JKR 11kV Transformer Test
JKR 11kV Transformer Test
JKR 11kV Transformer Test
ITEM
CONTENTS
PAGE
1.0
General
2.0
3.0
4.0
Transformers
4.1
Type of Transformers
5.0
5.1
Voltage Ratios
5.2
5.3
5.4
Impedance Voltage
5.5
Flux Density
5.6
Losses
5.7
5.8
5.9
5.10
Vibration
Noise
And
6.0
6.1
Core Materials
6.2
Core Construction
6.3
6.4
6.5
Winding Insulation
6.6
Oil Ducts
6.7
Winding tapping
Drying Process
6.8
ITEM
CONTENTS
PAGE
6.9
6.10
Cooling System
6.11
Cable Boxes
6.12
Gaskets
6.13
Valves
6.14
Fittings
6.15
6.16
6.17
Oil
7.0
8.0
Packing
10
9.0
Earthing
10
10.0
Padlocks
11
11.0
11
11.1
11
11.2
Site Testing
12
11.3
Commissioning
12
12.0
Rejection Of Plants
13
13.0
13
13.1
13
13.2
Recommended Spares
13
14.0
14
14.1
Working Drawings
14
14.2
14
ITEM
CONTENTS
PAGE
15.0
Transformer Room
15
16.0
15
17.0
16
17.1
As Installed Drawings
16
17.2
Manuals
17
17.3
Tools
17
18.0
18
19.0
Schedule Of Spares
19
iii
GENERAL
This section of the Specification describes and specifies
requirements for the supply, installation, testing, commissioning
handing over in approved working order and maintenance
during
the Defects Liability Period of distribution transformers all in
accordance with the Specification
Supplementary Notes, Bill Of
Qualities, Conditions Of Contract, Drawings etc.
2.0
3.0
4.0
TRANSFORMERS
The transformers shall be suitable for continuous operation on a
3 phase, 50 Hz electrical power distribution system with neutral
earthing conditions and maximum phase fault levels as follows :11 Kv
350 MVA
1
150 MVA
75 MVA
31 MVA
4.1
TYPE OF TRANSFORMER
The transformers shall be oil-immersed naturally cooled and
hermetically sealed type complying with BS 171 or IEC 76 and
suitable for indoor duties. Unless otherwise specified, they
shall be low loss, step-down type of distribution transformers
fitted with skid type bases.
5.0
5.1
VOLTAGE RATIOS
The standard voltage ratios at no-load shall be as specifiedin the
Bill Of Qualities and/or Drawings and shall in generalbe as
follows :-
5.2
(a)
(b)
11000/3300 V
(c)
6600/433-250 V
5.3
Delta
Star
Dyn 11
IMPEDANCE VOLTAGE
For the purpose of protection against short circuit stresses,the
minimum value of impedance voltage at 75 degrees Celsius rated
current shall be as follows :4.75%
5.5%
6.0%
5.5
FLUX DENSITY
The maximum flux density at any point in the magnetic circuit when
the
transformer is
connected on the
principal tapping and
operating at normal voltage and frequency shall normally be inthe
region of 1.55 to 1.65 Tesla, but at the time of tendering
alternative designs employing higher flux densities may bemay be
submitted. However with such higher flux densities for
consideration the magnetic circuit shall not unduly saturate
during system over voltage conditions.
5.6
LOSSES
The no-load and load losses shall be separately quoted in the
Schedule of Particulars And Guarantees at the time of tendering.
The losses shall be low commensurate with the economic use of
materials such that the total capitalised cost is a minimum. The
no- load and full load losses shall not exceed the values as
follows :-
No Load Loss
(Watt)
------------
100
250
315
500
800
1000
1250
1600
5.7
220
650
700
970
1450
1650
1900
2450
5.8
off
tap
the
tap
the
5.9
:
:
50 degrees Celsius
55 degrees Celsius
6.1
CORE MATERIALS
All transformer cores shall be fabricated from high grade cold
rolled grain oriented steel of low loss characteristics.
6.2
CORE CONSTRUCTION
All parts of the core shall be of robust design capable of
withstanding mechanical shocks. Bracing of the core and winding
assembly must be adequate to prevent any movement relative to the
tank during normal lifting transportation and handling of the
transformer.
The supporting framework of the core shall be design toavoid the
presence of pockets which would prevent complete emptying of the
tank through the drain valve, cause the trapping of air during
filling or cause the trapping of gases which involve during inservice faults.
Individual laminations shall be insulated with material which will
not deteriorate due to the action of pressure and hot oil.
6.3
6.5
WINDING INSULATION
Interturn insulation of winding, shall be of high grade paper.The
insulation barriers between windings and to the core shallbe
cylinders of synthetic bonded paper, pressed board , fibreglass or
equivalent, and shall be of high dielectric andmechanical
strength.
6.6
OIL DUCTS
Oil ducts be provided where necessary to ensure adequate cooling.
The coil clamping arrangement shall be such as will not impede the
free circulation of oil through the ducts.
6.7
WINDING TAPPING
Tapping shall be located in such a manner to maintain the
electrical balance of the windings and to reduce resulting axial
forces to a minimum.
6.8
DRYING PROCESS
Before final assembly the windings shall be subjected to a drying
process.
6.9
6.12 GASKETS
All gaskets shall be of synthetic rubber-bonded cork or other
similar material subject to the approval of the S.O.
6.13 VALVES
All valves shall be attached to the transformer by machined
flanges.
The outlet shall have female threads. A male threaded
plug incorporating a sampler shall be provided with each drain
valve.
Valves shall be closed by clockwise rotation of the
handle and provision for padlocking in the closed and open
positions shall be included.
6.14 FITTINGS
Unless otherwise
stated in the Bill of Quantities transformers
covered by this specification shall be provided with the following
standard fittings :(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
(k)
(l)
(m)
Type Tests
(i)
(ii)
(iii)
(iv)
(v)
(vi)
(b)
Routine Tests
(i)
(ii)
10
Measurement
impedance
of
impedance
voltage
and
short
circuit
(iv)
(v)
(vi)
(vii)
PACKING
Transformers shall be shipped with the core and windings fully
immersed in oil and hermetically sealed after the transformer has
been dried out in an approved manner.
All plant and equipment shall be packed in a manner so that they
are protected adequately against the tropical climatic conditions
encountered during
shipment and storage at site. All fragile
parts shall be packed separately in an approved manner. Pipe ends
and flanged openings shall be protected against external damage as
well as against ingress of dirt and moisture during transit and
storage at site.
9.0
EARTHING
The neutral point of the low voltage system of the transformer
shall be solidly earned to achieve an earth resistance not
exceeding one ohm. The frameworks and all non-current carrying
metal parts of the transformer shall be earthed similarly to
achieve an earth resistance not exceeding one ohm. An earth bar of
flat hard drawn copper with dimension not less than 25 mm x
6mm shall be installed around the four walls of the transformer
room at a height of 300 mm from the finished floor level.
The
earth bar shall be bolted to the frame earth of the transformer.
All joints of the earth bar shall be tinned and bolted. The earth
bars shall be painted with an approved green enamel.
Unless otherwise specified, the neutral earth and the frame earth
of the transformer shall be separately connected to its own group
of earth electrodes. The neutral earth and the frame earth shall
be
connected to its electrodes by means of two numbers
green PVC insulated copper cable of cross
11
sectional area not less than 70 sq.mm. The two groups of earth
electrodes after having been hang verifies by
the S.O.
to
be each of earth resistance not exceeding one ohm, shall be linked
together by means of PVC cables
as mentioned above unless
otherwise specified. At least two points of the frame earth system
of the transformer shall be connected to the earth electrodes.
Earth electrodes shall be of copper jacketed steel core rods with
16 mm
diameter and
supplied in 2.4 m length and shall have
provision for screw coupling with another standard length. The
copper jacket shall be of minimum thickness 0.25 mm and shall be
metallically bonded to the steel core to ensure that the
copper
jacket and steel core are not separable. Where the desired earth
resistance value cannot be driven, sufficient number of sets of
earth electrodes shall be installed outside the resistance area
and linked together by PVC copper cables as mentioned above until
the required value is reached. Each set
of earth electrode
shall be provided with brass connecting clamp and approved type of
precast heavy duty concrete inspection chamber with removable
cover.
The earthing points shall be identified by permanent label legibly
marked with the words `Transformer Frame Earth' or `Transformer
Neutral Earth' permanently fixed at the point of connection of
every earthing conductor to an earth electrode.
11.0 INSPECTION, TESTING AND COMMISSIONING
11.1 INSPECTION AND ACCEPTANCE TESTS
The whole of the plant and equipment to be supplied under the
Tender shall be subjected to inspection and acceptance tests by
the S.O.
and his officers in the factory prior to delivery. The
approval by the S.O. of the results of any such inspection or
test shall not prejudice the right of the S.O. to reject the
plant if it fails to comply with the specification when erected or
to give complete satisfaction in service within the Defect
Liability Period. The price quoted in the Bills Of Quantities for
the inspection and acceptance test as stated above shall include
the provision of all necessary equipment, facilities, expenses,
allowances etc for the S.O. and his officers to inspect the plant
and equipment and to verify the tests. Adequate notice shall be
given when the plant is ready for inspection and acceptance test.
12
(b)
(c)
(d)
The S.O. reserves the right to be present at all tests and the
Electrical Contractor shall give at least one week notice in
writing to the S.O. for this purpose.
In any case no test shall
be
carried out without prior approval of the S.O. Copies of all
the test certificates shall be submitted to the S.O. within one
week after the completion of the testing.
11.3 COMMISSIONING
On successful testing of the complete installation the Electrical
Contractor shall arrange to commission the
equipment in the
presence of the S.O. on a date to be decided by the S.O.
13
INSTALLATION,
OPERATION
AND
MAINTENANCE
15
16
(b)
Replacing and making good all loose and burnt cables and
terminations, all mechanical support and linkage, earth
electrodes, earth electrode chambers and covers, conduits
trunkings etc.
(c)
(d)
Site Plan.
(b)
(c)
Installation Manual.
(b)
Operation Manual.
(c)
(d)
Parts List
(e)
(f)
Test Certificates
18
the
18.0
DESCRIPTION
1.
General
(a)
Name of Manufacturer
(b)
Name of Supplier
(c)
2.
Capacity of Transformer
KVA
19
KVA
KVA
3.
Rated Power
4.
Number of phases
5.
Frequency
6.
7.
Winding connections
8.
a)
b)
9.
Tesla
A/sq.mm
A/sq.mm
10.
a)
b)
11.
a)
b)
KVA
Hz
Losses
No-load loss at rated
voltage frequency and
normal tap
KW
Load loss at rated current
and normal tap at 75
degree C
KW
20
12.
Efficiencies at :-
a)
b)
c)
d)
e)
f)
Full
Full
3/4
3/4
1/2
1/2
13.
14.
a)
b)
15.
a)
b)
H.V. Windings
L.V. Windings
16.
Type of windings :-
a)
b)
H.V. Windings
L.V. Windings
17.
Insulation materials :-
a)
b)
H.V. Windings
L.V. Windings
19.
20.
Core laminations
21.
Clearances :-
a)
b)
c)
load
load
load
load
load
load
unity
0.8
unity
0.8
unity
0.8
power
power
power
power
power
power
factor
factor
factor
factor
factor
factor
%
%
%
%
%
%
%
%
Kvp
Kvp
21
mm
mm
mm
22
b)
c)
d)
Thickness of bottom
Thickness of plate
Thickness of cooling fins
23.
a)
b)
24.
Overall Dimensions :-
a)
b)
For service
For transport
25.
Type of gasket
mm
mm
mm
litres
mm
mm
23
26.
:....................
Name of Tenderer:....................
....................
Chop of Tenderer:....................
....................
....................
Date
24
:....................
19.0
SCHEDULE OF SPARES
Item
Type Of Spares
Delivery
Period
Quantities
Recommended
Unit
Price
Total
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Total
The price quoted shall valid for acceptance during the
Contract Period (extended if applicable) of the project.
Signature
:.....................
Name of Tenderer:.....................
Chop of Tenderer:.....................
......................
25
:.....................
* * * * * * * * * * * * ** * * * * * * * * * * * * * * * *
26