HARYANA VIDYUT PRASARAN NIGAM LIMITED
TECHNICAL SPECIFICATION NO. HGD/S- 48 (R-7)/DGP-22
TECHNICAL SPECIFICATION
FOR
25/31.5 MVA 66/11 kV POWER TRANSFORMERS
CHIEF ENGINEER/MM
HVPNL, PANCHKULA
TELEPHONE & FAX:
0172- 2583724
(NOVEMBER, 2014)
-0-
TECHNICAL SPECIFICATION FOR
25/31.5 MVA, 66/11 kV POWER TRANSFORMERS
1.0
SCOPE:
a) This specification covers the Design, Engineering, manufacture, testing, supply on CIP basis,
transportation to site, insurance, storage, testing of 31.5 MVA 66/11 kV Power Transformers.
b) All drawings, schedules and annexures appended to this specification shall form part of the
specification and supplement the requirements specified. The equipment/materials offered by
the bidder shall be complete in all respects and whether called for specifically or not, all
accessories, hardware and services required for normal satisfactory operation of the system
shall be deemed to be included in unit rates quoted. Design and manufacture shall also be
such that equipment/accessories of the same type and rating would be interchangeable.
2.0
Specific reference in this specification and documents to any material by trade name, make
or catalogue number shall be construed as establishing standard of quality and performance
and not as limiting competition. All equipment/accessories offered shall also be of proven
design and manufacture. The make of all accessories and hardware shall be subject to
purchaser’s approval.
Codes & Standards :
All standards, specifications and codes of practice referred to herein shall be the latest
editions including all applicable official amendments and revisions as on date of opening of
bid. The following standard and codes shall be applicable:
IS : 5
Colour for ready mix paints.
IS : 325
Three phase induction motors
IS : 335
New insulating oils for transformer.
BS:148/IEC:296
IS : 375
Marking & arrangement of switch-gear bus bars main
connections and auxiliary wiring.
IS : 1866
Code of practice for maintenance of insulation oil.
IS : 2026 & IEC : 76
Specification Power transformers
IS : 2099 & 3347
Bushing for alternative voltages above 1000 volts
IS : 2147
Degree of protection provided by enclosures for low voltage
switchgear and control gear
IS : 2705
Current transformer
IS : 3637
Gas operated relay.
IS : 3639
Fittings and accessories for Power Transformers
IS : 6600 & IEC : 354
Guide for loading of oil immersed transformers
IS : 8468 & IEC : 214
On load tap changer.
IS : 5561
Electric power connectors
IS : 617
Aluminium Alloy grade.
IS : 2629
Recommended practice for hot dip galvanising
IS : 8478
On load tap changer application guide.
IS : 8603
Dimensions for porcelain transformer bushings for use in heavily
polluted atmosphere (36 kV Class) Dimensions for oil filled
porcelain transformer bushings for use in medium polluted
atmosphere.
IS : 9434
Guide for sampling and analysis of free and dissolved gas in oil
filled equipment.
IS : 10028
Code of practice for selection, installation and maintenance of
transformers
IS : 12676
Dimensions for OIP insulated condenser bushings
CBIP
Manual on transformer
Equipment complying with other internationally accepted standard will also be considered if
these ensure performance and constructional features equivalent or superior to standard
listed above. In such a case, the bidder shall clearly indicate the standards adopted, furnish a
copy in English of the latest revision of standard alongwith copies of all official amendments
3.0
4.0
4.1
4.2
4.2.1
4.2.2
4.2.3
4.2.4
4.2.5
4.2.6
4.2.7
4.2.8
4.2.9
and revisions in force as on date of opening of bid and clearly bring out the salient features
for comparison.
CLIMATIC CONDITIONS :
The transformers are required to operate satisfactorily under the following site conditions:
3.1
Max. Temperature
500 C
3.2
Min. Temperature
- 2.50 C
3.3
Max. Relative Humidity
100%
3.4
Min. Relative Humidity
26%
3.5
Average number of rainy days per annum
nearly 120 days
3.6
Average annual rainfall
900 m
3.7
Average number of dust storm days per annum
35
3.8
Isoceraunic level
45
3.9
Max. wind pressure
195-kg-sq.m
3.10
Altitude above mean sea level
Less than 1000 m.
TYPE AND RATING
The transformer shall be of two winding 3-phase oil immersed core type with ONAN/ONAF
cooling suitable for outdoor service as step down transformers.
These transformers shall not be provided with the tertiary delta winding.
The ratings and other characteristics which are not covered elsewhere shall be, as detailed in
following clauses :
Max. continuous capacity :
a)
ONAN
25 MVA
b)
ONAF
31.5 MVA
Number of phases
3
Frequency
50 Hz
s(± 5%)
Rated Voltage :
a)
HV side.
66 kV
b)
LV side.
11 kV
Connections :
a)
HV side.
Star
b)
LV side.
Star
Vector group
YYO
%age Impedance
10% at 31.5 MVA base
ON load taps on HV side.
a)
Insulation level
i)
Impulse withstand test voltage.
ii)
Power frequency withstand voltage.
b)
Insulation level of Bushings.
Impulse voltage.
Power frequency voltage.
4.2.10 Creepage Distance :
a)
Total
5.0
5.1
5.2
+5% to –15% in steps of 1.25% each
66 kV
11 kV
325 kV (P)
95 kV (P)
140 kV
38 kV
(rms)
(rms)
325 kV(P)
140 kV
(rms)
95 kV(P)
38 kV
(rms)
25 mm per kV corresponding to
highest system voltage i.e.72.5 kV
50% of the total creepage distance
b)
Protected
GENERAL DESIGN OF TRANSFORMER :
The transformer and accessories shall be so designed as to facilitate inspection cleaning and
repairs. The requirement of Indian Electricity Rules shall be kept in view.
The design shall ensure satisfactory operation under severe working conditions due to
fluctuating load of steel furnaces and voltage variations in the system including those due to
short circuits. The transformers shall be designed so as to minimize the risk of accidental
short circuits caused by animals, birds or vermins.
5.3
5.4
5.5
5.6
5.7
5.8
5.9
5.10
5.11
5.12
5.13
5.14
5.15
5.16
5.17
5.18
5.19
6.0
The design shall incorporate every reasonable precaution and provision for the safety of all
those concerned in the operation and maintenance of the equipment keeping in view the
requirements of Indian Electricity Rules.
All material used shall be of the best quality and of class most suitable for working under
specified conditions and shall withstand the atmospheric conditions and temperature
variations without undue deterioration or distortion or setting up of undue stress in any part
thereof.
Cast iron shall not be used for any parts other than the large valve bodies.
Corresponding parts liable to be replaced shall be interchangeable.
All taper pins to be used in the mechanism shall be split type as per latest edition of IS :
2393.
All mechanism should be rust and corrosion proof. Means shall be provided for lubrications of
moving parts not immersed in oil.
The construction shall be such as to avoid air or water pockets. Special care shall be
exercised to reduce noise and vibration to the minimum level.
Steel bolts of suitable finish will be used for diameters above 6 mm brass bolts or studs used
for electrical connections shall not be of less than 6 mm diameter. On outdoor equipment, all
bolts, nuts and washers in contact with current carrying non-ferrous parts shall be phosphor
bronze.
All nuts, bolts and pins shall be locked except those, which are external to the transformer. If
bolts and nuts are so placed as to be inaccessible by means of ordinary spanners, suitable
special spanners shall be provided by the supplier.
Labels shall be provided for all apparatus like relays, switches, fuses etc. housed in any
cubicle or marshalling kiosks. These shall be of in corrodible material with matt/satin finish
and permanent lettering. Labels mounted on black surface shall have white letters and
danger notices shall have red lettering on a white background. The labels shall be secured
by means of brass screws or rust protected steel screws.
Surface in contact with oil shall not be galvanized or cadmium plated.
Before painting, all un-galvanized parts shall be cleaned, made free from rust, scale and
grease and external wrought surfaces smoothened (filled with metal deposition). The interior
of the tank and other oil filled chambers shall be cleaned by shot blasting or any other
suitable method.
All external surfaces shall be given three coats of paints except for nuts, bolts and washers
which may be given one coat after assembly transformer at works. The final coat shall be
glossy oil and weather proof, non fading paint of shade 631 of IS : 5.
The interior of mechanism chambers and kiosks shall be given 3 coats of paint, the final coat
being of a light colored anti-condensation mixture.
The outer most radial spacers of the winding shall be locked in position by means of vertical
strips so that the same cannot fall off/got displaced.
Proper & complete tightening of the nuts of the coil clamping bolts must be ensured by the
manufacturers. The nuts of all the coil clamping bolts will be tightened to designed value and
the job be carried out with torque spanners.
The devices used for locking the nuts of coil clamping bolts must be of such a quality and
such care should be taken first in tightening the nuts and next in locking them in position so
that the arrangement does not become loose due to stresses caused by short circuits and
fluctuating loads etc.
The noise level shall not be more than 5 dB above NEMA standard publication TR:1.
The transformers shall be designed to have short circuit rating of five seconds as per IS:2026.
INSULATING OIL :
Sufficient insulating oil of Napthenic type (made from Naphthenic crude) in which paraffinic
content should be less than 50% and aromatic content 4 to 12% conforming to BS:
148/IEC:296 class-1 shall be supplied for first filling of each transformer. Particular attention
shall be paid to deliver the oil at site free from moisture and of uniform quality through out in
7.0
7.1
7.2
7.3
8.0
9.0
10.0
10.1
10.2
10.3
[
10.4(a)
non-returnable steels drums. The quantity of oil for first filling of each transformer shall be
stated in tender along-with trade mark of the oil to be supplied. Use of inhibitors in oil shall
not be resorted to. 10% extra oil of the total quantity of oil shall be supplied along with the
transformer.
LIMIT OF TEMPERATURE RISE
With the above climatic conditions, given in clause-3 each transformer shall be capable of
operating continuously on any tap at their normal rating without exceeding following
temperature rises :
i)
350 C in oil by thermometer.
ii)
450 C in winding by resistance.
iii)
Winding gradient i.e. the difference between average winding and average oil
temperature not to exceed 130 C.
iv)
Temperature of hot spot in winding not to exceed 950C when calculated over max.
Annual weighted average temperature of 400 C
The limits of temperature rise mentioned above will have to be satisfied by the manufacturer
by carrying out the heat run test at the lowest negative tap. This test shall be carried out by
feeding 1.1 times the total losses at 750 C at highest current tap.
OVERLOAD CAPACITY & CONTINUOUS RATING.
The safe over load capacity of the transformer and the duration of overload under maximum
temperature conditions without any damage to the winding or harmful effects on the
insulation shall be clearly stated in the tender which must be as per IEC-354/IS:6600, guide
for loading of oil immersed transformer.
IMPEDANCE:
The transformer shall have 10% impedance on 31.5 MVA base with tolerance as per
IS:2026/Part-1 (1983). Impedance shall include positive and zero sequence and shall be
expressed in terms of the branches of the star connected equivalent diagram, all on the
same kVA base and range shall be given for each branch of the equivalent circuit in turn.
The percentage impedance on normal tap should be 10% and on extreme taps i.e at tap
No.1 it should be 10.3% and on tap No.17 it should be 9.5%. Percentage tolerance allowed
at extreme tap be as applicable to normal tap.
FREQUENCY:
The transformer shall be suitable for continuous operation with a +/-5% frequency variation
from a normal of 50 Hz without exceeding the temperature rise as specified in Clause 7.1
above.
FLUX DENSITY, CORE CONSTRUCTION AND INSPECTION
The transformer should be so designed that the working flux density should not exceed 1.57
Tesla at normal voltage, frequency.
Tenders with higher flux density than specified limit shall not be considered.
The core shall be built up with thin laminations of high grade. non-ageing, low loss, high
permeability cold rolled super grain oriented silicon steel. Known as MOH High B Grade or
superior grade CRGO steels of maximum 0.27 mm or low lamination thickness especially
suitable for transformer core.
(i)Bidder should have in house core cutting facility for proper monitoring & control on quality
and also to avoid any possibility of mixing of prime material with defective/second grade
material. The purchaser may witness the core-cutting operation. In case the in house core
cutting facility for core cutting is not available then the same shall be carried out in the
presence of the representative of HVPN.
(ii)Inspection call notice for the purpose should be accompanied with the following documents
as applicable as a proof toward use of Prime core materials :a) Invoice of supplier.
b) Mills test certificates.
c) Packing list.
d) Bill of loading.
e) Bill of entry certificates by customs.
Core material shall be directly procured either from the manufacturer or through their
accredited marketing organisation of repute and not through any agent.
10.4(b)After being sheared, the laminations shall be treated to remove all burrs. They shall be
coated with a baked enamel insulation coating. The insulation shall be inert to the action of
hot transformer oil and shall be perfectly adhesive. Paper and varnish insulation shall not be
accepted. Particulars of proposed insulation shall be stated in the tender. Laminations shall
be checked for burrs during stage inspection.
10.5
10.6
10.7
10.8
The core shall be rigidly clamped and/or bolted to ensure adequate mechanical strength and
to prevent vibrations during operation. The bolts used in the assembly of the core shall be
suitably insulated and the clamping structure shall be constructed that the eddy currents will
be minimum.
Construction of the core shall be such that number of steps in the limb and yoke shall be
matching and dimensionally identical to minimize the effect of cross fluxing and better
mechanical strength.
The core shall be provided with Lugs suitable for lifting the complete core and coil assembly
of transformer. The Core & coil shall be fixed in the tank such that its shifting will not occur
when the transformer in moved or when a short circuit occurs.
The design of magnetic circuit shall be such as to avoid static discharge development of
short circuit paths within itself or to the earthing clamping structure and the production of flux
components at right angles to the plane of the lamination which may cause local heating.
10.9
Every care shall be exercised in the selection treatment and handling of core steel to ensure
that the laminations are flat and that finally assembled core is free from distortions.
10.10 The supporting frame work of the core shall be so designed as to avoid the presence of
pockets which would prevent complete emptying of the tank through the drain valve or cause
trapping of air during filling.
10.11 Oil ducts where necessary should be formed across the plane of the lamination and be given
a suitable slope to assist oil circulation. The overall design of core and winding should be
such that free flow of oil is not obstructed.
10.12 The frame work and clamping arrangement shall be earthed by connecting to the tank body
through a copper strip. Yoke bolt area should be compensated if bolts are used for fastening
of the core.
10.13 The insulation of core to bolts and core to clamp plates shall be able to withstand a voltage of
2 KV RMS for one minute.
10.14 Core and windings shall be capable of withstanding shocks during transport, installation,
service and adequate provision shall be made to prevent movement of core and winding
relative to tank during these conditions.
10.15 All steel sections used for supporting the core shall be thoroughly sand blasted after cutting
drilling and welding.
10.16 All the CRGO vendors having BIS certification and approval from PGCIL shall be considered.
10.17 The tenderers should indicate the maximum flux density allowable continuously as well as for
time intervals of 1 minute and 5 secs. and the limit of flux density at which core material used
by them saturates.
10.18 The name of the core material must be mentioned in the tender. The successful tenderer
shall be required to furnish magnetization curves of the core material/design calculations and
such other data/documents deemed fit by the Purchaser for being satisfied that flux density is
as desired.
10.19 Purchaser shall inspect the built-up core for verification of flux density for which all facilities
shall be provided. The purchaser shall inspect/test the core material for various tests as per
relevant IEC/IS to ensure quality. Core may also be inspected during horizontal assembly,
built-up assembly.
NOTES :
i) The above flux density has been specified to meet with the over fluxing of the core due to
temporary over voltage of the order of 31% for l min, 44%for 5 sec. that may appear
abnormal conditions such as those following sudden loss of large loads.
ii) Yoke bolt area and flitch plate areas shall not be counted in the net core area if these are
provided for fastening core.
iii) The design of limb and yoke shall be so co-ordinate that there is no cross fluxing at the
joints.
iv) The tenderer shall ensure that the CRGO supplier should have BIS certification.
11.0 SUPPRESSION OF HARMONICS:
The transformer shall be so designed as to suppress the harmonics voltage specially the 3 rd
& 5th, to eliminate wave form distortion and interference with communication circuits due to
higher frequency disturbances. Percentage of harmonics at normal voltage and at maximum
system voltage shall be stated in the tender.
12.0 WINDING:
12.1 The 66 kV winding shall have graded insulation whereas all other windings shall be fully
insulated and the neutral points shall be insulated as amended in IS:2026.
12.2 The transformers shall be capable of operation without danger on any particular tapping at
the rated KVA when the voltage may vary by +/- 10% of the voltage corresponding to the
tapping.
12.3 The windings and connections as well as the insulations material shall not soften ooze,
shrink or collapse during service.
12.4 No strip conductor wound on edge shall have a width exceeding six times its thickness. The
conductors shall be transposed at sufficient intervals to minimize eddy currents and equalize
the current and temperature distribution along the windings.
12.5 The windings and connections shall be properly brazed to withstand shocks during
transportation or transient conditions during service.
12.6 The adequate pre-shrinkage of the coil assembly using pre-compressed press board material
having low moisture content for the radial spacer blocks shall be ensured by the
manufacturers so that there is no displacement of the radial spacer blocks due to frequent
short circuits on the transformers.
12.7 All windings after being wound and all fibrous hygroscopic materials used in the construction
of the transformer shall be dried under vacuum and impregnated with hot oil.
In addition to this the drying process be sufficiently extended for proper stabilization of the
coil assembly. More than one cycle of soaking in oil followed by re-tightening of the coil
assembly should be adopted.
12.8 The coil clamping rings wherever used shall preferably be of flat insulated steel laminations.
Axial laminated material except bakelised paper shall not be used.
12.9 The clamping arrangement shall exert equal pressure on all columns of spacers of the
transformer windings built of sections or disc-coils separated by spacers. In no case, spiral
winding will be used either for HV or LV windings.
12.10 The radial spacer blocks must be made of pre-compressed pressboard material. Which will
not soften out while in contact with oil or fray out into fibers or edges. The slots should be so
dimensioned that the blocks will not come out of the slots.
Uniform distribution of coil clamping force shall be designed by using an adequately large
number of coil clamping bolts and by transferring the clamping force from clamping bolts to
the clamping plates through intermediate members which can spread the clamping force over
a large area.
12.11 All joints shall be brazed/crimped considering the vibrations due to short circuits and load
fluctuations.
13.0 CURRENT DENSITY:
The transformer shall be so designed that the current density at any tap should not exceed
250 Amp./cm. Sq. in HV and regulating winding and 200Amp./cm. Sq. in LV winding.
[
The purchaser shall be at liberty to inspect built-up winding for its quality, weight of copper,
insulation and overall weight of coil assembly. The size of conductor used for different
windings shall also be checked during stage inspection to check the current density vis-à-vis
guaranteed values.
14.1 TANK CONSTRUCTION :
14.1.1 The tank shall be fabricated of a suitable grade steel and strong enough to allow the lifting of
complete transformer with oil by means of a crane or jacks and transported to site without
over-straining the joints etc.
14.1.2 The main tank body shall be capable of withstanding a vacuum of 100.64 kNm2 (760 mm of
Hg.)
14.1.3 The base shall be so designed as to allow the transformer to be moved by skidding without
any injury.
14.1.4 All channeled constructions and stiffeners shall be designed to avoid retention of water.
14.1.5 The tank construction shall be free of air pockets. Where such pockets cannot be avoided,
vent pipes of 15-mm internal diameter shall be provided to vent gases into the main
expansion pipes. In case of short branch pipes, however, minimum diameter may be taken
as 6mm.
14.1.6 All joints other than those, which may have to be broken, shall be welded. When required
they shall be double welded. All bolted joints to the tank shall be fitted with suitable oil tight
gaskets, which shall give satisfactory service under the operating conditions and guaranteed
temperature rise conditions. Special attention shall be given to the methods of making hot oil
tight joints between the tank and the cover and also, between the cover and the bushings
and all other out-lets to ensure that the joints can be remade satisfactorily at site and with
ease by semi-skilled labour.
14.1.7 Suitable lifting lugs for lifting the transformer filled with oil shall be provided on the tank.
14.1.8 Four jacking lugs shall be provided to enable the transformer complete with oil to be lifted or
lowered by means of jacks. The lugs shall be fitted at a minimum height (excluding under
base if detachable) of 300mm for transformer upto 10 tonnes weight and of 500 mm for
transformer above 10 tonnes weights.
14.1.9 The transformer shall be provided with detachable steel flanged wheels of 250 mm dia and
suitable for moving transformer complete with oil. These shall be bi-directional and mounted
on swivels which may be turned through 900 when the tank is jacked up and capable of being
locked in position paralled to and at right angles to the longitudinal axis. The wheel be
suitable for standard gauge track of 1676mm.
14.1.10 The Transformer tank should be designed in such a way that over all length of transformer
does not exceed 7 meters.
14.2
TANK COVER:
14.2.1 The tank cover shall be of bolted type and of adequate strength so as not to distort, when
lifted. Suitable inspection cover shall be provided with lifting arrangements to give access to
bushings, winding connections or testing the earth connections. The weight of each
inspection cover shall not exceed 25 Kg.
14.2.2 Pockets shall be provided in the position of Max. oil temperature at CMR for fitting a
thermometer and for bolts of oil and winding temperature indicators. The thermometer
pockets shall be fitted with a captive screwed cap to prevent ingress of water.
14.2.3 Suitable No. of jacking bolts shall be provided on tank cover, inspection covers/windows
including OLTC.
14.3 CONSERVATOR TANK, OIL GUAGE AND BREATHER :
14.3.1 An adequate conservator tank complete with sump and drain valves shall be provided in such
a position as not to obstruct the electrical connections to the transformer.
14.3.2 If the sump is formed by extending the feed pipe inside the conservator, this extension shall
be atleast 25mm.
14.3.3 One end of the conservator shall be bolted type to facilitate cleaning.
14.3.4 The conservator shall be provided with a magnetic oil level gauge.
14.3.5 The oil connections from the transformer tank to the conservator shall be at rising angle of 3
to 9 degrees to the horizontal upto Buchholz relay. The inside diameter of the pipe shall be 80
mm. the buchholz relay will have suitable valves on its both side so as to facilitate its testing
at site as well as cut off oil supply to the transformer.
14.3.6 The conservator shall be provided with oil preservation system, which should be suitable
either to remove moisture continuously from air entering the air space with which they are
connected or may not allow direct contact of atmospheric air with oil during operation, in
addition to silica gel breather.
14.4 VALVES:
14.4.1 The transformers shall be provided with a filter valve of 50 mm size mounted on top of the
main tank oil circulations and one drain valve of 80 mm size with plug. The conservator shall
have drain plug of 25 mm size.
14.4.2 Three robust sampling valves with spouts suitable for taking samples of top middle and
bottom oil shall be provided. The top and middle sampling valves shall be brought down by
internal pipe connections. Suitable nameplates shall be affixed to the sampling valves. The
sampling device shall not be fitted on the filter valve.
14.4.3 Two – air release plug of 15 mm shall be provided.
14.4.4 Plugs shall be supplied for all valves opening to atmosphere.
14.4.5 All valves shall comply with the latest edition of IS:3639.
14.5 PRESSURE RELIEF DEVICES:A suitable pressure relief device of 6” dia shall be provided on the main tank and of 3” dia
shall be provided on OLTC for rapid release of any pressure in transformers which may
endanger the equipment. The device(s) shall operate at static pressure of less than hydraulic
test pressure for transformers tank OLTC chamber. If the device is mounted on tank cover, it
shall be fitted with a skirt projecting 25 mm inside the tank and of such construction as to
avoid gas accumulation.
In addition to pressure relief device(s) the provision of explosion vent should also be made
and the diaphragm shall be situated above max. oil level.
14.6 EARTHING TERMINAL:14.6.1 Two earthing pads suitable for connecting 50x8 mm mild steel flat shall be provided at
positions close to the two diagonally opposite bottom corners of tank. These grounding
terminal shall be suitable for bolted connection. Two earthing terminal shall also be provided
each on marshalling box an any other equipment mounted separately.
14.7 JOINTS AND GASKETS:14.7.1 All gaskets used for making oil tight joints shall be of granulated cork bonded with synthetic
rubber. Metal tops shall be provided for preventing over compression wherever compressible
gaskets are provided.
14.8 RATING AND DIAGRAM PLATES:14.8.1 Each transformer shall carry a diagram plate showing internal connections, voltage vector
relationship of different windings, plan view of the transformers showing physical relationship
of the terminals and no load voltage for each tap.
14.8.2 Each transformers shall be provided with a rating plate & diagram as specified in IS:2026.
14.8.3 I. R. values along with oil temperature at the time of testing at manufacturer’s works shall be
indicated on rating plate or separate plate, to be provided on transformers.
14.9 THERMOSYPHON FILTER ARRANGEMENT
Thermosyphon filter arrangement shall be provided on the transformer for preserving the
quality of Transformer Oil. The filter assembly shall be mounted on the Transformer as well
as ground supported and connected with pipes and shut off valves. Suitable instructions
required to be followed for commissioning, dismantlement & maintenance of the filter
arrangement, re-generation and storage of the adsorbent etc. must be included in the
instruction manual. A detailed drawing showing internal arrangement, shall also be required
to be submitted. Suitable capacity pump (alongwith motor) shall also be provided to boost
circulation of oil. The pump and motor should not be in main pipe line. It should be in bypass
pipe line having suitable valve to isolate from main pipe line. The main pipe line should have
two shut off valves at the bottom.
NOTE : The pump and motor should be weather proof(Flow well Type).
The oil & sorbent capacity required in the Thermosyphon Filter is as under: (i)
Quantity of oil
2.0% of total oil by weight.
(ii)
Quantity of adsorbent
1.25% of total oil by weight.
15.0
15.1
COOLING PLANT:Detachable radiators shall be fitted on the main tank with machined flanged outlet and inlet.
Each radiator shall be provided with 19 mm drain plug at bottom and 19 mm air release plug
at the top. Valves shall be provided on the tank at each point of connection to radiators.
15.2 In case separate cooler banks are used, they shall be suitable for mounting on a flat concrete
base. These shall be provided with a valve (25mm) at each point of connection to the
transformers tank, removable blanking plates to blank off main oil connections to each cooler.
Thermometer pockets with captive screwed cap at inlet and outlet of each separate cooler,
filter value at top and bottom and air release plug of 15 mm shall be provided.
15.3 The motor blowers shall be direct driven suitable for continuous out door operation and
complete with necessary air dusting. These shall be mounted independently from the radiator
and in case, these are radiator mounting type use shall be made of some anti-vibration
means. Care shall be taken that the lower unit is capable of being removed without disturbing
the radiator structure. The blades shall be suitably painted and shall not be of hollow
sections. Suitably painted wire mesh guards with mesh not greater than 25 mm shall be
provided to prevent accidental contact with the blades.
15.4 MOTORS:15.4.1 The motor shall be squirrel cage totally enclosed weatherproof type suitable for direct starting
and for continuous running from 415/240 volts, three phase/single phase 50 HZ supply. The
motors shall comply with IS as applicable for continuous rated machine.
15.4.2 All motors shall be capable of continuous operation at frequency 50 Hz with variation of “5%
and 415/240 V AC” 10% variation of the normal voltage without injurious over heating.
15.4.3 All motors shall have ball or roller bearing with hexagonal nipples for greasing. In case of
vertical spindle, motor shall have bearing capable of withstanding thrust, due to weight of the
moving parts.
15.4.4 Varnished cambric or glass insulator shall be used for connections from stator winding to the
terminal suitable for external wiring. The motor terminals shall be of stud type and totally
enclosed.
15.5 COOLER CONTROL:15.5.1 Each motor or group of motors shall be provided with a 3 pole electrically operated contractor
with control gear for motor operation by hand and automatically through winding temperature
indicator. Provision shall be made for over load protection but no volt release coil shall not be
provided.
15.5.2 All connection shall be so arranged as to allow either individual or collective operation of the
motors. Alarm indication (audio and visual) for failure of fans and to indicate failure of power
supply shall be provided.
15.5.3 The control equipment shall be installed in the marshalling box as specified in CL:23 in a
readily accessible position.
15.5.4 The alarm indication for failure of power supply and failure of individual fans be provided
through independent non trip alarm scheme to be wired on the remote tap change control
cubicle conforming to the following:i. The closing of an initiating contact shall actuate a buzzer and will be accompanied by a flag
indication on the concerned auxiliary relay.
ii. The closing of an initiating contact shall glow a lamp, which will not reset until the fault has
been cleared.
iii. It shall be possible to silence the buzzer by pressing ‘Accept’ push button. If, after canceling
the alarm but before resetting the visual signal, the same fault persists the buzzer shall be
suppressed.
iv. If after canceling the alarm but before resetting the visual signal, some other fault takes
place, the alarm accompanied by flat indication on appropriate auxiliary relay shall take
place.
v. If after canceling the alarm and after resetting the visual signal, the same fault appears or
some other fault take place, the alarm, flag indication and non-trip lamp indication shall
reappear as usual.
vi. The non-trip alarm acceptance shall be by means of push button and resetting of visual
signal may also preferably be done through a push button.
vii. Means shall be provided for test checking the lamp and alarm circuit at frequent intervals.
viii. The equipment shall be suitable for 220 Volt DC operation.
Static facia annunciator conforming to the foregoing requirements of non-trip alarm scheme
too would be acceptable.
16.0 VOLTAGE CONTROL (ON LOAD TYPE) :
16.1 The transformers shall be provided with voltage control equipment of the tap changing type
for varying its effective transformation ratio while the transformers are on loan and without
producing phase displacement.
16.2 Equipment for ‘local’ an ‘remote’ electrical and ‘local’ manual operation shall be provided and
shall comply with the following conditions. Local/remote switch may be housed in remote
control panel or in tap changer drive mechanism.
16.2.1 It shall not be possible to operate the electric drive when the manual operating gear in use.
16.2.2 It shall not be possible for any two electric controls to be in operation at the same time.
16.2.3 The equipment suitable for supervisory control and indication on a multi way switch, makebefore break having one fixed contact for each tap position, shall be provided and wired to
the tap changer drive gear. This switch shall be provided in addition to any, which may be
required for remote tap change position indication purpose. Supervisory indication shall also
be provided in the form of contacts to close on. “Tap change incomplete” condition. All other
components of the supervisory gear, if required be specified separately.
16.2.4 Operation from the local or remote control switch shall cause one tap movement only. The
control switch shall be returned to the ‘neutral’ position between successive operations.
16.2.5 All Electrical control switches on the local operation gear shall be clearly labeled in a suitable
manner to indicate the direction of tap changing.
16.2.6 The local control switches shall be mounted, in the drive gear housing.
16.3 The equipment shall be so arranged as to ensure that when a tap change has commenced, it
shall be competed independent to the operation of the control relays or switches. In case of
failure of the auxiliary supply while the tap change is in progress or any other contingency
such as stuck tap changer, adequate means shall be provided to safe guard the transformers
and its auxiliary equipment.
16.4 Suitable apparatus shall be provided for each transformer to give indications as follows:16.4.1 To give indication, mechanically at the transformer and electrically at the remote control
cubicle of the position of tap in use.
16.4.2 To give an indication at the remote control cubicle that a tap change is in progress, by means
of an illuminated lamp.
16.5
For remote control, the switches, tap position indicator, etc shall be supplied duly mounted on
remote control cubicle.
16.6 All relays and operating devices shall be operated correctly at any voltage between the limits
specified in the relevant ISS.
16.7 The tap changing mechanism shall be mounted in the oil tank or compartment mounted in an
accessible position on the transformer.
16.8 Any non-oil filled compartment shall be adequately ventilated, Thermostatically controlled
heaters shall be provided in the driving mechanism chamber and in the marshalling box. All
contactors & auxiliary relay coils or other parts shall be suitably protected against corrosion
or deterioration due to condensation, fungi etc.
16.9 The tap changer contacts which are not used for making or breaking current like separate
selector switch contacts inside main transformer tank where tap changer construction permits
such as arrangement. In case of on load tap changer having separate compartment for
selector contacts the oil in such compartment shall be maintained under conservator head by
means of pipe connection from the highest point of the chamber to the conservator. Such
pipe connection shall be controlled by suitable valve and shall be arranged so that any gas
leaving the chamber will pass into the gas oil actuated relay. A separate buchholz relay may
be provided for this compartment.
16.10 It shall not be possible for the oil in these compartments of the tap change equipment which
contain contacts used for making or breaking current, to mix with the oil in the compartments
containing contacts and not used for making or breaking current.
16.11 Any ‘DROP DOWN’ tanks associated with the tap changing apparatus shall be fitted with
guide rods to control the movement during lifting or lowering operations. The guide rods shall
be so designed as to take support of the associated tank when in the fully lowered position
with oil. Lifting gear fitted to ‘Drop Down’ tanks shall include suitable device to prevent runaway during lifting & lowering operations.
They shall be provided with adequate breathing arrangement. The tap changer shall be
mounted in such a way that the cover of the transformer can be lifted without removing
connections between windings and tap changer.
16.12 Each compartment in which the oil is not maintained under conservator head shall be
provided with a suitable direct reading oil gauge.
16.13 The alternating supply for electrical operation of the control and indicating gear shall be
standard 415 Volts, three-phase, 3 Wire, 50 HZ. alongwith 240 Volts single phase, 2 wire 50
HZ, subject to a variation of + 5 percent so that the equipment offered can withstand
variation in AC.
16.14 Limit switches shall be provided to prevent over-running of the mechanism and except where
modified in clause 16.15 shall be directly connected in the circuit of the operating motor. In
addition a mechanical stopper or other approved device shall be provided to prevent overrunning of the mechanism under any condition.
16.15 Limit switches may be connected in the control circuit of the operating motor provided that a
mechanical de-clutching mechanism is incorporated.
16.16 Thermal devices or other means like motor circuit breakers with shunt trip coil shall be
provided to protect the motor and control circuits. All relays, switches, fuses, etc. shall be
mounted in the marshalling box or driving gear housing. These shall be clearly marked for
purpose of identification. They shall withstand the viberation associated with tap changer
gear operation.
16.17 The control circuits shall operate at 110V single phase to be supplied from a transformer
having a ratio of 415 0r 240/55-0-55 V with the center point earthed through a removable link
mounted in tap changer drive.
16.18 The whole of the apparatus shall be of robust design and capable of giving satisfactory
service under conditions to be met in service including frequent operation.
16.19 A five-digit counter shall be fitted to the tap changing mechanism to indicate the number of
operations completed by the equipment.
16.20 A permanently legible lubrication chart shall be fitted within the driving mechanism chamber,
where applicable.
16.21 The indigenous make OLTC (Internal/External) suitable for 66 kV voltage class & current
rating 350 Amp. should be duly. Type tested from CPRI or other Govt. Test House or reputed
lab abroad to the extent the facilities of Type test available in CPRI.
17.0 PARALLEL OPERATION:
17.1 In addition to individual control of tap changer, provision shall be made to enable parallel
operation of the tap changer when one unit is running in parallel with another similar unit of
same rating.
17.2 Suitable selector switch and controls shall be provided so that any transformer of the group
can at a time be selected as master, follower or independent. Arrangement shall be made
that only one of the transformers can be selected as master at a time.
17.3 An out of step device shall an indicating lamp be provided for each transformer indicating out
of step condition by an indicating lamp and buzzer. It shall be arranged to prevent further tap
changing when transformers in a group operating in parallel control are one tap out of step.
18.0 BUSHING INSULATORS AND TERMINALS:
18.1 Transformer shall be fitted with bushing insulators as follows:L.V. Bushing: 36kV class oil communicating type porcelain bushing of 2000 Amp. rating with
suitable arcing horns.
LV-N Bushing: 36kV class oil communicating type porcelain bushing of 2000 Amp. rating but
without arcing horns.
HV Bushing: 72.5 kV class. Condenser bushing of 800 Amp. rating with arcing horns.
HV-N Bushing: 36kV class oil communicating type porcelain bushing of 630 Amp. rating but
without arcing horns.
18.2
18.3
18.4
18.5
18.6
18.7
18.8
19.0
19.1
19.2
19.3
19.4
19.5
19.6
19.7
20.0
20.1
20.2
The characteristics of the bushings shall be in accordance with IS: 2099 and
IS: 3347.
The bushing insulators except for neutral bushing shall be provided with adjustable arcing
horns and the bidder shall furnish calibration gap to decide actual gap setting.
A continuous flexible pull through lead suitably sweated to the end of winding copper shall be
connected to the connector in the helmet of the 66 kV Bushing. The bushings may be filled
with oil, which may not be in communication with the oil in transformer.
All porcelain shall be free from defects and thoroughly vitrified with a smooth, hard and
uniform brown glaze. It should be capable of satisfactory use under the climatic conditions
as specified in clause-3.0.
In case of paper insulation care shall be taken to prevent ingress of moisture and a final coat
of non-hygroscopic varnish shall be given to them.
All clamps and fittings made of malleable iron or steel shall be galvanized as per IS: 2629.
The bushing flanges shall not be of re-entrant shape, which may trap air.
Bi-metallic terminal connectors shall be supplied suitable for single 0.4 Sq. inch ACSR Zebra
conductor for HV side, LV Neutral & HV Neutral. For LV side the terminal connectors shall be
suitable for triple 0.4 sq. inch ACSR ZEBRA conductor. The take off for H.V & L.V
connectors will be Vertical and for H.V Neutral and L.V. Neutral, it should be suitable for
horizontal take off.
The connectors shall have six number bolts provided with check nuts & washers. The
connectors shall have rating corresponding to those equipment or higher and shall be
designed most liberally with a higher factor of safety to comply in all respects with
temperatures rise. Resistance, tensile strength short-circuit withstand capability tests as
specified in IS: 5561-1970 or amendment thereof (Latest edition). Aluminum alloy used in
the manufacture of bimetallic connectors shall conform to designation Grade 4600 of IS: 6171975. The steel bolts, nuts washers and check nuts shall be hot dip galvanized marked with
ISI certification mark or of GKW make.
TEMPERATURE INDICATING DEVICES:
All transformers shall be provided with a dial type thermometer for indicating oil temperature.
The indicator shall be fitted with a pointer to register maximum temp recorded and adjustable
set of mercury contact for alarm and trip.
In addition, all the transformer shall be provided with a dial type Hot Spot winding
temperature indicator in HV and LV winding. The indicator shall have a pointer to register
maximum temperature reached and four sets of adjustable mercury contacts for alarm trip for
automatic control of fans. The static remote repeater (for winding temperature indicator)
suitable for flush mounting shall be installed on remote tap change control cubicle.
The temperature indicators shall be housed in marshalling box.
The alarm (mercury) contact of WTI & OTI shall be adjustable between 500C to 1000C where
as their trip (mercury) contacts shall be adjustable between 600C and 1200C. The
temperature differential between opening & closing of these mercury contacts shall not be
more than 100C.
The mercury contacts used for controlling cooling plant motors shall be adjustable to close
between 500C and 1000C. The temperature differential between opening & closing of this
mercury contact shall be between 100C to 150C.
All contacts should be accessible on removal of the cover adjustable to scale. It shall also be
possible to move the pointers by hand for checking the operation of contacts and associated
equipment.
In addition each transformer shall be provided with a dial type thermometer for indicating the
ambient temperature.
GAS AND OIL ACTUATED RELAYS:
The transformer shall be provided with a gas and oil actuated relay fitted with alarm and trip
contacts for main tank & a oil surge relay for its OLTC as per IS 3637.
Each such relay shall be provided with a test cock to take a flexible connection for checking
relay operation.
20.3
20.4
20.5
21.0
21.1
21.2
21.3
21.4
21.5
22.0
22.1
22.2
22.3
22.4
22.5
22.6
22.7
23.0
A machined surface shall be provided on top of checking mounting angles in the pipe crosslevel of relay and its setting.
The pipe work shall be such as to allow any gas formed in the tank to pass through the relay.
The oil circuit through the relay shall not form a parallel delivery path with any circulating oil
pipe, nor shall be tied into or connected through the pressure relief vent.
Adequate clearance between oil pipe work and live metal parts shall be provided.
MARSHALING BOX:
A sheet steel (of 10 SWG size) vermin proof well ventilated and weather proof marshaling
box of suitable construction shall be provided for the transformer auxiliary apparatus. The box
shall have domed or sloping roofs. Ventilation louvers, suitably padded with felt shall also be
provided. It shall be painted as per Cl.5.14.
The marshaling box shall accommodate temperature indicators. Local electrical control of tap
changer (if same cannot be housed in motor drive housing.), control & protection equipment
for cooling plant, terminal boards and gland plants for cable etc. The equipment shall be
mounted on panels and panels wiring shall be done at the back for interconnections.
The temperature indicators shall be mounted at about 1600mm from ground level.
A metal clad heater with thermostat, controlled by a waterproof rotary switch on the outside of
the both, shall be provided.
The incoming cables shall enter from the bottom with gland plate not less than 450mm from
the base of the box. Care shall be taken to avoid ingress of water from the cable trench.
CONTROL CONNECTIONS, INSTRUMENTS WIRING, TERMINAL BOARD AND FUSES:
All cables and wiring shall be suitable for use under the conditions as specified in Clause 3.0.
Any wiring liable to come in contact with oil shall be of oil resisting insulation. The bare ends
of stranded wire shall be sweated together to prevent oil from creeping along the wire.
The instrument and panel wiring shall be run in PVC or non-rusting metal cleats of limited
compression type.
The box wiring shall be as per relevant ISS. All wiring shall be of stranded copper of 660V
grade and size not less than 4 sq. mm. For CT leads and not less than 2.5 sq. mm. for other
connections. The panels wires and multi core cable shall bear ferrules of white insulation
material with indelible marking in black and as per relevant ISS. Same ferrule number shall
not be used on wires in different circuits. Double ferrules may be provided where a change in
number is required.
Stranded wires shall be terminated with tinned Ross Courtney terminals, washers or crimped
tubular lugs. Separate washers shall be used for each wire. Wire shall not be jointed/tied
between terminal points.
Where apparatus is mounted on panels all metal cases shall be separately earthed by
copper wire of strip not less than 2.5 sq. mm. The screens of screened pairs of multi core
cables shall be earthed at one end of the cable only.
All terminal boards shall be of stud-type & mounted obliquely towards the rear door and
these boards shall be spaced not less than 100mm apart. Suitable insulation barriers shall be
provided between adjacent connections. No live metal shall be exposed at the back of
terminal boards.
All fuses shall be of cartridge type and fuses and links shall be properly labelled.
EQUALIZATION FORMULA:
The losses at principal tap of each transformer shall be stated in the tender ONAF rating at
full load at 750C.
For the purpose of arriving at comparable prices, the iron, copper and auxiliary losses shall
be capitalised as per capitalization formula given below:
=3,86,700( Wi + 0.45 Wc + 0.45 Wp)
Where
Wi
=
Iron (No load) Losses
Wc
=
Copper (Load Losses)
Wp
=
Auxiliary Losses
The maximum sealing of component and weightage average losses shall be as per clause
24.0 and no positive tolerance shall be allowed on these values
In case losses of the T/F are found to be higher then the specified values at any stage within
three years from the date of commissioning the capaitalized value of excess losses, as compare
to the specified value shall be recovered as per following capitalization formula:Amount recoverable (Rs.)= 3,86,700(Wi + 0.45 Wc + 0.45Wp)
24.0
Losses:The losses of each transformer shall be stated in the tender for OFAF rating at principal tap
(at full load at 75 deg. C) which shall be less than:Sr. No.
1
2
3
4
24.1
Type of Losses
No Load Losses
Load Losses
Auxiliary Losses
Maximum weighted average losses
31.5 MVA, 66/11 KV T/F
17.70 KW (Max)
118.00 KW(Max)
2.00 KW (Max)
65KW
Noise level
:
80 dB
Transformer offers shall be rejected if audible sound level is higher than max. 80 dB.
25.0
25.1
TESTS:
ROUTINE TESTS:
All routine tests shall be carried out on each transformer as per IS-2026/IEC-76.
25.2 TYPE TEST:
Following type tests and over load withstand capacity test (as per IEC-354) shall be carried
out on one of units ordered on the successful bidder as per IEC-76/ISS:2026.
i. Temp. rise test (Along with DGA test before and after temp. rise test).
ii. Impulse voltage withstand test with chopped impulse on any one phase.
iii. Power drawn by cooling fans/oil pumps as perISS:2026.
25.3
In addition, the following tests shall be carried out on the transformer tank.
25.3.1 OIL LEAKAGE TEST:
All tanks and oil filled compartments shall be tested for oil tightness by being completely filled
with oil of viscosity not greater than that of insulating oil to IS:335 at ambient temperature and
subjected to a pressure equal to normal pressure plus 35KN/M2 (5Ibs/Sq. inch.) measured at
the base of the tank. This pressure shall be maintained for period not less than 12 hours,
during which period no leakage shall occur.
25.3.2 Following tests shall be carried out on each Transformer as reference test.
i)
Measurement of tan delta and capacitance of T/F Winding and bushings at 5 kV &
10 kV.
ii)
Magnetic balance test.
iii)
Magnetising current at low voltage.
iv)
Measurement of percentage impedance at all taps at low voltage.
25.3.3 TRANSFORMER OIL:
Sufficient quantity (along with 10% extra) of insulating oil of napthenic type (as per Clause-6
of specification) conforming to BS:148/IEC-296 Class-1 shall be put up for inspection, at least
3 weeks before putting up the transformer for testing/inspection, at sub-supplier works as per
IS:335/BS/IEC. One sample of the oil shall also be got tested from CPRI or any other Govt.
approved testing house. The inspected oil shall be dispatched to site as per dispatch
instructions of purchaser.
25.3.4 SHORT CIRCUIT TEST
Short circuit test in accordance with latest IS-2026 Part (5) clause 4.2, IEC-60076-5 and CEA
regulation-2010 shall be got conducted on one of the units of each voltage and capacity at
any test Agencies where facilities exist in the presence of Purchaser's representative.
However, in case of those manufacturers who have already got short circuit test in
accordance with Cl. 4.2 of IS-2026 Part(5) or latest edition conducted during the last 7 years
on same design and capacity of the Transformer, fresh short circuit test is not required to be
conducted. The bidder in such a case shall submit the copy of type test report along with the
bid. If this test is not conducted by the firm earlier, then charges for this test shall be borne by
the bidder.
The warranty in case of Power Transformer shall be 18 months from the date of
commissioning or 24 months from the date of receipt whichever is earlier. All other
stipulations of Warranty Clause as per Schedule-D of purchase regulation shall remain
same
25.3.5 The purchaser reserves the right to have any other, reasonable test carried out at his
expense either before shipment or at site to ensure that the transformer complies with the
requirement of this specification.
25.4 STAGE INSPECTION :
Stage inspection of built up core (in horizontal/vertical position), windings, tank and radiators
shall be carried-out as detailed below:a.
CORE:
i.
Measurement of flux Density.
ii.
No Load Loss Measurement by providing dummy oils.
iii.
Tests of CRGO sample taken from the core shall be carried-out for Carlite test
(Resistance Measurement), Watt Loss Test, Lamination Thickness & Aging
Tests.
iv.
Physical inspection for quality of workmanship.
v.
Slitting/Cutting of core.
b.
WINDINGS :
i.
Measurement of cross-sectional area for current density.
ii.
Measurement of weight of bare copper/cover by resistance methods.
iii.
The purity test of copper for winding shall be got conducted on sample of
copper for assessing its quality, from two independent NABL accredited
laboratories.
c.
TANK :
i.
Vacuum Test
One transformer tank out of the lot shall be subjected to vacuum pressure of
100.64 kN (760 mm of Hg.). the tanks to be designed for full vacuum shall be
tested at an internal pressure of 3.33 KN/M2 (25mm of Hg.) for one hour.
The permanent deflection of flat plates after the vacuum has been released
shall not exceed the values given below without affecting the performance of
the transformer.
Horizontal length of flat plate(mm).
Permanent deflection (mm)
Upto & including 750
5.0
751-1250
6.5
1251-1750
8.0
1751-2000
9.5
2001-2250
11.0
2251-2500
12.5
2501-3000
16.0
above 3000
19.0
ii.
d.
NOTE:
a.
b.
c.
d.
26.0
26.1
26.1.1.
26.1.2
26.2
PRESSURE TEST:
One transformer out of the lot shall be subjected to the pressure
corresponding to twice the normal head of oil or normal pressure plus
35KN/M2 (which ever is lower) measured at the base of the tank and
maintained for one hour. The permanent deflection of flat plates after removal
of excess pressure shall not exceed the figures specified as above.
RADIATORS:
Radiators shall be routine type tested at sub-supplier’s works as per relevant
standard. Test reports are required to be supplied at the time of final
inspection.
The insulation resistance values of the transformer windings will be recorded
at the time of carrying out routine tests, for 20 seconds, one minute, two
minutes with the help of 5000V motorised meggar (preferably
EVERSHED/AVO & VIGNOLE MAKE). The polarisation index values (ratio of
120/20-Sec. Value) will be accordingly calculated and recorded in the test
certificates and it should not be less than 1.5.
Dissolved gas analysis test shall be got carried out before and after heat run
test at CPRI Bangalore.
Capacitance and Tan Delta values for each transformer and condenser
bushings will be taken and recorded in the test certificates at 5 kV & 10 kV.
Insulation resistance value of condenser bushings shall also be recorded.
Lightening impulse test with the chopped wave applications as per clause 13
of IS:2026/1981 (Part-III) amended upto date. This test will be carried out on
one of the limbs of HV and LV winding with positive polarity.
e.
The tenderer should clearly indicate the testing facilities available with them
and tests, which are to be arranged outside.
Supplier shall submit in-house test certificates at lest 15 days in advance for final
testing of T/F. for testing T/F: all measuring instruments shall be of highest efficiency
and best quality. These shall be got calibrated from NPL/Govt. Agency and be got
sealed by calibrating agency. HVPN reserves the right to calibrate the instruments in
the manner it desires.
Losses shall be measured with 3-wattmeter method only. Resistance shall be taken
with Double-Kelvin Bridge. Losses can be measured directly from CTs and PTs and
not through the panel. Ratio of the measuring instrument shall be such that the
multiplying factor is the minimum.
All tests shall be carried out in the presence of the purchaser before despatching the
material. Test certificates in quadruplicate will be submitted to the purchaser for
approval. No material shall be despatched without prior inspection and approval of
test certificates unless otherwise agreed to. Type and routine test certificates of all
bought out items from recognised testing agency shall be submitted for approval
before commencing supplies. OLTC scheme including the master follower functioning
shall also be checked. Only fully assembled transformer including mounting of
radiators shall be put-up for inspection.
DRAWINGS:
The following drawings shall be supplied as part of the tender.
Outline dimensional drawing of transformer and accessories.
Bushing and terminal connectors drawings.
The successful bidder shall submit final version of drawings complete in all respects in
quadruplicate within 15 days of placement of order for purchaser's approval. The
purchaser shall communicate his comments/ approval on the drawings to the supplier
within one month of their receipt. The manufacturer shall, if so required by the
purchaser, modify the drawings and resubmit the same for purchaser's approval
within two weeks of receipt of comments. Such duly revised drawings will be
approved by the purchaser within two weeks of their receipt.
After receipt of purchaser's approval to drawings, the manufacturer will submit five
sets of all approved drawings and five sets of manual of instructions to our Design
Office.
26.2.1
a.
b.
c.
d.
e.
f.
g.
h.
26.2.2
26.2.3
26.2.4
26.2.5
26.2.6
26.2.7
26.2.8
26.2.9
26.2.10
26.2.11
One set of all the approved drawings and manual of instructions will be
supplied along with each equipment without which the supply will not be
considered as complete supply.
Outline general arrangement drawings showing plan, front elevation & side elevation
with all fittings and accessories etc. The following information must be specifically
included on drawings:Make of transformer oil.
Electrical clearances, minimum as well as actual.
The no. of radiator headers, number of radiator element in each header.
Small sketch showing un-tanking details.
Thickness of transformer tank bottom, sides & top plates.
Type, shade and shade No. and thickness of transformer paints.
Roller, rail gauge sketch.
Weight of oil, bare copper weight windings core, un-tanking mass, transportation
mass and dimensions etc.
Detailed drawing of bushings showing plan, elevation, terminal details, mounting
details make and type number incorporating electrical characteristics, description of
various parts, total creepage & protected creepage distance, weight of oil, total weight
of bushing, dimensions, short time current rating etc.
Drawing showing HV & LV windings with arrangement of insulation and terminal
connections.
Schematic control and wiring diagram for auxiliary equipment like OLTC control gear,
cooler control gear, marshaling kiosk. Detailed write-up for schematic shall also be
supplied.
Combined rating & diagram plate.
Valve schedule plate.
Core assembly drawing with flux density calculations.
Interconnection diagram between OLTC panel, drive mechanism and marshalling
kiosk.
Detailed calculations showing short circuit withstand capacity due to radial and axial
forces during short circuit also calculation for thermal withstand capability during short
circuit will be supplied.
Cable arrangement on the transformers.
Drawings showing connection of HV, LV lead with the respective bushing and their
place of storage during transportation.
1.
2.
2.
FITTINGS AND ACCESSORIES
Each transformer shall be complete with the following fittings and accessories:
One 150mm (16”) dial type indicating thermometer (OTI) of robust construction mounted on
the side of the transformer at a convenient height to read the temperature of oil and fitted
with alarm and trip contacts. Provision in the OTI for connection to repeater in RTCC shall
also be provided.
2 Nos. 150mm dial type winding hot spot temperature indicators (WTI) one each placed in
HV & LV winding, as described below.
“It shall be indicating type responsive to the combination of top oil temperature and winding
current calibrated to follow the hot spot temperature of transformer winding. The device shall
have on additional pointer to register the highest temperature reached. Each winding
temperature indicator should have four sets of contacts. Two contacts of one of the WTI shall
be used for trip and alarm purpose, wiring of which will go to the main control and relay panel
of the transformer (External control cables from the marshalling box to the C&R panel to be
provided by the purchaser).
[
Third set of contacts shall be spare. Provision in the WTI for connection to repeater in RTCC
shall also be provided.
The contacts of each WTI should be adjustable to close between 600C to 120 0C and shall
reopen when the temperature has fallen by 100C-150C. However, supplier should mention in
the their manuals the actual adjustable settings of these contacts.”
Repeater for both WTIs shall also be provided in the RTCC Panel.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
One conservator alongwith 2 no. shut off valves, oil surge relay, breather connecting pipe
etc. exclusively for OLTC.
One pressure relief valve/device (PRV) of minimum 6 inch size for main tank and
1 No. PRV for OLTC of size 3 inch (approx.) with provision for trip contacts.
Inspection covers with jacking bolts in the top cover plate of the tank.
One drain valve with plug or blanking flange at the bottom of the tank size 80 mm.
One filter valve each at top & bottom of transformer tank size 50mm
Three oil sampling valves for taking samples of top, middle and bottom oil.
Set of lifting lugs/jacking lugs and eyebolts on all parts for ease of handling.
One double float gas/oil surge detecting (Buchholz) relay in the pipe connecting the
conservator with tank, complete with alarm and tripping contacts to detect accumulation of
gas and sudden changes of oil pressure, complete with shut off valves on conservator side
as well as tank side. Th size of shut off valve shall be 80 mm.
Two grounding terminals on diagonally opposite bottom corners of tank. However, if
provided on the length side of tank, then these grounding terminal shall be out side the rail
gauge.
One ONAN cooling equipment comprising of suitable radiators with shut off valves, air
release and drain plugs.
One ONAF cooling equipment comprising of fan motors with auto & manual control.
Skids and pulling eyes on both sides.
One marshalling box housing dial type thermometers for winding and oil temperature
indicators, heater, fan, control switches with fan fail alarm and complete wiring and local/auto
selector switch, and supply isolating switches with HRC fuses.
Two thermometer pockets for mercury in glass thermometer.
A set of universal type bi-metallic multi-bolt double grooved conductor clamps each capable
of receiving single ACSR Zebra/ double ACSR ZEBRA conductor respectively for HV side LV
side.
Suitable bi-metallic flexible connectors for neutral terminals.
Suitable size bi-directional wheels for 1676 mm rail gauge in both direction-4 No.
19.
20.
21.
22.
23.
24.
One OLTC alongwith remote control panel with each transformer complete with wiring, oil
surge relay etc.
a)
OLTC conservator pipe and valve diameter should be 25mm.
c)
The height of RTCC panel should be 2312 mm & shade of paint should be of 631 of
IS:5.
The following plates in English shall be fixed to the transformer tank at about 1750-mm
above ground level:
a)
Rating Plate bearing data as specified in IS: 2026/1977. It must contain insulation
levels of various windings, impedance at tap 1/5/17 & short circuit duration.
b)
Terminal marking plate showing the internal connections and voltage vector
relationship of various windings in accordance with IS: 2026/1977 (Latest Edition).
c)
Valve schedule plate showing the location and function of all valves and air release
cocks/plugs.
A plate showing the rated no load voltage at various taps shall be affixed on the RTCC in
order to facilitate the operator in deciding the tap position on which the transformer is to be
operated corresponding to the incoming voltage.
Oil conservator (for main tank) fitted with flexible separator (as oil preservative system)
complete with magnetic type oil level gauge, filling hole and cap, drain valve-size 19mm, shut
off valve, inter connecting pipes etc. Magnetic type oil level gauge shall be provided with low
oil level alarm contacts and a dial showing minimum, maximum and normal oil level. The
gauge shall be readable from the transformer base level. Silica gel breather with oil seal,
shall be fitted as already prescribed. Breather should be made of see through material. One
drain pipe upto floor level with one valve may be provided.
One No. ladder with provision for anti-climbing.
Any other item which is not included above but it is essential for the satisfactory operation of
the equipment.
GTP OF 25/31.5 MVA, 66/11 KV T/F
S. NO.
DESCRIPTION
1
Manufacturers Name
2
Rating (MVA)
3
Voltage Ratio (KV)
4
Winding Connection
5
Vector Group
6
Number of Phase
7
Frequency (Hz)
8
Type of cooling
9
Rating available at different cooling %
10
Impedance data
a
Guaranteed positive sequence impedance
between HV-LV at 75 deg.C with 100% rating
at
i. Principal Tap
ii. Maximum Tap
Iii. Minimum Tap
b
Zero sequence impedance at principal tap
11
Guaranteed losses at 100% rated voltage
(excluding cooler loss) at 75 deg.C between
HV and LV
a
Iron loss (KW) (max)
b
Copper loss (KW) (max)
c
Maximum Weighted average loss
12
Guaranteed cooler losses at
a
100% load (max) (KW)
13
Cooling equipment details
a
Number of coolers and rating as per % of
transformer cooling equipment
b
Mounting
c
Fan motor data (Manufacture)
PARTICULARS
Required
Offered
GTP OF 25/31.5 MVA, 66/11 KV T/F
S. NO.
DESCRIPTION
i
Number per cooler and rating as % of cooler
requirement (also indicate no.of spare fans)
ii
Type
iii
Rating (KW)
iv
Locked rotor current (Amps)
v
Temp. range over which cooler control is
adjustable (deg.c to deg.C)
d
Oil pump motor data
i
Number per cooler and rating as % of cooler
requirement (also indicate no.of spare pump)
ii
Type
iii
Rating (KW)
iv
Locked rotor current (Amps)
v
Temp. range over which cooler control is
adjustable (deg.c to deg.C)
e
Type of oil pump and motor (whether oil
submerged type)
f
Radiator details
i
Overall dimensions lxbxh (mm)
ii
Total weight with oil (Kg)
iii
Total weight without oil (Kg)
iv
Thickness of Radiator tube (mm)
v
Type of mounting
14
Thermal Data
a
Temperature rise in top oil over an ambient
of 50 deg.C
b
Temp rise in winding by resistance
measurement method over an ambient of 50
deg.C
c
Thermal time constant (Hours)
PARTICULARS
Required
Offered
GTP OF 25/31.5 MVA, 66/11 KV T/F
S. NO.
DESCRIPTION
15
Withstand time for three phases short circuit
at terminals (secs)
16
Over excitation withstand time (sec)
i
1.25
ii
1.4
iii
1.5
17
Bushings
a
High voltage
i)
Manufacturer
ii)
Type
iii)
Total creepage distance (mm)
iv)
Protected creepage distance (mm)
v)
Mounting
vi)
Rated current (Amps)
b
Low voltage
i)
Manufacturer
ii)
Type
iii)
Mounting
iv)
Total creepage distance (mm)
v
Protected creepage distance (mm)
vi)
Rated current (Amps)
C
Neutral Bushing (HV & LV)
i)
Manufacturer
ii)
Type
iii)
Mounting
iv)
Total creepage distance (mm)
PARTICULARS
Required
Offered
GTP OF 25/31.5 MVA, 66/11 KV T/F
S. NO.
DESCRIPTION
v)
Protected creepage distance (mm)
vi)
Rated current (Amps)
18
Is Vacuum filling required, if so state absolute
pressure (mm of Hg)
19
Total quantity of oil (ltrs) & Manufacture
20
Tap changing equipment (Manufacture)
a)
Voltage class and current
b)
Number of steps
c)
Range
d)
Step voltage
e)
Type
f)
Rated voltage of drive motor (volts)
g)
No.of revolutions to complete one step
h)
Time to complete one step on manual / auto
operation (sec)
i)
Power required (kw)
21
Insulation level
a)
HV windings
i)
Lightning impulse withstand voltage
ii)
Power frequency withstand voltage (kv rms)
b)
LV Winding
i)
Lightning impulse withstand voltage
ii)
Power frequency withstand voltage (kv rms)
c)
HV Bushing
i)
Lightning impulse withstand voltage
ii)
Power frequency withstand voltage (kv rms)
d)
LV Bushing
PARTICULARS
Required
Offered
GTP OF 25/31.5 MVA, 66/11 KV T/F
S. NO.
DESCRIPTION
i)
Lightning impulse withstand voltage
ii)
Power frequency withstand voltage (kv rms)
e)
Neutral Bushing
i)
Lightning impulse withstand voltage
ii)
Power frequency withstand voltage (kv rms)
22
Approximate dimensions
a)
Tank (lxbxh) mm
b)
Overall dimensions with (mm) coolers lxbxh
c)
Shipping dimensions (mm) (lxbxh)
d)
Height for untanking (mm)
e)
Dimensions of largest (mm) package (lxbxh)
23
Weights of transformer components
a)
Core (Kg)
b
Windings (Kg)
c)
Insulation (Kg)
d)
Tank and fittings (Kg)
e)
Oil (Kg)
f)
Untanking weight (heaviest piece) (Kg)
g)
Total weight Kg
h)
Weight of heaviest package KG
i)
Total shipping weight (Kg)
j)
Parts detached for transport
24
Permissible overload (% of rating & time in
minutes)
25
Clearances
a)
Minimum clearance between phases
i)
In oil (mm)
PARTICULARS
Required
Offered
GTP OF 25/31.5 MVA, 66/11 KV T/F
S. NO.
DESCRIPTION
ii)
In air (mm)
b)
Minimum clearance of HV winding to tank in
oil (mm)
c)
Minimum clearance of HV winding of earth in
oil (mm)
d)
Clearance between core (mm) and coil
e)
Clearance between coil (mm)
f)
Clearance between neutral to ground in air
(mm)
26
Conservator
a)
Total volume (ltrs)
b)
Volume between highest and lowest levels
(ltrs)
27
Capacitance values
a)
HV to earth (pf)
b)
LV to earth (pf)
28a)
Type of oil preservation
b)
Material of air cell
c)
Continuous temp. withstand capability of the
air cell
29 a)
No.of pressure relief device provided
b)
Operation pressure of pressure relief device
30
Oil
a)
Quality of oil
i)
Moisture content (ppm)
ii)
Max tan delta value (at 90 deg.C)
iii)
Resistivity (ohm – cm)
iv)
Breakdown strength (kv)
PARTICULARS
Required
Offered
GTP OF 25/31.5 MVA, 66/11 KV T/F
S. NO.
DESCRIPTION
v)
Interfacial tension at 27 deg.C (min)
b)
Quantity including 10% extra (Ltrs)
c)
Standards applicable
31
Core
a)
Type of construction
b)
Net core area (mm.sq)
c)
Core material and grade used
d)
Type of joint between core and yoke
e)
Thickness of stamping (mm)
f)
Percentage silicon content (%)
g)
Maximum flux density in core at rated
frequency at
i)
90% voltage (wb/sq.m)
ii)
100% voltage (wb/sq.m)
iii)
110% voltage (wb/sq.m)
32
Winding
a)
Type of winding
b)
Current density at rated load
i)
HV (A/Sq.cm)
ii)
LV (A/Sq.cm)
iii)
Regulating winding (A/Sq.cm)
c)
Conductor area
i) HV (sq.mm)
ii) LV (sq.mm)
Iii) Regulating winding
d)
Maximum current density under short circuit
PARTICULARS
Required
Offered
GTP OF 25/31.5 MVA, 66/11 KV T/F
S. NO.
i)
DESCRIPTION
i) HV (sq.mm)
ii) LV (sq.mm)
e)
Magnetising inrush current (Amps)
f)
No load current (Amps) at rated frequency
and at
i)
90% voltage (wb/sq.m)
ii)
100% voltage (wb/sq.m)
iii)
110% voltage (wb/sq.m)
g)
Magnetising current at rated frequency and
at rated voltage
33
Tank
a)
Type
b)
Material
c)
Approx Thickness of
i)
Sides (mm)
ii)
Bottom (mm)
iii)
Cover (mm)
34
Radiator
a)
Make
b)
Material
c)
Thickness
35
Vacuum withstand capability of
a)
Main tank (torr)
b)
Radiators accessories (torr)
36
Pressure withstanding capability of
a)
Main Tank
b)
Radiator and accessories
PARTICULARS
Required
Offered
GTP OF 25/31.5 MVA, 66/11 KV T/F
S. NO.
DESCRIPTION
37
Temperature indicators
a)
OTI
i)
Manufacturer
ii)
Range
iii)
Accuracy
b)
WTI
i)
Manufacturer
ii)
Range
iii)
Accuracy
c)
RWTI
i)
Manufacturer
ii)
Range
iii)
Accuracy
iv)
Auxiliary supply used
38
Terminal connectors
a)
Make
b)
Whether type tested
PARTICULARS
Required
Offered
c)
Governing standard
Note: If there is any change in the above GTPs, same shall conform to Technical
Specifications/relevant ISS. If there is any change in GTPs, so warranted by specific make of
equipment, same shall be taken care at the time of approval of drawings.