvented distribution oil fuse cutouts generally incorporate insulating materials in the fuse
carriers that may be damaged dielectrically by excessive exposure to moisture or to a humid atmosphere. Keep the cutout sealed so that components
and oil are protected from any contaminating exposure.
(3) Fuse elements are generally not interchangeable, and any substitution for the manufacturers fuses may seriously affect the interrupting
characteristics of the device.
(4) Examine cutouts for any evidence of oil
leakage, and maintain the prescribed oil level.
(5) Check moveable bearing gasket surfaces,
yoke compression, and interlocking features for satisfactory operation.
Section III-SWITCHES
8-9. Switch usage.
8-3
--
.-
(2) Visual aids. Binoculars can facilitate spotting switches that are obviously in need of repair or
maintenance because of broken insulators or other
parts. Visual inspection of a wet switch, or the use
of a temperature-scanning detector,. may indicate
hot spots which are possible sources of trouble. Directional microphones or ultrasonic detectors can be
used to locate local corona sources needing removal.
b. Scheduling. A relatively small amount of
maintenance is required on modern switches, so
where possible, it is recommended that the schedule
for such maintenance be coordinated with that of
associated equipment. Schedule special inspection
and maintenance whenever the switch has carried
heavy short-circuit current.
c. Checking. Examination of de-energized and
grounded switches should include the following
items:
(1) Operating mechanism. Check the adjustment of the operating mechanism, operating rod,
and interphase tie rods (if used) to ensure simultaneous and smooth operation of the switch blades.
Mechanisms should be cleaned and lubricated only
when so recommended, and then in accordance with
the manufacturers instructions. (Many modern
switches are built with self-lubricating bearings.)
Examine all metallic parts of an operating mechanism including operating handle connection for
signs of rust, corrosion, and loose or broken connectors. Switches located outside of a fenced and locked
area, and having operating handles at ground level,
require locking provisions on handles for both the
open and closed positions. Switches located within a
fenced and locked area, are subject to local regulations for locking.
(a) Inspect all live parts for scarring, gouging, or sharp points, which could contribute to excessive radio noise and corona. Check corona balls
and rings for damage which could impair their effectiveness.
(b) Power-operating
mechanisms
for
switches are usually of the motor-driven, spring,
hydraulic, or pneumatic type. Follow the manufacturers instructions with regard to the limit switch
adjustment. Check associated relay equipment for
poor contacts, burned out coils, and adequacy of
supply voltage. The complete electrical circuit of a
motor-operated mechanism should be checked to ensure proper operation and wiring which is secure
and free of insulation defects.
(c) Inspect, check, and test all safety interlocks for proper operation.
(2) Insulators. Examine insulators for cracks,
chips, breaks, and evidence of flashover. Bad insulators should be replaced. Insulators should be
cleaned to remove any contaminating materials
8-5
instructions. Interrupter contacts should be inspected for damage caused by arcing. Contacts
showing evidence of excessive wear should be replaced in accordance with manufacturers recommendations. Interrupters with sealed gas-filled
chambers have pressure gages to indicate loss of
pressure. Field experience indicates that interrupters using a sealed gas chamber will require recharging every 2.5 to 3 years or more often.
8-6
always be successful. Too much opening spring pressure can cause excessive friction at the tripping
latch and should be avoided. Electromagnetic
forces, due to the flow of heavy short-circuit currents through the circuit breaker, may cause extra
pressure on the tripping latch.
(2) Lubricate the bearing surfaces of the operating mechanism as recommended in the manufacturers instruction book. Avoid excessive lubrication
because oily surfaces collect dust and get stiff in
cold weather, resulting in excessive friction.
(3) If possible, observe the circuit breaker operation under load.
(4) Operate the circuit breaker manually and
electrically, and look for malfunctions. Determine
the presence of excessive friction in the tripping
mechanism and the margin of safety in the tripping
function by testing the minimum voltage required
to trip the circuit breaker. This can be accomplished
by connecting a switch and rheostat in series with
the trip-coil circuit at the circuit breaker (across the
terminals to the remote control switch) and a voltmeter across the trip coil. Starting below 50 percent
of rated trip-coil voltage, gradually increase the
voltage until the trip-coil plunger picks up and successfully trips the circuit breaker. Make several
trial tripping operations of the circuit breaker, and
record the minimum tripping voltage. Most circuit
breakers should trip at about 56 percent of rated
trip-coil voltage. Measure the trip-coil resistance
and compare it with the factory test value to disclose shorted turns. Many modern circuit breakers
have trip coils which will overheat or burn out if left
energized for more than a short period. An auxiliary
switch is used, in series with the coil, to open the
circuit as soon as the circuit breaker has opened.
The auxiliary switch must be properly adjusted to
successfully break the arc without damage to the
contacts. Record the minimum voltage that will
close the breaker and the closing coil resistance.
(5) Trip the circuit breaker by protective relay
action.
(6) Check adjustments by measuring the mechanical clearances of the operating mechanism associated with each tank or pole. Appreciable variation between the clearance measured and the
previous setting usually indicates mechanical
trouble. Temperature, and difference of temperature, between parts of the mechanism affect the
clearances. The manufacturers recommended tolerances usually allow for these effects.
(7) Check the power factor of bushings and the
circuit breaker.
(8) The measurement of the electrical resistance between external bushing terminals of each
pole can indicate whether maintenance is required.
8-7
kilovolts, even though some manufacturers instructions allow 16 kilovolts. If the oil is carbonized,
filtering may remove the suspended particles, but
the interrupters, bushings, and other internal parts
must be wiped clean. If the dielectric strength has
been lowered by moisture, check and eliminate the
source of the moisture (such as fiber or wood parts);
and dry the affected parts thoroughly before placing
the circuit breaker in service.
(2) Circuit breakers insulated with SF,. Circuit
breakers having SF, insulation should be tested
every 3 months during the first year of service, and
at least every 12 months thereafter, to determine
the moisture content of the SF, gas. Moisture content must also be tested when gas is added. Service
equipment according to the manufacturers instructions. Moisture content should be less than 50 parts
per million by volume (ppm,). Do not energize a
section of the gas-insulated equipment, if the SF,
gas density is less than 50 percent of nominal or if
the moisture content of the gas exceeds 1000 ppm,.
Refer to chapter 15, section II in regard to the toxicity of SF, gas.
c. Internal inspection guidelines. When an internal inspection is required it should be made at the
same time as an external inspection. The circuit
breaker tanks or contact heads should be opened
and the contacts and interrupting parts inspected.
Follow these guidelines and the checklist furnished
by the manufacturer. Such a checklist may provide
forms useful for recording inspection and maintenance data.
(1) Internal difficulties are most likely to appear early in the use of a circuit breaker, which is
why early internal inspections are recommended.
As unsatisfactory internal conditions are corrected,
and if one or two later inspections indicate satisfactory internal conditions, the frequency of internal
inspections may safely be decreased.
(2) For circuit breakers equipped with pneumatic operators, drain and inspect the air tanks.
(3) Perform post maintenance diagnostic tests
on circuit breakers in accordance with instructions
from test equipment and circuit breaker manufacturers, and follow established maintenance procedures.
(4) Test operate the circuit breaker and record
the number of operations. The tests should include
all alarms (including control alarms), switches, and
the manufacturers recommendations.
d. Internal inspection guidelines specific to the
insulating medium used. The insulating medium
must be removed, as necessary, to examine the circuit breaker internally.
(1) Oil-insulated circuit breakers. Inspecting
the tank includes removing the oil, ventilating the
8-8
__
f . Influence of duty imposed. The need for maintenance is influenced by any circuit breakers operating duty. The influence of operating duty given
below for oil circuit breakers will also apply (except
for the different insulating medium) to SF, gasinsulated circuit breakers.
(1) Influence of light duty. If the circuit breaker
has been energized on both sides, but the contacts
are open, erosion in the form of irregular grooves
(called tracking) may appear on the inner surface of
the interrupter or shields, due to electrostatic
charging current. This is usually aggravated by a
deposit of carbon sludge, which has previously been
generated by some interrupting operation. If the
circuit breaker has remained closed and is carrying
current, evidence of heating of the contacts may be
found if the contact surfaces were not clean, have
oxidized, or if the contact pressure was improper.
Any shrinkage and loosening of wood or fiber parts
(due to loss of absorbed moisture into the dry oil)
will take place following the circuit breaker installation, independent of the circuit breaker operation.
However, mechanical operation will make any loosening more evident. If possible, before inspection,
open and close the circuit breaker while energized.
If this is not possible, additional information may be
gained by operating the deenergized circuit breaker
several times, measuring the contact resistance of
each pole before and after each operation.
(2) Influence of normal duty. The severity of
duty imposed by load switching, line deenergizing,
and fault interruptions depends upon the type of
circuit breaker involved. In circuit breakers which
employ an oil blast generated by the power arc, the
interruption of low current faults or line charging
current may cause more deterioration, because of
low oil pressure, than the interruption of high current faults. In some designs using this basic principle of interruption, distress at low interrupting
duty is minimized by multiple breaks, rapid contact
travel, and turbulence of the oil caused by movement of the contact and mechanism. In designs employing a mechanically driven piston to supplement
the arc-driven oil blast, the performance is more
uniform. Better performance is yielded b y designs
which depend upon a mechanically driven oil blast
for arc interruption. In this type, contact erosion
may appear only with heavy interruptions. The mechanical stresses that accompany heavy interruptions are always more severe. These variations of
performance among various designs must be considered when evaluating the need for maintenance and
performance of a circuit breaker. Because of these
variations, the practice of evaluating each fault interruption as the equivalent of 100 no-load opera-
8-9
TM 5-684/NAVFAC M O - 2 0 0 / A F J M N
A 32-1082
tions is approximate, although it may be a useful
guide in the absence of other information.
(3) Influence of seuere duty. Contact erosion
and damage from severe mechanical stresses may
occur during large fault interruption. Reliable indication of the stress, which a circuit breaker is subjected to during fault interruptions, can be obtained
by automatic oscillograph records on systems which
provide this feature. Deterioration of the circuit
breaker is proportional to the energy dissipated in
the circuit breaker during the interruption. The energy dissipated is proportional to the current and
the duration of arcing, that is, the time from the
moment the contacts part to current interruption.
However, oscillographs do not always record the
moment that the contacts part, and it may be necessary to determine the parting from indicated relay time and the known time for circuit breaker
contacts to part. When automatic oscillograph
records are available, they may be as useful in guiding oil circuit breaker maintenance as in showing
relay and system performance. When automatic
oscillographs are not available, an approximate indication of fault duty imposed on the circuit breakers may be obtained from relay targets and accompanying system conditions. All such data should be
tabulated in the circuit breaker maintenance file.
8-15. Maintenance of metalclad circuit breakers.
The insulating media covered include air and
vacuum.
a. General maintenance procedures. The following suggestions are for use in conjunction with
manufacturers instruction books for the maintenance of drawout medium-voltage circuit breakers
installed in metal-clad switchgear. Record all problems.
(1) Basic requirements. Drawout devices
should be removed for inspection and operation.
During inspection all deposits or dust will be removed with a clean lint-free cloth; a vacuum cleaner
might be helpful. All smoothing of surfaces should
be done with crocus cloth.
(2) Operating history. Record the number of operations of the circuit breaker.
(3) Test position. Before complete removal put
the circuit breaker in the test position. Use a test
coupler to operate the circuit breaker electrically.
Check the performance of all controls such as protective relays, switches, motors, indicating devices,
and alarms.
(4) Remove the drawout portion of the circuit
breaker and perform visual inspections, operations,
8-10
measurements, tests, and final checks before inserting the drawout portion into the switchgear cubicle
for re-energization as appropriate.
b. Air-circuit breaker maintenance requirements.
Remove box barriers from the circuit breaker and
clean all insulating parts including the bushings
and the inside of the box barriers. The unit is now
ready to be inspected, operated, and tested.
(1) Visual inspections. Inspect the unit to determine its operating condition. Perform any repairs in accordance with the manufacturers instructions.
(a) Check the bushing primary disconnect
stubs and finger cluster. Bushing insulation should
be clean, dry, smooth, hard, and unmarred.
(b) Check i nsulation and outside of arc
chutes for holes or breaks; small cracks are normal.
If ceramics or fins are broken replace arc chutes.
The throat area of arc chutes may need to be cleared
of contamination with crocus cloth.
(c) Check arcing and primary contacts for
uneven wear, or impairment from burns and pitting. Correction of damage by smoothing or resilvering may be necessary. Replace badly damaged contacts. Follow the same procedure for primary
disconnect stubs and other current-carrying parts.
Grease contacts with an approved grease.
(d) The tightness of all connections is of
paramount importance. Check and tighten or secure, as necessary, any loose nuts, bolts, retaining
rings, and mechanical linkages which are a part of
the circuit breaker and its operating mechanism.
Ensure that all electrical wiring connections are
secure.
(e) Check all bearings, cams, rollers, latches,
and buffer blocks for wear. Teflon-coated sleeve
bearings do not require lubrication. All other sleeve
bearings, rollers, and needle bearings should be lubricated with SAE 20 or 30 machine oil. Lubrication
is not required on ground surfaces having a dark
molybdenum disulfide coating. Lubricate all other
ground surfaces such as latches, rollers, or props
with an approved grease.
( f ) Check actuator relays, the charging motor, and secondary disconnects for damage, evidence
of overheating, or insulation breakdown.
(g) Check contacts of control relays for wear
and clean as necessary.
(h) Check for possible damage to wiring and
replace any wiring with worn insulation.
( i ) Check for damage to magnetic blow-out
coils if they are used.
(2) Operations and measurements. After correcting any deficiencies revealed by the visual inspection, perform these circuit breaker operations
and measurements.
(a) If the primary contact gap required adjustment, operate the circuit breaker several times
to verify correct performance.
(b) Check the operation and the clearance of
the trip armature travel, and release the latch in
accordance with the appropriate instruction book.
Replace any worn or damaged parts disclosed by
this operation.
(c) On stored-energy circuit breakers, operate the circuit breaker slowly. By using the spring
blocking device, check for binding or friction, and
correct if necessary. Make sure contacts can be
opened or closed fully.
(d) Reinstall box barriers and measure insulation resistance of each bushing terminal to ground
and phase to phase. Record resistance readings and
also temperature and humidity.
(3) Tests. Per form tests every 1 to 3 years dependent upon the severity of duty encountered by
the circuit breaker.
(a) Perform a hi-pot test on the circuit
breaker bushings.
(b) Check the c1 osed circuit breaker contact
resistance.
(c) Perform a power factor test.
(d) Perform a corona test.
(4) Final checks.
(a) Using the coupler, test operate the circuit
breaker both electrically and manually. Check all
interlocks.
(b) Insert and operate the circuit breaker in
the switchgear cubicle. Watch for proper operation
of the positive interlock trip-free mechanism. The
circuit breaker should trip whenever it has not been
fully inserted, or whenever it is in the test position.
(c) Remove the circuit breaker from the
switchgear cubicle and check the primary disconnect wipe. Refer to the appropriate instruction book.
(d) Insert the circuit breaker into the
switchgear cubicle, ready for energization.
c. Vacuum circuit breaker procedures. Direct inspection of the primary contacts is not possible, because they are enclosed in vacuum containers. The
operating mechanisms are similar to the air circuit
breakers, and may be maintained in the same manner. It is not recommended that a vacuum circuit
breaker be operated more than 2,000 times without
an inspection.
(1) Specific checks applying to vacuum circuit
breakers. Checking for contact erosion and vacuum
condition is made with the circuit breaker removed
from its switchgear cubicle.
(a) Close the circuit breaker and measure
the spring plate overtravel. Consult the manufac-
Cause
Remedy
Sludging of oil.
Overheating.
Gaskets leaking.
Insulation failure.
8-12
-_
Trouble
Cause
Overheating
Remedy
(2) Burned and pitted because of lack of attention after many heavy operations, or too
frequent operation.
(4) If the circuit breaker is overheating because of excess current, one of two remedies
can be followed:
(a) Replace with circuit breaker having an
adequate rating for the present or future load.
(b) Arrange circuits to remove the excess
load.
Failure to trip
(5) Transmission of heat to the circuit breakers from overheated or inadequate cables or
connection bars.
(6) Tighten.
(1) Lubricate mechanism. Adjust all mechanical devices, such as toggles, stops, buffers, and
opening springs, according to the instruction
book.
(2) Examine the latch surface. If worn or corroded, it should be replaced. Check latch wipe,
and adjust according to the instruction book.
(1) Lubricate mechanism. Adjust all mechanical devices, such as toggles, stops, buffers, and
opening springs, to specifications in the circuit
breaker instruction book.
8-13
Cause
Remedy
(6) Insufficient control voltage (of an electrically operated circuit breaker) caused by:
(a) Too much drop in leads
(b) On ac control-poor regulation.
(c) On dc control-battery not fully charged
or in poor condition.
(7) Blown fuse in control circuit, faulty connection or broken wire in control circuit,
damaged or dirty contacts on control switch
(electrically operated circuit breaker)
(7) Replace blown fuse; repair faulty connection or broken wire; dress or replace damaged
contacts or clean dirty contacts in control
switch.
_-
-_
8-15
CHAPTER 9
OVERVOLTAGE PROTECTION
Section I-CONSIDERATIONS
9-1. Overvoltage protection.
This chapter describes the maintenance and repair
of protective devices installed to limit transient
over-voltages on lines. Abnormal voltages are caused
most frequently by lightning, but system disturbances can also cause damaging voltage surges.
9-2. Lightning-induced voltage surges.
Overhead lines are extremely vulnerable to direct
strokes or to induced voltage influences. Underground systems derived from aerial lines may also
be affected.
a. Causes. Lightning results from the potential
difference between clouds or between a cloud and
earth. A lightning stroke may be in direct contact
with an electric line and equipment. The charged
clouds of a passing lightning storm may also cause
an electrostatically induced voltage.
b. Protection. The high voltage of a lightning
surge, imposed on lines and devices without surge
protection, will flash over the insulation in the majority of cases. Where flashover occurs, through air
or on insulators, it rarely causes permanent damage, but flashover occurring through the solid insulation on equipment or cable can result in permanent damage.
9-3. System operating voltage disturbances.
Transferring a system from one operating condition
to another may generate a short-time transient
overvoltage, known as a switching surge. A line-to-
ground fault may increase the line-to-ground voltage of the unfaulted phases. An overvoltage results
when resonance occurs from single-pole switching of
three-phase circuits. Accidental contact with a
higher-voltage system may cause an overvoltage.
Forced-current zero interruptions, improperly applied, may cause a high transient voltage. The protective devices discussed for lightning-induced
surges will also protect the system from these
system-generated over-voltages.
9-4. Surge limiting protective device requirements.
A surge limiting protective device must limit transient over-voltages or surge voltages that could damage apparatus. The device must bypass the surge to
ground and discharge severe surge currents of high
magnitude and long duration without injury. The
device must continuously withstand the rated
power voltage for which it is designed. The devices
protective ratio is the maximum surge voltage it
will discharge, compared to the maximum crest
power voltage it will withstand following discharge.
Surge arresters provide the most accepted method
of surge limiting protection, since they provide the
highest degree of surge elimination. Other methods
include shielding lines and equipment from direct
lightning strokes; and providing devices designed to
divert or change the wave form of the surge, such as
protective gaps, surge capacitors, and bypass resistors.
9-l
--
9-3
CHAPTER 10
GROUNDING
Section II-MAINTENANCE
10-l
a. Stainless steel ground rods. Do not use stainless steel ground rods. Their performance can be
unpredictable because of their tendency toward localized corrosion.
b. Underground pipe lines. The bonding of interior metallic pipelines to an electrical systems
ground provisions of copper (which is required by
code) if done incorrectly, can result in galvanic corrosion of the underground pipeline. Installation of a
dielectrically-insulated fitting on the pipe above
ground, and before the copper ground connection,
will eliminate the earths electrolytic coupling between the underground cable and the ground wire.
Section III-TESTING
10-6. Ground resistance tests.
In addition to visual inspections of grounding systems and connections, resistance measurements
will be made periodically to determine whether
there is any trend toward an increase in the ground
resistance of an installation. Maximum permissible
resistance for grounds and grounding systems will
be in accordance with departmental standards,
ANSI C2, or the National Electrical Safety Code,
whichever is lower.
a. ANSI C2 requirements. No specific ground resistance is given, except that a single-grounded,
individually-made electrode, with a ground resistance exceeding 25 ohms, requires two parallel and
interconnected electrodes. Supply stations (dependent upon size) require an extensive grounding system, consisting of either multiple buried conductors
or electrodes or both, to limit touch, step, mesh, and
transferred potentials in accordance with industry
practices. All grounding systems must be designed
to minimize hazard to personnel and have resistances low enough to permit prompt operation of
circuit protective devices.
b. Departmental standards. Departmental standards will require values ranging from 1 ohm up to
a maximum of 25 ohms depending on the size of the
system.
c. Measurement records. Continuous records will
be kept for all grounding installations, which require a ground resistance of 10 ohms or less, to
verify that design resistances are still being provided.
1O-7. Ground value measurements.
The following ground resistance measurements
should be made in order to ensure safe operating
practices.
a. Measure the ground path resistance of all
branches of the grounding system from the point of
10-2
--
-4
sary. Auxiliary reference grounds and test instruThis arrangement is shown in figure 10-3. The
ground rods should be driven 8 to 10 feet (2.5 to 3
ments are necessary for ANSI/IEEE 80 and
meters) into the earth and spaced not less than 50
ANSI/IEEE 81 methods.
feet (15 meters) apart. Three separate tests are
a. Minor grounding installations. The following
made to determine the resistance of each of the
methods are suitable for measuring the resistance
series circuits when composed of only two grounds.
of isolated ground rods or small grounding installaThe unknown resistance may then be calculated as
tions. Precision in measurements is difficult to obfollows by equation 10-l.
tain. Normally an accuracy of 25 percent is sufficient, since the surrounding soil will not have
R, + R, - R,
consistent values of temperature, moisture, and
R, =
(eq. 10-l)
2
depth.
Actual resistances may be determined by using one
(1) Portable ground testing instruments. A
of the following methods.
usual way to measure the ground resistance is with
(a) AC voltmeter-ammeter method. The cona low-range, self-contained, portable earth-tester innections for the ac voltmeter-ammeter test are
strument such as the Megger Ground Tester or
shown in figure 10-3. The resistances of the ground
Ground Ohmer. The manufacturers instructions
circuits are determined from the meter readings
should be followed in the use of this instrument.
and these values are then used in calculating R,.
The two most common methods of measuring the
Stray alternating currents of the same frequency as
ground resistance with this type of instrument are
the direct-reference or two-point method shown in
the test current, if present, will introduce some erfigure 10-l and the auxiliary ground method shown
ror in measurements.
in figure 10-2.
(b) DC voltmeter-ammeter method. A dc
(2) Three-point method. The three-point
voltmeter-ammeter method may also be used to determine the resistance of each pair of grounds in
method of measuring ground resistance requires
series. Like the ac method, it is limited to locations
two auxiliary grounds, similar to those required
where power is available or where a battery source
with portable ground testing equipment, except
may be used with the regulating apparatus rethat each auxiliary ground should have a resistance
quired to control the current flow. The line supplyapproximately equal to the ground being tested.
------_-- 1
I
r-PORTABLE GROUND
RESISTANCE MEASURING
INSTRUMENT
GROUND TO
B E TESTEDd
I_
- W A T E R
SYSTEM
5 (LOW RESISTANCE)
Figure 10-l. Direct-reference or two-point ground test
t--PORTABLE GROUND
RESISTANCE MEASURING
INSTRUMENT
,
GROUND TO
BE TESTED
C
=
fT( 15M) M I N I M U M
_I
50 fT( 15M)
MAXIMUM
10-3
ing the current must be free from grounds to minimize the effect of cross-currents. To compensate for
the effect of stray dc voltage currents in the area,
readings should be made at both polarities.
b. Major grounding installations. Where accurate
measurements of extensive low-resistance grounding systems are required, more elaborate test methods and equipment are needed using considerably
larger separation distances between test electrodes.
Normally large facility substations are tested with
the fall-of-potential method in accordance with
ANSI/IEEE 81 requirements. Figure 10-4 shows a
field setup for this method and the ground resistance curve. The resistance shown on the flat part of
the curve is taken as the resistance of the ground.
The self-contained earth tester instrument shown
should be used rather than a voltmeter-ammeter
combination, as the earth tester is designed to
eliminate the effects of stray currents. The primary
advantage of this method is that potential and current electrodes (probes) may have substantially
higher resistance than the ground system being
tested without significantly affecting the accuracy
of the measurement.
(1) Major substations. To allow for seasonal
variations it is recommended that tests be made at
the same time each year or for each season of the
year to allow for accurate comparison.
(2) Procedures. Tests should be performed in
accordance with written procedures. Provide adequate safety precautions as all electrical conducting paths for overvoltage and fault currents are
connected to the substation grid.
10-9. Method of reducing ground resistances.
Ground tests may indicate that the ground resistance exceeds safety requirements. Adding rods, increasing rod lengths, soil treatment, or a combina10-4
00
/////////r////f//
7tentiol
l-c
Probe: j ?
LA-..aLI-
IvIuvuulc
Fixed C u r r e n t
Probe C
--ANSI/IEEE 8 1 Distances
obstructions to deep driving. There are two practical ways of accomplishing this as shown in figure
10-5. Where space is limited, a length of tile pipe is
sunk into the ground a few inches (millimeters)
from the ground rod and filled to within approximately 1 foot (0.3 meters) of the ground level with
the treating chemical. The second method is applicable where a circular or semicircular trench can be
dug around the ground rod to hold the chemical.
The chemical must be kept several inches (millimeters) away from direct contact with the ground rod
to avoid corrosion of the rod. The first treatment
usually requires 50 to 100 pounds (22 to 45 kilograms) of material and will retain its effectiveness
for 2 to 3 years. Each replenishment of the chemical
extends its effectiveness for a longer period, thus
increasing treatment intervals. To start the action
promptly, the first treatment of chemical should be
flooded.
d. Specialized rods. In lieu of adding additional
rods or lengthening rods, a copper tubing grounding
system can be used. There is an Underwriters-listed
grounding system that uses a 2-inch (50-millimeter) copper tube filled with metallic salts and available in various lengths. Since this method uses metallic salts it is not recommended except as a last
resort. The tube is also available as a straight unit,
or in an L-shaped configuration which allows the
tube to be installed on its side in a shallow trench.
Changes in atmospheric pressure pump air
through the breather holes at the top of the tube.
Moisture in the air condenses inside the tube to
move slowly down through the bed of metallic salts,
providing a self-maintaining low-resistance system
with a much greater life expectancy than conventional ground rods.
e. Combination methods. A combination of methods may be advantageous and necessary to provide
the desired ground resistance. Adding specialized
rods or a combination of multiple rods and soil
treatment may be effective. Multiple of longer rods
are effective where conditions permit this type of
installation.
10-5
--4//(WH
REMOVABLE COVER
HOLES)
\c\ __
-/
I _- . .
.f/l=_
,, __
901L TREATMENT
a. CONTAINER METHOD
b. TRENCH METHOD
10-6
T-0
CHAPTER 11
RELAYS AND CONTROLS
- -
11-l
dures. Major repairs and testing should be conducted in a facilitys testing laboratory, or by
contract personnel with access to any special testing
equipment needed.
a. Electromechanical relays. Check contacts,
moving parts, connections, and the case and covers
of these relays.
(1) Contacts. Contacts must be kept clean. A
flexible burnishing tool should be used for cleaning
silver contacts. Silver contacts should not be
cleaned with knives, files, abrasive paper or cloth,
as these items may leave scratches which can increase arcing and hasten deterioration of the contacts. Abrasive paper or cloth may, in addition, leave
minute particles or insulating abrasive material in
the contacts, and thus prevent closing. Contact wipe
and resistance are important in all relays and
should be checked as part of the maintenance procedure. Contact resistance can be determined by
using an ohmmeter. Where this resistance depends
on springs, the contact pressure should be checked
using a spring gage. High resistance of such contacts may indicate insufficient spring pressure,
which will require replacement of the spring. The
relay must be deenergized and disconnected when
the contacts are tested.
(2) Moving parts. It is important that all moving parts operate smoothly, so keep all bearings,
shafts, linkages, and other moving parts free and
clear of dirt or gum. Relays normally require oiling
only when replacing a jewel, shaft, or moving part.
Too much lubrication of these parts can lead to
serious troubles and should be avoided. The relay
disks should be cleaned with a thin brass or bronze
magnet cleaner having a steel edge or insert. Relays
should be quiet when operating. A noisy relay
should be checked for loose parts or excessive play,
and corrective measures should be taken.
(3) Connections. Relay connections should be
thoroughly checked as part of the maintenance inspection. Check all screws and nuts for tightness.
Check the relays, and as much of the circuitry as
possible, for continuity, grounds, and shorts.
(4) Case and cover. To prevent dirt from entering the case, ensure there is a tight seal between
the relay cover and its gasket. Any dust or dirt
within the case should be brushed, blown, or vacuumed out. Care should be taken that dirt is not
blown deeper into the relay necessitating removal
and overhaul of the relay.
b. Solid-state relays. Many solid-state relays
have easy-to-use built-in operational test diagnostics. Calibration tests are made in the conventional
manner. Maintenance is generally not required, in
the usual sense of adjusting, cleaning, or lubricating. Check external connections. It may be neces-
-_-
These tests are usually provided for equipment acceptance, but may be necessary if the relay is completely replaced.
a. Operational checks. Before returning a relay to
service, test the complete wiring installation for
continuity and operate the relay contacts, preferably by test current, to ensure that everything is in
order for the intended function. Any changes in the
relay calibration, or needed adjustments should be
made at this time. Normally adjustments in the
relay settings will not be necessary, but proof checks
must be made. Manufacturers instruction books
should also be checked to determine the proper procedure and test equipment required for specific relays. In some cases, the relay may have to be removed and inspected in a laboratory.
b. Directional test. Where directional relays are
used, an overall test should be made to ensure that
they operate in the proper direction.
c. Dielectric test. When dielectric or insulation
tests are made, they should be performed on the
complete installation or on all the component parts.
For relays rated up to 6000 volts, the test should be
made at twice rated voltage plus 1000 volts (with a
minimum of 1500 volts ac for one minute).
d. Calibration and performance tests. Some of the
tests that are run on the more common relays are
shown herein. In addition, the manufacturers instruction book should be checked for proper testing
procedure of a specific relay. The time between tests
will be determined by installation conditions and
changes in the system. Regularly scheduled tests
should be supplemented by special tests, made at
any time protective equipment damage is suspected
and while protected equipment is out of service.
11-3
IiLl
POUR
COIL
MM
OPERATING
OPERATING
COIL
POTCNTIAL
POW?lZlNC
CIRCUIT
C U R R E N T POLAAIZING
CIRCUIT
o==
AMMETERS
OPERATING COIL
RC = RESTRAINING COIL
R = R HEOSTAT
Let-t
1 1 5 V O L T S , 6 0 HZ
g(
a. Advance field testing preparation. Study system protection, including station single lines and
relay instruction books. Obtain and review previous
tests and arrange to have all required test equipment. Check that outage requests, switching arrangements, and any remote operations have been
scheduled.
b. Field test equipment. The test equipment for
field testing must be portable, so tests can be made
at the relay panel. For most of the common relays,
the following will be needed: a variable voltage
autotransformer, a multirange ac and dc voltmeter,
a multirange ac and dc ammeter, an ohmmeter,
auxiliary current transformers, a timer, a threephase shifter, and auxiliary relays. Test plugs,
leads, noninductive resistors, and a relay tool kit
will also be required. In general, most laboratory
test equipment is portable and can be used in the
field. Test instruments are available in prepackaged
test sets. The use of these sets simplifies testing.
c. Laboratory testing. If the field testing indicates
that a relay needs a shop repair, then engineering
evaluation is necessary in determining what effect
its removal will have on the reliability of the protective system. Short time removals of one phase of
three-phase protective items, switching to alternate
power sources, or a replacement relay with correct
settings may be necessary. Such judgment should be
made as a part of the advance field testing preparation.
d. Laboratory test equipment. Some of the common test equipment that should be available in a
laboratory for servicing relays is shown in table
11-l. In addition to these devices, a relay tool kit,
test plugs, test leads, printed circuit board extenders, a frequency generator, ac and dc power supplies, a portable test unit, an oscillograph, a power
amplifier, and special equipment testers, as required for certain types of relays, will be needed.
When selecting types and outputs of test equipment, consideration should be given to the various
.-
--
POW?l~ CHECK
THRFE PHASE 1 1 5 V O L T . G O HZ
AUTOTRANSFORMf R
AMMETER
I
M A X I M U M TORQuE
RELAY
LoAD
RESISTOR
equate tools and testing facilities are provided. Before removal of any parts, the manufacturers
instructions should be checked for the proper procedures.
c. Overhauling. Exercise care in overhauling, as
relays are easily damaged. There are a wide variety
of relays with many complicated and delicate parts
and it is impractical to list all the details that
should be checked. Consult and follow the manufacturers instruction and parts manual for the specific
style of the relay being overhauled. Relays should
be thoroughly cleaned at the time of overhaul. Test
taps and tap blocks if coils are replaced. Where
required repairs are extensive, return the relays to
the factory.
d. Adjustments. After the overhaul,various adjustments and alignments are required. Adjustment
must be coordinated with other protective devices,
as provided by a relay coordination analysis. The
manufacturers instruction manual should be referred to for the proper procedure. A few of the more
important items that will require checking include
shaft end play, contact gap, and torque and clutch
adjustment. Depending on the degree of overhaul,
some of these adjustments may not have to be
changed; for instance, shaft end play should be
11-5
Test equipment
Variable voltage
autotransformer . . . . . . . .
Multirange dc voltmeter.
Multirange ac ammeter .
.....
.....
.....
RELAY
R - RESTt?ANIL(G
Description
COIC
0-OPERATWC COIL
Section II-CONTROLS
11-10. Control functions.
Controls are broadly defined as the methods and
means of governing the performance of any electric
apparatus, machine, or system, by sensing any need
for a change and facilitating that change. In performing these duties, control circuits or systems
may act to regulate, protect, indicate, open, close, or
time an operation. Control devices execute control
functions.
a. Control equipment. Some of the more common
equipment controlled are switches, circuit breakers,
contactors, lights, rheostats, timers, and valves.
Control schemes use combinations of the following
component parts to produce the desired operation:
alarms, batteries, coils, fuses, relays, solenoids, timers, switches, and transformers. Other special electrical equipment may be used also.
(1) Electromechanical controls. Electromechanical controls are operated by magnets, thermal
action, motors, or other mechanical or static actions.
(2) Solid-stat e controls. Solid-state controls
perform similar functions to electromechanical controls, but their characteristics are affected to a
11-6
of these items may be necessary at times, particularly after a faulty operation. These tests will have
to be conducted when the machine or equipment
being controlled can be removed from service.
Monthly inspection should be adequate. Annual
testing of the insulation will detect defective wiring
before the insulation breaks down.
e. Thermally-operated devices. Thermostats, thermal overload units, and temperature devices operate on the heating effect of electric current. Inspect
units about once a month for dirt, excess heating,
freedom of moving parts, corrosion, wear, and condition of the heating elements. As elements which
normally operate only when an overload or trouble
takes place in the equipment being controlled, they
must be in good operating condition at all times.
f. Motor-operated devices. Motor-operated timers,
thrusters, valves, and brakes are included in this
category. Periodic inspections should be made for
evidence of dirt, heating, corrosion, wear, noisy operation, and vibration. Such inspections should ensure correct voltage, freedom of moving parts,
proper lubrication, adequate gaskets, and satisfactory condition of gearing. Cleanliness is particularly
important in mechanical linkages. Trial operation of
moving parts may be necessary to detect trouble. As
this may necessitate temporary removal from service, actual operation tests if necessary should be
coordinated with scheduled equipment outages.
Monthly inspections should be satisfactory, but for
extremely dirty locations more frequent inspections
are desirable.
g. Mechanically-operated devices. Mechanicallyoperated devices include master, selector, knife,
limit, speed, flow, float, and pressure switches;
drum controllers; push buttons; and manual starters. Inspections of these parts for dirt, heating, corrosion, restriction of moving parts, contact and
alignment wear, general condition, sealing, sludge,
and lubrication are required. Each individual case
must be studied on its own merits to determine if
the seriousness of the condition justifies an interruption of operation for maintenance. In some
cases, temporarily disconnecting the control circuit
long enough for repairs may be possible. Inspections
every 6 months should be satisfactory, but more
frequent inspections may be necessary where contamination is severe.
h. Static accessories. Static accessories include
resistors, rectifiers, capacitors, arc chutes, shunts,
interlocks, transformers, fuses, wiring, and bus
cables. Inspect for dirt, heating, corrosion, proper
clearances, and loose connections. The urgency of
any required corrective measures should be established in accordance with the seriousness of the
condition. In general, inspections should be made
11-7
Trouble
CONTACTS:
Contact chatter.
.................
j. Test equipment. Commonly used test equipment includes multirange ac and dc ammeters and
voltmeters, timers, ohmmeters, and auxiliary relays. Test leads, resistors, and tool kits are also
required for servicing controls. A suitable shop
should be available when major repairs are to be
made. If solid-state equipment is to be checked, an
oscilloscope or oscillograph and a high resistance
voltmeter will be required.
k. Repair parts. Spare parts should be kept on
hand, particularly if the equipment cannot be taken
out of service for long periods of time. Parts should
be stocked if they receive considerable wear or experience frequent replacement. A list of spare parts
from the appropriate manufacturer can be used as a
general guide for stocking. When broken or damaged parts are returned to the manufacturer, they
should be accompanied with complete information
regarding model number, nameplate data, duty
cycle, service conditions, description of the failure,
and probable reasons for the failure.
11-12. Troubleshooting controls.
In order to expedite repair work, it is important
that the technician be thoroughly familiar with the
equipment and the control operation. An elementary wiring diagram is most useful in maintenance
or inspection work and should be available near
the equipment. Portable testing instruments for
checking continuity, resistance and adequacy of insulation, voltage, and current should also be available.
a. Solid-state devices. The list of possible troubles
which can occur in solid-state control equipment is
too length to be of value here. Instruction books
prepared and furnished by equipment manufacturers usually contain troubleshooting guides, which
should be used.
b. Electromagnetic devices. Table 11-2 lists some
of the more common troubles (with their causes and
remedies) encountered in general control equipment.
Cause
Course of action
.
.
.
11-8
....................
..
..........
Welding or freezing
..........
--
COILS:
Coil failure
........
..........
Overheated, roasted.
.........
.............
.......
Course of action
Cause
Trouble
..
............
Tighten connections.
Relocate coils or use special resistant coils.
Dry out coils.
Do not handle coils by the leads.
Check manufacturer.
Check application and circuit.
Check manufacturer.
Replace coil and correct conditions if practical
to do so.
Check application.
Check circuit interlock.
Install larger coil, or reduce current.
Relocate, or reduce temperature.
If connection is hot, clean before tightening.
See manufacturers instructions.
Replace shunt.
Replace shunt.
Replace shunt and correct condition.
Check application and system voltage.
11-9
Cause
Noisy magnet.
.....
..................
.............
SLIDING CONTACTS:
Abrasion . . . . . . . . . . . . . . . . . . . . . . .
roughening of contacts
Arc.............................
..
Insulation failure
................
.. .............
Replace.
(For locations where the ac hum is objectionable, use dc magnets. Hum can be reduced by
mounting on rubber or springs.)
Clean magnet.
Check system voltage.
Replace and correct the cause.
..
Clean.
Replace the part.
Replace magnet.
1. Wrong coil.
.............................
...
Magnet-operated inverse-time
type, slow type. ..................
11-10
.......
OVERLOAD RELAYS:
Magnet-operated instantaneoustype, high trip or low trip. . . . . .
Fast trip
Course of
..........................
Cause
Trouble
Use heavier fluid or close vent slightly or regulate temperature. Dashpots should be cleaned
periodically and refilled with new oil.
Check rating with manufacturers instruction
sheet.
Clean and adjust relay.
...................
.......,............
..
1. Wrong heater..
.....
..........................
2. Assembled wrong.. . . . . . . . . . . . . . . . .
3. Relay in high ambient temperature.
Failure to reset.
.................
....
TIMING RELAYS:
Mechanical escapement type,
mechanical wear or broken parts
Jamming or sticking
....... ......
..
.,
1. Abrasive dirt. . . . . . . . . . . . . . . . . . . . . . . . . . . .
2. Wrong application. . . . . . . . . . . . . . . . . . . . . . .
3. Very heavy service cycle .................
1. Dirt; corrosion; moisture; lack of lubrication; worn or broken parts. .................
1. Dirtinairgap.. . . . . . . . . . . . . . . . . . . . . . . . . .
2. Shim too thick. .........................
3. Excess spring and tip pressure. ..........
4. Misalignment. . . . . . . . . . . . . . . . . . . . . . . . . . .
1. S h i m w o r n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2. Weak spring and contact pressure. Gum or
dirt on magnet faces, or mechanical binding..
1. Dirt or gum in air gaps. . . . . . . . . . . . . . . . . .
1
2
3
4
1.
.....
..
2. Corrosion, dirt..
3. Motor damaged.
Failure to reset . . . . . . . . . . . . . . . .
BRAKES:
Magnet-operated or thrustoroperated, worn or broken parts
.
...
a.
Replace relay.
Install motor and control near to each other, or
make temperature uniform for both. Use
ambient-compensated relay.
Check rating with manufacturers instruction
sheet.
See instruction sheet.
Install controls closer to each other, or make
temperature uniform. Use ambientcompensated relay.
Consult manufacturer.
Replace broken parts, clean, and adjust.
..............
Clean.
Check condition of motor electrically and mechanically.
Check circuit.
Replace parts and adjust.
.
Check application. A larger or different type
brake may be needed.
11-11
Trouble
Failure to set.
Cause
Failure to release
1.
2.
3.
4.
5.
................
..............,......
THRUSTORS:
Failure to more load
.......
...
. ..
1. Worn parts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2. No voltage on motor. ....................
3. Misapplication. .........................
1. Mechanical binding. . . . . . . . . . . . . . . . . . . . . .
2. Temperature too far above normal. . . . . . . .
1
Liquid frozen in capillary tube, or tube
1.
stopped up.. . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . .
1.
1.
2.
3.
1.
2.
3.
1. Overvoltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2. Overcurrent, intermittent-rated unit left
on continously ..............................
3. High ambient. ..........................
4. Misapplication. .........................
1. Overheating, corrosive atmosphere,
overvoltage, mechanical damage ............
1. Overvoltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2. Voltage surges caused by switching or
lightning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3. Some types not usable on ac.. . . . . . . . . . . . .
4. Moisture, corrosion, or high temperature. .
5. Continuous voltage on intermittent-rated
unit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6. Mechanical damage.. . . . . . . . . . . . . . . . . . . . .
7. Wrong polarity on dc unit. . . . . . . . . . . . . . . .
Check application.
THERMOSTATS:
Bulb and bellows type, with
expanding fluid, bellows
distorted
Bulb distorted
...................
RESISTORS:
Insulation failure
Overheating. . . . .
Open circuit.
................
................
....................
RECTIFIERS-DIODES:
Dry type, overheating
............
...
CAPACITORS:
Breakdown or failure of dielectric
FUSES:
Premature blowing.
3. Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Noise
Course of action
.............
..........................
Check applications.
Correct condition, or install special unit.
Install proper unit.
Replace capacitor.
Replace capacitor and reconnect, changing polarity.
11-12
................
1. Overcurrent or overvoltage. . . . . . . . . . . . . . .
2. Intermittent-rated unti left on continuously.
3. High ambient. . . . . . . . . . . . . . . . . . . . . . . . . . .
4. Shorted turns. . . . . . . . . . . . . . . . . . . . . . . . . . .
1. See insulation failure. . . . . . . . . . . . . . . . . . . .
Insulation failure . . . . . . . . . . . . . . . .
These causes are similar to those listed under
MASTER, SELECTOR, LIMIT,
SPEED, FLOAT, FLOW, PRESSURE, contacts, mechanical parts, and insulation. . .
KNIFE, AND DRUM SWITCHES;
PUSH BUTTONS. MANUAL
CONTACORS, RHEOSTATS:
These causes are similar to those listed under
MANUAL STARTERS:
contacts, sliding contacts, mechanical parts,
insulation failure, and thermal overload relays.
MOTOR STARTER CIRCUIT
BREAKERS:
Premature tripping . . . . . . . . . . . . . . 1. Setting too low. . . . . . . . . . . . . . . . . . . . . . . . . .
2. Repetitive closing and jogging. . . . . . . . . . . .
3. Undervoltage device and control circuit
and auxiliary pilot devices affected by operating circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4. Incorrectrating. . . . . . . . . . . . . . . . . . . . . . . . .
1 Incorrect adjustment .....................
Failure to latch in or open and
reset......................... . . .
2. Worn parts ..............................
3. Excessive currents causing contact wear ...
4. Fault in remote control circuit ............
5. Door mechanism out of adjustment. ......
6. Trip element or mechanism damaged. ....
7. Corrosion or dirt .........................
8. Arc chutes damaged. ....................
Short contact life . . . . . . . . . . . . . . . . 1. Corrosion. ..............................
2. High currents and frequent operation causing burning. ...............................
3. Misapplication. .........................
4. Excessive filing and dressing. ............
Welding of contacts ............... 1. High inrush currents during motor starting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2. Rapid jogging. ..........................
3. Incomplete manual closure. ..............
4. Inadequate maintenance for renewal of
contacts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
................
Course of action
Cause
Check circuits.
Replace circuit breaker.
See circuit breakers instructions. Check and
adjust parts.
Replace parts.
Replace circuit breaker.
Check circuits.
Readjust.
Replace parts.
Clean.
Replace parts.
Check starting current, reduce duty cycle.
Check starting current, reduce duty cycle.
Refer to manufacturer.
Do not file contacts.
Reduce currents.
Use suitable contactor.
Frequent inspection.
Renew contacts.
11-13
CHAPTER 12
INSTRUMENTS AND METERS
Section I-CONSIDERATIONS
-_
12-l
tion was made. Units should always meet codeaccess requirements and be protected from mechanical damage.
12-10. Maintenance of instruments and
meters.
Accuracy tests, repairs, calibrations, and adjustments of instruments and meters should be performed only by personnel trained and qualified for
this type of work, or done under the immediate
supervision of such personnel. Where activities do
not have such specialists on board, arrangements
should be made with a nearby activity equipped for
this type of work; with local electric power companies on a maintenance contract basis; or through
use of manufacturers service shop facilities. It
should be recognized that accuracy requirements
for meters should be appropriate f o r the use to
which readings and records are put, and that the
cost of high accuracy must be economically justified.
(eq. 12-l)
12-2
JUMPER
__---e-w------
LINE
I
LOAD
Figure 12-1. Method of connecting a phantom load for a field test, if on a single-phase, two-wire watthour meter
CONNC?TlON
LINE
I
JUMPERS
FOR LAGGING
POWER FACTOR TEST
1
h/
-----l
,r - - - - - - - , LOAO
1
,__i---------i--l-_
I
I
METER
UNDER TEST
for solid-state units may be different from the following general data applying to electromechanical
units. Some adjustments of fixed instruments can
be made without removal from their panel assembly
mounting. Other adjustments, however, require
that the instrument be taken to a shop or laboratory. All instruments should be adjusted for null
(zero) reading. In most cases, this reading can be
obtained with the instrument disconnected. For
watt and varmeters, the null reading should be
checked with only the current coil energized from a
test source. The full scale adjustment should be
obtained by slowly increasing the load to be measured to the full scale value. For example, a voltmeter is adjusted by varying the series resistance connected to the test power supply. Watch the pointer
as the instrument is slowly loaded to its full scale
value to check whether there is any friction in the
movement. When a watt or varmeter is being adjusted, an ammeter should be used in series with
the current coil of the meter and the current should
be limited to the rating of the coil to prevent overheating. After the instrument has been calibrated
and adjusted for full scale reading, the load should
be gradually decreased and the null position
checked again.
c. Procedures for meters. Meter adjustments are
made for full load, light load, lag, and creep. Most
polyphase meters have an additional adjustment to
obtain balance between elements. The meter manufacturers instruction book should be consulted for
instructions before making any adjustments. General instructions given here may differ from manufacturers instructions for solid-state meters. The
lag and balance adjustments are usually made in a
shop before installation. The adjustment of a meter
is done by loading it with a phantom (artificial) load
and comparing its performance with that of a cali12-3
--
Section IV-REPAIRS
12-13. Field repairs of instruments and
meters.
Minor replacement of parts, such as dial faces,
pointers, bearings and pivots, chart paper, and
meter registers, may be made in the field. If extensive repairs are required, they should be made in a
shop. When meter bearings or registers are replaced, recalibration of the meter is required.
12-14. Shop repairs of instruments and
meters.
Reference should be made to the manufacturers
instruction books for methods of assembly and adjustment. After parts have been replaced, meters or
instruments should be recalibrated. The methods to
be followed are given in section III.
a. Overhauling. Major repair of a meter or instrument should be performed in a shop.
(1) Instruments. Repair of instruments should
not be undertaken, except by qualified personnel
equipped with proper tools. The manufacturers instruction book should be consulted when making
major repairs and when overhauling instruments.
After the work is completed, the instrument should
be adjusted and checked for accuracy.
(2) Meters. The following steps should be taken
when a meter is brought to a shop for a complete
overhaul:
(a) Take an initial reading, known as an as
found reading as an accuracy check, and record the
data.
(b) Clean the meter thoroughly, removing
any dust or dirt with special attention to the magnet poles.
(c) Remove and examine the register to detect any defects that may prevent its correct registration. The worm or pinion on the shaft should be
examined to see that it matches properly with the
register wheel, which it drives. A slight amount of
12-4
Section V-TROUBLESHOOTING
-
12-5
Cause
Remedial action
No indication,
......................
Increased friction
...............
..............
Noinkrecord...............
No registration
.............
Inaccurate readings.
........
Cause
Remedia action
12-6
--
CHAPTER 13
POWER CAPACITORS
Section I-CONSIDERATIONS
13-1. Description of power capacitors.
Power capacitors for use on electrical distribution
systems provide a static source of leading reactive
current. Power capacitors normally consist of aluminum foil, paper, or film-insulated cells immersed in
a biodegradable insulating fluid and sealed in a
metallic container. Depending on size and rating,
they are available as either single- or three-phase
units. Power capacitors are rated for a fundamental
frequency, voltage, and kilovar (kilovoltamperesreactive) capacity and are generally available in
voltage ratings up to 34,500 volts and 200 kilovar.
Individual units may be connected in series and
multiples to provide banks of various capacities and
voltage ratings.
13-2. Types of power capacitors.
The terms series capacitor and shunt capacitor
are used to identify the type of connection and do
not indicate a difference in the power capacitor construction.
a. Series power capacitors. Series power capacitors are primarily used for voltage regulation and
receive very limited application in electrical distribution systems. In the usual application for power
service, the series-capacitor kilovar rating is too low
to improve the power factor significantly.
b. Shunt power capacitors. The shunt power capacitor is a capacitive reactance in shunt with the
electrical load or system and is fundamentally pro-
13-1
Mounting arrangement
Isolated capacitor . . . . . . . . . . . . . . . .
Single row of capacitors . . . . . . . . . .
Multiple rows and tiers of capacitors.............................
Metal enclosed or housed equipments...........................
24 hour
average 3
46
40
.........
.........
Normal
annual 4
. . . 35
. . . 25
35
. . . . . . . . . ...20
35
. . . . . . . . . . . . 20
Section III-TESTS
13-12. Field tests for power capacitors.
Field tests differ depending on whether a power
capacitor is being put into service or whether it is
being checked after it has been in service. Switched
capacitor banks must be checked for correct switching operation.
a. Before service tests. Experience has shown that
these tests may not be necessary on all capacitors.
13-2
.-
Type of control
.-
Time clock. . . . . . . . . . . . . . . . . .
Voltage. . . . . . . . . . . . . . . . . . . . . .
Dual temperature. . . . . . . . . . . .
Temperature only. . . . . . . . . . . .
Time clock and temperature . .
Maintenance
schedule,
years
3
3
5
8
8
(1) Terminal-to-terminal voltage test. The purpose of this test is to determine whether a capacitor
unit is functioning in accordance with its rating.
Capacitor units found to be internally defective are
more economically replaced than repaired.
(a) Procedure. With the capacitor unit insulated from ground, apply a terminal-to-terminal
voltage equal to the rated capacitor voltage, in accordance with figure 13-l. Voltage should be applied for one minute with the test circuit fused.
Fuse rating should be that recommended for the
capacitor, or if that size is not readily available, one
rated twice the normal load current. Measure the
voltage and current. The ammeter should be provided with a short circuiting switch. The switch
should be opened only after it has been determined
that no short circuit exists.
(b) Interpretation. Blowing of the fuse indicates a short-circuited capacitor. Absence of current
indicates an open-circuited capacitor. Good capacitors should have current readings of 100 to 115
percent of rated value, with the case and internal
temperature at 25 degrees C. Current readings
above 115 percent of rated current may indicate an
internal short or the presence of harmonics in the
test voltage. If waveform of the test voltage is suspect, the test should be repeated using an alternate
source of electric power.
(2) Terminal-to-case insulation test. The purpose of this test is to determine the adequacy of the
insulation to ground of a given capacitor unit. This
test may be applied to two bushing, single-phase
capacitor units, but not to capacitor units where the
case is used as a terminal.
(a) Procedure. With the capacitor unit insulated from ground, apply a voltage equal to twice
rated voltage between case and terminals (all terminals connected together) in accordance with figure
13-2. Voltage should be applied for one minute,
with the test circuit fused and containing sufficient
impedance to limit the current, should the capacitor
under test be shorted.
SWITCH OR
CIRCUIT BREAKER
FUSE
POWER SOURCE
RATED VOLTAGE
AN0 FREQUENCY
13-3
SWITCH OR
CIRCUIT BREAKER
MAXIMUM
POWER SOURCE 1
RATED VOLTAGE
AND FREOUENCY
CAPACITOR
+ CAPuC$R /
1.
I
CASE INSUIA~EO
FROM GROUND
13-4
A 32-1082
TM 5-684/NAVFAC M O - 2 0 0 / A F J MN
CHAPTER 14
STORAGE BATTERIES
Section I--CONSIDERATIONS
14-1. Battery usage.
Storage batteries are used in exterior facility electrical distribution systems to provide a power supply to devices whose control response will be damaged by an electrical system power outage. This
chapter describes station batteries as they are generally called, as opposed to uninterruptible power
system batteries or automotive type batteries. A
storage battery is composed of one or more rechargeable electrochemical type cells. Systems are
designed for full-float operation, with a battery
charger to maintain the battery in a charged condition. Batteries used for control of substation and
power equipment are required to provide low currents for long periods and high currents for short
periods. A batterys reserve capacity requirements
are based on a duty cycle (usually an 8-hour operating time period) when all continuous and momentary loads must be supplied by the battery with no
recharging available from the battery charger.
.-_
--
there is a large volume of free electrolyte. The electrolyte maintains uniform contact with the plates.
Vented units are characterized by a removable vent
cap which allows the electrolyte to be checked and
adjusted as needed. Overcharge will produce gases
which vent through the cell, requiring regular water replacement. Vent caps must be accessible, so
batteries are larger than valve-regulated types and
are provided with flame arresters. Gassing requires
ventilation to avoid explosive possibilities and possible corrosive damage to battery terminals.
d. Valve-regulated batteries. Valve-regulated cells
are sealed, with the exception of a valve that opens
periodically to relieve excessive internal pressure.
To limit water consumption, cells are designed to
provide recombination of charge gases by passing
oxygen evolved from the positive plate over the
negative plate, where the recombination reaction
occurs. The valve regulates the internal pressure to
optimize recombination efficiency (hence the term
valve-regulated). The valve opens when the cells
internal pressure exceeds a set limit and once the
pressure is relieved the valve closes and reseals. No
cell check of an electrolyte level nor the specific
gravity of each cell is required. These batteries are
not maintenance-free as some 10 or more maintenance checks are still necessary. Outgassing of
these batteries is low at normal charge rates, but it
can occur when there is a battery or battery charger
failure. Cells can pose a hazard if enclosed so as to
inhibit cooling air, or installed so as to place them in
the heat flow of electronics which may occupy the
same enclosure.
14-3. Battery safety.
Safety precautions cannot be ignored, since every
station battery installation presents hazards. The
importance of using safety equipment, such as rubber gloves, goggles, aprons, and of having an eyewash water bottle present, cannot be overemphasized. The three major hazards are from the
electrolyte in the battery, the gases emitted by the
battery, and the potential electrical short circuit
capability available from the batterys stored energy. Most persons trained to work in an electrical
environment are aware that batteries are dangerous, but need to be warned and advised again as to
the extent of the hazards posed by all station battery systems, regardless of size or type.
14-1
Hazardous voltage.
Will cause severe
injury or death.
USE INSULATED TOOLS
WEAR EYE PROTECTION
Figure 14-1. Battery warning sign
14-2
Always follow the battery manufacturers maintenance procedures and check warranty requirements. Battery temperature examples given are not
justification for ignoring the temperature requirements given in this chapter for battery rooms or
areas. Manufacturers will normally provide assist-
ance in developing a maintenance program for batteries which they supply. All manufacturers have
maintenance instructions for their cells and some
will conduct maintenance seminars or presentations. This important source of information should
not be overlooked. Also become familiar with procedures for maintenance, testing, and replacement of
storage batteries, as described in ANSI/IEEE 450
and ANSI/IEEE 1106 for lead-acid and nickelcadmium types, respectively.
a. Maintenance program. The maintenance program selected should address the specific needs of
the battery installed and should be both consistent
and regular. Recommended maintenance intervals
should never be longer than those required by the
manufacturer to satisfy warranty requirements. In
addition, critical load requirements may dictate
more frequent maintenance based upon the importance of the installation and the impact of a battery
failure on the load it serves. Proper maintenance
will ensure optimum battery life, assuming the battery has been properly sized and installed. When
allocating time to battery maintenance, ensure that
it is sufficient for the tasks to be performed. Small
inaccuracies that can occur when personnel are
rushed can result in useless data, and overlooking
of other obvious problems. Wherever practicable,
tests should be carried out in a manner that accomplishes one or more objectives at the same time. For
example, a capacity test also can be used to check
for high connection resistance.
b. Battery specifics. A maintenance program must
address the specific battery installed. Although the
tests and frequency of maintenance may be the
same, there are subtle differences between batteries. For example, the nominal float voltage will vary
between lead-antimony and lead-calcium cells. In
addition, the total float (terminal) voltage will be
different when the total number of cells provided
varies (as for nickel-cadmium units) even though
the nominal voltage per cell may be the same. For
instance, a nominal 24-volt lead-acid battery system can be made up from 12 to 14 cells of the same
type. Another consideration is that the float voltage
used will vary with the nominal specific gravity of
the cell.
(1) Battery system replacement. When a battery
is replaced, the new battery often continues to be
maintained in the same manner as the old one.
However, the new battery may be of a different alloy
or nominal specific gravity, or may contain a different number of cells. Maintenance personnel may
not recognize the differences, which can lead to irreversible damage.
(2) Battery condition. Battery condition can be
assessed based upon comparisons of current and
14-3
more frequent inspection of batteries may be necessary. Routine inspection should include the checking and recording of all pertinent information, such
as voltage, specific gravity, level of electrolyte,
charging rate, internal and ambient temperatures,
ventilation, and cleanliness.
c. Understanding requirements. In the following
sections, general information on basic battery maintenance is presented for flooded lead-cell batteries.
Flooded lead-acid batteries are discussed, since
these are most often encountered. Valve-regulated
lead-acid batteries and nickel-cadmium batteries
are discussed in separate sections to the extent that
their maintenance differs from that of flooded leadacid cells. Periodic maintenance tasks are summarized in a following section.
--
14-5
highest specific gravity, highest voltage, or combinations of both. Pilot cells should be rotated periodically, usually on a monthly basis. One reason for
this is to limit electrolyte loss. Whenever a cells
specific gravity is read, some small amount of electrolyte will remain in the hydrometer. For a frequently read pilot cell, this loss of electrolyte, although very small, could ultimately affect the cell
over a long period of time.
h. Temperature readings. Electrolyte temperatures should be read and be recorded any time
specific-gravity or voltage readings are taken. The
specific gravity of the electrolyte varies with temperature. In order to compensate for this effect, the
temperature needs to be recorded at the same time
that the hydrometer is read.
(1) Differential temperature. Differential electrolyte temperatures, greater than 5 degrees F (2.75
degrees C), between cells can be a problem. This
problem normally occurs when one portion of a battery is located near a localized heat source, such as
a sunny window or when a battery rack with more
than two steps or tiers is used. A battery temperature differential will cause some cells to be overcharged and some cells to be undercharged.
(2) Ambient temperature. Ambient temperature of the battery area should be read and recorded
periodically, even where the room or area is environmentally conditioned. Battery performance is based
upon the cell electrolyte temperature, which can
differ from the room ambient temperature. Optimum battery performance is obtained when electrolyte temperature is maintained at 77 degrees F (25
degrees C).
(3) Recording temperature. Some hydrometers
have a thermometer and table showing the temperature correction that should be applied to the
reading. If the hydrometer being used does not have
a thermometer, a battery thermometer should be
placed into the cell and the electrolyte temperature
recorded.
(4) Temperature correction. Comparisons are
made for readings corrected to 77 degrees F (25
degrees C). The temperature correction for lead-acid
batteries requires adding one point (.00l) to the
hydrometer reading for every 3 degrees F (1.67 degrees C) above 77 degrees F (25 degrees C) and
subtracting one point for every 3 degrees F (1.67
degrees C) below 77 degrees F (25 degrees C).
c. Specific-gravity readings. Specific gravity is a
good indication of state-of-charge of lead-acid cells.
Corrections for electrolyte temperature and level
must be applied to adjust the specific-gravity readings to a standard reference temperature. Level corrections can vary for each cell type and should be
obtained from the manufacturer. Note that specific-
__
--
._
gravity readings, taken within 72 hours of the termination of an equalizing charge or a water addition, will not be correct. These specific-gravity
readings are inaccurate because the added water
has not been properly mixed with the existing electrolyte solution and stratification occurs.
(1) Differences in specific gravity. Leadantimony or lead-calcium battery electrolytes do not
always have the same nominal specific gravities,
even if the plate alloy is the same. Maintenance
personnel should not install a replacement cell
which requires a specific-gravity electrolyte different from the existing cells. In similar cells with
different specific gravities, the higher specific gravity cells will have higher float voltage requirements,
provide increased local action, and consume more
water. Some application considerations may also
cause a manufacturer to vary the nominal 1.200
specific gravity for stationary cells. High or low ambient temperatures influence specific-gravity requirements. A higher specific gravity electrolyte is
provided when ambient temperatures are extremely
low. This increases cell performance and serves to
lower the freezing point of the electrolyte. Similarly,
with high ambient temperatures, normally above 90
degrees F (32 degrees C), a lower specific-gravity
electrolyte is provided to reduce losses and maintain expected life.
(2) Comparisons. The measured specific gravity should be corrected to the reference temperature
and compared to previous data. Readings should be
uniform, with a minimum different between the
high and low readings. Where specific gravities vary
considerably over the battery, they are termed
ragged and corrective action is required, as covered in ANSI/IEEE 450 and ANSE/IEEE 1106.
(3) Method of measurement. With all cells connected in series, the specific gravity reading of one
cell, known as a pilot cell, indicates the state of
discharge or charge of the whole battery. When a
reading is being taken, the nozzle of the hydrometer
syringe is inserted into the cell, and just enough
electrolyte is drawn from the cell to float the hydrometer freely without touching at the top or bottom. Read the specific gravity on the float, making
sure to obtain this reading at the bottom of the
meniscus (the bottom of the liquid-surface curvature). For correct readings be sure to hold the hydrometer in a true vertical position to avoid the
floats touching the cylinder walls. After testing, the
electrolyte should ways be returned to the cell. Cell
readings can be inaccurate if taken sooner than 72
hours after equalizing or water corrections.
d. Voltage readings. The open-circuit voltage of a
lead-acid cell is a direct function of specific gravity
and can be approximated by equation 14-1. This
relationship holds for cells that are truly opencircuited (that is, there is no current flowing
through the cell). The battery should have a wellmixed electrolyte and been off charge for more than
16 hours. A voltage below that expected by equation
14-l indicates there may be a problem.
Open-circuit voltage =
Specific gravity + 0.84
(eq. 14-1)
14-7
c. Proper charging. The proper charging of a battery is as important as any other maintenance consideration , since a battery cannot function without
a charger to provide its original and replacement
energy.
d. Water quality. Use of distilled or deionized water is recommended to eliminate the possible addition of foreign contaminants, which will reduce cell
life and performance. The battery manufacturer
will provide information on the maximum allowable
impurities in water used for maintaining electrolyte
levels if it is desired to test whether a local water
system provides the desired water quality. Approved
battery water should be stored in chemically inert,
nonmetallic containers.
(1) Additives. Nothing but approved battery
water should be added to storage batteries. Never
add acid, electrolyte, any special powders, solutions,
or jellies. Special powders, solutions, or jellies may
be injurious; and have a corrosive or rotting action
on the battery plates, reducing the voltage and capacity of the cells. The use of such additives will
void the battery manufacturers warranty.
(2) Impurities. Impurities in the electrolyte, beyond the manufacturers maximum levels will cause
irregular cell operation and should be removed as
soon as discovered. If removal is delayed and foreign matter becomes dissolved, the battery should
be replaced immediately. It may be possible to replace the electrolyte, but only if the manufacturer
recommends a procedure to correct the specific condition which has occurred.
Disposition
Special
Special
Special
Normal
Normal
Normal
Normal
Normal
Normal
Normal
Safety
Safety
Safety
Safety
.-
Batteries are normally connected to their permanent charging equipment, but there may be occasions where testing or charging of new batteries
requires connection to a test-shop charging device.
a. All charging. The following precautions will
always be taken:
(1) Use tools with insulated handles.
(2) Prohibit smoking and open flames, and
keep possible arcing devices removed from the immediate vicinity of the battery.
(3) Ensure that the load test leads are connected with suficient cable length to prevent accidental arcing in the vicinity of the battery.
(4) Ensure that all connections to load test
equipment include short-circuit protection.
(5) Ensure that battery area ventilation is operable.
(6) Ensure unobstructed egress from the battery area.
14-9
c. Float voltages. Float voltages are directly related to cell type and plate alloy, as well as to the
specific gravity of the cell. The higher the specific
gravity, the higher the minimum float voltage must
be. This ensures that sufficient charging current is
available to overcome the increased local action. Too
high a float voltage will result in overcharging and
reduce battery life. A slightly higher float voltage is
sometimes selected for maintenance purposes to reduce or even eliminate the need for periodic equalizing charges required because of nonuniform cell
voltages.
14-12. Equalizing battery charge.
An equalizing charge is an extended charge to a
measured end point on a storage battery cell to
ensure complete restoration of the active materials
in plates of the cell. Equalizing charges are provided
after a battery discharge or for periodic maintenance. Equalizing voltages are selected by the battery chargers equalizing timer, as covered in section
VII. Equalizing charges may need to be given a
monthly check.
a. After discharge equalizing. An equalizing
charge is required after any battery discharge. Although it is called an equalizing charge, it is basically a recharge, at about a 10 percent higher voltage, than the float voltage to restore the discharged
battery to a fully charged state within a reasonable
length of time.
b. Periodic equalizing. Lead-acid battery individual cell voltages will begin to drift apart, even if
the battery is not discharged. A manually set charging rate will be necessary to equalize the voltage
irregularities. Nonuniformity of cells can result
from a low float voltage due to improper adjustment
of the battery charger, a panel voltmeter that is
reading an incorrect output voltage, or variations in
cell temperatures greater than 5 degrees F (2.75
degrees C).
(1) Provision. Equalizing voltages should be
given if the float voltage of the pilot cell is less than
2.20 volts per cell or more than 0.04 volts per cell
below the average of the battery. Equalizing voltage
is required if the individual pilot cell voltages show
an increase in spread since the previous readings,
or if the periodic check of all cell voltages reveals a
difference of 0.04 volts between any cell and the
average cell voltage.
(2) Action. An equalizing charge is made at a
rate not higher than the normal charging rate of the
battery. It is continued until all the cells gas freely
and any low cells are fully charged. Low cells are
usually found in the warmest section of the battery.
They normally have the lowest voltage while on
---
Battery voltage
for 60 cells (volts)
145 . . . . . . . . . . . . . . .
143 . . . . . . . . . . . . . . .
142 . . . . . . . . . . . . . .
140 . . . . . . . . . . . . . . .
138 . . . . . . . . . . . . . . .
Length of monthly
Charge (hours)
3 to 8
4 to 12
6to 16
8 to 24
11 to 34
14-11
-.
trolyte should be changed. Follow the manufacturers instruction when renewing the electrolyte. The
battery warranty may not permit renewal without
the manufacturers permission.
e. Charging. Specific gravity or cell voltage readings generally cannot be used to determine the state
of charge of a nickel-cadmium battery. To ensure
that the battery is fully charged, it should be given
a booster charge once a month, after any heavy or
intermittent discharges, or after the battery charger
has been out of service. Maintenance personnel
should maintain a record of the monthly booster
charges. The accuracy of the charger voltmeter
should be checked against a recently calibrated voltmeter at least once a year. A summary of charging
requirements for nickel-cadmium batteries is given
in table 14-4.
f. Precautions. In addition to the precautions
given for lead-acid cell batteries, prohibit the use of
acid-contaminated tools and equipment, such as hydrometers and thermometers used for lead-acid cell
maintenance.
Table 144. Charging of nickel-cadmium batteries
Charge
Initial
charge
Float
charge
Booster
charge
Requirements
1. The first charge of batteries that are delivered
discharged should be carried out at constant current.
2. When the battery chargers maximum voltage
setting is too low to supply constant current charging, divide the battery system into two parts to be
charged individually.
3. Follow the manufacturers instructions for setting the charging rates.
1. Float charge voltage should be maintained at
1.43 volts to 1.45 volts per cell to avoid gassing.
2. Maintain constant voltage charging to prevent
the battery from discharging at a depressed voltage
level.
3. To prevent excessive water consumption, avoid
charging the battery at higher values than recommended.
1. The booster charge should be 1.65 volts per cell.
2. A fully discharged battery in good condition can
be fully charged in 4 hours.
3. If the float charge has maintained the battery in
a fully charged condition during the month, the
monthly booster charge will be minimal.
4. The booster charge should be continued until the
charging current has leveled off for two consecutive
readings one-half hour apart.
5. When applying a booster charge, it is important
to watch the electrolyte temperature in the cells. If
the temperature reaches 100 degrees F (43 degrees
C), the charging rate should be reduced at once.
14-13
charging starts to limit current flow. Battery chargers are designed to limit charging currents to values
that keep the charging equipment within a reasonable size and cost. Battery chargers must also maintain a sufficiently high current throughout charging, so that at least 95 percent of the complete
storage capacity is replaced within an acceptable
time period. This recharge time is usually not more
than 8 hours for station service.
b. Charging equipment. Batteries must be
charged by direct-current. The available sources are
an ac-to-dc rectifier and an ac-to-dc motor-generator
set. The use of motor-generator sets to supply station batteries is an unusual practice now because
the function is so reliably and economically handled
by rectifier type battery chargers. If motorgenerator sets are used, maintenance should be in
accordance with the manufacturers instructions.
14-21. Rectifier type battery chargers.
14-15
_--
14-16
__-
Unless tested and proven otherwise, batteries, because of their electrolytes, are classified as hazardous waste. Recycling is the most cost-effective and
trouble-free method of disposal, and therefore is the
preferred disposal method when batteries are removed from service. The Resource Conservation and
Recovery Act (RCRA) governs the requirements for
management and control of all wastes, hazardous or
nonhazardous, and applies to the disposal of batteries. RCRA states that spent batteries must be sent
to a battery manufacturer for recycling or regeneration. Other recyclers are not acceptable. Some
manufacturers will accept old batteries for recycling
and regeneration. Although manufacturers generally accept lead-acid batteries more willingly than
nickel-cadmium batteries, a fee may be charged for
regeneration. Actual disposal must meet both RCRA
and local facility requirements.
14-17
CHAPTER 15
TOOLS AND EQUIPMENT
Section I-USE
15-1. Electrical tools and equipment standards.
Industry standards describe the requirements for
electrical protective equipment and for tools. These
standards were developed so that the tools, equipment, materials, and test methods used by electrical
workers will provide protection from electrical hazards. Electrical protective equipment is included in
the ASTM F 18 series specifications. Tool and equipment terminology and in-service maintenance and
electrical testing are included in ANSI/IEEE 935
and IEEE 978 respectively. Safety manuals TM
5-682, NAVFAC P-1060, and AFM 32-1078 also
contain tool and equipment requirements. In case of
conflict, always use the most stringent safety requirement.
15-2. Tools and equipment classification.
For simplicity and convenience, the tools and equipment required for electrical inspection and maintenance are classified as follows:
a. Tools. Tools include hand tools, digging tools,
hot line tools, miscellaneous and special tools, and
tackle.
b. Protective equipment. Protective equipment includes rubber gloves, lie hose, matting, blankets,
insulator hoods, sleeves, barricades and warning
devices.
c. Climbing equipment. Climbing equipment includes body belts, safety and climber straps, climbers, and ladders.
d. Electrical inspecting and testing equipment.
Electrical inspecting and testing equipment in-
15-1
thumb, fingers, and palm. Listen and feel for escaping air. Inspect the entire glove surface for imbedded foreign material, cuts, deep scratches, or punctures. Gloves found to be defective should be tagged
and turned in for replacement.
(b) Electrical test for rubber sleeves and
gloves. Rubber gloves and sleeves in service should
be given an electrical proof test periodically. If possible, the test should be accomplished by a local
utility company or an independent testing laboratory, who should also provide electrical testing for
all other rubber goods used. If independent testing
is not possible, then test equipment and test voltage
should comply with ASTM F 496, which also covers
in-service care. The Linemans and Cablemans
Handbook covers the procedure and shows the complexity and expertise required for in-service testing
of rubber goods.
(2) Line hose. The outside of line hose should
be inspected for checks and cracks by bending the
hose 180 degrees. at successive points along its
length to stretch the rubber enough to expose possible defects. The inside of line hose is inspected by
opening and spreading. Periodic electrical in-service
tests should be given in accordance with ASTM F
478 which also covers in-service care.
(3) Other equipment. All other rubber protective equipment should be inspected for cuts, tears,
--.
15-3
__
---
15-5
15-7
STEP 1
STEP 2
STEP 3
BACKLASH
WHIPPED
15-8
STEP 4
Figure 15-2. Making an eye splice
STEP 1
STEP 2
YYX
STEP 3
Figure 15-3. Making a short splice
STEP 1
STEP 4
STEP 6
STEP 5
STEP 7
STEP 8
15-9
15-10
Test equipment
Automatic insulation tester.
Channel disturbance
waveform analyzer
Dielectric test
set
..............
.....................
...........................
Digital ground.
resistance tester
..........................
Automatically performs insulation test routines in minutes, with high accuracy and sensitivity. Easy to operate, rugged and durable, the unit can be used on equipment or networks rated from low voltage to 400 kilovolts.
The unit controls the dc voltage across the conductors and measures the leakage current
through and over the insulation with one microprocessor and directs the display, control
panel, and power supply via a second microprocessor. They communicate through a
fiber-optic link.
The unit combines basic and automatic insulation testing capabilities. Typical tests include:
l Insulation resistance tests at 500, 1,000, 2,500, and 5,000 volts dc (with resistance
readings up to 500,000 megohms at 5,000 volts dc).
l Automatic polarization index (PI) tests at any of the voltages listed above.
l Automatic step voltage (SV) tests in five equal steps up to 2,500 or 5,000 volts dc.
The unit is powered by an internal rechargeable, sealed lead-acid battery (12 volt, 6.5
amperehour) or power supply cord (110/120 volts at 50/60 hertz or 2201240 volts at 50/60
hertz).
Included Accessories:
Power supply cord (1)
High-voltage test leads-high, low, and guard terminal, 9 feet (3 meters) long
Instruction manual (1)
Optional Accessories:
High-voltage test leads-high, low, and guard terminal, 30 feet (10 meters) long
How to operate manual (1)
Captures, displays, analyzes, and records power line disturbances. Digital sampling
techniques have 512 kilobytes of nonvolatile random access memory. Waveforms are
viewed on the built-in cathode ray tube display and stored on the dual 3.5-inch (90 millimeter) disk drives. Standard summary reports or custom reports are created using the
attached keyboard. A built-in thermal graphics printer provides high-quality output of
waveforms and reports. Four two-wire ac input channels are provided with selectable
ranges of 0 to 60 volts and 60 to 600 volts. Frequency range is 45 hertz to 65 hertz. Impulses of greater than one microsecond can be recorded and the range is 25 to 6,000
volts peak.
Measures leakage current while applying a dc voltage at or above the insulation systerns operating level. This measurement aids in determining the insulation systems
ability to withstand overvoltages such as lightning strikes and switching surges.
Unit is compact and portable, air-insulated, uses no oil, and has a plus or minus 2 percent accuracy. Unit measures current as low as 0.1 microamperes and has a continuously variable test voltage with zero-start safety interlock. Unit provides fast charging of
high-capacitance samples. Includes a current guard circuit for highly accurate measurements. An optional strip chart recorder for hard copies is available.
Complete with separate measuring and charging modules. A Kelvin-type, four-wire measurement eliminates errors caused by lead and contact resistances Digital readout with
automatic zero. Range: 0 to 6 ohms in 5 ranges. Resolution: 1.0 microhms. Includes a
7-foot (2 meter) helical lead set.
15-11
.......................
15-12
......................
Description
Provides an infrared thermal measuring and imaging system with thermoelectric cooling. Temperature measurement range: 20 to 2,700 degrees F (minus 7 to 1,480 degrees
C). Color images can be displayed using standard video equipment. Has a 3.5inch (90millimeter) floppy disk drive and includes two battery packs and battery chargers, a 20
by 20 inch (500 by 500 millimeter) lens, a shoulder strap, and a high-temperature flame
filter.
Megohmeter earth tester. Hand-cranked device for measuring resistance to earth ground
connections. Null balance principle eliminates probe resistance from measurements.
Four ranges from 0.01 to 9,990 ohms with digital readout. Self-contained and portable.
Provides true rms measurements for ac voltage and current to a crest factor of 3 (frequency wave form distortions less than 2.5 hertz). Measures ac and dc current to 1,000
amperes at frequencies to 2,000 hertz. Has a 3% digit liquid crystal display (LCD) with
1.77 inch (45 millimeter) conductor jaw. Provides autoranging measurements, data hold
and peak hold, zero adjust, and a millivolt recorder output of current input, low battery
indication, a continuity check, a sampling time of 0.4 seconds and is complete with carrying case, test leads, alligator clips, wrist strap, and a 9-volt battery.
CHAPTER 16
ELECTRICAL SERVICE INTERFERENCE
Section I-DISTURBANCE PRODUCERS
16-1. Electrical power quality.
Electrical end-users are experiencing increased
problems from the expanding use of disturbanceproducing electrical equipment. Most equipment
served by electrical facility exterior distribution
lines can tolerate short-term voltage and current
variations without operational problems. The concerns discussed in this chapter are voltage and current sources which produce excessive and/or continuous electrical noise, resulting in unacceptable
electric power quality. These sources may interfere
with adjacent communications equipment or generate damaging waveforms, which flow back into the
electrical distribution system and extend the interference.
16-2. Electromagnetic interference (EMI).
EMI occurs when undesirable electrical signals
from an emitting source are transferred, by radiated or conducting media, to a receptor or receiver
element. These unwanted electrical signals with
their undesirable effects are known as electrical
noise (designated simply as noise hereafter). EM1
includes radio interference (RI) which, as defined by
the Federal Communications Commission (FCC),
includes only 10 kilohertz to 300 gigahertz disturSection
bances. The first evidence of this type of interference will usually show up as impaired radio or television set reception.
16-3. Harmonic interference.
Harmonic interference is produced by nonlinear
loads which draw current discontinuously, or whose
impedance varies with the applied voltage.
a. Sources. Gaseous discharge lamps and solidstate equipment, such as variable frequency drives
and computers, are harmonic interference sources.
The accelerated use of solid-state devices has multiplied harmonic input sources operating on residential, commercial, and industrial electrical systems.
b. Occurrence. Harmonics can be differentiated
from transients, since harmonics occur as a periodic
wave which contains multiples of the fundamental
60-hertz frequency and transients occur as a temporary variable of the fundamental frequency only.
Harmonics have always occurred in power systems
but increased use of high-level harmonic-producing
equipment has made harmonic interference control
a matter of general concern to both electrical power
distributors and users.
II-ELECTROMAGNETIC
INTERFERENCE
16-1
16-3
tion and maintenance responsibilities. This responsibility includes the facility electrical power distribution systems and required actions to ensure these
systems will supply the standard voltage ranges
given in ANSI C84.1. The electrical supervisor is
not responsible for the successful and reliable operation of high tech electronic equipment, except
in accordance with ANSI C84.1. However, to ensure
overall proper operation of electrical systems, recommended harmonic distortion limits for voltages
should not be exceeded. Limits are for individual
harmonic distortion and for total harmonic distortion (THD). THD is defined by equation. The permitted harmonic distortion limits are given in table
16-1. These limits are the permissible maximum
harmonic distortion limits for service voltage at the
point of common coupling (PCC) with the user or at
the building service point.
THD = [
1 x 100%
(Square of the rms magnitude of the fundamental)
(eq. 16-1)
__
Individual
harmonic
distortion ( % )
Total harmonic
distortion THD (%)
5.0
2.5
1.5
(1) Oscilloscopes
(2) Spectrum analyzers
(3) Harmonic or wave analyzers
(4) Distortion analyzers
c measuring equipment
(5) Digital h armonic
b. Control of power quality. Maintenance personnel are not responsible for controlling power quality
beyond determining, by measurements, whether
the harmonic distortion of the PCC voltage exceeds
table 16-1. Verify that panelboard loads are balanced, where applicable, and check wiring and
grounds. A majority of power quality problems result from loose connections and improper grounding
techniques, and unbalanced loads. If correcting
these deficiencies does not alleviate excessive harmonics, then harmonic mitigation measures must
be developed utilizing engineering solutions beyond
the scope of this manual.
16-13. Electrical distribution system interference.
AIthough harmonic mitigation is not the responsibility of the electrical supervisor, it is the supervisors responsibility to keep informed on both the
quantity and quality of electrical service available
to facility users. Therefore, an awareness of apparatus actions, which may indicate unacceptable harmonic levels, is necessary to determine where more
precise data should be acquired.
a. Capacitors. Capacitor impedance decreases
with frequency, and a capacitor bank acts as a harmonic sink where most harmonic problems are first
noticed. Fuse blowing, without any obvious reason,
or a capacitor unit failure, can be signs of a possible
harmonic problem. A supply system inductance, in
resonance with the capacitor bank, can cause large
currents and voltages to develop. When, for no obvious reason, all fuses of a capacitor bank blow, it is
probably a harmonic problem. If only one fuse
blows, it is probably a reasonance problem.
b. Transformers. Harmonic currents cause increase copper and eddy current losses, and harmonic voltages cause increased iron and dielectric
losses and insulation stress. There can be a possibil-
16-5
TM 5-684/NAVFAC M O - 2 0 0 / A F J MN
A 32-1082
CHAPTER 17
MAINTENANCE SCHEDULES
Section I-CONSIDERATIONS
17-1. Maintenance planning.
The electrical supervisor is responsible for determining the priority of each preventive maintenance
operation. These priorities should reflect the function of each piece of equipment and local conditions
that affect the serviceability of the equipment.
Section II-SCHEDULES
17-3. Maintenance frequency guides.
.A
g
ma2
4k
X
X
X
X
X
X
X
X
.......
.......
X
X
X
.......
.......
.......
.......
.......
.......
X
X
.......
.......
X
X
X
X
X
X
X
X
....... .......
....... .......
x
.......
x
....... .......
x
x
X
X
X
X
X
X
.......
.......
.......
.......
x
.......
.......
.......
.......
.......
.......
.......
Equipment
Aerial lift devices ..............................
Anchor assemblies .............................
Anchors, submarine cable ......................
Arresters, surge, visual inspection. ..............
Arresters, surge, electrical tests. ................
Batteries, booster charge .......................
Batteries, check. ...............................
Batteries, equalizing charge ....................
Batteries in storage. ...........................
Battery maintenance test equipment ............
Battery chargers. ..............................
Buses, substation ..............................
Bushings, inspection ...........................
Bushings, power factor tests ....................
Bushings, insulation resistance test .............
Cable maintenance tests. .......................
Cable, overhead. ...............................
Cable, paper-insulated .........................
Cable, pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cablerecords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cable, submarine ..............................
Cable, underground, routine inspection. .........
Cable, underground, insulation resistance .......
Cable, underground, potential tests .............
Cable, underground corrosion. ..................
Cable, varnished-cambric. ......................
Capacitors. ....................................
Capacitor bushings. ............................
Capacitor busbar supports. .....................
Circuit breaker maintenance. ...................
Circuit breaker, high-voltage. ...................
Circuit breaker, medium-voltage ................
15-26.d
4-54
5.7
9-9.a
9-9.b
14-17.f
14-4.b(3)14-18
14-12
14-28
Table 14-3
14-23a
3-24.b
3-33
3-34.a
3-36
5-26.b
4-43
5-24.b
5-24.e
5-30
5-l8.c,5-20
5-5
5-27
5-28
5-33
5-24.a
13-5
13-8
13-8
8-13
8-14
8-15
17-1
.r(
d
x
x
.......
.......
....... .......
x
.......
....... ....... ....... ....... ....... .......
....... ....... ....... ....... ....... .......
....... .......
x
x
.......
.......
.......
x
x
x
.......
.......
.......
.......
.......
..............
.......
.......
.......
.......
.......
.......
.......
.......
.......
.......
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
x .......
....... ....... ....... ....... ....... .......
....... ....... ....... .......
x
.......
....... .......
.......
x ....... .......
....... ....... ....... ....... ....... .......
....... ....... ....... ....... .......
X
....... .......
.......
.......
....... .......
....... .......
x
....... ....... ....... .......
x
....... ....... ....... .......
.......
.......
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.......
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.......
.......
.......
x
.......
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....... .......
.......
X
.......
.......
.......
.......
.......
.......
x
x
x
....... ....... ....... .......
x
....... .......
x .......
.......
.......
.......
.......
.......
x
....... ....... ....... .......
x
x ....... .......
x ....... .......
....... ....... ....... .......
x
x ....... .......
....... ....... ....... .......
x .......
.......
.......
x
.......
.......
.......
x
x
.......
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x
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.......
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.......
.......
.......
.......
.......
.......
.......
.......
.......
.......
.......
Equipment
Circuit breaker, low-voltage. ....................
8-16
Circuit switchers. ..............................
8-18
Conductor resagging ...........................
4-39a
Connections ...................................
1-16
Connectors, tap. ...............................
4-46
Contacts.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1l.ll.c
Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11-11
Control magnet-operated devices. ...............
11-1l.d
Control thermally-operated devices. .............
11-1l.e
Control motor-operated devices .................
ll-1l.f
Control mechanically-operated devices. ..........
ll-1l.g
Control static accessories .......................
11-1l.h
Control, nonelectromagnetic ....................
11-1l.i
Crossarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-23
cutouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-8(b),(c)
Disconnecting switches ........................ .8-9.c(1),8-l0.b,8-ll
Fuses......: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-8.a
Grounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
l0-4,10-6
Guys and anchors. .............................
4-52c
Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-32
Instruments and meters-inspection ............
12-6
Instruments and meters-tests .................
12-7
Insulating liquids. .............................
Table 7-l
Insulators, distribution. ........................
4-5 lc
Insulators, substation ..........................
3-20
Interference, electromagnetic ...................
16-5
Interference, harmonic .........................
16-13
Lamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6-5
Leathergoods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15-14
Lightning protection shielding devices. ..........
9-10
Luminaires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6-7
Manholes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.9
Meters and instruments-inspection ............
12-6
Meters and instruments-tests .................
12-7
Poles,wood
d ....................................
4-16.b
Poles,metal...................................
4-29
Poles,concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-34
Portable or mobile substations ..................
15-26c
Potheads
s ......................................
5-25
Reclosers, automatic circuit. ....................
8-19
Regulator,voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-2.b(2)
Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11-4.b
Relay settings .................................
11-4.b
Resistors, bypass ..............................
9-13
Rubber goods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15-9
Servicedrop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 4-13
Streetlighting fixtures. .........................
6-4
Streetlighting lamps ...........................
6-5
Streetlighting photocells. .......................
6-8.c
Streetlighting protective relays .................
6-14.a
Streetlighting primary oil switch ................
6-14.b
Substation fence and gate ......................
3-16.c
Substation signs ...............................
3-17
Substation yard. ...............................
3-18
Substation overall, infrared. ....................
3-5
Substation overall, visual. ......................
3-5
Switch, load interrupter. .......................
8-9.c(2),8-11
Switch, photoelectric ...........................
6-8.C
17-2
*s
4%
.I-!
X
X
X
X
X
X
X
X
X
.......
.......
....... .......
....... ....... .......
x
....... .......
x
x
....... .......
....... .......
Equipment
Switch, time (accuracy). ........................
Switch, time (contacts) .........................
Tap changer, load ..............................
Telephone interference .........................
Terminations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Test instrument calibrations, analog. ............
Test instrument calibrations, other. .............
Tools, live-line inspection. ......................
Tools, live-line test records. .....................
Transformer, constant current ..................
Transformer, distribution. ......................
Transformer, instrument . . . . . . . . . . . . . . . . . . . . . . .
Transformer, power ............................
Tree trimming. ................................
6-8.a
6-8.a
Table 7-l
16-9
5-25
2-4.b
2-4.b
15-17.b
15-17.a
6-15.a
7-4.b
3-29. 3-30
7-4.a
4-57.c
17-3
iaim
TM 5-684/NAVFAC MO-200/AFJMAN 32-1082
APPENDIX A
REFERENCES
u
Government Publications
29 CFR 1926
Occupational Safety and Health, Safety and Health Regulations for Construction.
TM 5-683/NAVFAC
Electrical Interior Facilities.
MO-ll6/AFJMAN 32-1083
TM 5-811-7
NAVFAC MO-202
NAVFAC P-1060
AFI 32-1054
Corrosion Control.
AFI 32-1078
AFT0 36C-1-4
MIL-HDBK-1003A/ll
MIL-HDBK-100400
FAA AC-150/5340-26
Varnish, Moisture and Fungus Resistant (for Treatment of Communications, Electronic, and Associated Equipment).
Nongovernment Publications
American Association of State Highway and Transportation Officials (ASSHTO).
444 N. Capitol Street NW, Washington, DC 20001
AASHTO Division II. 13.2
ANSI c29.2
ANSI c29.5
ANSI C29.6
ANSI c29.7
ANSI C84.1
ANSI c119.4
Electric Connectors, Connectors for Use Between Aluminum-toAluminum or Aluminum-to-Copper Bare Overhead Conductors.
ANSI 05.1
ANSI 289.1
ANSI 2133.1
ANSI/IEEE 18
ANSI/IEEE 48
ANSI/IEEE 80
ANSI/IEEE 81
ANSI/IEEE 400
ANSI/IEEE 450
ANSI/IEEE 516
ANSI/IEEE 935
ANSI/IEEE 957
ANSI/IEEE 1106
ANSI/IEEE C367.60
Standard Requirements for Overhead, Pad-mounted, Dry Vault and Submersible Automatic Circuit Reclosers and Fault Interrupters for AC
Systems.
Standard Guide for the Application, Operation, and Maintenance of Automatic Circuit Reclosers.
ANSI/IEEE C37.90
Standard for Relays and Relay Systems Associated with Electric Power
Apparatus.
ANSI/IEEE C57.12.80
A-2
Standard Test Code for Liquid-Immersed Distribution, Power, and Regulating Transformers and Guide for Short-Circuit Testing of Distribution and Power Transformers.
ANSI/IEEE C57.91
ANSI/IEEE C57.92
ANSI/IEEE C57.96
ANSI/IEEE C57.106
ANSI/SIA A92.9
Standard Test Method for Weight (Mass) of Coating on Iron and Steel
Articles with Zinc or Zinc-Alloy Coatings.
ASTM D 117
Standard Guide To Test Methods and Specifications for Electrical Insulating Oils of Petroleum Origin.
ASTM D 150
Standard Test Methods for AC Loss Characteristics and Perxnitivity (Dielectric Constant) of Solid Electrical Insulation.
ASTM D 178
ASTM D 877
ASTM D 923
ASTM D 924
Standard Test Method for Dissipation Factor (or Power Factor) and
Relative Permitivity (Dielectric Constant) of Electrical Insulating Liquids.
ASTM D 971
Standard Test Method for Interfacial Tension of Oil Against Water by the
Ring Method.
ASTM D 1524
Standard Test Method for Visual Examination of Used Electrical Insulating Oils of Petroleum Origin in the Field.
ASTM D 1534
ASTM D 2285
ASTM D 3612
Standard Test Method for Analysis of Gases Dissolved in Electrical Insulating Oil by Gas Chromatography.
ASTM F 18-Series
ASTM F 478
ASTM F 479
ASTM F 496
ASTM F 855
A-3
ASTM F 1236
IEEE 142
IEEE 519
Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems.
IEEE 978
IEEE 1048
IEEE C37.2
IEEE C57.104
IEEE S-135-l
IEEE S-135-2
NFPA 70B
A-4
TM 5-684/NAVFAC
MO-200/AFJMAN 32-10822
APPENDIX B
BIBLIOGRAPHY
Cordage Institute (CI).
CIE-4
CIF-1
Bibliography 1
APPENDIX C
ADDITIONAL WOOD POLE DATA
C-1. Related pole data.
This appendix provides related data on wood poles
which is not readily available in regard to general
factors affecting pole life. Understanding the influence of these variables will help maintenance workers understand what contributes to the life of a
wood pole installation both by the quality of its
initial treatment and by the actions of the environment in which the pole is installed.
C-2. Why wood poles fail.
Wood poles generally fail because of pest damage or
from wood-rotting fungi. A good preservative treatment discourages both. The ability of treated poles
to resist deterioration depends principally upon the
thoroughness and quality of the original preservative treatment and to a lesser extent on the type of
wood and local climatic conditions.
C-3. Initial installation.
C-l
C-2
__
6il
Figure C-l. Twelve-inch (300-millimeter) pole with l-inch (25millimeter) surface decay
1(
150n
41n( 1 OOmm) -L
Figure C-2. Twelve-inch (300-millimeter) pole with 2-inch (50millimeter) surface decay
b. Interior damage. Interior damage from internal decay that occurs in the interior of the pole is
known as heart rot or hollow heart and requires
sound testing or probing to reveal its existence and
extent.
(1) Internal decay. When the preservative in
the sapwood is shallow in depth, fungi may gain
access through a check or injury to attack the untreated inner sapwood and the heartwood. Pine
poles are particularly susceptible to internal decay
if not thoroughly treated. Deep separations
(checks), occurring after treatment, or woodpecker
holes expose untreated wood to internal decay. Occasionally deep-seated infection in seasoned poles is
not killed during the treating process and continues
to grow, resulting in premature reduction of
strength.
C-3
4in (1OOmm)
Figure C-3. Twelve-inch (300-millimeter) pole with 4-inch (100centimeter) radial heart-rot
C-4
DENNIS J. REIMER
General, United States Army
Chief of Staff
JOEL B. HUDSON
Administrative Assistant to the
Secretary of the Army
D. J. NASH
Rear Admiral, C.E.C., United States Army
Commander, Naval Facilities
Engineering Command
BY ORDER OF THE SECRETARY OF THE AIR FORCE
EUGENE A. LUPIA, Maj General,
USAF, The Civil Engineer
Distribution:
Army:
To be distributed according with DA Form 12-34-E, block number 0695,
requirements for nonequipment technical manuals.
Navy:
SNDL DISTRIBUTION
25 copies each: FKAlC COMNAVFACENGCOM, FKNl EFDs
10 copies each: FA46 PWCLANT, FB54 PWCPAC, FKP7 NAVSHIPYDs,
FT104 PWCCNET
2 copies each: E3A LABONR, FA6 NASLANT, FA7 NAVSTALANT, FAlO
SUBASELANT, FA18 NAVPHIBASELANT, FA24 COMNAVBASELANT,
FB7 NASPAC FBl0 NAVSTAPAC, FB13 SUBBASEPAC, FB21
NAVPHIBASEPAC, FB28 COMNAVBASEPAC FB30 NAVSHIPREPFAC,
FB36 NAVFACPAC, FB45 TRIREFFACPAC, FC3 COMNAVACTEUR, FC5
NAVSUPACTEUR, FC7 NAVSTAEUR, FC14 NASEUR, FD4 OCEANCEN,
FFl COMNAVDICT Washington, DC, FF3 NAVSTACNO, FF6 NAVOBSY,
FF32 FLDSUPPACT, FF38 USNA, FF42 NAVPGSCOL, FG2
NAVCOMMSTA, FH3 NAVHOSP, FJA4 NAVAL HOME, FKA8F5 SUBASE,
FKM9 NSC, FKM12 NAVPETOFF, FKM13 SPCC, FKN2 CBCCS, FKN3
OICCs, FKN7 NEESA, FKNl0 NAVSUPPFAC, FKNll NAVCIVENGRLAB,
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*U.S. G.P.0.:1996-418-285:40035