Meeting NEC For Selective Coordination - Long R2
Meeting NEC For Selective Coordination - Long R2
Meeting NEC For Selective Coordination - Long R2
Selective
Coordination
Requirements
Robert E. Fuhr, P.E.
PowerStudies, Inc.
Maple Valley, WA.
NEC® is a trademark of the National Fire
Protection Association, Inc.
Agenda
Definitions
NEC Code Requirements
Fuse Selective Coordination
Breaker Trip Unit Types
Breaker Selective Coordination
Procedure to Achieve Selective Coordination
– Fuses
– Breakers
Arc Flash and Selective Coordination
Examples
Special Thanks
Square D Company
Data Bulletin
“Enhancing Short Circuit Selective
Coordination with Low Voltage Breakers”
http://ecatalog.squared.com/pubs/Circuit
%20Protection/0100DB0403.pdf
Special Thanks
Cooper Bussmann
White paper & SPD p21
– Traces the Codeology for Selective
Coordination Requirements
Papers and Online Voiceover Training
Module
www.CooperBussmann.com
NFPA 70 and NFPA 70E
Primarily Fire Protection Primarily Personnel Protection
Chapters 1 through 4:
– Generally for all electrical installations
– No selective coordination requirements
Selective coordination requirements under
“special” Chapters
Chapter 7 Special Conditions
– Emergency Systems: 700.27
– Legally Required Standby Systems: 701.27
– Critical Operations Power Systems: 708.54
13
517.2 Definitions
Emergency System.
– A system of circuits and equipment intended
to supply alternate power to a limited number
of prescribed functions vital to the protection
of life and safety.
– Essential for safety of human life.
NEC® 700.2 Informational Note:
– Emergency systems are generally installed in
places of assembly where artificial illumination
is required for safe exiting and for panic
control in buildings subject to occupancy by
large numbers of persons....,
– such as hotels, theaters, sports arenas, health
care facilities, and similar institutions.
Emergency systems may also provide power
for such functions as ventilation where
essential to maintain life, fire detection and
alarm systems, elevators, fire pumps, public
safety communications systems, industrial
processes where current interruption would
produce serious life safety or health hazards,
and similar functions.”
Emergency
Backup Power
ARTICLE 100 Definitions
Coordination (Selective).
– Localization of an overcurrent condition to
restrict outages to the circuit or equipment
affected, accomplished by the choice of
overcurrent protective devices and their
ratings or settings.
240.12 Electrical System
Coordination
Where an orderly shutdown is required to
minimize the hazard(s) to personnel and
equipment, a system of coordination
based on the following two conditions
shall be permitted:
– (1) Coordinated short-circuit protection
– (2) Overload indication based on monitoring
systems or devices
P
2- XFMR-UTILS
Sample
S
XFMR-UTILS
One Line 3
3-MSWBD MAIN
5-Fdr to ATS-E
2
E N
ATS 260 Amp
6-PNL-A MAIN
1
PNL-A - 250 A
P
2- XFMR-UTILS
Sample
S
XFMR-UTILS
One Line 1
3-MSWBD MAIN
5-Fdr to ATS-E
1
E N
ATS 260 Amp
6-PNL-A MAIN
1
PNL-A - 250 A
701.2 Definitions
Legally Required Standby Systems.
– Those systems required and so classed as
legally required standby by municipal, state,
federal, or other codes or by any
governmental agency having jurisdiction.
– These systems are intended to automatically
supply power to selected loads (other than
those classed as emergency systems) in the
event of failure of the normal source.
701.2 Definitions
Informational Note:
– Legally required standby systems are
typically installed to serve loads, such as
heating and refrigeration systems,
communications systems, ventilation and
smoke removal systems, sewage disposal,
lighting systems, and industrial processes,
that, when stopped during any interruption of
the normal electrical supply, could create
hazards or hamper rescue or fire-fighting
operations.
517.2 Health Care Facilities
Definitions
Essential Electrical System.
– A system comprised of alternate sources of
power and all connected distribution systems
and ancillary equipment, designed to ensure
continuity of electrical power to designated
areas and functions of a health care facility
during disruption of normal power sources,
and also designed to minimize disruption
within the internal wiring system.
517.2 Health Care Facilities
Definitions
Alternate Power Source.
– One or more generator sets, or battery
systems where permitted, intended to provide
power during the interruption of the normal
electrical services or the public utility electrical
service intended to provide power during
interruption of service normally provided by
the generating facilities on the premises.
517.2 Health Care Facilities
Definitions
Critical Branch.
– A subsystem of the emergency system
consisting of feeders and branch circuits
supplying energy to task illumination, special
power circuits, and selected receptacles
serving areas and functions related to patient
care and that are connected to alternate
power sources by one or more transfer
switches during interruption of normal power
source.
517.30 (A) Essential Electrical
System
708.1 Definition
Critical Operations Power Systems (COPS)
– (COPS) are those systems so classed by
municipal, state, federal, or other codes by
any governmental agency having jurisdiction
or by facility engineering documentation
establishing the necessity for such a system.
These systems include but are not limited to
power systems, HVAC, fire alarm, security,
communications, and signaling for designated
critical operations areas.
708.1 Definition
Critical Operations Power Systems
– Informational Note No. 1: Critical operations
power systems are generally installed in vital
infrastructure facilities that, if destroyed or
incapacitated, would disrupt national security,
the economy, public health or safety; and
where enhanced electrical infrastructure for
continuity of operation has been deemed
necessary by governmental authority.”
History & FPN to Mandatory
620.62 for elevators since 1993 NEC®
Fine Print Notes (FPN): non-mandatory
– Design consideration
– Unenforceable point of interest
2005 NEC® cycle, CMP 13 moved selective
coordination from FPN to Requirement
– Society is changing
– Building systems evolving
– Dependency on availability of power for life
safety loads
History: FPN to Mandatory
NEC® Panel 13 Statement:
– “The panel agrees that selective coordination
of emergency system overcurrent devices
with the supply side overcurrent devices will
provide for a more reliable emergency
system.”
History: FPN to Mandatory
700.27 & 701.27: 2005, 2008, & 2011 NEC®
708.54 placed in 2008 NEC® by specially
created Code Panel with expertise for COPS.
The requirements in four Articles:
Minimum standards for circuits supplying a
few vital life safety loads
The substantiation for the original (2005) NEC®
proposal for Section 700.27
33
The substantiation for the original (2005) NEC®
proposal for Section 700.27
34
The substantiation for the original (2005) NEC®
proposal for Section 700.27
35
Problems with this Code
Requirement
– Circuit Breakers
Most breakers
have an
instantaneous
trip function.
– Fixed
– Adjustable
– For Faults -
Breaker trips
instantaneously
(no time delay)
Problems with this Code Requirement –
Circuit Breakers
Breakers without an instantaneous trip
function are expensive.
Limited Selective Coordination Testing for
Thermal/Magnetic Breakers
Breakers without instantaneous trips
require more costly equipment (i.e. ATSs
& Switchgear construction.)
Limited equipment w/o Instantaneous
Higher fault current = Increases
complexity to selectively coordinate
Problems with this Code Requirement –
Circuit Breakers
Requires larger frame breakers with Solid
State Trip units
Larger Framed Breakers Means Larger
Electrical Room - Less rental or usable
building space
Not all trip units function the same way
Difficult to obtain competitive bids
Difficult to intermix fuses and circuit
breakers
Problems with this Code
Requirement - Fuses
Requires larger equipment than using T/M
CBs
Larger Electrical Room – Less rental or
usable building space
Reduces Levels of downstream equipment
Fusible Panelboards and Elevator Modules
are more expensive than T/M circuit
breakers
Reality
PowerStudies, Inc.
Maple Valley, WA.
ARTICLE 620 Elevators,
Dumbwaiters, Escalators, Moving
Walks, Wheelchair Lifts, and
Stairway Chair Lifts
620.62 Selective Coordination.
– Where more than one driving machine
disconnecting means is supplied by a single
feeder, the overcurrent protective devices in
each disconnecting means shall be selectively
coordinated with any other supply side
overcurrent protective devices.
Emergency Systems
700.27 Coordination.
– Emergency system(s) overcurrent devices
shall be selectively coordinated with all supply
side overcurrent protective devices.
– “The provisions of this article apply to the
electrical safety of the installation, operation,
and maintenance”
– “Essential for safety of human life”
ARTICLE 701 Legally Required
Standby Systems
701.18 Coordination.
– Legally required standby system(s)
overcurrent devices shall be selectively
coordinated with all supply side overcurrent
protective devices.
ARTICLE 708.54 Critical
Operations Power Systems
708.54 Coordination.
– Critical operations power system(s)
overcurrent devices shall be selectively
coordinated with all supply side overcurrent
protective devices.
ARTICLE 517 Health Care Facilities
Essential Electrical Systems must meet
Section 700 (except as amended by 517)
Implies that Essential Electrical Systems
must be selectively coordinated. (700.27 &
701.18)
ARTICLE 517.17(C) Selectivity
– Ground-fault protection for operation of the
service and feeder disconnecting means shall
be fully selective such that the feeder device,
but not the service device, shall open on
ground faults on the load side of the feeder
device. Separation of ground-fault protection
time-current characteristics shall conform to
manufacturer’s recommendations and shall
consider all required tolerances and
disconnect operating time to achieve 100
percent selectivity.
ARTICLE 695 Fire Pumps
Multi-building Campus-Style Complexes.
695.3(C)(3) Selective Coordination.
– The overcurrent protective device(s) in each
disconnecting means shall be selectively
coordinated with any other supply-side
overcurrent protective device(s).
Sample
4
One Line
Normal Power
Must be Selectively 3
Coordinated 2
1
Sample 4
One Line
3
Emergency Power
2
Must be Selectively
Coordinated
1
Definitions
MCCB – Molded Case
Circuit Breaker
Definitions
ICCB – Insulated Case Circuit Breaker
Definitions
LVPCB –
Low
Voltage
Power
Circuit
Breaker
Time Current Curves
Time Current Curve (TCC)
The log-log graph of time versus current.
Each breaker, fuse, and relay has a time
current characteristic curve
Fuse
TCC
@15 kA
This Fuse
is Current
3-6 Sec Limiting –
Clearing
time is
0.004
seconds
5 kA
Thermal
Magnetic
Breaker
20-50 Sec
4 kA
0.01-0.025 Sec 20 kA
Solid
State Trip 170-210 Sec
SQ D NW 6 kA
40H
4000 Amp
Micrologic
0.08-0.12 Sec 30 kA
100 kA
0.01-0.06 Sec
Manufacture
TCC
SQ D NW
40H
4000 Amp
Micrologic
Manufacture
TCC
SQ D NW
40H
4000 Amp
Micrologic
Manufacture
TCC
SQ D NW
40H
4000 Amp
Micrologic
What is Selective Device
Coordination
Devices closest to the fault must operate
first.
Upstream devices trip in sequence
No overlap on TCCs
P
2- XFMR-UTILS
Sample
S
XFMR-UTILS
One Line 3
3-MSWBD MAIN
SWBD
5-Fdr to ATS-E
2
E N
ATS 260 Amp
6-PNL-A MAIN
1
PNL-A - 250 A
Selective
Coordination
Breakers
Three
Breakers in
Series
No Overlap
Easy Right?
UTIL
XFMR-UTILP
1600 A GEN
4
SWBD-EMSB-1
P
XFMR-UTIL
400 A
3 S
XFMR-UTILS
PNL-F
200 A Fdr ATS-E(E) 3
2 300 0 A SWBD
E N
ATS-E
PNL-A - 200 A
100 A 1
Selective
Coordination
Fuses
No Overlap –
Does not
guarantee
coordination.
Must use Mfg
coordination
tables
Need 2-2.5
ratio
Problems with this Code
Requirement - Fuses
Requires larger equipment than using T/M
CBs
Larger Electrical Room – Less rental or
usable building space
Reduces Levels of downstream equipment
Fusible Panelboards and Elevator Modules
are more expensive than T/M circuit
breakers
Problems with this Code Requirement –
Circuit Breakers
Most breakers have an instantaneous trip
function.
– Breaker trips instantaneously (no time delay)
No Selective Coordination Testing for
Thermal/Magnetic Breakers
Limited equipment w/o Instantaneous
Higher fault current = Increases
complexity to selectively coordinate
Problems with this Code Requirement –
Circuit Breakers
Requires larger frame breakers with Solid
State Trip units
Larger Framed Breakers Means Larger
Electrical Room - Less rental or usable
building space
Not all trip units function the same way
Difficult to obtain competitive bids
Reality
Varies for
each Trip
Unit! Short Time Pickup (STPU)
Some
Short Time
Functions Delay I2T-IN
(I2T)
are Not Short Time Delay (STD)
Adjustable!
Instantaneous (I)
Solid
Current Sensors
State Trip Rating Plugs
Current Setting
Unit
SQ D NW
40H
4000 Amp
Micrologic
Solid State Trip Unit
Why is
this
Difficult?
Three
Breakers in
Series
No Overlap
Easy Right?
Why is P
S
2- XFMR-UTILS
XFMR-UTILS
this 480 V
3-MSWBD MAIN
Difficult?
SQUARE D
NW40H
Sensor/Trip 4000 A
SWBD
480 V
SWBD Main 5-Fdr to ATS-E
SQUARE D
– SS w/ LI LE
Sensor/Trip 250 A
Plug 250 A
Feeder E N
ATS 260 Amp
– SS w/ LSI
Panel Main 6-PNL-A MAIN
SQUARE D
LA
Sensor/Trip 250 A
– T/M
PNL-A - 250 A
480 V
Panel Branch
– T/M 12-Lrgst Fdr
SQUARE D
FH
Sensor/Trip 100 A
Why is
this
Difficult?
Instantaneous
Function
Per UL &
NEMA –
Required on
MCCBs &
ICCBs
LVPCBs – Not
Required
Solution
Eliminate the Instantaneous Function by:
– Reducing the fault current
Transformers
Reactors
Long Conductor Lengths
– Setting Instantaneous above fault current.
Instantaneous
Function –
T/M Trip
Selectively
coordinates
only if
difference
in fault
current
Instantaneous
Function –
SS Trip
Instantaneous
curve ends at
available fault
current
100,000 Amps
Instantaneous
Function –
SS Trip
Instantaneous
curve ends at
available fault
current
60,000 Amps
Instantaneous
Function –
SS Trip
Instantaneous
curve ends at
available fault
current
30,000 Amps
Instantaneous
Function –
SS Trip
Instantaneous
curve ends at
available fault
current
25,000 Amps
Instantaneous
Function –
SS Trip
Instantaneous
curve ends at
available fault
current
15,000 Amps
Instantaneous
Function –
SS Trip
Instantaneous
curve ends at
available fault
current
10,000 Amps
Instantaneous
Function –
SS Trip
Adjust
Instantaneous
curve above
the available
fault current
3X
Instantaneous
Function –
SS Trip
Adjust
Instantaneous
curve above
the available
fault current
4X
Instantaneous
Function –
SS Trip
Adjust
Instantaneous
curve above
the available
fault current
6X
Instantaneous
Function –
SS Trip
Adjust
Instantaneous
curve above
the available
fault current
8X
Instantaneous
Function –
SS Trip
Adjust
Instantaneous
curve above
the available
fault current
10X
Instantaneous
Function –
SS Trip
Adjust
Instantaneous
curve above
the available
fault current
12X
Problem – Large Equipment
Switchboard Feeder and Panelboard Mains
many times are ICCB
Tip #2 – Eliminate Main Breakers in
Panelboards.
Switchgear & Switchboard
Switchgear and switchboard, Panelboard
structures are built and tested to different
standards:
Switchgear
ANSI standard C37.20.1
UL standard 1558
NEMA standard SG-5
Switchgear uses power circuit breakers (PCB)
– ANSI C37.13
– NEMA SG-3
– UL-1066
Unfused switchgear short circuit tested 30 cycles
Switchgear
Instantaneous trip function not required for
LVPCBs.
Switchboards
Group Mounted
Switchboards Standards
– NEMA PB-2
– UL-891.
Switchboards may use a combination of
protective devices
Switchboards – Devices to Use
Insulated case (ICCB)
Molded-case circuit breakers (MCCB)
Fusible switches
Power circuit breakers
Group-mounted Switchboards, –
Short Circuit Testing
Short Circuit tested for only 3 cycles
Protective devices must have
instantaneous for UL 891 label
This Instantaneous trip function reduces
selectivity between the main and feeder
circuits breakers.
Compartmented Switchboards
Short Circuit tested for 30 cycles.
UL 891 Listed
SWBD
& SWGR
Testing
ANSI, NEMA, &
Manufacturers
….. We need SWGR W/S 65 KA
@ 30 Cycles (0. 5 Seconds)
an I2T
Withstand
Curve!!!! SWBD W/S Tested for
3 Cycles (0.05 Seconds) SWBD W/S 65 KA
More Tips
Tip #3
– T/M breakers must have a 3:1 ratio to
selectively coordinate.
Tip #4
– Impedance aids in selective coordination
– Long feeder lengths
– Air core reactors
– Transformers
P
2- XFMR-UTILS
Tip #5 – Feeders to S
XFMR-UTILS
480 V
SWBD
480 V
Feeders to Equipment Main
Devices, do not need to 2 5-Fdr to ATS-E
SQUARE D
LE
Sensor/Trip 250 A
Plug 250 A
coordinate. E N
ATS 260 Amp
700.27 & 701.27 (but not
708.54) Coordination. 6-PNL-A MAIN
2 SQUARE D
Emergency system(s) LA
Sensor/Trip 250 A
1 12-Lrgst Fdr
SQUARE D
FH
Sensor/Trip 100 A
P
2- XFMR-UTILS
Tip #5 – Feeders to S
XFMR-UTILS
480 V
SWBD
480 V
– Selective coordination shall not be
required between two overcurrent 2 5-Fdr to ATS-E
SQUARE D
LE
Sensor/Trip 250 A
devices located in series if no Plug 250 A
PNL-C
More Tips
Tip #8* - Use SS Trips with LSI(0ff) or
Fixed Instantaneous Override
Tip #9* – Specify that SS Trip Units have
adjustable:
– LTPU / LTD
– STPU / STD / I2T
– INST(OFF) or Instantaneous Override (above
110% fault current at downstream device)
* - Do not forget the generator breaker
Elevator Selective Coordination
Elevator Circuits must be selectively
coordinated.
PNL-A - 250 A
Circuit Coordination
Feeder and Shunt Trip Devices,
do not need to coordinate. 23-ELEV ST
They feed the same load! CB-ELEV-2
Impossible to do with fuses if
fuses are same size.
ELEV-2
Impossible with CBs
ELEV-2 MOTOR
3-MSWBD MAIN
2
Elevator SWBD
Circuit 1
29-FDR ELEV-1 27-FDR ELEV-3
Coordination 1
30-ELEV 1 ST 28-ELEV 3 ST
CB-ELEV-1 CB-ELEV-3
ELEV-1 ELEV-3
Generator
Coordination 23-GEN MAIN #1
2
Must Coordinate as GEN
well
Good News! - Lower
Fault Currents SWBD-EMSB-1
Easier to Coordinate
24-FDR PNL F
1
PNL-F
Gen
PDC
Decrement
Curve
Fault Current <
Instantaneous
Setting
Requires 30
Cycle ATSs?
Series Rating of Devices
Two or More Devices are Short Circuit Tested in
Series
Combinations can be
– Circuit Breaker
– Fuses
– Fuses and Circuit Breakers
Last device AIC (SC) Rating < Available
All Devices will operate
SWBD
41638 Amps 3P
Series Rating
of Devices 1 25-Fdr Pnl-B
InterruptingRating 65 kA
UL Listed
Combination is
Series Rated 65 kA
No Selective PNL-B
Coordination 36029 Amps 3P
4
Incident Energy
3.5
3
2.5
2
1.5
1 1 1 1 1 1 1 1
0.5
0 0 0 0
0 20 40 60 80 100
Fault Current
30
20
10
3 3 3 4
0 1 1 1 2 2
0 0.1 0.2 0.3 0.4 0.5 0.6
Device Operating Time
UTILITY
>4 (116)
Using T/M 480 V
Breakers @ MAIN
800 A
HRC (Cal/cm2)
0 (1.2) XFMR A PRIM
480 V
P
XFMR A
S 300 kVA
PANEL A
4 (32) 208 V
Main Breaker
- Thermal
Magnetic
Breaker
0.025 Sec 29 kA
UTILITY SOURCE
Isc 3P 30000 Amps
Isc SLG 30000 Amps
UTILITY
>4 (116)
Using T/M 480 V
Breakers @ MAIN
800 A
HRC (Cal/cm2)
0 (1.2) XFMR A PRIM
480 V
P
XFMR A
S 300 kVA
PANEL A
4 (32) 208 V
Arcing Fault Current @ Panel A – 5.0 kA
Panel A is protected by 400A Feeder
Breaker in Main Switchboard
Current is reduced due to transformer:
– 5.0 kA @ 208 Volts
– @ 480 V = 5.0*208/480 = 2.2 kA
Feeder breaker sees only 2.2 kA for a fault
at Panel A!!!
Feeder
Breaker - 59 Sec
Thermal
Magnetic
Breaker
2.2 kA
Selective
Coordination
& Arc Flash
Energy
Main and
Feeder
Breakers
with (LS)
Trip Units
UTILITY SOURCE
Isc 3P 30000 Amps
Isc SLG 30000 Amps
MAIN SWBD
30 kA
480 V
FDR XFMR A
400 A
Available
HRC (Cal/cm2) XFMR A PRIM
3 (9) 480 V
P
XFMR A
S 300 kVA
PANEL A
1 (3) 208 V
Main Breaker
- Solid State
Trip Breaker
0.32 Sec
29 kA
UTILITY SOURCE
Isc 3P 30000 Amps
Isc SLG 30000 Amps
State MAIN
Breakers @ 3 (16)
800 A
MAIN SWBD
30 kA
480 V
FDR XFMR A
400 A
Available
HRC (Cal/cm2) 3 (9) XFMR A PRIM
480 V
P
XFMR A
S 300 kVA
1 (3) PANEL A
208 V
Arcing Fault Current @ Panel A – 5.0 kA
Panel A is protected by 400A Feeder
Breaker in Main Switchboard
Current is reduced due to transformer:
– 5.0 kA @ 208 Volts
– @ 480 V = 5.0*208/480 = 2.2 kA
Feeder breaker sees only 2.2 kA for a fault
at Panel A!!!
Feeder
Breaker -
Solid State
Trip Breaker
0.21 Sec
2.2 kA
UTILITY SOURCE
Isc 3P 30000 Amps
Isc SLG 30000 Amps
UTILITY
>4 (116) 480 V
Using CL MAIN
Fuses @ 30 800 A
MAIN SWBD
0 (1.1)
kA Available
480 V
FDR XFMR A
400 A
HRC (Cal/cm2)
XFMR A PRIM
0 (1.4) 480 V
P
XFMR A
S 300 kVA
PANEL A
3 (23) 208 V
Main- Current
Limiting Fuse
0.004 Sec
15.5
kA
UTILITY SOURCE
Isc 3P 30000 Amps
Isc SLG 30000 Amps
UTILITY
>4 (116) 480 V
Using CL MAIN
Fuses @ 30 800 A
MAIN SWBD
0 (1.1)
kA Available
480 V
FDR XFMR A
400 A
HRC (Cal/cm2)
XFMR A PRIM
0 (1.4) 480 V
P
XFMR A
S 300 kVA
PANEL A
3 (23) 208 V
Arcing Fault Current @ Panel A – 5.0 kA
Panel A is protected by 400A Feeder Fuse
in Main Switchboard
Current is reduced due to transformer:
– 5.0 kA @ 208 Volts
– @ 480 V = 5.0*208/480 = 2.2 kA
Feeder fuse sees only 2.2 kA for a fault at
Panel A!!!
Feeder Fuse -
Current
Limiting Fuse
0.9 Sec
2.2 kA
Tools for Selective Coordination
All Fuse Manufacturers have Fuse
Selectivity Charts
– Coordination not affected by higher fault
currents
GE, Eaton, Siemens, and Square D –
– Breaker Selectivity Charts
– Breaker Coordination Excel Spreadsheet
– Coordination can be affected by higher fault
currents
Tools for Selective Coordination
Siemens EasyTCC software program
SKM PowerTools for windows
– Special Selective Coordination Feature
Any others I have not mentioned??
New Products to Help!
Bussmann -
Coordination Panel
Board 30A – 400A
Fusible
Ferraz Shawmut –
Coordination Panel
New Products to Help!
New Circuit
Breakers being
Introduced
Additional Breaker
Testing
Resources and Additional Info
http://www.geindustrial.com/solutions/en
gineers/selective_coordination.html
http://www.eaton.com/Electrical/Consulta
nts/SelectiveCoordination/index.htm
http://www.schneider-
electric.us/sites/us/en/customers/consultin
g-engineer/selective-coordination.page
Resources and Additional Info
http://www.sea.siemens.com/us/Support/
Consulting-
Engineers/Pages/SelectiveCoordination.as
px
http://www1.cooperbussmann.com/2/Sele
ctiveCoordination.html
http://us.ferrazshawmut.com/resources/ar
ticles-white-papers.cfm
http://us.ferrazshawmut.com/resources/o
nline-training.cfm
Coordination Table.
All Values (Typical) in RMS Current Levels @ 240, 415 / 480 Vac
Company Name
Transformer Calculations
Primary Voltage 480 Volts
Primary Current 361 Amperes
Maximum Primary Protection per NEC 450.3(B) 902 Amperes
Recommended Primary Breaker Rating 1000 Amperes
Example 1 SWBD
41638 Amps 3P
41081 Amps SLG
12-Fdr ATS-E
Determine the Short
Circuit Currents
Determine the breaker
E N
type
ATS 260 Amp
– SWBD Main (4000 Amp)
– Feeder to ATS (200 Amp) 12-PNL-A MAIN
– Panelboard Main (200 Amp)
PNL-A - 250 A
– Largest Feeder is 70A KH 30933 Amps 3P
AMP 27901 Amps SLG
76-Lrgst Brnch
Example 1
32-MSWBD MAIN
SQUARE D
NW40H
Sensor/Trip 4000 A
Settings Phase
LTPU/LTD (A 0.4-1.0 x S) 1 (4000A); 0.5
STPU (1.5-10 x LTPU) 5 (20000A)
STD (INST-0.4) 0.3(I^2 T Out)
INST (2-15 x S) 15 (60000A)
12-Fdr ATS-E
SQUARE D
NT08H
Sensor/Trip 400 A
Settings Phase
LTPU/LTD (A 0.4-1.0 x S) 0.5 (200A); 24
STPU (1.5-10 x LTPU) 6 (1200A)
STD (INST-0.4) 0.2(I^2 T Out)
INST Override Fixed (40000A)
Example 1
12-PNL-A MAIN
SQUARE D
NT08H
Sensor/Trip 400 A
Settings Phase
LTPU/LTD (A 0.4-1.0 x S) 0.5 (200A); 16
STPU (1.5-10 x LTPU) 5 (1000A)
STD (INST-0.4) 0.1(I^2 T Out)
INST Override Fixed (40000A)
76-Lrgst Brnch
SQUARE D
KH
Sensor/Trip 70 A
Settings Phase
Thermal Curve (Fixed)
INST (5-10 x Trip) 10.0 (700A)
Example 1
Determine
the
– SWBD Main -
– Feeder to
ATS
– PNLBD Main
– Largest
Feeder is
70A KH AMP
Example 2
Determine the
– Panel A Feeder
– Panel C Main
– Panel C Largest Feeder is 20A QO
Step 1 – Determine 208 V Fault
in 480 V amperes.
3,094 X 208/480 = 1,341 A
Example 2
Pick 125 Amp Feeder Breaker T-3
– Instantaneous OR > 1,341
– 1,341 / 125 = 10.7 (Can not use T/M)
– Must Use SS Trip
Pick Panel C 100 Ampere Main
– Must Coordinate with Largest Branch Breaker
Example 2
13-Pnl C MAIN
SQUARE D
PG
Sensor/Trip 250 A
Settings Phase
LTPU/LTD (A 0.4-1.0 x S) 0.4 (100A); 4
STPU (1.5-10 x LTPU) 10 (1000A)
STD (0-0.4) 0.1(I^2 T In)
INST Override Fixed (24000A)
17-Lrgst Brnch
SQUARE D
QO3
Sensor/Trip 20 A
Settings Phase
Fixed
12-PNL-A MAIN
SQUARE D Example 2
NT08H
Sensor/Trip 400 A
Settings Phase
LTPU/LTD (A 0.4-1.0 x S) 0.5 (200A); 16
STPU (1.5-10 x LTPU) 5 (1000A)
STD (INST-0.4) 0.2(I^2 T Out)
INST Override Fixed (40000A)
14-Fdr to T-3
SQUARE D
LE
Sensor/Trip 250 A
Plug 250 A
Settings Phase
LTPU (0.5-1.0 x P) 0.5 (125A)
LTD (2-14 Sec.) 2
STPU (2-8 x P) 2.5 (625A)
STD (0.1-0.5 Sec.) 0.1(I^2 T Out)
INST (2.5-8 x P) 8.0 (2000A)
Example 2
Selective Coordination -
Ensuring Compliance
Requires
proper engineering,
Specification,
Installation, and Testing
205
Selective Coordination –
Ensuring Compliance
Engineer
– Designs must allow selective coordination –
Use less levels of OCPDs.
– For competitive bidding, design should be
generic and simple.
– Require that PDC study be done after
manufacture has provided submittals for
proposed equipment.
Selective Coordination –
Ensuring Compliance
Contractors
– Purchase and install OCPDs as specified.
– Substitutions must be approved by the
designer and verified that is can be selectively
coordinated.
– Make sure devices are set per the PDC study.
– Test the devices to verify proper operation.
Selective Coordination –
Ensuring Compliance
Plan Review and Inspection by AHJ
– Require PDC Study after Manufacture has
provided OCPD submittals.
– Require that PDC study be done and
submitted for review (1 month) after OCPD
submittals are provided.
– Final Inspections and Equipment Energization
not allowed until PDC study is reviewed by
AHJ.
Selective
Coordination
Check List
http://www.cooperindustr
ies.com/content/dam/publ
ic/bussmann/Electrical/Re
sources/Solution%20Cent
er/electrical_inspector_to
ols/BUS_Ele_Selective_Co
ord_Req_ChkList.pdf
209
Summary
You must change the way you design
circuits for:
– Emergency
– Standby
– Elevators
– Fire Pumps
Manufacturers must provide:
– New Equipment to meet the code
– Tools (tables, spreadsheets, charts)
– I2T Withstand curves for Equipment
Need more Information
www.powerstudies.com
– Articles
– Links
– Specifications for Power System Studies
Short Circuit
Protective Device Coordination
Arc Flash Hazard
Questions??