MEGHALAYA ENERGY CORPORATION LIMITED
PLANNING & DESIGN CELL
TECHNICAL SPECIFICATION
FOR
POWER TRANSFORMER
RATING 132/33 KV, 25 MVA.
SHILLONG
NOVEMBER, 2011
SPECIFICATION FOR 132/33 KV, 25 MVA POWER TRANSFORMER.
01.
SCOPE:
1.
This section of the specification covers the design, manufacture, shop testing,
supply, delivery at site, unloading, supervision of erection, testing and
commissioning of the power transformer as given in the schedule of requirements
appended to these specifications.
2.
The manufacturer shall despatch the power transformer filled with nitrogen gas or
some other inert gas and complete with pressure devices for replenishing gas
pressure.
02.
TYPE AND RATINGS:
1.
i)
ii)
iii)
iv)
v)
vi)
vii)
The transformer shall be core type or shell type construction. The 3-phase step down
oil-immersed transformer shall be ONAN/ONAF type with external heat exchangers
and shall be suitable for outdoor service in the climatic conditions at site. The rating
and electrical characteristics of the transformer shall be as follows
Maximum continuous capacity.
Type of cooling
No. of Phases
Frequency
Double wound or auto
Cooling medium
a)Rated voltage on HV side
b)Rated voltage on LV side
(a) High voltage winding connection
b) Low voltage winding connection
viii)
ix)
x)
Vector group
Taps
xi)
Method of tap changing
xii)
Installation
xiii)
Impedance voltage per cent
2.
03.
16/25 MVA
ONAN/ONAF
Three
50 Hz
Double wound.
Mineral oil.
132 KV (between lines)
33 KV (between lines)
a) Star connected and neutrally
grounded.
b) Star connected and neutrally
grounded.
YNyno
Taps required on HV winding to give
a variation of +5% to -15% in 16
equal steps.
Off load tap changing gear with
remote and local control system.
Outdoor on rails with provision for
clamping of wheels to the rails.
10
The primary winding shall be designed to operate continuously at its rated MVA and
with the incoming voltage varying by ± 10% of the rated voltage.
STANDARDS:
1.
The transformers shall conform in all respects to the following relevant standards
with latest amendments thereof.
1
IS: 2026 (Part-I)
IS: 2026 (Part-II)
IS: 2026 (Part-III)
IS:2026 (Part-IV)
IS:2026 (Part-V)
IS: 3639
IS:2099
IS:6600
IS: 3347
IS: 3637
IS: 3639
IS: 335
IS: 2312
IEC-60076
CBIP Publication No. 295
2.
04.
General Specification for Power Transformers
Temperature rise.
Insulation levels and dielectric tests.
Terminal markings, tappings and connections.
Bushings
Fittings and accessories for power transformers.
Specification for bushings for alternating voltages above
1000 Volts.
Guide for loading of oil immersed transformers.
Dimensions for 36KV porcelain transformer bushings:.
Gas operated relay.
Fittings and accessories for Power Transformers.
Specification of mineral oil
Cooling fan
Specification for Power Transformers
Manual on Transformers
Other equipments shall comply with relevant national or international standards
except where specified otherwise. Equipments meeting with any other authoritative
standard which ensures equal or better quality than the standard mentioned above
are also acceptable. Where the equipments offered conform to any other standard,
the salient point of difference between the standard adopted and the standard
specified shall be clearly brought out in the tender.
QUALITY ASSURANCE:
The supplier shall include a quality assurance programme (QAP) that will be used to
ensure that the transformer design, materials, workmanship, test, service capability,
maintenance and documentation, will fulfill the requirements stated in the contract
documents, standards, specifications and regulations. The QAP shall be based on
and include relevant parts to fulfill the requirements of ISO-9001.
A quality plan describes:
i.
List of activities involved in design, procurement of raw materials and
components, manufacture, stage inspection and final testing, preparation for
despatch, delivery, installation and commissioning.
ii.
The identification reference of all documentation, standards, procedures,
works instructions, drawing, test methods, acceptance criteria etc.
05.
DESIGN REQUIREMENTS:
05.01
GENERAL:
1.
The transformer and accessories shall be designed to facilitate inspection, cleaning,
repairs and to give satisfactory operation under sudden variations of load and
voltage as may be met with under working conditions on the system including those
due to short circuits.
2
2.
All materials used shall be of the best quality and of the class most suitable for
working under the specified conditions. Corresponding parts liable to replacement
shall be interchangeable.
3.
All outdoor apparatus including bushing insulators with their mountings shall be
designed so as to avoid pockets in which water can collect. All connections and
contacts shall have ample cross-sections and surfaces for carrying continuously the
specified currents without undue heating and fixed connections shall be secured by
bolts or screws of ample size and adequately locked. Lock nuts shall be used on steel
connections carrying current.
4.
The design, materials and processes used in the construction of transformer shall be
such as to reduce to a minimum the risk of the development of acidity in the oil.
5.
The transformer shall be free from excessive vibration and noise.
05.02
INSULATION:
1.
The dielectric strength of the winding insulation shall conform to the value given in
the latest issue of IS: 2026 as mentioned below:-
Nominal system
voltage
(KVrms)
Rated Lightning
impulse withstand
voltage
(KV peak)
170
550
Highest system
voltage
(KVrms)
33
132
36
145
Rated short duration
power frequency
withstand voltage
(KVrms)
70
230
2.
Transformer bushing shall conform to latest issue of IS: 2099.
3.
The HV winding of the transformer shall have graded insulation.
05.03
TEMPERATURE RISE:
Each transformer shall be capable of operating continuously at the normal rating
without exceeding the temperature limit for winding and oil as specified in the latest
issue of IS: 2026.
05.04
IMPEDANCES:
The supplier shall specify the range of impedance which can be provided without an
increase in the quoted price. Impedance shall include positive and zero sequences
and shall be expressed in terms of the branches of the star connected equivalent
diagrams, all on the same MVA basis, and the range shall be given for each branch
of the equivalent circuit in turn.
05.05
SHORT CIRCUIT WITHSTAND ABILITY:
1.
The transformer shall be designed and constructed to withstand without damage the
thermal and dynamic effects of the external short circuit.
3
2.
The transformer shall be capable of withstanding the symmetrical short circuit
current at least for 2 seconds.
3.
The winding shall be so designed that highest average temperature of the winding
after loading with symmetrical short circuit current and duration as specified above
shall not exceed the permissible values specified in latest issue of IS: 2026 (Part-I).
4.
The transformer shall possess the dynamic ability of withstanding short circuit
currents of magnitude and duration as specified in the latest issue of IS: 2026 (PartI).
05.06
FREQUENCY:
The transformer shall be suitable for continuous operation with a frequency variation
of ± 3% from normal of 50 c/s without exceeding the specified temperature rise.
05.07
SUPPRESSION OF HARMONICS:
The transformer shall be designed with particular attention to the suppression of
harmonic voltages so as to eliminate waveform distortion and any possibility of high
frequency disturbances, inductive effects of circulating currents between neutral
points of different transformers reaching such a magnitude as to cause interference
in the communication circuits.
05.08
CLIMATIC CONDITIONS AT SITE:
The transformer shall operate satisfactorily
below:
Maximum dry bulb temperature
Minimum dry bulb temperature
Relative humidity
Average annual rainfall
Number of months of tropic monsoon
Maximum altitude
Seismic Zone
06.
in conditions prevailing at site as shown
-
25 - 35°C
2.5°C
62% to 89%
2280mm
5 months (May – Oct)
Above 1000m above sea level.
V
GUARANTEE, PENALTIES AND BID EVALUATION:
1.
The no-load losses in kilowatts at rated voltage and rated frequency, the total losses
in kilowatts at rated output, rated voltage and rated frequency at the maximum
auxiliary losses on account of cooling fans shall be guaranteed under penalty for
each transformer. For the purpose of penalty computation, the test figures of the no
load and total losses shall be compared with the corresponding guaranteed figures.
2.
The penalties shall be separately evaluated from :i)
the excess of the test figure of the no load losses in kilowatts over the
corresponding guaranteed figure.
ii)
The excess of the difference between the test value of the total losses and the
no load losses in kilowatts, over the difference of the corresponding
guaranteed value.
4
3.
The penalties shall be calculated at the rate of P 1,50,000/- per kilowatt for the
excess of no load loss and at the rate of P 62,000/-per kilowatt for the excess of the
difference in the total and no load losses.
4.
Auxiliary losses in the fans, etc., shall be considered separately from the load losses.
The penalty shall be calculated at the rate of P 60,000/- per kilowatt from the excess
of auxiliary losses over the guaranteed values.
5.
For fraction of a kilowatt the penalties will be applied prorate.
6.
For the purpose of comparison of tender, the quoted prices shall be equalized for the
transformer losses at the same rate as given for the penalty on the basis of the
guaranteed loss figures.
7.
No change in the tendered values of the transformer loss will be permitted after
opening of bids and evaluation shall be carried on the basis of information furnished
by the tenderer.
8.
The purchaser reserves the right to reject any transformer if during tests at works,
the total no load losses, or total load losses (including the auxiliary losses) exceed
the guaranteed values by more than 20%.
9.
The tenderer shall indicate whether the figures given for the guaranteed losses in the
Schedule of Guaranteed Technical Particulars are with or without tolerance. If
tolerances are applicable, the limit for the same shall be indicated. In absence of any
information to this effect, the figures for no load losses and load losses etc. shall be
increased as per latest edition of IS : 2026.
07.
CONSTRUCTION DETAILS:
07.01
CORE:
1.
The core shall be constructed from high grade, cold rolled, non-ageing, low loss,
high permeability super grain oriented silicon steel laminations specially suitable for
transformer cores.
2.
After being sheared the laminations shall be reannealed as to remove all residual
stress. At least one side of each lamination shall be coated with a durable baked
enamel insulation coating, which shall be inert to the action of the hot transformer
oil. Paper and varnish insulation will not be accepted. The nature of insulation
should be specified in the tender.
3.
Suitable axial cooling ducts shall be provided in the core to ensure free circulation of
oil and sufficient cooling of the core. The ducts shall be so proportioned that the
maximum temperature at any point shall be within safe working limits.
4.
The core shall be rigidly clamped and bolted to ensure adequate mechanical strength
and to prevent vibration during operation. The bolts used in the assembly of the core
shall be suitably insulated and clamping structure be constructed that eddy current
will be minimum.
5
5.
Suitable lifting eyes or lugs shall be provided to enable the core and coil assembly to
be lifted.
6.
The core and the winding assembly shall be capable of withstanding the shock
during transport, installation or while in service, and adequate provision shall be
made to prevent movement of core and winding relative to the tank during these
conditions.
7.
The supporting frame work of the core shall be so designed as to avoid presence of
pocket which would prevent complete emptying of the tank through the drain valve
or cause trapping of air during filling.
8.
All steel sections used for supporting the core shall be thoroughly sand blasted after
cutting, drilling and welding.
9.
The design of the magnetic circuit shall be such as to eliminate the occupancy of
static discharges, development of short circuit paths within itself or to the earthed
clamping structure and the production of flux components at right angles to the
plane of lamination which may cause local heating.
10.
Each core lamination shall be insulated with a material that will not deteriorate due
to pressure and hot oil.
11.
The maximum flux density in any part of the core and yokes of each transformer at
normal voltage and frequency shall not exceed 1.9 Tesla.
07.02
WINDINGS:
1.
132 KV windings shall have graded insulation as per IS: 2026. The 33 KV windings
shall be fully insulated and all neutral points shall be insulated for the voltage
specified in IS:2026.
2.
The windings shall be so designed that all coil assemblies of identical voltage rating
shall be inter-changeable and field repairs to the windings can be made readily
without special equipment. The coils shall be supported between adjacent sections
by insulating spacers and barriers. Bracings and other insulation used in the
assembly of the windings shall be arranged to ensure free circulation of the oil and
to reduce hot spots in the windings.
3.
The insulation of the coils shall be suitably treated to develop the full electrical
strength of the winding. All materials used in the insulation and assembly of the
windings shall be insoluble, non-catalytic and chemically inactive in the hot
transformer oil and shall not soften or otherwise be adversely affected under the
operating conditions.
4.
All threaded connections shall be provided with locking facilities. All leads from the
windings to the terminal boards and bushing shall be rigidly supported to prevent
injury from vibration. Guide tubes shall be used where practicable.
5.
The windings shall be clamped securely in place so that they will not get displaced
or deformed during short circuits. The assembled core and windings shall be vacuum
dried and suitably impregnated before removal from the treating tank. The copper
6
conductors used in the coil structure shall be welded or brazed. Special core shall be
given to design and construction of tapped coils and connections.
6.
The windings shall be designed to reduce to a minimum the out of balance forces in
the transformer at all voltage ratios. Further, no strip conductor wound on edge shall
have a width exceeding six times its thickness.
7.
Coil clamping rings, if provided, shall be of steel or of suitable insulating material
built up from flat laminations. Steel clamping rings shall be maintained at a definite
potential and if earthed, they will be connected to the adjacent core clamping
structure on the same side of the transformer as the main earth connection.
8.
The design of the power transformer shall ensure that the amplitude of surges
transferred from the HV winding to the LV winding is effectively controlled well
below the maximum limit admissible with the BIL of the LV winding.
07.03
TANK AND ACCESSORIES:
A) TANK AND COVER:
1.
The transformer tank and cover shall be fabricated from good commercial grade low
carbon steel of adequate thickness. The tank shall be of welded construction. All
seams shall be double welded and all welding shall be stress relieved.
2.
The tank wall shall be adequately reinforced by stiffeners of structural steel for
general rigidity as and where necessary that it is sufficiently strong to withstand
without any deformation the mechanical stresses caused during transportation or oil
filling by vacuum.
3.
The tank cover shall be bolted into the tank with weather proof, hot oil resistant
gasket in between for complete oil tightness. If compressible gaskets are provided
metallic stops shall be provided to prevent over compression. Bushing turrets, access
hole covers etc shall be so constructed as to prevent any leakage of oil or water in
the tank.
4.
Jacking pads, lifting eyes and pulling lugs shall be provided in the tank to facilitate
movement of the transformer. All heavy removable parts shall be provided with
screwed in eye bolts for ease of handling.
5.
The design of the tank, the lifting lugs and bosses shall be such that the complete
transformer assembly filled with oil can be lifted with the use of these lugs without
any damage or distortion.
6.
Each tank cover shall be of adequate strength and shall not distort when lifted.
Inspection openings shall be provided as necessary to give easy access to bushings
or changing ratio or testing of earth connection. Each inspection opening shall be of
ample size for the purpose for which it is provided and at least two openings, one at
each end of the tank, shall be provided.
7.
The tank cover and inspection cover shall be provided with suitable lifting
arrangements. Unless otherwise approved inspection covers shall not weigh more
than 25 kgs each.
7
8.
The tank cover shall be fitted with pockets for a thermometer and for the bulbs of oil
and winding temperature indicators. Protection shall be provided where necessary
for each capillary tube.
9.
The thermometer pocket shall be fitted with captive screwed top to prevent the
ingress of water.
10.
The pockets shall be located in position of maximum oil temperature and it shall be
possible to remove the instrument bulbs without lowering the oil in the tank.
B) UNDER CARRIAGE:
1.
The transformer tank shall be supported on a structural steel base equipped with
forged steel or cast steel single flanged wheels (four Nos), suitable for moving the
transformer completely filled with oil. Arrangement for clamping of the wheel with
the rails capable of being put on and off easily shall also be provided.
2.
Jacking steps shall be provided. It shall be possible to change the direction of the
wheels through an angle of 90° when the transformer is moved both in longitudinal
and transverse directions. A 1676 mm convenient track gauge in both longitudinal
and transverse direction shall be provided. Means shall be provided for locking the
swivel movements in positions parallel to and at right angles to the longitudinal axis
of the tank. Suitable stoppers for the track wheel shall also be supplied. Adequate
number of hydraulic jacks for lifting the transformer for changing the plane of
rotation of wheels shall be provided by the supplier.
3.
Pulling eyes shall be provided to facilitate moving the transformer and they shall be
suitably braced in a vertical direction so that bending does not occur when the pull
has vertical components.
C.
CONSERVATOR VESSELS, OIL GAUGES AND BREATHERS:
1.
A conservator complete with sump and drain valve shall be provided in such a
position as not to obstruct the electrical connections to the transformer having a
capacity between highest and lowest visible levels of 7.5% of the total cold oil
volume in the transformer and cooling equipment. This is to meet the requirements
of expansion of the total cold oil volume in the transformer and cooling equipment
from the minimum ambient temperature to 90° C. The minimum indicated oil level
shall be with the feed pipe from the main tank covered with not less than 15 mm
depth of oil and the indicated range of oil level shall be from minimum to maximum.
2.
The conservator shall be designed so that it can be completely drained by means of
the drain valve provided, when mounted as in service.
3.
One end of the conservator shall be bolted into position so that it can be removed for
cleaning purposes.
4.
One oil gauge/magnetic type shall be provided.
5.
One sight gauge for oil level shall also be provided.
6.
The oil level at 30° C shall be marked on the gauge.
8
7.
Taps or valves shall not be fitted to oil gauge.
8.
The oil connection from the transformer tank to the conservator vessel shall be
arranged at a rising angle of 3 to 9 degrees to the horizontal upto the Buchholz Relay
and shall consist of 80 mm inside diameter pipes as per latest edition of IS: 3639.
9.
A valve shall be provided at the conservator to cut-off the oil supply to the
transformer, after providing a straight run of pipe for at least a length of five times
the internal diameter of the pipe on the tank side of the gas and oil actuated relay and
at least three times the internal diameter of the pipe on the conservator side of the
gas and oil actuated relay.
10.
Two filter valves, one at bottom at one end, and other at top at the other end shall
also be provided.
11.
Each conservator vessel shall be fitted with a breather in which silica gel is the
dehydrating agent and designed so that :
i)
ii)
iii)
iv)
The passage of air is through the silica gel.
The external atmosphere is not continuously in contact with the silica gel.
The moisture absorption indicated by a change in colour of the tinted crystals
can be easily observed from a distance.
All breathers shall be mounted at approximately 1400 mm above ground
level.
D.
FILTER AND DRAIN VALVES, SAMPLING DEVICES AND AIR RELEASE
PLUGS:
1.
Each transformer shall be fitted with the following:
i)
ii)
iii)
iv)
Filter and drain valves,
A drain valve as specified below shall be fitted to each conservator.
a) For diameter upto 650 mm
: Size of the valve 15 mm.
b) For diameter above 650 mm : Size of the valve 25 mm.
A robust oil sampling device shall be provided at the top and bottom of the
main tank. The sampling device shall not be fitted on the filter valves,
specified under (i) above.
One 15 mm air release plug.
2.
All other valves opening to atmosphere shall be fitted with blank flanges.
E.
VALVES FOR RADIATOR CONNECTION:
1.
All valves shall be of gun-metal or cast steel or may have cast iron bodies with gun
metal fittings. They shall be of full way type with internal screw and shall be opened
by turning counter clock-wise when facing the hand wheel.
2.
Means shall be provided for padlocking the bottom valves in the open and closed
positions. This is required for the valves where opening device like hand wheel, keys
etc. are the integral part.
9
3.
Every valve shall be provided with an indicator to show clearly the position of the
valve.
4.
All valves shall be provided with flanges having machined faces.
5.
The drilling of valve flanges shall comply with the requirement of the latest edition
of IS: 3639.
F.
PRESSURE RELIEF DEVICE:
1.
The pressure relief device shall be provided of sufficient sizes for rapid release of
any pressure that may be generated within the tank, and which might result in
damage to the equipment. The device shall be capable of resetting itself
automatically to its original condition after release of excess pressure. The device
shall be designed to eliminate any chattering of the valve during operation. The
device shall be provided with suitable alarm and trip contacts. The device shall
operate at a static pressure of less than the hydraulic test pressure for transformer
tank. Means shall be provided to prevent the ingress of rain water.
2.
An equalizer pipe connecting the pressure relief device to the conservator shall be
provided for relieving or equalizing the pressure in the pressure relief device. A
suitable pipe shall be provided for draining the oil from the pressure relief device
down to the oil pit.
G.
EARTHING TERMINAL:
Two earthing terminals capable of carrying for 4 seconds the full lower voltage and
short circuit current of the transformer shall be provided. Provision shall be made at
positions close to each of the bottom two corners of the tank for bolting the earthing
terminals to the tank structure to suit local conditions. The earthing terminals shall
be suitable for bolted connections with the grounding system.
H.
RATING AND DIAGRAM PLATES:
1.
The following plates shall be fixed to the transformer tank at an average height of
about 1750mm above ground level.
i)
A rating plate bearing the date specified in the appropriate clauses of IS:
2026.
ii)
A diagram plate showing the internal connections and also the voltage vector
relationship of the several windings in accordance with IS: 2026 and in
addition a plan view of the transformer, giving the correct physical
relationship of the terminals. When links are provided for changing the
transformer ratio, then approved means shall be provided for clearly
indicating ratio for which the transformer is connected. No load voltage shall
be indicated for each tap.
iii)
A plate showing the location and function of all valves and air release cocks
or plugs. This plate shall also warn operators to refer to the maintenance
instructions before applying the vacuum treatment for drying.
10
3.
The above plates shall be of material capable of withstanding continuous outdoor
service.
I.
JOINTS AND GASKETS:
All gaskets used for making oil tight joints shall be of proven material such as
granulated cork bonded with synthetic rubber or synthetic rubber gaskets
conforming to latest edition of IS: 4253.
08.
TAP CHANGING MECHANISM:
1.
The tapping shall be provided on the high voltage side of the winding.
2.
The transformer shall give full load output on all taps.
3.
The OFF load tap changing shall be effected as per standard practice and design of
the manufacturer. Details or calculation, schematic drawing, wiring etc shall be
furnished along with the tender.
4.
A visual tap-position indicator for the tapping in use shall be provided near the
operating hand wheel for convenience of operation.
5.
Provision shall be made to enable padlocking of the handle in each tap position with
a 35 to 55 mm padlock. The arrangement shall be such that the lock cannot be
inserted unless the contacts are properly engaged..
6.
The tap changing mechanism shall be of strong construction and shall provide
positive low resistance contacts.
7.
All contacts shall be silver plated and held in position under strong contact pressure
so as to avoid contact pitting of any part.
09.
INTERNAL EARTHING ARRANGEMENT:
09.01
GENERAL:
All metal parts of the transformer with the exception of the individual core
laminations, core bolts and associated individual clamping plates shall be maintained
at same fixed potential.
09.02
EARTHING OF CORE CLAMPING STRUCTURE:
The top main core clamping structure shall be connected to the tank body by a
copper strap. The bottom clamping structure shall be earthed by
i)
ii)
iii)
Connection through vertical tie rods to the top structure.
Direct metal to metal contact with the tank base by the weight of core and
windings.
Connection to the top structure on the same side of the core as the main earth
connection to the tank.
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09.03
EARTHING OF MAGNETIC CIRCUIT:
The magnetic circuit shall be earthed at one point only through a link placed in an
accessible position beneath an inspection opening in the tank cover. The connection
to the link shall be on the same side of the core as the main earth connection.
09.04
EARTHING OF CLAMPING RINGS:
Where coil clamping rings are of metal at earth potential, each ring shall be
connected to the adjacent core clamping structure on the same side of transformer as
the main earth connections.
09.05
SIZE OF EARTHING CONNECTION:
All earthing connections with the exception of those from the individual coil
clamping rings shall have cross sectional area of not less than 0.8 sq. cms.
Connections inserted between laminations shall have a cross sectional area of not
less than 0.2 sq. cm.
10.
BUSHINGS:
1.
The bushings shall have high factor of safety against leakage to ground and shall be
so located as to provide adequate electrical clearance between bushings and between
bushings and grounded parts. Bushings of identical voltages shall be
interchangeable. All bushings shall be equipped with suitable terminals of approved
type and sizes. Multibolt bimetallic clamps shall be provided at bushing terminals
suitable for connecting ACSR conductor of size to be intimated later on.
2.
The star connection on the LV side and star connection on the HV side shall be
made inside the transformer and main HV, LV and neutral leads shall be brought out
through outdoor type bushings which shall be so located that adequate phase
clearance shall be available.
3.
Each bushing shall be so coordinated with the transformer insulation that all
flashovers will occur outside the tank.
4.
Porcelain used in the bushing shall be of wet process homogeneous and free from
cavities and other flaws. The glazing shall be of uniform colour and free from
blisters, burns and other defects.
5.
All HV bushings shall be condenser type with plain sheds. The LV and neutral
bushings may be of condenser type/porcelain type with plain sheds. The oil used
will be the same at that used in the transformer. Bushing shall have an oil level
indicator and shall have provision for oil draining from the bottom and arrangement
for oil sampling. Bushings shall have creepage distance as per latest IS: 2099.
6.
All bushings shall have puncture strength greater than the dry flash-over voltage.
7.
Main terminals shall be solderless terminals and shall be of the type and size
specified in the schedule of requirement or drawings (to be given later).
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8.
The spacing between the bushings must be adequate to prevent flash-over between
phases under all conditions of operation.
9.
Special adjustable arcing horns shall be provided for the bushings. The tenderer shall
give the guaranteed withstand voltages for the above and also furnish a calibration
curve with difference settings of the coordination gap to enable the purchaser to
decide the actual gap setting. Tenderers shall give recommendations in this respect.
11.
COOLING SYSTEM (ONAN/ONAF):
11.01
GENERAL
The transformer shall be equipped with cooling system complete with radiator
banks, motors and fans along with associated control gear, pipes, valves, etc. so as to
provide a completely independent ONAN/ONAF system for each transformer.
11.02
RADIATORS:
1.
At least two separate radiator banks shall be furnished with each transformer.
2.
Radiators shall be designed for pressure and vacuum conditions specified for the
tanks.
3.
The clearance between all pipe work and live parts shall be more than the clearance
for live parts to earth.
4.
The radiators shall be so designed as to prevent accumulation of water on the outer
surfaces and to completely drain oil into tank and to ensure against formation of gas
pocket when the tank is being filled.
5.
Radiators shall be connected to the tank by steel flanges welded to the radiators and
to the tank and provided with gaskets at each radiator connection to the tank. An
indicating shut off valve which can be locked either in closed or open position and a
separate oil tight blank flange for use when the radiator is detached shall be
provided. The radiator bank shall have lifting eye, an oil drain valve at the bottom
and a vent at the top.
6.
Each radiator bank shall be arranged for detaching from the transformer without
draining the oil in the transformer tank. Fans shall be located so that they are readily
accessible for inspection and repairs.
7.
A thermometer pocket fitted with a captive screwed cap on the inlet and outlet oil
branches of each separately mounted radiator bank shall also be provided. A filter
valve at the top and bottom of each radiator bank shall also be provided.
8.
The tenderer shall specify the loading of the transformer in case of failure of one or
more sets of fans.
11.03
AIR BLOWERS
1.
Air blowers for use with air blast cooling shall be motor driven. They shall be
suitable for continuous operation outdoor and capable of dealing with the maximum
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output and total head required in service. The bearings shall be of sealed type, which
does not require frequent lubrication.
2.
Air blower shall be capable of withstanding the stress imposed when brought up to
speed by the direct application of full line voltage to the motor.
3.
In order to reduce the transmission of noise and vibration, blowers shall also be
mounted independently.
4.
Blades and runners fabricated to form hollow sections shall be used.
5.
Blades shall be suitably painted for outdoor use.
6.
If fans are mounted at a height less than 2.5 m, suitably painted wire-mesh guards
with a mesh not greater than 25 mm shall be provided to prevent accidental contacts
with the blades. Fans mounted at more than 2.5 m height shall be provided with
outside guards against birdage. Guards shall be provided over all moving shaft and
couplings.
7.
Blowers shall conform to relevant Indian Standard.
11.04
MOTORS:
1.
Motors shall be of squirrel cage totally enclosed weather proof type and shall
comply with the latest edition of the Indian standard as applicable for continuously
rated machine. The motors shall be capable of operating at all loads without undue
vibrations and without any noise. They shall be suitable for direct starting and for
continuous running for 415-240V, three phase, 4 wire, 50 Hz power supply.
2.
All motors shall be capable of continuous operation at any frequency between 48.5
Hz to 51.5 Hz and shall also be capable of continuous operation at 85% of the
normal voltage without injurious overheating.
3.
All motors shall have roller or ball bearing and grease lubrication shall be filled with
hexagon nipples according to the latest edition of relevant Indian standard.
4.
Vertical spindle motors shall have bearings capable of withstanding the thrust due to
the weight of the moving parts and the action of the impeller.
5.
The stator windings shall be adequately braced and suitably impregnated to render
them non-hydroscopic and oil resistant. Weather proof motors shall be provided
with suitable means of breathing and drainage to prevent accumulation of water.
6.
Each terminal box shall be fitted with means of terminating the external wiring for
outdoor use.
7.
Varnished cambric or glass insulation shall be used for connections from the
windings to the terminals. All motor terminals shall be of the stud type and totally
enclosed.
8.
Each blower and its motors shall be mounted on a common base plate and the drive
shall be direct.
14
9.
11.05
12.
Motors shall conform to the latest edition of the relevant Indian standard.
MOTOR CONTROL
1.
All necessary protective and control equipment for the motor shall be furnished and
installed in a weather proof steel cabinet on one side of the transformer tank. The
control equipment shall be fully automatic, designed to start and stop fan motors as
the transformer windings require.
2.
The power supply for the motors shall be 415 volts, 3 phase, 50 Hz. One 3 pole, 415
volts molded case circuit breaker of proper current rating conforming to the latest
edition of IS: 13118 shall be provided in the control cabinet.
3.
Each motor shall be provided with a three pole electrically operated contactor and
with control gear of suitable design both for starting and stopping the motor
manually and also automatically from the contacts of the winding temperature
indicating device. An “ON” - “OFF” - “AUTO” switch shall be provided. Additional
terminal for remote, manual electrical control of motors shall be provided. Overload
and single phasing protection shall be provided but no-volt release shall not be
fitted.
4.
All contacts and other parts which may be required for renewal of adjustment or
inspection shall be readily accessible.
5.
Provision of alarm indication for failure of group fans shall be provided.
6.
Provision of alarm indication shall be provided to indicate failure of power supply.
CENTRE OF GRAVITY:
The centre of gravity of the assembled transformer shall be low and as near the
vertical centre line as possible. The transformer shall be stable with or without oil. If
the centre of gravity is eccentric relative to track either with or without oil, its
location shall be shown on the outline drawing.
13.
CONTROL ANNUNCIATION AND INDICATION:
The control equipment shall have the provision in the control panel (to be arranged
by the purchaser) for annunciation with flags, alarms and trips for following
abnormal conditions. Sufficient numbers of contacts shall be provided on the
initiating relay/device for this purpose.
a)
Alarm.
i) Winding temperature “High”
ii) Buchholz relay “High”
iii) Oil temperature “High”
iv) Oil level “Low”
v) Fans motor failure
b)
Tripping.
i) Winding temperature “High”
ii) Buchholz relay “High”
iii) Oil temperature “High”
15
c)
14.
Indication
i) Indicating lamp for each fan motor running.
AUXILIARY EQUIPMENT AND ACCESSORIES:
1.
Each transformer shall be provided with the following accessories:
i)
One oil temperature indicator with maximum pointer and one electrical
contact.
ii)
Six Nos. winding temperature indicators for each phase of HV and LV with
maximum pointer and three sets of contacts.
iii)
One magnetic type oil level gauge with low oil level alarm contacts suitable
for 220/110VDC and a dial showing minimum, maximum and 30°C oil
levels which should be clearly visible from ground level.
iv)
v)
Repeater dial of winding temperature indicator for remote indication.
One oil filling valve (inlet).
vi)
One oil drain valve (outlet) for the tank with plug or blocking flange of
adequate size.
vii)
One filter valve of adequate size with threaded adaptors located at the top of
the tank on the HV side.
viii)
One filter valve of adequate size with threaded adaptors located near the
bottom of tank on the LV side of the transformer (diagonally) opposite to the
filter valves at the top.
ix)
Two oil sampling valves of adequate sizes. One each at top and bottom of
main tank. The sampling valves shall be provided with provision for
connection to a PVC pipe.
x)
Shut off valves between conservator and tank.
xi)
Shut off valves for detachable radiators, if any.
xii)
Oil valve between cooler and main tank.
xiii)
Pressure Relief Vent or spring operated pressure relief devices.
xiv)
Double float type Buchholz relay with adequate flange connection with one
shut off valve shall be provided at the pipe connecting the tank of the
conservator, with proper provision for collections of all vapour or air bubbles
in the oil in the Buchholz relay chamber/alarm and trips contact controlled
by the two floats shall be suitable for 220/110VDC supply.
xv)
Heat exchangers or radiators, complete with fans and other equipments as
detailed elsewhere in the specification or otherwise deemed necessary.
xvi)
Conservator complete with oil filling hole, cap and drain valve.
16
xvii)
An explosion vent of standard design with double diaphragm shall be
provided on the top cover of each transformer.
xviii) Two grounding terminals.
xix)
Diagram and rating plate.
xx)
Marshalling box.
xxi)
A set of devices for lifting the various parts of the transformers as also the
complete transformer with oil.
xxii)
Suitable number of jacking lugs, hauling lugs and lifting lugs in accessible
position for raising/lowering/hauling the transformer complete with oil.
Core’s lifting lugs shall be provided.
xxiii) Terminal connectors.
xxiv) Clamping devices against earthquake.
xxv)
Silica gel breather of adequate size with oil seal shall be provided from the
top of the conservator tank.
xxvi) Bi-directional flanged rollers with locking and bolting device.
xxvii) Pocket on tank cover for thermometers.
xxviii) Skids and pulling eyes on both sides.
xxix) Inspection cover.
xxx)
Wiring up to marshalling box with PVC copper cables. 660/1100 grade.
xxxi) Off-Load tap changing mechanism.
15.
2.
The equipment and accessories furnished with the transformer shall be suitably
mounted on the transformer for ease of operation, inspection and maintenance and
the mounting details shall be subject to the approval of the purchaser. All valves
shall be provided with blind companion flanges or with pipe plug for protection.
3.
Indication, alarm and relay equipment shall have contacts suitable for operation with
220/110 volts DC Supply. Any other accessories or appliances recommended by the
manufacturer for the satisfactory operation of the transformer together with their
prices shall be given in the tender.
INSULATING OIL:
Sufficient quantity of oil shall be furnished with each power transformer for filling
each tank, heat exchangers and bushing etc. to the proper level. The quantity of oil
required shall be stated in the tender with full specification in conformity with latest
edition of IS: 335 as a separate item. The purchaser shall have the option to procure
the necessary quantity of oil required for the transformer either from the tenderer or
17
from other sources. The Transformer oil shall be supplied in non-returnable drums
along with the transformers.
16.
MARSHALLING BOX:
1.
A weather and vermin proof steel enclosure having degree of protection IP55 shall
be provided for the transformer ancillary apparatus. The box shall have sloping roofs
and the interior and exterior painted. The marshalling box shall be suitably mounted
and the mounting arrangements drawing shall be supplied for approval during the
design stage.
2.
The marshalling box shall accommodate the following equipments:
i.
ii.
iii.
iv.
Temperature indicators
Control and protection equipments for the cooling system
Terminal Boards and gland plates for incoming and outgoing cables
Illumination lamp and 5 Amp, 230V, 3 pin socket and switch.
3.
All the above equipments except (iii) shall be mounted and panels and back of panel
wiring shall be used for interconnection.
4.
The temperature indicators shall be mounted such that the dials are not more than
1600 mm from ground level and the door(s) are of adequate size.
5.
To prevent internal condensation an approved type of metal clad heater shall be
provided controlled by suitable thermostat.
6.
All incoming cables shall enter the kiosk from the bottom and the gland plate shall
not be less than 450 mm from the base of the box. The gland plate and associated
compartment shall be sealed in suitable manner to prevent the ingress of moisture.
7.
Undrilled gland plate shall be provided for accommodating glands for incoming and
outgoing cables.
17.
COMPLETENESS OF EQUIPMENT:
The tender shall be complete in all respects and include all accessories which may
not be specifically mentioned in this specification but which are essential for the
completeness of equipment ordered.
18.
SHOP INSPECTION:
1.
No material or equipment shall be supplied from the point of manufacture before it
has been inspected by the purchaser and/or his authorized representative. The
purchaser’s representative shall have access and facilities for unrestricted inspection
of manufacturer’s work at all stages of work.
2.
The tenderer shall also submit test certificates as per relevant Indian Standards for
bushings, fans, motors, dial type thermometers, relays, gauges, control equipment
etc.
18
19.
FACTORY ASSEMBLY AND TESTS:
19.01
GENERAL.
19.02
1.
Each transformer shall be completely assembled and tested at the factory. If the
purchaser wishes tests shall be performed in purchaser’s presence and/or his
representative, tests will be performed as per latest issue of IS: 2026.
2.
The following mechanical and electrical tests shall be made on the transformer:
MECHANICAL TESTS:
a)
Routine Tests:
i)
Oil Leakage Tests:- All tanks and oil filled compartments shall be tested for
oil tightness by being completely filled with air/oil of a viscosity not greater
than that of insulating oil conforming to the latest edition of IS: 335 at an
ambient temperature and subjected to a pressure equal to the normal pressure
plus 0.35 Kg/cm2 (5 lbs/sq.in) measured at the base for a period not less than
12 hours for oil and I hour for air during which time no leakage shall occur.
b)
Type Tests:
i)
Vacuum Tests:- The tank shall be designed for full vacuum and shall be
tested at an internal pressure of 0.033 Kg/cm2 (25mm of mercury)for one
hour. The permanent deflection of flat plates after the vacuum has been
released shall not exceed the value specified below without affecting the
performance of transformers.
Horizontal length of flat plate (in mm)
Upto and including 750
751 to 1250
1251 to 1750
1751 to 2000
2001 to 2250
2251 to 2500
2501 to 3000
Above 3000
ii)
19.03
Permanent deflection (in mm)
5
6.5
8
9
11
12.5
16
19
Pressure Test:- One transformer tank together with its radiators, conservator
vessel and other fittings shall be subjected to a pressure corresponding to
twice the normal pressure plus 0.35 Kg/cm2 (5lb/sq.in) for one hour. The
permanent deflection of flat plates after the excess pressure has been released
shall not exceed the figure specified in (i) above.
ELECTRICAL TESTS:
a)
Type Tests:
i)
ii)
Lightning Impulse voltage withstand test.
Temperature rise test.
19
b)
Routine Tests:
i)
ii)
iv)
v)
vi)
vii)
viii)
Measurement of winding resistance.
Measurement of polarity, voltage ratio and check of voltage vector
relationship.
Measurement of impedance voltage/short circuit impedance (principal
tapping) and load loss.
Measurement of no-load loss and excitation current.
Measurement of insulation resistance.
Induced over voltage withstand test.
Separate source voltage withstand test.
Lightning Impulse voltage withstand test.
c)
Special Test:
i)
ii)
iii)
iv)
v)
vi)
Measurement of zero-sequence impedance of three phase transformers.
Short circuit tests.
Measurement of acoustic noise level.
Measurement of the harmonic of the no-load current.
Measurement of the power taken by the fan.
Control circuit Dielectric Test. The control devices circuit and fan motor
control circuit for auxiliary equipment shall be given dielectric tests in
accordance with the latest edition of relevant IS.
Test with lightning impulse chopped on the tail.
Determination of capacitance3s dissipation factor between winding-to-earth
and between windings.
Determination of transient voltage transfer characteristics.
Lightning impulse test on neutral terminal.
iii)
vii)
viii)
ix)
x)
19.04
TESTS AT SITE:
1.
After erection at site, the main transformer shall be subjected to the following tests:
i)
ii)
iii)
iv)
19.05
Insulation resistance test.
Verification of vector group and polarity test.
Measurement of voltage ratio and winding resistance.
Dielectric test on oil.
FURTHER TESTS:
The purchaser reserves the right of having other reasonable tests carried out at his
own expense either before shipment, or at site to ensure that the transformer
complies with requirements of this specification.
19.06
TEST REPORTS:
After all the tests have been completed, seven certified copies of each test
report shall be furnished. Each report shall supply the following information:
i)
Complete identification data including serial number of the transformer.
Oscillographs of impulse tests shall form part of the test report.
20
20.
ii)
Method of application, where applied, duration and interpretation of results
of each test. Quantities required to be corrected to 75° C shall be given.
iii)
Temperature data including ambient temperature.
PAINT AND FINISH:
1.
Before painting or filling with oil, all ungalvanised parts shall be completely clean
and free from rust, scale and grease, and all external surface cavities on castings
shall be filled by metal deposition.
2.
External and internal surfaces of transformer tanks and chambers and other
fabricated steel items shall be cleared of scale, rust and surface dirt by blast cleaning
or suitable approved method. After cleaning, these surfaces should be immediately
covered with paint. Hot oil resistant varnish on white synthetic enamel/epoxy paint
is to be used for painting the inside of all oil filled chambers, including transformer
tanks. Only one thin layer (=25 microns) of this is to be applied.
3.
Except for hardware which may have to be removed at site, all external surfaces
shall receive at least four coats of paint, consisting of two coats of epoxy zinc
phosphate or zinc chromate primer with two coats of aliphatic polyurethane glossy
finish paints. The total dry film thickness should preferably between 100 and 130
microns.
4.
All interior surface chambers or kiosks that are in contact with air shall receive at
least three coats of paints, of which the top coat shall be of light shade. If heaters are
not provided in the chamber, then the top coat should be of anti condensation type.
5.
Any scratch, bruise or paint damage incurred during transportation and unloading at
site shall be made good by the purchaser as soon as the damage is detected. This is
to be done by thoroughly cleaning the damaged area and applying the full number of
coats as was applied originally. Manufacturer shall supply the necessary paint for
this touch of painting at site.
21.
LABELS AND PLATES:
1.
Labels shall be provided for all apparatus contained in any cubicle or marshalling
kiosks.
2.
Labels shall be of incorrigible materials and will ensure permanence of lettering and
shall avoid dazzle from light.
3.
The rating plates shall give the information as required in IS: 2026 (Latest).
22.
PACKING AND TRANSPORT:
1.
The packing may be in accordance with the tenderer’s standard practice but he
should give full particulars of packing for the approval of the purchaser. Special
arrangement shall be made to facilitate handling and to protect the projecting
connections from damage during transits.
21
2.
The transformer shall be dispatched filled with nitrogen gas. The oil shall be
supplied in non-returnable standard drums.
3.
All parts shall be adequately marked to facilitate field erection. Boxes and crates
shall be marked with the contract number and shall have a packing list enclosed
showing the parts contained therein.
4.
Care shall be taken that the packing is such as will satisfy the conditions of road/rail
transport existing to place were the transformer is to be erected. The tenderer shall
be fully responsible for informing himself of the details of road and transport to site
and maximum size of packages conveyed by railways. The purchaser shall however
give all possible help to the contractor in this connection.
23.
TOOLS AND SPARE PARTS:
The tenderer shall supply:
24.
a.
A full outfit of tools, spanners, jacks, special tools for assembling and
dismantling the transformer, with a rack for handling them. All spanners
shall be suitably ended and case hardened.
b.
Spares parts as listed in schedule of requirement shall be supplied. The
tenderer may also recommend the spare parts needed for first five years of
operation of transformer. In such a case tenderer shall also furnish the
itemized prices for such recommended spares as per proforma at Annexure VI. The purchaser shall decide the actual quantity of such recommended
spares to be ordered at the time of placing the order.
DRAWINGS:
1.
The drawings and technical literature listed below shall be submitted in
quadruplicate by each tenderer with the tender.
i)
General outline drawing showing dimensions, net weights and shipping
weights, quantity of insulating oil, spacing of wheels in either direction of
motion, centre of gravity, location of coolers etc.
ii)
Sectional view showing the general constructional features and disposition of
various fittings.
iii)
General arrangements of foundations.
iv)
Dimensions of the largest part to be transported and the position in which it
should be transported.
v)
Full details of construction of bushings and other relevant data.
vi)
Crane requirement for assembly and dismantling of the transformer.
vii)
Technical literature on tap changer control, cooling systems, meters and
general constructional features of winding temperature indicator, Buchholz
relay, oil temperature indicator etc.
22
2.
Within two months after the award of the contract the manufacturer shall supply six
copies of drawings which shall describe the equipment in full details for approval,
and shall subsequently provide eight complete sets of final approved drawings, one
of which shall be a soft copy suitable for reproduction. After the completion of the
erection works, the contractor shall furnish 7 sets (including one soft copy) of the
complete drawings.
3.
The following drawings for each item are to be supplied as part of the contract:
(a)
General dimensional drawings for transformer and accessories
(b)
Assembly drawings and weights of main components.
(c)
Shipping drawings showing main dimensions and weight of each package,
arrangement for inert gas retention and monitoring and other protective
arrangements during transit.
(d)
Drawings giving the weights and fixing details for design of foundation.
(e)
Tap changing and name plate diagram.
(f)
Schematic control and wiring diagram for all auxiliary equipment
(g)
Drawings showing the flow of air in the cooling system as well as each limb and
winding.
(h)
Large scale drawing of high and low tension windings of the transformers showing
the nature and arrangement of insulation and terminal connections.
(i)
Drawings and specifications for bushings.
(j)
Test reports.
(k)
A complete bill of materials for all equipments.
25.
26.
INSTRUCTION MANUAL AND DESCRIPTIVE DATA:
1.
Operation, maintenance and erection manual (6 copies each) shall be supplied by the
tenderer one month prior to the shipment of the transformers. The manuals shall
contain all the drawings and maintenance of the transformer.
2.
Descriptive literature and data on transformer, windings, bushings, heat exchangers,
tap changing gear, temperature detectors, buchholz, instruments and control etc.
shall also be supplied by the manufacturer along with the instruction manuals.
DEVIATIONS FROM SPECIFICATIONS:
All deviations from the specifications shall be separately listed as per proforma
given in Annexure-III, in absence of which it shall be presumed that the provisions
of the specifications are complied with by the tenderer.
23
27.
DELIVERY:
The tenderer shall state the shortest delivery period, he can guarantee counting from
the date of letter of intent. Delivery period shall be given as per Annexure- V.
28.
GUARANTEED TECHNICAL PARTICULARS:
The guaranteed technical particulars as called for in Annexure-I shall be furnished
along with tender. Any tender lacking complete information in this respect is likely
to be rejected.
29.
PRICES:
1.
The tenderer shall quote firm itemized prices for supply of equipment on the basis of
F.O.R. destination and as per proforma given in Annexure-II. Prices shall be
inclusive of freight and insurance upto destination and 30 days thereafter.
2.
All prices shall be exclusive of sales tax. Other duties shall be included in the quoted
price. The quoted prices shall be firm.
30.
ERECTION AND SUPERVISION:
1.
The purchaser may at his direction ask the tenderer to do either the complete
erection or supervision of erection at site of the equipment covered by this
specification. The tenderer shall, therefore, quote their charges separately for:
i)
ii)
2.
31.
Erection and
Rates for supervision of erection.
However, if it is decided to do the erection of the above equipment departmentally,
or otherwise the tenderer shall furnish full and detailed instructions complete with
drawings and leaflets to enable the satisfactory erection and commissioning of
equipment by the purchaser. Such instructions shall reach the purchaser well in
advance so that there is no delay in commencement of erection. The successful
tenderer shall supply all special tools necessary for erection. Details of such tools
and the prices thereof shall be stated in the tender separately.
SCHEDULE OF INSTALLATION:
Tenderer shall furnish a list of similar equipment supplied by him and presently in
service as per proforma given in Annexure-IV.
32.
SCHEDULE OF REQUIREMENTS:
(i)
1 No.
Outdoor type, 25 MVA, three phase 50 HZ, 132KV/33KV
ONAN/ONAF cooling, step-down YNyno power
transformer complete with all accessories as detailed in the
specification.
(ii)
Lot-
Oil for first filling plus 10% to account for spillage etc. during filling
operation for the transformer.
24
(iii)
1 Set-
Tools for operation.
(iv)
1 Set-
Jacks for changing the direction of (4 Nos) bidirectional wheels of
the transformer.
(v)
One set of spares as specified below:
a)
b)
c)
d)
e)
f)
g)
h)
i)
j)
Two Nos. H.T. bushing complete with gaskets etc.
Two Nos. L.T.bushing complete with gaskets etc.
One No. neutral bushing with gasket etc.
One set of gaskets.
One set of fans with motors.
One set of recommended spare parts for off load tap changing mechanism.
Two sets of pressure relief diaphragms.
One set of winding temperature indicator alongwith temperature detector,
indicator and capillary etc.
One magnetic oil level gauge.
Any other item recommended for five years operation.
25
ANNEXURE-I
SCHEDULE OF GUARANTEED TECHNICAL PARTICULARS
(To be filled in by the Tenderer)
1.
Name of manufacturer and country of origin :
2.
Installation Indoor/Outdoor.
:
3.
Reference Standard
:
4.
Continuous rating under conditions specified in IS: 2026:
i)
Type of cooling
ii)
Rating MVA (ONAN)
(a)
(b)
:
HV
With ONAN cooling
With ONAF cooling
:
:
ii)
Rated voltage of HV winding (KV) :
iii)
Rated voltage of LV winding (KV) :
iv)
Rated frequency (C/S)
:
v)
Number of phases
:
vi)
Current at rated no load voltage and on principal tap
(a) HV Amps
(b) LV Amps
5.
:
:
Phase connections:
i)
ii)
iii)
6.
LV
HV winding
LV winding
Connection symbol
:
:
:
Temperature rise
i)
Temperature rise of oil above reference peak ambient temperature
(by thermometer - °C)
(a) At full ONAN rating in °C
(b) At full ONAF rating in °C
ii)
:
:
Temperature rise of winding above reference peak ambient temperature
(by resistance method- °C)
(a) At full ONAN rating in °C
:
26
(b) At full ONAF rating in °C
iii)
Limit of hot spot temperature for which the transformer
is designed (°C)
:
7.
Type of tap changing switch
8.
Tappings on windings HV/LV for:
9.
Constant flux/variable flux/combined regulation:
Location (Line/Central/Neutral) end winding:
Number of steps
:
Variation of (HV/LV)
:
i)
No load loss at rated voltage and frequency
at principal tap (KW)
:
No load loss at the voltage corresponding to
the highest tap (KW)
:
Tolerance, if any, on the above values:
iii)
11.
:
i)
ii)
iii)
iv)
ii)
10.
:
Load loss at rated output, rated frequency and corrected
for 75°C winding temperature at:
i)
ii)
iii)
iv)
Principal tap (KW)
:
Highest tap (KW)
:
Lowest tap (KW)
:
Tolerance, if any, on the above values:
(a)
Auxiliary losses at rated output, normal ratio,
rated voltage, rated frequency and ambient
temperature (KW)
:
Tolerance, if any, on the above values:
(b)
12.
Total losses at normal ratio inclusive of auxiliary
equipment losses (KW)
:
13.
Positive sequence impedance on rated MVA base,
at rated current and frequency one 75°C
winding temperature at:
i)
ii)
iii)
Principal tap (%)
Highest tap (%)
Lowest tap (%)
:
:
:
14.
Zero sequence impedance at reference temperature
of 75°C at principal tap (%)
:
15.
Reactance at rated MVA base at rated current and frequency (%):
27
16.
Regulation at full load and 75°C winding temperature expressed
as a percentage of normal voltage at:
i)
ii)
17.
Unity power factor (%)
0.85 power factor (lagging) (%)
:
:
Efficiencies at normal ratio, rated voltage, rates frequency at 75°C average winding
temperature at unity power factor and 0.85 power factor lagging for the out put of:
Unity P.F.
i) Full load.
ii) ¾ full Load
iii) ½ full Load
iv) ¼ full Load
0.85 P.F. .lagging
%
%
%
%
%
%
%
%
18.
i)
ii)
19.
Time in minutes for which the transformer can be run at full load without exceeding the
maximum permissible temperature at reference ambient temperature when:
i)
20.
:
HV winding
LV winding.
:
:
Permissible overloading:
(a)
(b)
22.
Supply of fans is cut off
Short time rating for 2 seconds of:
(a)
(b)
21.
Maximum efficiency (%)
:
Load at which maximum efficiency occur (% of full load):
HV winding
LV winding.
:
:
Terminal arrangement:
(a)
(b)
(c)
High voltage (HV)
Low voltage (LV)
Neutral – HV/LV
23.
Insulating and cooling medium
24.
Test Voltage:
:
:
:
:
HV
i)
ii)
iii)
Lightning impulse withstand test voltage (KV peak):
Power frequency withstand test voltage (dry & wet)
for 1 minute ((KV rms)
:
Switching impulse withstand test voltage (KV peakP:
25.
Partial discharge level at 1.5 Um/√3 KVrms (PC):
26.
Noise level when energised at normal voltage and
frequency without load (db)
:
28
LV
27.
External short circuit withstand capacity (MVA) and duration (seconds):
28.
Over flux withstand capability of the transformer:
29.
Details of core:
i)
ii)
iii)
iv)
v)
vi)
vii)
viii)
ix)
x)
30.
Type of core construction
:
Type of core joints
:
Flux density at rated voltage and frequency and at principal tap (Tesla):
Magnetizing current at normal ratio and frequency (Amps):
i)
85% of rated voltage
:
ii)
100% of rated voltage
:
iii)
105% of rated voltage
:
Power factor of magnetizing current at normal voltage ratio and frequency:
(i) Material of core lamination
:
(ii) Thickness of core laminations (mm):
(i) Whether core construction is without core bolts:
(ii) Insulation of core bolt
:
(iii) Insulation of core bolt washers :
(iv) Insulation between core laminations:
(v) Core bolt insulation withstand voltage for 1 minute (KV rms):
(vi) Are the core bolts grounded. If so how:
(i) Materials of core clamping plate :
(ii) Thickness of core clamping plate :
(iii) Insulation of core clamping plate :
Describe location/Method of core grounding:
Details of oil ducts in core
:
Details of windings:
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
HV
LV
Type of windings
:
Materials of the winding conductor :
Maximum current density (at rated current)-(A/cm2):
i)
HV
:
ii)
LV
:
iii)
Regulating
:
Whether HV windings are interleaved:
Whether windings are preshrunk
:
Whether adjustable coil clamps are provided for HV and LV windings:
Whether steel rings used for the windings if so, whether they are split:
Whether electro-static shields are provided to obtain uniform voltage distribution in
the HV windings
:
Insulating materials used for:
i)
HV winding
:
ii)
LV winding
:
iii)
Regulating winding
:
Insulating material used between:
i)
HV and LV winding
:
ii)
LV winding and core
:
iii)
Regulating winding & earth :
29
(k)
(l)
(m)
31.
Bushings:
i)
ii)
iii)
iv)
v)
vi)
vii)
viii)
ix)
x)
xi)
xii)
xiii)
xiv)
32.
Type of axial coil supports:
i)
HV winding
:
ii)
LV winding
:
Type of radial coil supports:
i)
HV winding
:
ii)
LV winding
:
Maximum allowable torque on coil clamping bolts:
HV
Minimum clearance (mm):
i)
ii)
HV
LV
Approximate weight:
(a)
(b)
(c)
(d)
(e)
(f)
(g)
34.
Neutral.
Make and type
:
Reference standard
:
Rated voltage class (KV)
:
Rated current (Amps)
:
Lightning impulse withstand test voltage
(1.2 x 50 microsecond) (KV peak) :
Switching surge withstand test voltage (KV peak):
Power frequency withstand test voltage:
(i)
Wet for 1 minute (KVrms) :
(ii)
Dry for 1 minute (KVrms) :
Partial discharge level
:
Creepage distance (mm)
:
Creepage distance (protected)
:
Whether test tap is provided
:
Quantity of oil in bushing and specification of oil used (Kg):
Weight of assembled bushing (Kg) :
Minimum clearance height for removal of bushing (mm):
In oil
Between
Phase to
Phases
Ground
33.
LV
Core with clamping (Kg)
:
Coil with insulation (Kg)
:
Core and winding (Kg)
:
Oil required for first filling (Kg)
:
Tank and fittings with accessories (Kg):
Untanking weight (Kg)
:
Total weight with oil and fittings (Kg):
Details of Tank:
(a)
(b)
Type of tank
Approximate thickness of sheet:
i)
Sides (mm)
ii)
Bottom (mm)
iii)
Cover (mm)
:
:
:
:
30
In Air
Between
Phase to
Phases
Ground
(c)
(d)
(e)
(f)
(g)
(h)
35.
Conservator:
i)
ii)
iii)
36.
iii)
iv)
v)
vi)
vii)
Governing standard
:
Specific resistance (ohm-cms) at:
(a)
27°C
:
(b)
90°C
:
Tan delta
:
Water content (ppm)
:
Dielectric strength (Breakdown voltage) (KV):
Characteristic of oil after ageing test:
(a)
Specific resistance (ohm-cms) at:
27°C
:
90°C
:
(b)
Tan delta
:
(c)
Sludge content
:
(d)
Neutralisation Number
:
Details of oil preserving equipment offered:
Radiator:
i)
ii)
iii)
iv)
v)
vi)
38.
Total volume (Litres)
:
Volume between highest and lowest visible oil level (Litres):
Power required by heaters (if provided) (KW):
Oil Quality:
i)
ii)
37.
iv)
Cooling tubes/radiators (mm) :
Vacuum recommended for hot oil circulation (torr):
Vacuum to be maintained during oil filling in transformer tank (torr):
Vacuum to which the tank can be subjected without distortion (torr):
No. of bi-directional wheels provided:
Track gauge required for the wheels
Transverse Axis
Longitudinal Axis
Type of pressure relief device/explosion
Vent and pressure at which it operates:
Overall dimensions l x b x h (mm)
Total weight with oil (Kg)
Total weight without oil (Kg)
Thickness of radiator tube (mm)
Types of mounting
Vacuum withstand capability
:
:
:
:
:
:
Cooling System:
(a)
(b)
(c)
(d)
(e)
(f)
(g)
Fan Motor
Make and type
No. of connected units
No. of standby units
Rated power input
Capacity (cum/min) or (litres/min)
Rated voltage (volts)
Locked rotor current (Amp)
31
:
:
:
:
:
:
:
(h)
(i)
(j)
(k)
(l)
(m)
Efficiency of motor at full load (%) :
Temperature rise of motor at full load (°C):
BHP of driven equipment
:
Temperature range over which control is adjustable (°C):
Whether the fan and/or pumps suitable for continuous operation
at 85% of their rated voltage
:
Estimated time constant in hours for:
i)
Natural cooling
:
ii)
Forced air cooling
:
39.
Gas and oil operated relay make and type
40.
Temperature indicators:
i)
ii)
iii)
iv)
v)
41.
:
Oil temperature
Indicator
Winding temperature
indicator
Make and type
:
Permissible setting
ranges for alarm and trip:
Number of contacts :
Current rating of each contact:
Whether remote indicators provided.
If so, whether equipment required
at purchaser’s control room is included:
Approximate overall dimension:
i)
ii)
iii)
Length (mm)
Breadth (mm)
Height (mm)
42.
i)
ii)
Minimum clearance height for lifting core and winding from tank (mm):
Minimum clearance height for lifting tank cover (mm):
43.
Shipping Details:
(a)
(b)
:
:
:
Approximate weight of heaviest package (Kg):
Approximate dimensions of largest package:
44.
Transformer will be transported with oil/gas :
45.
Size of rail recommended for the track
46.
Lifting Jacks:
i)
ii)
iii)
iv)
v)
vi)
vii)
viii)
:
Governing standard
No. of jacks in one set
Type and make
Capacity (tonnes)
Pitch (mm)
Lift (mm)
Height in closed position (mm)
Mean diameter of thread (mm)
:
:
:
:
:
:
:
:
32
47.
Marshalling kiosk:
48.
i)
Make & type
:
ii)
Details of apparatus proposed to be housed in the kiosk:
Details of anti-earthquake device provided :
49.
Separate conservator and Buchholz relay provided:
50.
Tap changing equipment:
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
(k)
(i)
(m)
(n)
(o)
(p)
(q)
(r)
(s)
(t)
(u)
(v)
(w)
Make
Type
Power flow-unidirectional/bi-directional/restricted bi-directional:
Rated voltage to earth (KV)
:
Rated current (Amps)
:
Step voltage (volts)
:
Number of steps
:
Control-Manual/Local Electrical/Remote Electrical:
Voltage control-Automatic/Non Automatic:
Line drop compensation provided/Not provided:
Parallel operation
:
Protective devices
:
Auxiliary supply details
:
Time for complete tap change (one step( sec.:
Divertor selector switch transient time (cycles):
Value of maximum short circuit current (Amps):
Maximum impulse withstand test voltage with 1.2/50 micro-seconds full wave
between switch assembly and ground (KV peak):
Maximum power frequency test voltage between switch assembly and earth (KV
rms)
:
Maximum impulse withstand test voltage with 1.2/50 microseconds across the
tapping range (KV peak)
:
Approximate overall dimensions of tap changer
(In case of separate tank type)
:
Approximate overall weight (Kg)
(In case of separate tank type)
:
Approximate mass of oil (Kg)
(In case of separate tank type)
:
Particulars of the OLTC control panel for installation in the control room:
51.
Driving mechanism box:
i)
ii)
Make & type
:
Details of apparatus proposed to be housed in the box:
(Signature of Tenderer)
Name (in block letters)
Stamp:
33
ANNEXURE-II
SCHEDULE OF PRICES
(to be filled in by the Tenderer)
6
1
34
1
1
Unit Rate
FOR
Destination
(P)
Total
Amount (P)
(viii)
(ix)=(v)+
(vi)+(vii)+
(viii)
(x)=(iv)
x (ix)
(vii)
Freight &
Insurance
(P)
Tax (P)
Excise Duty
(P)
Ex - Work
Rate (P)
Quantity
(iv)
(vi)
1
(v)
1
Unit
(iii)
No
Lot
25 MVA three phase 50
Hz, 132/33 KV YNyno,
ONAN/ONAF
cooled
outdoor type step down
transformer
complete
with all accessories,
fittings, bushings etc. as
detailed
in
the
specification
(without
oil)
Insulating oil for first
filling
of
above
transformer (including
10% extra)
Jacks for lifting the
transformer
Spare parts (details of
items and prices as
enclosed at AnnexureVI)
Itemised prices for T & P
for
erection
and
maintenance (attach a list
giving details of items)
Erection
and
commissioning charges
for
the
above
equipments.
Set
(ii)
Set
Description
Set
5
4
3
2
1
(i)
Sl. No.
Note:- In addition to filling up this schedule, the Tenderer shall attach separately a detailed list of
material he is supplying
7
Number of supervisory
personnel recommended
for
satisfactory
supervision of erection
and commissioning in
case only the supervision
of
erection,
commissioning
is
entrusted
to
the
contractor, alongwith the
daily charges for the
services
of
each
supervisory staff.
(Signature of tenderer)
Name (in block letters)
Stamp:
35
ANNEXURE-III
SCHEDULE OF DEVIATION
Unless specifically mentioned in this schedule the Tenderer shall be deemed to conform to the
purchasers specification.
1
Specification Clause
Deviation by the
Tenderer
Justification by the
Tenderer.
(Signature of Tenderer)
Name (in block letters)
Stamp:
36
ANNEXURE-IV
SCHEDULE OF INSTALLATION
The Tenderer shall furnish here a list of similar equipment supplied by him and presently in service.
1
Name of brief description of
installation.
Customer
Year of supply.
(Signature of Tenderer)
Name (in block letters)
Stamp:
37
ANNEXURE-V
SCHEDULE OF DELIVERY
(Earliest delivery period for transformer/component parts, oil etc. shall be specified).
Sl.No.
Description of item quantity
Earliest delivery.
(Signature of Tenderer)
Name (in block letters)
Stamp:
38
ANNEXURE - VI
SCHEDULE OF PRICES FOR SPARES
(to be filled in by Tenderer)
Sl. No.
Item
Price
Quantity
Each
Signature of Tenderer
Name (in block letters)
Stamp:
39
Total