SPECIFICATION

FOR
54 MVA, 220/2x27 kV SCOTT CONNECTED
TRACTION POWER TRANSFORMER
FOR
2 x 25 kV AT FEEDING SYSTEM
FOR
RAILWAY ac TRACTION SUBSTATIONS

No. ETI/PSI/124(07/95)

ISSUED BY:

TRACTION INSTALLATION DIRECTORATE

RESEARCH DESIGNS & STANDARDS ORGANISATION
MINISTRY OF RAILWAYS, GOVERNMENT OF INDIA,
MANAK NAGAR, LUCKNOW 226 011, INDIA.

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 GOVERNMENT OF INDIA : MINISTRY OF RAILWAYS
RESEARCH DESIGNS & STANDARDS ORGANISATION

Specification No. ETI/PSI/124(7/95)

54 MVA, 220 kV/2x27 kV SCOTT-CONNECTED TRACTION POWER
TRANSFORMER FOR AT FEEDING SYSTEM

1.0 SCOPE
1.1 This specification applies to 54 MVA, ONAN, 220kV/2x27kV
Scott-connected traction power transformer for autotransformer (AT)
feeding system for installation in Indian Railway's unattended traction
substation in any part of India.
1.2 The transformer shall be complete with all parts, fittings and
accessories necessary for its efficient operation in the unattended traction
substation. All such parts, fittings and accessories shall be deemed to be
within the scope of this specification, whether specifically mentioned
herein or not.
1.3 This specification supersedes the specification
No.ETI/PSI/124(8/89)
2.0 GOVERNING SPECIFICATION
2.1 In the preparation of this specification assistance has been
derived from the following Standards and Codes of Practices (latest
version), and Indian Electricity Rules wherever applicable.
1. IS:5 Colours for ready mixed paints and enamels.
2. IS:335 New insulating oils.
3. IS:1554 PVC insulated (Heavy duty) electric cables for working
(Part-I) voltages up to and including 1100 volts.
4. IS:1570 Stainless and heat resisting steels.
(Part-V)
5. IS:1576 Solid pressboard for electrical purposes.
6. IS:1866 Code of practice for maintenance and supervision of
mineral insulating oil in equipment.
7. IS:2026 Power Transformers.
8. IS:2099 Bushing for alternating voltages above 1000 volts.
9. IS:2705 Current transformers.
10. IS:2927 Brazing alloys
11. IS:3024 Electrical steel sheets (oriented)
12. IS:3637 Gas operated relays.
13. IS:3639 Fittings and accessories for power transformers.
14. IS:4253 Cork and rubber.
(Part-II)
15. IS:5561 Electrical power connectors.

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16. IS:5621 Hollow insulators for use in electrical equipment.
17. IS:5728 Guide for short-circuit calculations.
18. IS:6209 Methods for partial discharge measurements.
19. IS:6600 Guide for loading of oil-immersed transformers.
20. IS:8468 On-load tap-changers.
21. IS:10028 Code of practice for selection, installation and
maintenance of transformers.
22. IS:10593 Method of evaluating the analysis of gases in oil-filled
electrical equipment in service
23. IS:12676 Oil impregnated paper insulated condenser bushings-
dimensions and requirements.
24. IEC:76 Power transformers.
25. IEC:137 Bushings for alternating voltages above 1000 volts.
26. IEC:185 Current transformers.
27. DIN:7733 Laminated products, pressboard for electrical
engineering, types.

2.2 In case of any conflict between the contents of the above

specifications and this specification, the latter shall prevail.
2.3 Any deviation from this specification, proposed by the tenderer,
calculated to improve the performance, utility and efficiency of the
equipment, will be given due consideration provided full particulars of
the deviation with justification therefor are furnished. In such a case, the
tenderer shall quote according to this specification and the deviations, if
any, proposed by him shall be quoted as an alternative/alternatives.

3.0 ENVIRONMENTAL CONDITIONS

3.1 The transformer shall be suitable for outdoor use in moist tropical
climate and in areas subject to heavy rainfall, pollution due to industry
and marine atmosphere and severe lightning. The limiting weather
conditions which the equipment has to withstand in service are indicated
below:
1. Maximum ambient air temperature 500C
2. Average ambient air temperature over a 400C
period of 24 hours
3. Maximum relative humidity 100%
4. Annual rainfall Ranging from
1750 to 6250 mm
5. Maximum number of thunder storm days per 85
annum
6. Maximum number of dust storm days per 35
annum
7. Number of rainy days per annum 120
8. Basic wind pressure 200 kgf/m2
9. Altitude Not exceeding 1000 m
10. Minimum ambient air temperature 00 C

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3.2 The transformer would also be subjected to vibrations on account of
trains running on nearby railway tracks. The amplitude of those
vibrations which occur with rapidly varying time periods in the range of
15 to 70 ms lies in the range of 30 to 150 microns at present, with the
instantaneous peaks going up to 350 microns. These vibrations may
become more severe as the speeds and loads of trains increase in future.

4.0 TRACTION POWER SUPPLY SYSTEM (2x25 kV AT FEEDING

SYSTEM)

4.1 General Scheme

4.1.1 The electric power for railway traction is supplied in ac 50 Hz,
single-phase through 2x25 kV AT feeding system which has a feeding
voltage (2x25 kV) from the traction substation (TSS) two times as high
as the catenary voltage which is 25 kV with respect to earth/rail. The
power fed from the TSS through catenary wire and feeder wire is
stepped down to the catenary voltage by means of autotransformers
(ATs) installed about every 13 to 17 km along the track, and then fed to
the locomotives. In other words, both the catenary voltage and feeder
voltage are 25 kV with respect to the earth/rail, although the substation
feeding voltage between catenary and feeder wires is 50 kV. The
catenary voltage is, therefore, the same as that in the conventional 25 kV
system.
4.1.2 Since the power is supplied at 50 kV, the AT feeding system is
suitable for a large power supply, and it has the following advantages as
compared with the conventional feeding system:
1. Lower voltage drop in feeder circuit.
2. Larger spacing between traction substations.
3. Lower interference to adjacent telecommunication lines, if any.

4.1.3 The power is obtained from the 220 kV or 132 kV or 110 kV

or 66 kV, three-phase, effectively earthed transmission network of the
State Electricity Board, through single-phase transformers or Scott-
connected transformer installed at the TSS. The primary winding of the
single-phase transformer is connected to two phases of the transmission
network. Where Scott-connected transformer is used, the primary
windings are connected to the three phases of the transmission network.
The single-phase transformers at a TSS are connected to the same two
phases of the transmission network (referred as single-phase
connection), or alternatively to different pairs of phases- the three single-
phase transformers forming a delta-connection on the primary side. Out
of three single-phase transformers, one transformer feeds the overhead
equipment (OHE) on one side of the TSS, another feeds the OHE on the
other side of the TSS, and the third remains as standby. Thus the two
single-phase transformers which feed the OHE constitute an open-delta
connection (alternatively, referred as V-connection) on the three-phase
transformers network. The Scott-connected transformer and V-connected
single-phase transformers are effective in reducing voltage imbalance on
the transmission network. The spacing between adjacent substations is
normally between 70 and 100 km.

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4.1.4 One outer terminal of the secondary windings of the traction
transformer is connected to the catenary, and the other outer terminal is
connected to the feeder. The two inner terminals are connected to each
other, either directly or through series capacitors, and then solidly
earthed and connected to the traction rails.

4.1.5 Generally, the load current (current drawn by electric

locomotives) from the TSS flows through the catenary and returns to the
TSS through the feeder. For a train in an AT-cell (distance between two
consecutive ATs), most of the current is fed to the electric locomotive by
the ATs of that AT-cell; the current returns in the rails/earth and is
boosted up to the feeder through the neutral terminals of the
autotransformers.

4.1.6 Approximately midway between adjacent TSSs, a sectioning

and paralleling post (SP) is provided. In order to prevent wrong phase
coupling of power supply, a dead zone known as neutral section is
provided in the OHE opposite the TSS as well as SP. At the TSS, there
are two feeder circuit breakers for either side of the TSS for controlling
the power fed to the OHE, in a double track section. Out of the two
feeder circuit breakers for one side, one feeds the OHE of that side while
the other remains (open) as standby. There is also a paralleling
interruptor, which is normally closed, for either side of the TSS for
paralleling the OHE of the UP and DOWN tracks. For maintenance
work and keeping the voltage drop within limit, one or more
subsectioning and paralleling post (SSP) are provided between the TSS
and SP. In a double track section, as SSP has four sectioning interruptors
and one paralleling interruptor, whereas an SP has two bridging circuit
breakers (which remain open under normal feeding condition) and two
paralleling interruptors. In case of fault in the OHE, the feeder circuit
breaker of the TSS trips to isolate it.
4.1.7 Figures showing the principle of AT feeding system and
typical power supply diagram and sectioning of the OHE are at the
Appendix-1.
4.2 Protection System

4.2.1 The protection system of the traction transformer comprises the following:
1. Differential protection.
2. Instantaneous and IDMT over current, and earth fault protection
on the primary side.
3. Protection against phase-failure on the secondary side (i.e. to
detect malfunction of feeder/transformer circuit breaker).

4.2.2 The protection system for the OHE comprises the following:
1. Distance protection.
2. Delta-I type fault selective protection.
3. Instantaneous over current protection.
4. Under voltage protection to avoid wrong phase coupling.

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4.3 OHE- general data

4.3.1 The OHE consists of (i) a grooved copper contact wire of 107
mm2 section suspended directly from a stranded cadmium copper
catenary of 65 mm2 section by a number of vertical dropper wires,
usually at regular intervals (the contact wire and catenary together
generally being referred as 'catenary' or 'catenary wire'), and (ii) a feeder
wire of stranded all aluminium conductor (size 19/3.99 mm) of 240 mm2
section.

4.4 Traction transformer - general data

4.4.1 The transformer is either single-phase of 21.6 MVA (ONAN) rating, or

Scott-connected of 54 MVA (ONAN) rating, The percentage impedance
voltage of the transformer is 12% at the principal tapping.

4.5 Nature of Traction loads and faults on the OHE system

4.5.1 The traction load is a frequently and rapidly varying one between no-
load and over load. The TSS equipment is subject to frequent earth
faults/ short circuits caused by failure of insulation, snapping of OHE
touching the earth, wire dropped by bird connecting the OHE to earth/
over line structure, and miscreant activity. On an average the number of
faults/ short circuits per month is about 40 but in exceptional cases the
number could be as high as 120. The magnitude of the fault current may
vary between 40% and 100% of the dead short-circuit value. These
faults are cleared by the feeder circuit breaker on operation of the
distance, delta-I and instantaneous over current relays associated with
the concerned feeder circuit breaker.

4.5.2 The ac electric locomotives are fitted, for conversion of ac to dc, with
single-phase bridge-connected silicon rectifiers with smoothing reactor
for feeding the dc traction motors. The rectifiers introduce harmonic
currents in the 25 kV power supply system. On few of the electrified
sections, locomotives fitted with phase controlled asymmetrical thyristor
bridge, in place of silicon rectifiers are also in use; these introduce
further harmonics in the system. The typical percentages of harmonics
present in the traction current with electric locomotives are as follows:

Harmonics With diode With

rectifier thyristor
3rd (150 Hz) 15% 32%
5th (250 Hz) 6% 18%
7th (350 Hz) 4% 8%
9th (450 Hz) - 4%
11th (550 Hz) - 5%

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4.5.3 The average power-factor of electric locomotives and electric multiple
units generally varies between 0.7 and 0.8 lagging, without reactive
power compensation.

4.6 Short-circuit apparent power of the system

4.6.1 The Short-circuit apparent power at the transformer location for various
system voltages is as under:
Highest system voltage Short-circuit apparent
kV power, MVA
72.5 3,500
123 6,000
145 10,000
245 20,000

4.7 Auxiliary power supplies at TSS

4.7.1 The following auxiliary power supplies are available:

1. 110V dc from a battery.
2. 240 V ac, 50 Hz, single-phase from a 25/0.24 kV auxiliary
transformer.

4.7.2 Alarm/trip devices, relays and motor for the off-circuit tap-changer on
the traction power transformer shall operate off 110 V dc.

5. RATTING AND GENERAL DATA

5.1 The rating and general data of the transformer shall be as follows:
1. Type : ONAN cooled, Scott-connected (3 phase/2
phase), step down power transformer, double
limb wound, core-type for outdoor
installation.
2. Windings : Primary windings shall be T-connected for
three phase supply.

Secondary windings shall have two phases,

Main-phase (M-phase) and Teaser-phase (T-
phase), with a phase difference of 90 degree.
Each phase shall have two secondary
windings, each secondary winding having a
rated voltage of 27 kV and a rated current of
500 A.

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 The primary and secondary windings shall be
uniformly insulated.

The terminals of the secondary windings of

each of 'M' and 'T' phases shall be brought
out separately, for cascade connection
externally.

The winding shall be of concentric disc or

interleaved for primary, and disc or helical/
cylindrical for the secondary.
3. Rated frequency, Hz : 50 +/- 3%
4. Rated primary voltage : 220
Un, kV
5. Highest system voltage : 245
Um, kV
6. Rated secondary : Two sets of 2 x 27
voltage (at no-load),
kV
7. Rated power, MVA : 54 (Each secondary winding shall have a
rated power of 13.5 MVA)
8. Rated current at the
principal tapping:
1. Rated primary 141.7
current, A
2. Rated secondary 500 (for each secondary winding)
current, A
9. Percentage impedance The percentage impedance voltages, as
voltages at 13.5 MVA measured and calculated using the method
base at principal indicated in Annexure-1, shall be as under
tapping
%Zt = 12 +/- 1.2 %
%Zf = 12 +/- 1.2 %
%Zn = - 0.2 % to + 3.5 %
10. Non-cumulative over 1. 150 % rated load for 15 min
load capacity after the 2. 200 % rated load for 5 min
transformer has
reached steady
temperature on
continuous operation at
rated load (i.e. at rated
power)

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11. Polarity : Subtractive
12. Tappings (off-circuit) : Separate tapped winding on each
secondary winding to give rated
secondary voltage for variation in
primary voltage of +10% to -15 %, in
steps of 5% each.
13. Temperature rise : The temperature rise over an ambient
temperature of 500C both at rated and
overload conditions shall not exceed the
value indicated below:
1. Winding: 50 K at rated load, and 60
K for overloads as specified in Clause
5.1(10) (temperature measured by
resistance method).
2. Top oil: 40 K (temperature rise
measured by thermometer).
3. Current carrying parts in air: 40 K
(temperature rise measured by
thermometer).
14. Maximum permissible 40.0
losses at the principal
tapping:
1. No-load loss, kW
2. Load loss, kW 200.0
15. Ability to withstand :
short circuit:
1. Thermal ability 5 s
2. Dynamic ability : 0.5 s
16. Flux density at rated : Shall not exceed 1.55 tesla.
voltage and frequency
at principal tapping
17. Current density in the Shall preferable not exceed 2.5 A/mm2
windings at rated
current.
18. Acoustic sound level Not more than 75 dB at a distance of one
when energised at rated meter.
voltage and at no-load.

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19. Bushings:

Item Secondary Primary

1. Type OIP condenser OIP condenser
2. Highest voltage for equipment 52 245
Um, kV
3. Rated current, A 1250 800
4. Minimum creepage distance in 1300 6125
air, mm

20 Bushing type current

transformers for differential protection
of transformer :

Item Secondary Primary

1. Highest voltage for equipment 52 245
Um, kV
2. CT ratio 1000/5 300/5
3. Frequency, Hz 50 +/-3%
4. Class of accuracy as per IS PS
2705
(Part IV)
5. Minimum knee-point emf, V 150 125
6. Maximum excitation
current at knee- 0.25 0.75
point voltage, A
7. Maximum resistance
of the secondary
winding, ohm 0.5 0.25

6.0 SALIENT DESIGN FEATURES

6.1 Overall dimensions

6.1.1 The overall dimensions of the transformer shall be kept as low as

possible and in any case shall not exceed the values given below - refer the
sketch at Annexure-2:
1. Length x width : 14,000 x 6,500
(in mm)
2. Height of the topmost
point of primary : 7500 mm
bushing terminal
3. Height of the topmost
point of secondary
bushing terminal : 5500 mm

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6.2 Tank
6.2.1 The tank for the transformer shall be of bell type construction with
flanges on the outside, and shall have a flat top. The flanges of the upper
and lower tanks shall be jointed by bolts, nuts and washers. The winding
and core shall be fully exposed when the bell tank cover is lifted.

6.2.2 The tank shall be constructed from mild steel of a quality that allows
welding without any defect/flaw, with a single tier construction so
shaped as to reduce welding to the minimum. The welded joints shall be
made using the latest welding rigidity to permit hoisting of the
transformer filled with oil by crane. The tank body shall be designed to
withstand a vacuum of 760 mm of Hg.

6.2.3 The tank shall be fitted with four lifting pads at the lower end to enable
lifting of the transformer filled with oil by means of lifting jacks.

6.2.4 The tank shall be fitted with an under carriage and mounted on eight bi-
directional swivelling type flanged rollers for being rolled on 1676mm
(5' 6") gauge track on which it shall also rest in the final position-
reference the sketch at Annexure-2. The rollers shall be provided with
detachable type locking arrangement to enable their locking after
installing the transformer in the final position, to prevent any accidental
movement of the transformer.

6.2.5 There shall be at least five inspection covers of suitable size on the tank
to enable inspection of the lower portions of bushings. and the leads as
well as various connections of the motorised off- circuit tap-changer.

6.2.6 The rubberised cork gaskets used in the transformer shall conform to
IS:4253 (Part-II).

6.2.7 All valves used in the transformer shall conform to IS:3639 and shall be
of good quality and leak proof. The manufacturer shall ensure that
suitable anti-theft measures are provided on these valves so as to prevent
theft of oil during transit/service.

6.3 Marshalling box

6.3.1 A vermin proof, weatherproof and well ventilated marshalling box made
of sheet steel of thickness not less than 2mm, strengthened with adequate
stiffeners, shall be provided on the left hand side of the transformer
thank as viewed from, the secondary terminals side. It shall have a
hinged door with provision for padlocking- the door opening outward
horizontally.

6.3.2 The marshalling box shall have a sloping roof. The top of the
marshalling box shall be at a height of about 2 m from the rail level.

6.3.3 The marshalling box shall house the winding and oil temperature
indicators and terminal board. To prevent condensation of moisture in

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 the marshalling box metal clad space heater, controlled by an associated
thermostat and switch, shall also be provided, Cable glands shall be
provided for the incoming and outgoing cables.
6.3.4 The temperature indicators shall be so mounted that their dials are at a
height of not more than 1.6 m from the rail level. Transparent windows
of tough acrylic plastic or similar non-fragile transparent material shall
be provided on the marshalling box so as to enable reading of the
temperature indicators without opening the door of the marshalling box.

6.3.5 All cables from the bushing current transformers. Buchhlz relay,
magnetic oil level gauge, pressure relief device and temperature
indicators shall be run through suitable conduits/perforated covered
cable trays up to the marshalling box. The cables shall be of 1100 V
grade, PVC insulated, PVC sheathed, steel wire armoured, stranded
copper conductor conforming to IS:1554 (Part-I). The cable shall be
adequately insulated for heat from the tank surface and the sun.

6.3.6 All wiring in the marshalling box shall be clearly identified by

lettered/figured ferrules of the inter lock type, preferable of yellow
colour with black letters/figures. The ac and dc circuits shall be clearly
distinguished and well separated from each other.

6.3.7 Suitable legend and schematic diagram plates made of anodised

aluminium with black lettering and lines shall be fixed on the inside
surface of the marshalling box door.

6.4 Core

6.4.1 The core shall be built-up of high permeability cod rolled grain oriented
silicon steel laminations conforming to IS: 3024. The flux density in any
part of the core and yokes at the principal tapping with primary winding
excited at the rated primary voltages and frequency shall not exceed 1.55
T. The successful tenderer/ manufacturer shall furnish calculations to
prove that this value shall not be exceeded.

6.4.2 The lamination for the core shall be free from waves, deformations and
signs of rust. Both sides of the laminations shall be coated with suitable
insulation capable of withstanding stress relief annealing. In assembling
the core, air gaps shall be avoided. Necessary cooling ducts shall be
provided in the core and yoke for heat dissipation. The core-clamping
frame shall be provided with lifting eyes for the purpose of tanking and
untanking the core and winding of the transformer.

6.4.3 The core shall be electrically connected to the tank.

6.4.4 Yoke/core clamping bolts shall have adequate threaded length beyond
the face of the nuts for tightening at a later stage, if need arises. Each of
the core clamping bots and the core clamping frame work shall be
insulated from the core laminations and tested after completion of the

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 core assembly to ensure that they withstand a voltage of 2 kV r.m.s. with
respect to core for duration of 60 s.

6.4.5 The transformer is required to be continuously in service, preferable

without requiring any attention from the date of its energisation up to the
periodical overhaul (POH) which is generally done after 7 years of
service. The need, therefore, for tightening of core clamping bolts should
not normally arise before the POH of the transformer. The successful
tenderer/ manufacturer of the transformer shall take this aspect into
account during core assemble/manufacture.

6.5 Windings

6.5.1 The winding shall be of concentric disc or interleaved for the primary,
and disc or helical/cylindrical for the secondary windings. The primary
and secondary windings shall be uniformly insulated. All the four
terminals of the two secondary windings of each of 'M' and 'T' phases
shall be brought out separately through 52 kV OIP condenser bushings,
for cascade connection externally.

6.5.2 The windings shall be made of continuous electrolytic copper conductor,

paper insulated to class-A insulation. The conductor shall not have
sharp edges which may damage the insulation.

6.5.3 Normally, no joint shall be used in the winding conductor. If a joint

becomes inescapable, if shall be brazed with high silver alloy grade BA
Cu Ag6 conforming to IS:2927 or electrically butt-welded.

6.5.4 The ratio of width to thickness of copper conductor used for winding
shall be as small as possible but shall not exceed 5:1 so as to avoid
tilting of conductors when the windings are subjected to axial and radial
forces during short circuits.

6.5.5 Separate tapped winding shall be provided for each secondary winding
for connection of the motorised off-circuit tap-changer. The tapped
windings shall be distributed in multi sections in order to reduce the
imbalance in apmere turns to the minimum at any tap position.

6.5.6 The transformer windings shall be designed for the following rated
withstand voltages:

Item Secondary Primary

1. Highest voltage for 52 245
equipment Um, kV
2. Rated short duration
power frequency 95 395
withstand voltage, kV
3. Rated lightning
impluse withstand
voltage, kV peak 250 950

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6.5.7 The windings shall be so designed that the transfer of lightning and
switching surges from primary to secondary windings and vice=versa is
kept to the minimum level.

6.5.8 The windings shall be designed to withstand the magnetising inrush

currents due to repeated switching on off the transformer.
6.5.9 The axial pre-compression on the winding shall preferable be double the
calculated axial thrust that may be set up under dead short-circuit
condition so as the ensure that the winding do not become loose due to
frequent short circuits in service.
6.5.10 During short circuits, the stresses actually set up in conductors, spacers,
and blocks, clamping rings and such other parts of the transformer shall
not exceed one third of the maximum permissible values.
6.5.11 Pre-compressed spacers shall be used between disc shaped coils of the
windings to transmit the axial forces generated due to the short circuits.
6.5.12 Wood insulation, if used, on the core and winding shall be seasoned,
dried and well compressed and shall have adequate strength.
6.5.13 A uniform shrinkage shall be ensured during the drying of the individual
coils or assembly of coils by providing a uniform clamping force with
the help of hydraulic jacks or similar such devices.
6.5.14 In order to cater for shrinkages that may occur in service, substantial
clamping rings shall be provided at the tops of the windings, being
pressed down upon them by means of adjustable prasoure screws or oil
dash pots or any other suitable device, so as to maintain a constant
pressure and obviate the need for any retightening in between successive
periodical overhauls.
6.5.15 The coil and core assemble shall be retightened after oil impregnation.
The successful tenderer/ manufacturer shall ensure that there is no
further shrinkage of the coil assembly in any additional cycle after the
final curing.
6.5.16 The successful tenderer/ manufacturer shall furnish details of various
stages of drying of coils, coil assembly up to and including oil
impregnation and final tightening of the coil assembly. Values of
pressure, duration, temperature and degree of vacuum maintained at
various stages of drying shall also be indicated.
6.5.17 In order to keep unbalanced axial forces due to non-uniform
shrinkage/unequal height of the coils to the minimum, wedges of pre-
compressed wood or similar such material shall be used.
6.5.18 To prevent displacement of the radial spacers used in the windings,
closed slots shall be provided and a vertical locking strip shall be passed
through these slots.
6.5.19 The vertical locking strips and slots of the radial spacers shall be so
designed as to withstand the forces generated due to short circuits.

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6.5.20 The vertical locking strips and radial spacers shall be made of pre-
compressed pressboard conforming to grade PSP:3052 of DIN 7733.
6.5.21 To prevent end blocks from shifting, pre-compressed pressboard ring
shall be provided in between the two adjacent blocks. Coil clamping
rings made of densified wood or mild steel shall be located in position
with pressure screws.
6.5.22 Leads from the windings to the terminals, from the tap switch to the
tappings of the secondary windings and other interconnections shall be
properly supported and secured.
6.5.23 The following particulars/ documents in respect of the radial spacer
blocks (winding blocks), vertical locking strips (axial ribs), end blocks,
insulating cylinder, angle rings, paper insulation of the conductor and
coil clamping plates used in the manufacture of the conductor and coil
clamping plates used in the manufacture of the windings shall be
furnished.
1. Reference to specification and grade of material.
2. Source(s) of supply.
3. Test certificates.

7.0 INSULATING OIL

7.1 The transformer shall be supplied with new insulating oil conforming to
IS:335 In addition, 10 % extra oil, by volume, shall be supplied in non-
returnable steel drums. The characteristics of the insulating oil before
energisation of the new transformer and during its maintenance and
supervision in service shall conform to IS: 1866.

8.0 BUSHINGS AND TERMINAL CONNECTORS

8.1 Both the primary and secondary side bushings shall conform to IS:2099.
On the primary side, sealed draw lead type oil impregnated paper (OIP)
condenser bushings shall be used. On the secondary side, sealed solid
stem type OIP condenser bushings shall be used. The dimensions of the
bushings shall conform to IS:12676.
8.2 The bushings on the primary side shall be designed for a rated current of
800 A, whereas the bushings on te secondary side for a rated current of
1250 A. The temperature rise of any part of the bushing shall not exceed
40 K over an ambient temperature of 500C while carrying the rated
current continuously.
8.3 The procelain housing of bushing shall be of a single piece construction
i.e. there shall be no joint in the porcelain. The shed profile shall have a
lip at the extremities but free from ribs on the underside so as to avoid
accumulation of dust and pollutants and to permit easy cleaning.
8.4 The bushings shall have a non-breathing oil expansion chamber. The
expansion chamber shall be provided with an oil Level indicator, which
shall be so designed and dimensioned that oil level is clearly visible
from ground level.

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8.5 A test tap shall be provided for dielectric or power factor measurement.
8.6 The bushings shall be designed for the following insulation Level:
1. Highest voltage for equipment 52 245
Um, kV
2. Rated short duration wet power 95 460
frequency withstand voltage, kV
3. Rated Lightning impulse 250 1050
withstand voltage, kV peak

8.7 Adjustable arcing horns shall be provided on both the primary and
secondary bushings. The horn gap setting shall be variable as indicated
below:

1. Highest voltage for equipment 52 245

Um, kV
2. Horn gap setting variable 150 and 300 1200 and 1500
between, mm

8.8 The design and construction of the bushing shall be such that stresses due
to expansion and contraction in any part of the bushings shall not lead to its
deterioration/breakage.
8.9 The bushings shall be free from corona and shall not cause radio
interference.
8.10 The bushing terminals shall be provided with terminal connectors of
bimetallic type and conform to the following:

1. Primary side : Rigid type terminal connector to suit 28.62 mm

overall dia. ACSR conductor (Zebra), size 54/7/3.18
mm, based on the Research, Designs and Standards
Organisation (RDSO)'s standard drawing No.
ETI/PSI/P/11010.
2. Secondary side : Rigid type terminal connector to suit 23.25 mm
overall dia. all aluminium conductor (Butterfly), size
19/4.65 mm, shall be as per the firm's drawing
approved by RDSO.

8.10.1 The terminal connectors shall conform to IS:5561. The design shall be
such as to be connected to the equipment terminal stud with a minimum of
four 12 mm diameter bolts, nuts, spring and flat washers. The fasteners
shall conform to Clause 14.0 of this specification.

9.0 BUSHING TYPE CURRENT TRANSFORMERS

9.1 The 52 kV and 245 kV bushings shall be so arranged as to accommodate

bushing type current transformers (BCTs) for the biased differential
protection of the transformer. The BCTs shall conform to IS:2705 and meet
with the stipulations in Clause 5.1(20) of this specification

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9.2 The BCTs shall be so designed as to withstand thermal and mechanical
stresses resulting from frequent short circuits experienced by the
transformer on which these are fitted.
9.3 Apart from the BCTs required for the biased differential protection, BCT
of accuracy class 5 and conforming to IS:2705, with suitable tappings,
shall be mounted inside one bushing of the left-hand side (as viewed from
the secondary terminals side) secondary winding (which feeds the catenary
and would carry a higher current in service as compared to the other
secondary winding which feeds the feeder) of each of 'M' and 'T' phases for
use with the winding temperature indicators.
9.4 The BCTs and the bushings shall be so mounted that removal of a
bushing without disturbing the current transformers, terminals and
connections or pipe work is easy and convenient.
9.5 The leads from the BCTs shall be terminated in terminal boxes provided
on the bushing turrets. Suitable links shall be provided in the terminal
boxes for shorting the secondary terminals of the BCTs, when not
connected to the external measuring circuits.
9.6 The leads from the secondary winding of the BCTs terminated in the
terminal box on the bushing turret upto the marshalling box shall be of
1100 V grade, PVC insulated, PVC sheathed, steel wire armoured, stranded
copper cable of cross-section not less than 4 mm2 to IS:1554 (Part-I).
9.7 Cable glands of proper size shall be provided in the terminal boxes to
lead in/lead out the cables.

10.0 CLEARANCES
10.1 The relative orientation in space of the bushings fitted with terminal
connectors, the main tank, radiators, conservator, pressure relief device, oil
piping and other parts when mounted on the transformer shall be such that
the various clearances in air from bushing live parts shall not be less than
the appropriate values given hereunder:
1. Highest voltage for equipment 52 245
Um, kV
2. Minimum clearance, mm 500 1900

The same distance shall apply for clearances phase-to-earth (including oil
piping work, conservator, pressure relief device and such other parts),
phase-to-phase, and towards terminals of a lower voltage winding.

11.0 MOTORISED OFF-CIRCUIT TAP-CHANGER

11.1 The transformer shall be fitted with a motor operated off-circuit rotary
type tap-changer to cater for the voltage range specified in Clause 5.1(12)
of this specification. The motor drive unit shall be installed in a weather
and corrosion proof, adequately ventilated cubicle made of sheet steel not

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 less than 2 mm thick with adequate stiffeners to prevent deformation
during transit and handling. The cubicle shall have a sloping roof. The top
of the cubicle shall be at a height of about 1.5 m from the rail level. The
cubicle shall be so positioned that the hinge of the operating handle- for
manual operation - is at a height of about 1.1 m from the rail level.
11.2 To prevent condensation of moisture in the cubicle, metal clad space
heater, controlled by an associated thermostat and switch, shall be
provided.
11.3 All wiring in the cubicle shall be clearly identified by lettered/figured
ferrules of the interlock type, preferable of yellow colour with black
letters/figures. The ac and dc circuits shall be clearly distinguished and
well separated from each other.
11.4 Suitable legend and schematic diagram plates made of anodised
aluminium with black lettering and lines shall be fixed on the inside
surface of the cubicle door.
11.5 A tap position indicator shall be provided to indicate the tap position
which shall be clearly visible to an operator standing on the ground.
11.6 The tap-changer shall be of 52 kV voltage class with a continuous
current rating of 1250 A and a short-circuit current withstand capability of
12.5 kA r.m.s. for 5 s. The tap-changer motor shall be suitable for
operation off 110 V from a battery. The voltage at the battery terminals
may vary between 110% and 85% of the normal value. The voltage at the
tap-changer motor terminals is likely to be less than 85% of the normal
value of 110 V due to voltage drop in control cable.
11.7 Once the tap changing operation has been initiated, it must be completed
automatically (snap action) even if there is a failure of 110 V dc supply. In
case off-circuit tap-changer with snap action is not readily available, on-
load tap-changer (without the diverter and other such parts necessary for
the on-load tap changing), shall be provided so as to have the snap action.
11.8 The tap-changer shall be provided with suitable interlocking
arrangement to prevent its operation (including manual tap changing) when
either one or both circuit breakers on the primary as well as on the
secondary sides of the transformer is/are in closed condition.
11.9 The tap-changer and its control circuit shall be designed for operation
from the Remote Control Centre (RCC) by the Traction Power Controller
(TPC) as well as from the tap-changer cubicle. A local/remote switch as
well as necessary terminations for telesignals and telecommands from and
to the tap-changer-for-operation from the RCC-shall therefore be provided
in the tap-changer cubicle.

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12.0 COLLING EQUIPMENT
12.1 The transformer shall be designed for ONAN type of cooling.
12.2 The radiators shall consist of a pressed steel plate assembly formed into
elleptical oil channels as per IEEMA (Indian Electrical & Electronic
Manufacturers Association)'s standard) or a series of separate elliptical
tubes. The radiators shall be designed in such a manner that the
temperature-rise limits specified under Clause 5.1 (13) of this specification
are not exceeded.
12.3 The radiators shall be removable (after isolating the same from the main
tank) to facilitate transportation of the transformer. A drain plug of size 19
mm and an air-release plug of size 19 mm shall be provided at the bottom
and at the top of each radiator bank for draining and filling of oil
respectively. Each radiator bank shall also be provided with shut-off valves
of size 80 mm.
12.4 The radiators shall preferable be supported directly on the transformer
tank. Each radiator bank shall be fitted with lifting lugs.
13.0 PARTS, FITTINGS AND ACCESSORIES
13.1 Apart from the parts, fittings and accessories specifically detailed in the
foregoing Clauses, the parts, fittings and accessories detailed hereunder
shall be supplied with each transformer.
13.1.1 Conservator tank: It shall be of adequate capacity and complete with
supporting bracket or structure, oil filling cap and drain valve of size 25
mm. The cylindrical portion of the conservator tank shall be of single piece
construction without any gasketed joint.
13.1.2 Oil level gauge: It shall be of magnetic type having a dial diameter of
250 mm. The gauge shall have markings corresponding to minimum oil
level, maximum oil level and oil level corresponding to oil temperature of
300C, 450C and 850C. The oil level indicator shall be so designed and
mounted that the oil level is clearly visible to an operator standing on the
ground.
13.1.3 Silicagel breather: It shall be complete with oil seal and connecting
pipes. The connecting pipes shall be secured properly. The container of the
silicagel breather shall be of transparent flexiglass or similar material
suitable for outdoor application.
13.1.4 Pressure relief device: It shall operate to release internal pressure at
preset value without endangering the equipment or operator and shall be of
instantaneous reset type.

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13.1.5 Filter Valves: The bottom and upper filter valves shall be of 50 mm size
and suitably baffled to reduce aeration of oil. The valves shall be flanged to
seat 40 mm adopter threaded to thread size P 1-1/2 for connection for
conection to oil filtration plant.
13.1.6 Drain valve: It shall be of size 80 mm fitted with an oil sampling
device of size 15 mm.
13.1.7 Earthing terminals: Two earthing terminals shall be provided on the
tank for its earthing with the help of 3 mild steel flats, each of size 75 mm
x 8 mm. The terminals shall be clearly marked for earthing.
13.1.8 Buchholz relay: It shall be of double float type, with two shut-off valves
of 80 mm size, one between the conservator tank and the Buchholz relay
and the other between the transformer tank and the Buchholz relay. The
relay shall have one alarm contact and one trip contact, none of the
contacts being earthed. The contacts shall be of mercury-switch type,
electrically independent and wired up to the marshalling box. A testing
petcock shall be brought down through a pipe for the purpose of sampling
the gas, if any, collected in the Buchholz relay.
13.1.9 Oil temperature indicator (OTI): It shall have one alarm contact, one
trip contact and two normally open spare contacts none of the contacts
being earthed. The contacts shall be electrically independent.
13.1.10 Winding temperature indicator (WTI): Two WTIs shall be
provided, one for the M-phase and the other for the T-phase. Each WTI
shall have one alarm contact, one trip contact and two normally open spare
contacts, none of the contacts being earthed. The contacts shall be
electrically independent.
13.1.11 Thermometer pockets: A separate thermometer pocket with cap shall
be provided on the bell tank for measuring the top oil temperature in the
tank.
13.1.12 Rating plate: The rating plate shall indicate the ratings of the
transformer, the connection diagram of the windings, the particulars of the
bushing current transformers and other details as per IS:2026. The rating
plate shall be both in English and Hindi version.
13.2 All valves shall be of the double flange type and fitted with suitable
blanking plates on the outer face of the exposed flange.
13.3 The capillary tubes for temperature indicators shall be able to withstand
normal bending. They shall be supported properly without sharp or
repeated bends or twists.
13.4 The parts, fittings and accessories for the transformer shall be only of
those manufacturers approved by RDSO. If any item from fresh
manufacturers/sources are proposed to be used, it shall have to be type
tested in the presence of RDSO's representative and approval obtained
before obtaining the item for use.

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14.0 FASTENERS
14.1 All fasteners of 12 mm diameter and less exposed to atmosphere shall be of
stainless steel and those above 12 mm diameter shall preferable be of
stainless steel or of mild steel hot dip galvanised to 610 g/m2 of zinc. The
material of the stainless steel fasteners shall conform to IS: 1570 (Part-V),
Grade 04Cr17Ni 12Mo2.
15.0 PAINTING
15.1 Shot blasting/sand blasting shall be done on the transformer tank to remove
all scales, rust and other residue before applying the paint inside the tank.
All steel surfaces which are in contact with insulating oil shall be painted
with heat resistant oil-insoluble insulating varnish. All steel surface
exposed to weather shall be given, one primer coat of zinc chromate and
two coats of grey paint to shad No. 631 of IS:5 An additional coat of paint
shall be applied at site by the manufacturer.
16.0 TESTING OF TRANSFORMER
16.1 General

16.1.1 Once a purchase order is placed for supply of a transformer the designs
and drawings together with the Quality Assurance Plan (QAP) shall be
furnished to the purchaser/Director General (Traction Installation),
Research Designs and Standards Organisation (DG(TI), RDSO), Lucknow,
as the case may be, within the period stipulated in the order. Only after all
the designs and drawings as well as the QAP have been approved for
prototype tests and a written advice given to that effect, shall the successful
tenderer/manufacturer take up manufacture of the prototype of the
transformer. It is to be clearly understood that any change or modification
required by the above authorities to be done in the prototype shall be done
expeditiously, not withstanding approval having already been given for the
designs and drawings. Such change or modification shall be incorporated
in the drawings. Such change or modification shall be incorporated in the
drawings as indicated in Clause 17.4 of this specification.
16.1.2 Prior to giving a call to the Purchaser/ DG(TI), RDSO Lucknow, for
inspection and testing of the prototype, the successful tenderer/
manufacturer shall submit a detailed test schedule consisting of schematic
circuit diagrams for each of the tests and the number of days required to
complete all the tests at one stretch. Once the schedule is approved, the
tests shall invariably be done accordingly. However, during the process of
type testing or even later, the purchaser reserves the right to conduct any
additional test(s), besides those specified here in on any equipment/items
as to test the equipment/item to his satisfaction or for gaining additional
information and knowledge, In case any dispute or disagreement arises
between the successful tenderer/ manufacturer and representative of the
Purchaser/DG(TI), RDSO, Lucknow, during the process of testing as
regards the procedure for type tests and/or the interpretation and
acceptability of the results of type tests, it shall be brought to the notice of
the Purchaser/DG(TI), RDSO, Lucknow, as the case may be, whose
decision shall be final and binding. Only after the prototype transformer is

- 21 -
 completed and ready in each and every respect, shall the successful
tenderer/manufacturer give the actual call for the inspection and testing
with at least 15 days notice for the purpose.
16.1.3 The type tests shall be carried out on the prototype transformer at the
works of the successful tenderer/manufacturer or at a reputed testing
laboratory in the presence of the representative of the purchaser/DG(TI),
RDSO, Lucknow, in accordance with the relevant specifications and as
modified or amplified by this specification.
16.2 Tests during manufacture
16.2.1 Though the tests described below shall form part of the type tests, the
manufacturer shall carry out these tests on each and every unit during the
process of manufacture and submit the test reports to the Purchaser's
Inspector deputed for witnessing the routine tests:
1. Oil leakage test.
2. Vacuum test.
3. Pressure test.
4. Insulation test for core bolts.
5. Test for pressure relief device.
6. Measurement of capacitance and tan-delta values.

16.2.1.1 Oil leakage test: The transformer with its radiators, conservator tank
and other parts, fittings and accessories completely assembled shall be
tested for oil leakage by being filled with oil conforming to IS:335 at the
ambient temperature and subjected to a pressure corresponding to twice the
normal static oil head or to the normal static oil head plus 35 kN/m2 (0.35
kgf/cm2) whichever is lower, the static oil head being measured at the base
of the tank. This pressure shall be maintained for a period of not less than
12 h, during which time no leakage shall occur.
16.2.1.2 Vacuum test: The transformer tank only shall be tested at a vacuum
of 3.33 kN/m2(0.0333 kgf/cm2) for 60 min. The permanent deflection of
flat plates after release of vacuum shall not exceed the values specified
below:-

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 Horizontal length of flat plate Permanent deflection, mm
upto and including 750 mm 5.0
751 mm to 1250 mm 6.5
1251 mm to 1750 mm 8.0
1751 mm to 2000 mm 9.5
2001 mm to 2250 mm 11.0
2251 mm to 2500 mm 12.5
2501 mm to 3000 mm 16.0
above 3000 mm 19.0

16.2.1.3 Pressure test: Every transformer tank, radiator and conservator tank
shall be subjected to an air pressure corresponding to twice the normal
static head of oil or to the normal static oil head pressure plus 35 kN/m2
(0.35 kgf/cm2) whichever is lower, as measured at the base of the tank.
The pressure shall remain constant for 1 h to indicate that there is no
leakage.
16.2.1.4 Insulation test for core bolts: This test shall be done as described in
Clause 6.4.4 of this specification.
16.2.1.5 Test for pressure relief device: Every pressure relief device shall be
subjected to gradually increasing oil pressure. It shall operate before the
pressure reaches the test pressure specified in Clause 16.2.1.3 hereof and
the value at which it has operated shall be recorded.
16.2.1.6 Measurement of capacitance and tan-delta values: The
measurement of capacitance and tan-delta (dielectric loss factor ) of the
transformer windings shall be made by Schering bridge.
16.2.2 The Purchaser may, if he so desires, carry out any checks or tests on the
quality of manufacture at any stage during coil winding, drying of coils,
assembly of coils on core and method of drying, vacuum impregnation,
tightness of core clamping bolts, adequacy of pressure on coils or any other
aspects as deemed necessary so as to ensure that proper quality is
maintained.
16.3 Type Tests
16.3.1 The type tests shall be carried out on the prototype transformer at the
works of the successful tenderer/manufacturer or at any reputed laboratory
in the presence of the representative of the Purchaser/DG(TI), RDSO,
Lucknow, and in accordance with the relevant specifications and as altered,
amended or supplemented by this specification. The following shall
constitute the type tests:

1. Temperature-rise test.

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 2. Lightning impulse test.
3. Test with lightning impulse, chopped on the tail.
4. Short-circuit test.
5. Measurement of acoustic sound level.
6. Measurement of partial discharge quantity.
7. Measurement of harmonics of no-load current.
16.3.2 Temperature-rise test
16.3.2.1 The temperature-rise test shall be done with the tap-changer on the
lowest tap position (-15%) in accordance with IS:2026(Part II) except as
modified hereunder.
1. At rated load.
2. At 150% rated load for 15 min after continuous operation at rated load
for 1 h.
3. At 200% rated load for 5 min after continuous operation at rated load for
1 h.
The tests shall be done continuously without any power supply
interruption. In case interruptions of power supply do take place for some
reason, then the entire test shall be repeated after steady state conditions
are attained.
16.3.2.2 The points to be ensured during the temperature-rise test shall be:
1. The ambient temperature shall be measured using alcohol in glass
thermometers only.
2. The winding temperature shall be determined by the resistance method
only.
3. The temperature of the top oil shall be measured by an alcohol in glass
thermometer placed in an oil-filled thermometer pocket.
4. The average oil temperature shall be calculated as the difference
between the top oil temperature and half the temperature drop in the
cooling equipment (radiators).
5. The temperature of the hot-spot in the winding shall be the sum of the
temperature rise of the winding above the average oil temperature.

16.3.2.3 The test shall be carried out as described below:

16.3.2.3.1 100 % load
1. A quantum of power equal to the sum of the measured losses viz. no-
load and load losses measured at minus 15% tap position, corrected to
750C plus 10% of such sum shall be fed to the primary winding of the
transformer with the secondary windings short-circuited.
2. The power so fed to the transformer shall be continuously maintained till
such time as the steady state temperature is reached i.e. the top oil

- 24 -
 temperature rise does not vary by more than 10C during four consecutive
hourly readings.
3. On attaining the steady state temperature, the current in the primary
winding of the transformer shall be brought to the rated current which
shall be maintained for 1 h. At the end of the period the power supply to
the transformer shall be switched off and the time of switching off
recorded.
4. The measurement of hot resistance shall commence as soon as is
possible after switching off. The first reading of the resistance shall be
taken before the expiry of 90 s from the instant of switching off and the
first ten readings shall be taken at intervals of 15 s apart. Thereafter,
another ten readings shall be taken at intervals of 30 s apart.
5. The time at which each of the resistance values is read shall also be
recorded.
6. The temperatures of the ambient, top oil, the top and bottom radiator
header oils shall also be recorded at half-hourly intervals throughout the
test starting from the instant power supply is switched on to commence
the test till it is switched off.
7. The WTI and OTI readings shall also be recorded at half-hourly
intervals right from the instant the power supply is switched on to
commence the test till it is switched off.
8. After power supply is switched off, the readings of OTI and WTI shall
be recorded at intervals of 1 min apart for 30 min.

16.3.2.3.2 150 % load

1. After completion of the test at 100% load, the transformer shall be fed
with power which shall be a value so as to cause circulation of the rated
current in the primary winding with secondary windings short-circuited.
This current shall be circulated for 1 h.
2. The current shall thereafter be increased to 150% of the rated current and
maintained for a period of 15 min. At the end of the 15 min period, the
power supply shall be switched off and the time of switching off
recorded.
3. Thereafter the readings as indicted in Clauses 16.3.2.3.1(4) to (8) shall
be recorded.
4. The temperatures of ambient, top oil, the top and bottom radiator header
oils and the temperatures indicated by OTI and WTI shall also be
recorded at the time of switching off the power supply.

16.3.2.3.3 200% load

1. After completion of the test at 150% load, the transformer shall be fed
with power which shall be a value so as to cause circulation of the rated
current in the primary winding with secondary windings short-circuited.
This current shall be circulated for 1 h.

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 2. The current shall thereafter be increased to 200% of the rated current and
maintained for a period of 5 min. At the end of the 5 min period the
power supply shall be switched off and the time of switching off
recorded.
3. Thereafter the readings as indicated in Clauses 16.3.2.3.1(4) to (8) shall
be recorded.
4. The temperatures of ambient, top oil, top and bottom radiator header oils
and the temperatures indicated by OTI and WTI shall also be recorded at
the time of switching on 200% load as well as at the time of switching
off the power supply.
16.3.2.4 Determination of thermal time constant of the windings: The thermal
time constant of the primary and secondary windings. under both rated
load and over loads shall be verified during the temperature-rise tests.
16.3.2.5 The temperature rise of the oil, windings and current carrying parts
in air under both the overload conditions stipulated in Clauses 16.3.2.3.2
and 16.3.2.3.3 above shall not exceed the values stipulated in Clause
5.1(13) of this specification. The winding hot-spot temperature under the
overload conditions shall not exceed 1150C.
16.3.2.6 Testing and calibration of the temperature indicators: The
functioning of the OTI and WTI shall be verified during the tests
described above. Both the OTI and WTI shall be recalibrated, if
necessary, to reflect the respective temperatures correctly. In particular,
the reading of the WTI shall be the same as the calculated value of the
hot-spot temperature of the winding.
16.3.2.7 Determination of the thermal time constant of the WTI: the thermal
time constant of the WTI shall be determined for comparison with the
thermal time constant of the winding of the transformer with respect to
the transformer oil. For this purpose, the indications of the WTI and the
OTI shall be recorded every 1 or 2 min during the first 1 h from the
instant the transformer is loaded. From the slope of the curve plotted
with the time on the X-axis and the difference between the readings of
the WTI and OTI at the particular time on the Y-axis, the thermal time
constant of the WTI shall be determined. This value shall not vary
appreciably from the thermal time constant of the winding as calculated
theoretically and as ascertained from the slope of the cooling curves.
16.3.3 Lightning impulse test
16.3.3.1 This test shall be done in accordance with IS:2026 (Part III). Each of
the terminals of the primary and secondary windings shall be tested with
the following voltages:
1. Highest voltage for equipment Um, kV 52 245
2. Lightning impulse withstand voltage, kV 250 950
peak

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16.3.4 Test with lightning impulse, chopped on the tail
16.3.5.1 This test shall be done in accordance with IS:2026 (Part III) with the
appropriate test voltage as stipulated in clause 16.3.3.1 above.
16.3.5 Short-circuit test
16.3.5.1 The short-circuit test shall be conducted in accordance with IS:2026
(Part-I) with the following schedule:
16.3.5.2 Prior to commencement of the test, the following measurements/tests
shall be made:
1. Insulation resistance of the windings with respect to the earth and
between the windings.
2. No-load current.
3. No-load loss.
4. Resistance of windings.
5. Percentage impedance voltages.
6. Load loss.
7. Voltage ratio.
8. Di-electric tests comprising:
1) Separate-source voltage withstand test, and
2) Induced over voltage withstand test.
9. Recording if recurrent surge oscillogram (RSO) at the breakers on the
secondary side of the transformer after energizing the primary windings
at its rated voltage.
16.3.5.3 The test shall preferable be done by closing the breakers on the
secondary side of the transformer after energisig the primary windings at
its rated voltage.
16.3.5.4 The transformer shall be subjected to a total of seven shots in the
following sequence:
1st Shot - Asymmetrical and symmetrical currents in M-phase and T-
phase respectively at the highest tap (+10%)
2nd Shot - Symmetrical and asymmetrical currents in M-phase and T-
phase respectively at the highest tap (+10%)
3rd Shot - Asymmetrical and symmetrical currents in M-phase and T-
phase respectively at the principal tap.
4th Shot - Symmetrical and asymmetrical currents in M-phase and T-
phase respectively at the principal tap.
5th Shot - Asymmetrical and symmetrical currents in M-phase and T-
phase respectively at the lowest tap (-15%).
6th Shot - Symmetrical and asymmetrical currents in M-phase and T-
phase respectively at the lowest tap (-15%).

- 27 -
7th Shot - Symmetrical currents in M-phase and T-phase at the lowest
tap (-15%).

16.3.5.5 The duration of each shot shall be 0.5 s.

16.3.5.6 Measurements shall be done after each shot for the following:
1. Percentage impedance voltages.
2. No-load current.
3. No-load loss.
16.3.5.7 Further testing and inspection of the transformer subjected to the short-
circuit test shall be carried out as per IS:2026 (Part-I) with the
modification that:
1. The dielectric routine tests shall be at 100% of the original test value.
2. The percentage impedance voltages measured after the short-circuit test
shall not vary by more than 2% from those measured before the short-
circuit test.
16.3.5.8 On completion of the short-circuit test the transformer shall be
untanked for inspection of the core and windings. In case the inspection
of the core and windings do not reveal any apparent defects and the
results of the short-circuit test, the values of percentage impedance
voltages as also the results of the routine tests done after the short-circuit
test are in order, the transformer shall be deemed to have passed the
short-circuit test. If any of the results of the tests are not in order or the
inspection of core and windings reveals any defect, then the transformer
shall necessarily have to be dismantled completely for detailed
inspection.
16.3.6 Measurement of acoustic sound level
16.3.6.1 Measurement of acoustic sound level of the transformer energised at
rated voltage and frequency shall be carried out either as per Indian
Electrical & Electronics Manufacturers Association (IEEMA) or as per
National Electrical Manufactures Association (NEMA) procedure.
16.3.7 Measurement of Partial discharge quantity
16.3.7.1 Partial discharge quantity of the windings shall be measured in
accordance with IS:6209 and IS:2026(Part-III).
16.3.8 Measurement of harmonics of no-load current
16.3.8.1 The magnitude of harmonics of no-load current, as expressed in
percentage of the fundamental, shall be measured by means of a
harmonic analyser, in accordance with IS:2026(Part-I).

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16.4 Type tests on parts, fittings and accessories
16.4.1 Motorised off-circuit tap-changer
16.4.1.1 Though there is no Indian Standard Specification at present for
motorised off-circuit tap-changer, the following tests shall be carried out
thereon in accordance with IS:8468.
16.4.1.2 Test for temperature rise of contacts: The test shall be carried out at
rated current of 1250 A. The temperature rise shall not exceed the limit
specified in IS:8468.
16.4.1.3 Mechanical endurance test: With the tap-changer in oil, 100
operations shall be done manually and 10,000 operations shall be done
with the motor drive unit. An operation shall comprise moving the tap-
changer from one tap position to the next higher or lower tap position. All
the taps of the tap-changer i.e. +10% position tap to the -15% position tap
shall be covered during the test. While testing with the motor drive unit
the d.c. voltage for the motor drive unit shall be adjusted to the value
indicated below, and the number of operations at each value of voltage
shall be as indicated against each.
1. At the minimum voltage of 93.5 V dc 2,500 operations
2. At the maximum voltage of 121 V dc 2,500 operations
3. At the rated voltage of 110 V dc 5,000 operations
16.4.1.4 Milli-volt drop test: The test shall be done both before and after the
mechanical endurance test to assess the condition of the contacts. The
variation in the milli-volt drop values shall be not more than 20%.
16.4.1.5 Short-circuit current test: The test shall be done in accordance with
IS:8468 with short-circuit currents of 12.5 kA r.m.s., each of 5 s duration.
16.4.1.6 Dielectric tests: The tests shall be done in accordance with IS:8468.
16.4.1.7 Auxiliary circuits insulation tests: Auxiliary circuits including the
motor and other auxiliary equipment shall be tested in accordance with
IS:8468.
16.4.2 Condenser bushings
16.4.2.1 The type tests shall be carried out in accordance with IS:5621 on
porcelain housing of the condenser bushings. The following shall
constitute the type tests:
1. Visual inspection.
2. Verification of dimensions.
3. Electrical routine test.
4. Porosity test.
5. Temperature cycle test.
6. Bending test.

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16.4.2.2 The type tests shall be carried out in accordance with IS:2099 on the
prototype of the condenser bushings. The following shall constitute the
type tests:
1. Wet power frequency withstand voltage test.
2. Dry lightning impulse voltage withstand test.
3. Thermal stability test.
4. Temperature-rise test.
5. Thermal short time current withstand test.
6. Dynamic current withstand test.
7. Cantilever load withstand test.
8. Tightness test.
9. Test of tap insulation.
10. Tightness test at flange or other fixing device.
11. Measurement of partial discharge quantity.
16.4.3 Bushing type current transformers
16.4.3.1 The bushing type current transformers shall be tested in accordance
with IS:2705(Part-I & IV).
16.4.4 Buchholz relay
16.4.4.1 The Buchholz relay shall be tested in accordance with IS:3637.
16.4.5 Terminal connectors
16.4.5.1 The terminal connectors shall be tested in accordance with IS:5561.
16.4.6 Temperature indicators
16.4.6.1 The following tests shall be conducted on prototypes of OTI and WTI:
1. Accuracy with reference to a standard instrument.
2. Calibration of the indictors to reflect the actual temperature of the
oil/winding.
3. Dielectric test at 2.5 kV for 60 s.
4. Vibration test.
5. Dust and water splash test to IP 55 degree of protection.
16.4.7 Pressure relief device
16.4.7.1 The following tests shall be conducted on the prototype of pressure
relief device:
1. Air pressure test.
2. Leakage test.
3. Contact rating and operation test.
4. Dielectric test on contacts at 2.5 kV for 60 s.

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16.4.8 Radiators
16.4.8.1 The radiators shall be tested for air leakage at a pressure of 2.5 kg/cm2.
The pressure shall remain constant for 1 h to indicate that there is no
leakage.
16.5 Insulating oil
16.5.1 The following tests shall be carried out in accordance with IS:335 on the
sample of new insulating oil for use in the prototype transformer:
1. Density at 270C.
2. Kinetic viscosity at 270C.
3. Interfacial tension at 270C.
4. Flash point.
5. Neutralisation value (acidity).
6. Electric strength (with 2.5 mm gap).
7. Dielectric dissipation factor (tan-delta).
8. Specific resistance at 270C and at 900C.
9. Oxidation stability.
10. Water content.
16.6 Routine tests
16.6.1 The following routine tests shall be performed on each transformer
including the prototype unit in accordance with IS:2026:
1. Visual examination.
2. Insulation resistance test.
3. Measurement of no-load current.
4. Measurement of no-load loss.
5. Measurement of resistance of the windings.
6. Measurement of percentage impedance voltages.
7. Measurement of load loss.
8. Polarity test.
9. Voltage ratio test.
10. Dielectric test comprising:
1) Separate-source voltage withstand test, and
2) Induced over voltage withstand test.

11. Recording of recurrent surge oscillorgam (RSO).

12. Tests on motorised off-circuit tap-changer.
16.6.2 Visual examination: A general examination shall be made to check that
the transformer conforms to the approved drawings, various items are
accessible for maintenance, the quality of workmanship and finish are of
acceptable standards and all parts, fittings and accessories are provided.
16.6.3 Insulation resistance test: The insulation resistance of the windings with
respect to the earth and between the windings shall be measured using a
5 kV megger.

- 31 -
16.6.4 Measurement of no-load current: Measurement of no-load current
referred to the primary side shall be done at:
1. 90%, 100% and 110% of the rated voltage at the principal tapping, and
2. the appropriate tap voltage at the +10% and -15% tap positions.
16.6.5 Measurement of no-load loss: Measurement of no-load loss referred to
the primary side shall be done at:
1. 90%, 100% and 110% of the rated voltage at the principal tapping, and
2. the appropriate tap voltage at the +10% and -15% tap positions.

16.6.6 Measurement of resistance of windings: The resistance of the

windings shall be measured at all tappings and computed at 750C.
16.6.7 Measurement of percentage impedance voltages: The percentage
impedance voltages at principal, +10% tap and -15% tap positions shall
be measured at rated current and at ambient temperature and computed
at 750C. The measuring and calculation methods shall be as indicated in
Annexure-1.
16.6.8 Measurement of load loss: Load losses at rated current shall be
measured at principal, +10% and -15% tap positions at ambient
temperature and computed at 750C.
16.6.9 Polarity test: The polarity (subtractive) and marking of the terminals for
the polarity shall be verified.
16.6.10Voltage ratio test: Voltage ratio shall be measured at all tap positions.
16.6.11Dielectric tests
16.6.11.1 Induced over voltage withstand test: The test shall be done by
applying the test voltage across the entire secondary winding as per
IS:2026 (Part-III).
16.6.11.2 Separate-source voltage withstand test: The test voltage to be applied
shall be as under:
1. Highest voltage for equipment 52 245
Um, kV
2. Rated short duration power 95 395
frequency withstand voltage, kV

- 32 -
16.6.12 Recording of recurrent surge oscillogram (RSO): The oscillorgams
shall be taken at the +10%, -15% and principal tappings.
16.6.13 Tests on motorised off-circuit tap-changer: The tests shall be conducted
in accordance with IS:8468.
16.6.14 During the routine tests on any unit if it is found that the sum of the
measured losses (i.e. no-load and load losses) measured at -15% tap
position (corrected to 750C) exceeds the value defined in Clause
16.3.2.3.1(1), or if the no-load loss/ load loss at the principal tapping
exceeds the maximum guaranteed figures, then the transformer shall be
rejected.
16.7 IF the prototype of a transformer conforming to this specification has
already been approved in connection with previous supplies to Indian
Railways, fresh type testing may be waived at the discreation of the
Purchaser, provided that no changes whatsoever in the design or material
(s) used or the process of manufacture have been made. However, the
Purchaser reserves the right to conduct type tests if he gained from
previous supplies.
16.8 Only after approval of the original tracings of drawings incorporating
changes, if any, as a result of the prototype tests and clear written
approval of the results of the tests on the prototype is communicated by
the Purchaser/DG(TI), RDSO, Lucknow, to the successful tenderer/
manufacturer, shall he taken up bulk manufacture of the transformer-
which shall be strictly with the same materials and process of
manufacture as adopted for the prototype. In no circumstances shall
materials other than those approved in the design/drawings and/or during
the prototype testing be used for bulk manufacture on the plea that they
had been obtained prior to the approval of the prototype.
16.9 The tenderer may quote separately his charges for short-circuit and
temperature-rise tests. No charges shall be payable for any other type
and routine tests.
17.0 TECHNICAL DATA AND DRAWINGS
17.1 The tenderer shall furnish along with his offer, in the proforma at
Annexure-3, the Schedule of Guaranteed Performance, Technical and
Other Particulars (SOGP) for the transformer. The particulars shall be
complete in all respects. If there is any entry like "shall be furnished
later" or a blank is left against any item, the offer is not likely to be
considered as the evaluation of the offer is rendered difficult and cannot
be compared with other offers, if any.
17.2 The tenderer shall specifically indicate in a "Statement of Compliance"
attached with the offer his compliance with each and every Clause of
this specification. In case to tenderer wishes to deviate from any Clause
of this specification, he may do so giving reference to the Clause(s) with
the reasons/justification for the deviation. This shall be in the form of a
separate statement called the "Statement of Deviations". If there is no
deviation at all, specific "NIL" "Statement of Deviations" shall be
attached with the offer. If the "Statement of Compliance" and Statement
of Deviations" are not attached with the offer, it is not likely to be

- 33 -
 considered for the reason that it is an incomplete offer which cannot be
properly evaluated and compared with other offers, if any.
17.3 The tenderer shall furnish the following information along with his offer:-
17.3.1 Calculations for:
1. Temperature rise of winding at rated current.
2. Hot-spot temperature of the winding at 150% and 200% rated loads for
15 min and 5 min respectively.
3. Thermal withstand capacity of the windings for a short circuit of 5 s
duration.
4. Mechanical forces in respect of the following as per IEEMA (Indian
Electrical & Electronic Manufacturer's Association) formulae given in
Annexure-4:
1) Asymmetrical short-circuit current
2) Hoop stress in primary and secondary windings.
3) Compressive pressure in the radial spacers.
4) Internal axial compressive force.
5) Axial imbalance force.
6) Radial bursting force.
7) Resistance to collapse.
8) Bending stress on clamping ring and densified wood.
9) Maximum allowable torque on pressure screws for coil clamping
bolts at the time of tightening, if any.
5. Flux density with the characteristic curve.
6. Maximum value of inrush current.
17.3.2 Drawings for:
1. Outline general arrangement drawing giving complete details of the
transformer.
2. Arrangement of the core, windings and magnetic path.
3. Magnetizing characteristic of CRGO sheet steel.
4. Drawing showing elevation of the core and winding and other insulation
materials.
5. A sectional view showing the position of core, cylinders, winding
blocks, vertical ribs and other insulating materials.
6. Details of coil claming arrangement.
7. General arrangement of the off-circuit tap-changer.

17.4 The successful tenderer/manufacturer shall submit to DG(TI), RDSO,

Lucknow for approval the following detailed dimensioned drawings as

- 34 -
 per Indian Railways standard in sizes of 210 mm x 297 mm or any
integral multiples thereof:-
1. Outline general arrangement of the transformer indicating plan, front
elevation, side elevation with all parts, fittings and accessories, electrical
clearances as well as salient guaranteed particulars.
2. Internal arrangement of the transformer indicating primary and
secondary bushing lead connections, core to core-clamp earthing, core-
clamp to tank earthing, core-clamp to core-base bolting, and the locking
arrangement of the core & coil assembly with the tank.
3. Cross sectional view of the core and windings with material
specifications and makes.
4. Details of the pressure screws/ oil dash-pot/ coil clamping bolts or other
devices and their location with materials specifications and makes.
5. Schematic view of the valves used on the transformer and the antitheft
device so as to prevent theft of oil.
6. Transport outline dimensional diagram.
7. General arrangement of the off-circuit tap-changer assembly with salient
technical parameters.
8. Tap-changer cubicle layout.
9. Schematic diagram for driving of motorised off-circuit tap-changer from
remote control centre by telecommand and corresponding telesignalling.
10. Name and rating plate of motorised off-circuit tap-changer.
11. General arrangement of marshalling box indicating protection and
control equipment.
12. Wiring diagram of marshalling box.
13. Schematic diagram of protection and control circuits in marshalling box
with cable schedule.
14. Legend plate showing protection and control circuits for fitment in the
marshalling box.
15. OIP condenser bushing for primary side including cross sectional view,
shed profile and salient electrical and mechanical characteristics.
16. OIP condenser bushing for secondary side including cross sectional
view, shed proview and salient electrical and mechanical characteristics.
17. Dimensional drawing, V-I characteristic and rating plate for bushing
type current transformers.
18. Rigid type terminal connector for primary side bushing terminal.
19. Rigid type terminal connector for secondary side bushing terminal.
20. Rating plate with diagram of connections, both in English and Hindi
versions.
21. Details of radiators.
22. Details of breather.
23. External cable run with cable schedule.
24. Any other drawings considered necessary by the successful tenderer/
manufacturer and/ or Purchaser.

17.4.1 The format of the title sheet to be adopted for preparation of the
drawings is attached at Appendix-2

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17.4.2 After approval, six copies of each of the approved drawings along with
two sets of reproducible prints for each drawing shall be supplied to each
consignee (s). Besides, two copies of drawings along with one set of
reproducible prints shall be supplied to DG(TI), RDSO, Lucknow.
17.4.3 Two copies of the "Operation/ Maintenance Manual" for each
transformer shall be supplied to the consignee(s). Two copies of the
manual shall be supplied to the DG(TI), RDSO, Lucknow.

18.0 CAPITALISATION OF TRANSFORMER LOSSES

18.1 The capitalised value of transformer losses shall be as low as possible,
and commensurate with optimum no-load and load losses. The
capitalised value shall be computed as detailed at Annexure-5 and
furnished with the offer.
19.0 SPARES
19.1 The tenderer shall quote separately for the following essential spares for
every lot of up to 5 transformers or part thereof:
1. One set of primary coil, secondary coil and tapping coil.
2. One primary bushing complete with parts, fittings and bushing type
current transformer.
3. One secondary bushing complete with parts, fittings and bushing type
current transformer.
4. One complete set of gaskets of all sizes required for use in the
transformer.
5. One breather unit with silicagel.
6. One set of radiator banks.
7. One Buchholz relay.
8. One complete off-circuit tap-changer.
9. One each of terminal connectors for primary and secondary side bushing
terminals.
10. One set of valves.
11. One pressure relief device.
19.2 A separate quotation shall be furnished for any other spares that the
manufacturer considers as necessary for maintenance of the transformer.
20.0 ERECTION, TESTING AND COMMISSIONING
20.1 The transformer shall be erected and commissioned by the Purchaser. The
successful tenderer/manufacturer shall invariably make available at site the
services of an engineer of his to ensure, by his continued presence, that the
process of erection, testing and commissioning of the transformer is in
accordance with established practices. For this purpose prior intimation
regarding the dates/period and locations at which the transformers are to be
erected and testing/commissioning done shall be given by the Purchaser to

- 36 -
 the successful tenderer/ manufacturer. No charges shall be payable by the
purchaser to the successful tenderer/manufacturer for the services of his
engineer in this regard.
20.2 If any transformer has been received at site in a damaged condition and in
the opinion of the Railway's engineer at site it is required to be repaired at
the successful tenderer/ manufacturer's works, the transformer shall be
taken back to the works promptly and after repairs, all necessary tests
including the routine tests shall be done on the complete transformer in the
presence of and to the satisfaction of the Railway's Engineer prior to
returning the transformer to site. Such tests are necessary to ensure that the
quality of the workmanship during repairs is satisfactory and shall be done
free of cost. Any tests, as decided by the Railway's engineer at site shall
also be conducted on the transformer at site free of cost.
21.0 TRAINING OF INDIAN RAILWAY'S ENGINEERS
21.1 The offer shall include the training of two Engineers of the Indian
Railways free of cost at the manufacturer's works and at the maintenance
depots/workshops on a railway system or other public utility where
transformers of similar design are in operation. The total duration of
training for each Engineer shall be 12 weeks of which approximately 6
weeks shall be at the manufacturer's works and 6 weeks on a railway
system or other public utility. The cost of travel to the place of manufacture
and back shall be borne by the Indian Railways. Other details shall be
settled at the time of finalizing the contract or Purchaser order.
22.0 AFTER SALES SERVICE
22.1 The successful tenderer/ manufacturer shall make necessary arrangements
for closely monitoring the performance of the transformer(s) through
periodical (preferable once in two months during the warranty period)
visits to the locations where they have been erected for observations and
interaction with the operating and maintenance personnel of the Indian
Railways. Arrangements shall also be made by the successful tenderer/
manufacturer for emergency/standby spare parts being kept readily
available to meet exigencies warranting replacement so as to keep the
transformers in service with least down time.
22.2 The successful tenderer/ manufacturer shall respond promptly and in a
workman-like manner to any call given by Indian Railways for any
assistance by way of attending to failures, investigation into the causes of
failures including tests, if any, to be done and such other items with a view
to seeing that the transformer serves the purpose for which it is intended.
Besides technical guidance to ensure proper operation and maintenance of
the traction transformer shall be constantly rendered.

- 37 -
23.0 WARRANTY
23.1 The successful tenderer/ manufacturer shall warrant that all equipment
shall be free from defects and faults in design, material, workmanship and
manufacture and of the highest grade consistent with the established and
generally accepted standards for the equipment of the type ordered and in
full conformity with the specifications and shall operate properly.
23.2 This warranty shall survive inspection of, payment for and acceptance of
the equipment, but shall expire 24 (Twenty Four) months after the delivery
at ultimate destination in India, or 18(Eighteen) months from the date of
commissioning and proving test of the equipment at ultimate destination in
India, whichever period expires earlier, except in respect of complaints,
defects and/or claims notified to the successful tenderer/ manufacturer
within 3 (Three) months of the expiry of such date. Any approval or
acceptance by the Purchaser of the equipment shall not in any way limit the
successful tenderer/ manufacturer's liability.
23.3 The successful tender/ manufacturer's liability in respect of any complaint,
defects and/or claims shall be limited to the furnishing and installation of
replacement parts free of any charge or the repair of defective parts only to
the extent that such replacement or repairs are attributable to or arise from
faulty workmanship or material or design in the manufacture of the goods,
provided that the defects are brought to the notice of the successful
tenderer/ manufacturer within 3(Three) months of their being first
discovered during the warranty period or 3 (Three) months from the date of
expiry of warranty period, or at the option of the Purchaser, to the payment
of the value, expenditure and damage as hereafter mentioned.
23.4 The successful tenderer/ manufacturer shall, if required, replace or repair
the equipment or such portion thereof as is rejected by the Purchaser free
of cost at the ultimate destination or at the option of the Purchaser, the
successful tenderer/ manufacturer shall pay to the Purchaser value thereof
at the contract price or in the absence of such price at a price decided by
the Purchaser and such other expenditure and damages as may arise by
reason of the breach of the conditions herein specified.
23.5 All replacements and repairs that the Purchaser shall call upon the
successful tenderer/ manufacturer to deliver or perform under this
Warranty shall be delivered and performed by the successful tenderer/
manufacturer promptly and satisfactorily and in any case within 2 (Two)
months of the date of advice to this effect.
23.6 If the successful tenderer/ manufacturer so desires, the parts that are
removed may be taken over by him or his representative for disposal as he
deems fit at the time of replacement with good parts. No claim whatsoever
shall lie on the Purchaser thereafter for the parts so removed.

- 38 -
23.7 The Warranty herein contained shall not apply to any material which shall
have been repaired or altered by the Purchaser or on his behalf in any way
without the consent of the successful tenderer/ manufacturer, so as to affect
the strength, performance or reliability or to any defects to any part due to
misuse, negligence or accident.
23.8 the decision of the Purchaser in regard to successful tenderer/
manufacturer's liability and the amount, if any, payable under this warranty
shall be final and conclusive.
24.0 SHIPMENT OF THE TRANSFORMER
24.1 The transformer shall be transported depending upon the transport
facilities available for the route i.e. by rail or truck or ship.
24.2 The transformer shall be dispatched with its core and windings along with
the tap-changer assembly in the transformer tank filled with oil and the
space above the oil filled with pure dry air or inert gas like nitrogen at a
pressure slightly above atmospheric pressure. However, if there are
limitations on account of weight, the tank shall be filled with nitrogen
under pressure and the oil for the first filling shall be supplied separately in
steel drums. In case the tank is filled with inert gas the temperature and
pressure at the time of filling shall be marked conspicuously on the
transformer.
24.3 All openings created on the tank by removal of any items shall be closed
with suitable blanking plates. All the parts, fitting and accessories such as
conservator tank, bushings, silicagel breather, radiator, Buchholz relay,
temperature indicators and other items shall be packed/crated separately
along with a packing list in each crate containing the following particulars:

Crate No. Description of Approx. gross weight Approx. outside

item/component in the in kg dimensions in mm
crate

24.4 The packing shall be done properly so that no damage occurs during
transit.
24.5 All the parts, fittings and accessories for each transformer shall be so
dispatched that they arrive at site together to enable erection of the
complete transformer without delay.
24.6 Necessary instructions for handling and storage of all items shall be
included along with the packing lists.
24.7 In case of overseas supply, packing shall be sea worthy.

*******************

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 ANNEXURE-'3'
(For Specification No. ETI/PSI/124(07/95)
SCHEDULE OF GUARANTEED PERFORMANCE, TECHNICAL AND
OTHER PARTICULARS (GUARANTEED PARTICULARS ARE TO BE
ESTABLISHED BY ACTUAL TESTS/ TEST REPORTS)
Sl. DESCRIPTION UNIT OF VALUE/
No. MEASUREMENT INFORMATION
1 2 3 4
A RATINGS/PARTICULARS
1. Name of the Manufacturer
2. Country of manufacture
3. Reference to specification based on
which performance data is prescribed
4. Rated power MVA
5. Primary current at:
a) Rated load A
b) 150% rated load for 15 min A
c) 200% rated load for 5 min A
6. Secondary current at:
a) Rated load A
b) 150% rated load for 15 min A
c) 200% rated load for 5 min A
7. Rated voltage :
a) Primary kV
b) Secondary (at no-load) kV
8. Rated frequency Hz
9. Temperature rise above ambient
temperature of 500C :
(i). Oil :
0
a) At rated load C
0
b) At 150% rated load for 15 min C
0
c) At 200% rated load for 5 min C

- 40 -
 (ii) Winding :
0
a) At rated load C
0
b) At 150% rated load for 15 min. C
0
c) At 200% rated load for 5 min C
10. Hot-spot temperature of winding
over ambient temperature of 500C
0
a) At rated load C
0
b) At 150% rated load for 15 min. C
0
c) At 200% rated load for 5 min C
11. Interval of time between two
successive overloads after
continuous working at full load,
at maximum ambient temperature
of 500C:
a) Between two consecutive over min
loads of 50% for 15 min.
b) Between two consecutive min
overloads of which one is of 50%
for 15 min and the other of 100%
for 5 min.
12. No-load current referred to
primary side at rated frequency
and at:
a) 90% rated voltage A
b) Rated voltage A
c) 110% rated voltage A
13. Power factor of no-load current at
rated voltage and rated frequency
14. Value of the inrush current at A
rated voltage on primary side, the
secondary side being open
circuited
15. Losses:
(i). No-load loss at rated
frequency and at:
a) 90% rated voltage at the kW
principal tapping.
b) rated voltage at the kW
principal tapping.
c) 110% rated voltage at the kW
primary tapping.

- 41 -
 d) Appropriate voltage at the - kW
15% tapping.
e) Appropriate voltage at the kW
+10% tapping/
(ii) Load loss (at 750C) at rated kW
current and frequency
a) Principal tapping kW
b) -15% tapping kW
c) +10% tapping kW
(iii) Total losses at rated
current and frequency
a) Principal tapping kW
b) -15% tapping kW
c) +10% tapping kW
16. Resistance voltage (at 750C) at %
rated current
17. Reactance voltage (at 750C) at %
rated current and frequency
18. Impedance voltage (at 750C) at %
rated current and frequency
19. Resistance (at 750C) of ohm
primary winding
20. Resistance (at 750C) of ohm
secondary winding
21. Reactance of winding : H
i) Primary H
II) Secondary at
a). Principal tapping H
b). +10% tapping H
c). -15% tapping H
0
22. Regulation (at 75 C) with
rated current and at power
factor of:
a) Unity %
b) 0.8 lagging %

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23. Efficiencies:
(i). Efficiency (at 750C) at unity
power factor at:
a). 100% load %
b). 75% load %
c). 50% load %
d). 25% load %
0
(ii). Efficiency (at 75 C) at 0.8 power
factor lagging at:
a). 100% load %
b). 75% load %
c). 50% load %
d). 25% load %
(iii). Percentage of rated load at which %
maximum efficiency occurs.
24. Ability to withstand short-circuit:
a). Thermal s
b). Dynamic s
25. Thermal time constant (calculated):
(i). for winding with respect to oil at:
a). rated current min
b). 150% rated current min
c). 200% rated current min
(ii). Complete transformer at rated min
current
26. Temperature gradient between oil and
winding at:
0
a). Rated current C
0
b). 150% rated current for 15 min C
c). 200% rated current for 5 min.
0
C
27. Temperature rise of oil:
(i). Calculated average temperature
rise of oil at:
0
a). Rated current C
0
b). 150% rated current for 15 min C

- 43 -
 0
c). 200% rated current for 5 min C
(ii) Estimated temperature rise of top
oil at:
0
a). Rated current C
0
b). 150% rated current for 15 min C
0
c). 200% rated current for 5 min C
28. Details of core:
(i) Type of core
(ii) Flux density at rated voltage tesla
and frequency
(iii) Flux density at 110% rated tesla
voltage and frequency
mm
(iv) Thickness of steel stampings
(v) Grade of core material and
conforming specification
(vi) Exciting VA/kg for core
stampings at:
a) Flux density of 1.55 tesla VA/kg
b) Flux density at rated voltage VA/kg
c) Flux density at 110% rated VA/kg
voltage
(vii) Exciting VA/kg for assembled
core at:
a) Flux density of 1.55 tesla VA/kg
b) Flux density at rated voltage VA/kg
c) Flux density at 110% rated Va/kg
voltage
(viii) Type of insulation between core
laminations.
(ix) Type of joint between the core
limbs and yoke.
(x) core bolt Insulation withstand kV
voltage
(xi) Core bolt insulation flashover kV
voltage

- 44 -
29. Details of windings:
(i) Type of winding
(a) Primary
(b) Secondary
(c) Number of turns of primary
winding
(d) Number of turns of
secondary winding
(e) Number of parallel paths in
primary winding
(f) Number of parallel paths in
secondary winding.
(g) Is interleaving/inter shielding Yes/No
of the winding adopted to
ensure better impulse voltage
distribution?

(i) Primary
(ii) Secondary

(h) Is the insulation of end turns of Yes/No

winding reinforced?
(i) Primary
(ii) Secondary

(i) Type of coil

(ii) Mode of connection (i.e. in
series or in parallel) of the
portions of the windings on
the two limbs of the core, if
applicable.
(iii) Dimensions of the copper
conductor used in the winding:
a) Primary mm x mm
b) Secondary mm x mm
c) Tapped winding. mm x mm
(iv) Current density at rated
current.

- 45 -
 a) Primary A/mm2
b) Secondary A/mm2
(v) Insulation used over the
conductor (details of material
and specification there for)
(vi) Type of joints, if any, in the
windings
(vii) Dielectric strength of
windings:
a) Full wave lightning
impulse withstand
voltage:
a) Primary winding kV peak
b) Secondary winding. kV peak
(b) Lightning Impulse
chopped on the tail
withstand voltage:
(i) Primary winding
kV peak
(ii) Secondary winding
kV peak
(c) Separate source power
frequency withstand
voltage kV
(i) Primary
(ii) Secondary
(d) Induced over voltage
withstand value
kV
(viii) Minimum flashover distance
to earth in oil of :
a) Secondary winding to
core
b) Primary winding to
yoke
c) Primary winding to
tank
(ix) Material used for coil
clamping rings and
specification there for
(x) Magnitude of axial pre-
compressive force on the
winding
(a) Primary
(b) Secondary

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 (xi) Calculated maximum axial
thrust in the winding due to
dead short circuit at the
terminals t
(a) Primary
(b) Secondary
(xii) Calculated short circuit forces:
a) Hoop stress in primary
winding kgf/cm2
b) Hoop stress in secondary
winding
kgf/cm2
c) Compressive pressure in the
radial spacers
2
d) Internal axial compressive kgf/cm
force kgf
e) Axial imbalance force
f) Resistance to college kgf
g) Bending stress on clamping kgf
ring
kgf/cm2
h) Radial bursting force
(xiii) Arrangement to maintain
constant pressure on the kgf
windings
(xiv) Maximum permissible torque
on pressure screws for coil
N.m
clamping at the time of
tightening, if any.
(xv) Can either end of each
secondary winding (25 kV) be Yes/No.
connected directly to earth?
30. Motorised off-circuit tap changer:
a) Name of the manufacturer
b) Country of origin.
c) Type designation
d) Governing specification.
e) Is a separate taped winding
provided n each secondary.
f) Number of tappings:
i) Plus tappings
ii) Minus tappings
g) Percentage variation of voltage
on different tapping.
h) Minimum contact pressure kgf
between moving and stationery

- 47 -
 contacts A
i) Maximum rated through current kV
j) Voltage class V(dc)
k) Rated voltage of control circuit
l) Tap changer motor particulars:
i) Make and type V(dc)
ii) Rated voltage A
iii) Rated current kW
iv) Rated power rpm.
v) Speed
vi) Class of insulation
31. Bushings:
(i). Primary side:
a) Name of the manufacturer
b) Country of origin
c) Governing specification
d) Type designation (specify as
to whether it is OIP condenser
bushing)
e) Voltage class kV
f) Rated current A
g) Visible power frequency
discharge voltage kV
h) Wet one minute power kV peak
frequency withstand voltage
i) Lightning impulse withstand mm
voltage
j) Creepage distance
k) Weight of assembled bushing kV

(ii). Secondary side

a) Name of the manufacturer
b) Country of origin
c) Governing specification
d) Type designation
e) Voltage class kV

- 48 -
 f) Rated current A
g) Visible power frequency kV
discharge voltage
h) Wet one minute power kV
frequency withstand voltage
i) Lightning impulse withstand kV peak
voltage
j) Creepage distance mm
k) Weight of assembled bushing kgf
32. Bushing type current transformers:
(i). Primary side:
a) Name of the manufacturer
b) Governing specification
c) Transformation ratio
d) Accuracy class and rated
accuracy limit factor
e) Rated current A
f) Rated output VA
g) Exciting current at the rated mA
knee point emf
h) Rated knee point emf V
i) Secondary winding resistance ohm
corrected to 750C
j) Short time thermal current and kA,s
duration.
(ii). Secondary side:
a) Name of the manufacturer
b) Governing specification
c) Transformation ration
d) Accuracy class
e) Rated current A
f) Rated output VA
g) Exciting current at the rated
knee point emf VA
h) Rated knee point emf V
i) Secondary winding resistance Ohm.
corrected to 750C.
j) Short time thermal current and kA,s.
duration

33. Insulating oil :

a) Governing specification
b) Grade of oil
c) Source of supply
d) Specific resistance at:
i) 270C ohm-cm
ii) 900C ohm-cm

- 49 -
40. Details of pressure relief device:
a) Make and type
b) Governing specification
c) Does it reset itself Yes/No
41. Bimetallic terminal connectors:
(i). Primary side:
a) Source of supply
b) Governing specification
c) Type
d) Rated current A
0
e) Temperature rise over an C
ambient temperature of 450C
while carrying rated current.
f) Short time current and duration kA,s
(ii). Secondary side:
a) Source of supply
b) Governing specification
c) Type
d) Rated current A
0
e) Temperature rise over an C
ambient temperature of 450C
while current rated current
f) Short time current and duration kA,s
42. Acoustic sound level at a distance dB
of 1 m, when energised at rated
voltage and rated frequency
without load.
43. Partial discharge value at 1.5Um/ 3 pC
kV r.m.s.
44. Weights and dimensions:
(i) Net weight of core
(ii) Net weight of cooper:
a) Primary winding kg
b) Secondary winding kg
(iii) Net untanking weight of core kg
frame and coils
(iv) Net weight of insulating oil kg

- 50 -
 e) Dielectric, dissipation factor (tan-
delta) at 90 C
f) Dielectric strength kV
g) Water content ppm
h) Interfacial tension N/m
i) Neutralisation value mg KOH/gm
0
j) Flash point C

34. Type of transformer tank

35. Details of radiators:
a) Make and type
b) Type of mounting
c) Overall dimensions (LxWxH) mm
x mm x mm
36. Details of Buchholz relay:
a) Make and type
b) Governing specification
c) Provision of shut-off valves on Yes/No
either side of the relay
d) Provision of alarm contact Yes/No
e) Provision of trip contact Yes/No
f) Rated current of contacts A
37. Details of winding temperature
indicator.
a) Make and type
b) Governing specification
c) Number of contacts provided
d) Rated current of contacts A
e) Dielectric withstand value of kV
contacts
38. Details of oil temperature indicator
a) make and type
b) Governing specification
c) Number of contacts provided
d) Rated current of contacts A
e) Dielectric withstand value of kV
contacts
39. Details of Magnetic oil level gauge:
a) Make and type
b) Governing specification
c) Diameter of dial mm
d) Number of contacts provided
e) Rated current of contact A
f) Dielectric withstand value of kV
contacts

- 51 -
(v) Volume of insulating oil l
(vi) Total weight of cooling equipment t

(vii) Total weight of transformer t

without oil

(viii) Total shipping weight of t

complete transformer including all
detachable parts, fittings and
assemblies

(ix)Shipping weight of largest t

package

(x) Crane lift (excluding slings) for un mm

tanking core and coils

(xi)Crane lift (excluding slings) for mm

removal of primary side bushings.

(xii) Dimensions of the complete

transformer including all parts,
fitting and accessories:

a) Overall length mm
b) Overall breadth mm
c) From rail level to the topmost mm
point
(xiii) Minimum thickness of steel
plate/ sheet used:
a) Bell tank mm
b) Tank bottom mm
c) Conservator mm
d) Radiator mm
e) Marshalling box. mm

(xiv) Overall shipping dimensions mm x mm x

of the largest package (Length x mm
width x height)
(xv) Mode of transportation of
transformer unit (filled with
oil/nitrogen gas.)

- 52 -
 Other particulars

45. Is the transformer tank fitted with Yes/ No

lifting pads? If yes, what is the
number of pads

46. What is the number of inspection

covers provided?
47. Are comfits/ trays provided for cable Yes/ No
run?
48. Is the core electrically connected with Yes/No
the tank?
49. Will the gaskets to be used in the Yes/No
transformer give trouble free service
for at least 7 years? If not, indicate
the life.

50. Is the core construction without core Yes/No

bolts?
51. Are the core bolts grounded, and if Yes/ No
so, how?
52. What is the number of radial spacers
used in the winding?
53. What is the number of joints
provided in the winding ?
54. Are the spacers/blocks/angle rings of
pre-compressed press boards? If no,
indicate the material with
specification.

55. Are arrangements made for ensuring Yes/ No

automatic constant pressure on the
coils? If no. give the reasons.

56. Are closed slots provided on outer Yes/ No

most winding for locking the vertical
strips ? If no, give the reason.

57. What is the periodicity for tightening Years

of coil clamping arrangement?

- 53 -
58. What are the designed values of
short-circuit current for:
a) Symmetrical :

i) Primary winding A

ii) Secondary winding A

b) Asymmetrical:

i) Primary winding A

ii) Secondary winding A

59 What is the over flux withstand Tesla

capability of the transformer
(Maximum permissible limit of flux
density) ?
60. Are windings pre-shrunk ? Yes/No

61. Have the details of drying cycles of Yes/ No

the coils/coil assembly including
final tightening values of pressure,
temperature and degree of vacuum at
various stages of drying been
furnished?
62. Are arcing horns provided for line Yes/ No
and neutral bushings ?
63. Is a test tap provided in the line Yes/ No
bushing ?
64. Are the procelain housing of the Yes/ No
bushings of single piece
construction?
65. Is the shed profile of porcelain Yes/ No
housing of the bushing free from
under-ribs but has a lip?
66. Is the busing type current transformer Yes/ No
of low reactance type?
67. Is Clause by Clause "Statement of Yes/ No
compliance" attached?
68. Is "Statement of deviation", if any, Yes/ No
attached?
69. Does the tap changer have snap
action ? If not, give reason.

- 54 -
70. Is the Buchholz relay provided with Yes/ No
two shut-off valves, one on either
side?
71. Is separate conservator tank & Yes/ No
Buchholz ralay provided for tap
chaning equipment?
72. Are fasteners of 12 mm diameter and Yes/ No
less exposed to atmosphere of
stainless steel to Grade 04Cr17
Ni12Mo to IS 1570 Part-V?
73. Are the fasteners of more than 12 Yes/ No
mm diameter exposed to atmosphere
of stainless steel or MS hot dip
galvanised?
74. Are test certificates for tests as per Yes/ No
Clause 15.0 attached?
75. Are all the calculations required as Yes/ No
per clause 16.3.1 attached?
76. Are all the drawings required as per Yes/ No
clause 16.3.2 attached ?
77. (a) Are all the parts, fittings and Yes/ No
accessories from RDSO's
approved manufacturers ?
(b) If not, list the items which are Yes/No
to be type tested in the
presence of RDSO's
representative

78. Is adequate space provided in the Yes/ No

marshalling box for housing the
wiring and components?
79. Is warranty as per clause 22.0? Yes/ No

80. Is the list of spares furnished or

no?

**********************

- 55 -
 ANNEXURE-5
CAPITALISATION OF TRANSFORMER LOSSES
Following formula shall be used for the purpose of calculating the
present worth of the transformer after taking in account capitalization of its
losses.
K = D{(1+i)n-1
i(1+i)n
Where, K = Present worth of transformer in Rupee.
D = Annual cost of combined no-load and load
losses in Rupee.
Rate of compound interest on unit price of
i =
transformer @ 12% per annum.

n =
Life of transformer.
Substituting value of D, which is :
D = ( I + F2 C) 365 x 24 x T
1000
where,
I = Maximum No- load loss in watt.
C = Maximum Load-loss in watt.
F = Load factor.
T = Tariff.
Assuming values of n as 25 year, F as 50% and T as Rupee 2 per kwh, the value
of K is,
K = (1+0.12)25-1
17.52 (I + 0.25 C)
0.12 (1+0.12)25
K = 137.41 (I +0.25 C)

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- 60 -