SECTION V: TECHNICAL SPECIFICATIONS
TECHNICAL SPECIFICATION FOR RECLAMATION OF OUTDOOR TYPE
DISTRIBUTION TRANSFORMERS 11 KV / 6.6KV/433 – 250 V.
SCOPE:
1.
This specification covers reclamation as per design, engineering, assembly, stage testing,
inspection and testing before dispatch of oil Immersed naturally cooled 3 phase 11
kV/6.6KV/433 - 250 V distribution transformers for outdoor use.
a) It is not the intent to specify completely herein all the details of the design and
reconstruction of Equipment. However the equipment shall conform in all respects to high
standards of engineering and workmanship and shall be capable of performing in continuous
commercial operation, in a manner acceptable to the authority for placing orders
(Department/Division) for repairs who will interpret the meanings of specifications and shall
have the power to reject any work or material which, in his judgment is not in accordance
therewith. The reclaimed transformer shall be complete with all components necessary for
their effective and trouble free operation. such components shall be deemed to be within the
scope of bidder's supply irrespective of whether those are specifically brought out in this
specification and' or the commercial order or not.
b) The transformer and accessories shall be reclaimed to facilitate the operation, inspection,
maintenance and repairs. The repair shall incorporate every precaution and provision for the
safety of equipment as well as staff engaged in operation and maintenance of equipment.
c) All outdoor apparatus, including bushing insulators with their mountings, shall be repaired
so as to avoid any accumulation of water.
2. STANDARD RATINGS:
a) The standard ratings shall be 25, 63, 100, 250, 400, 500 & 630 KVA for 11 KV/6.6KV /440
volt distribution transformers.
However any other Ratings not included in standard Ratings required to be repaired is
deemed to be included.
3. STANDARDS:
a) Unless otherwise modified in the specification, the Reclaimed transformers shall comply
with the requirement of ISS: 2026 (latest issue) or any equivalent International Standards and
REC specification 2/1973 and ISS: 2099 (latest issue) or any equivalent International
Standards. The bushings used shall conform to ISS: 2099 (latest issue) or any equivalent
International Standards except as modified herein.
b) The materials to be used for reclamation shall conform in all respects to the relevant Indian
/International Standards, with latest amendments thereof unless otherwise specified herein.
Some of them are listed below:
1
Indian
Standard
Title
1S -2026 (Part I- IV)
Specification for Power Transformers
Outdoor distribution Transformer up to
IS – 1 180 ( Part I & II)
and including 100KVA
IS- 12444
Specification for Copper wire rod
IS-335
Specification for Transformer Oil
IS-5
Specification for colors for ready mixed paints
Ready mixed paint. brushing zinc chromate,
priming
Classification of insulating materials for
Electrical machinery and apparatus in relation
to their thermal stability in service.
Specification for high voltage porcelain
bushing
Testing for steel sheets and strips and magnetic
circuits
Dimensions for clamping arrangements for
bushings
Specification for Low Voltage bushings
Specification for Outdoor Bushings
Specification for Al Wire rods
Specification for Insulating Kraft Paper
Specification for Insulating Press Board
Guide for loading of oil Immersed
Transformers
Determination of water content in 011 for
porcelain bushing of transformer
Paper covered aluminum conductor
Rectangular Electrical conductor for
electrical machines
Electrical power connector
Testing of specific resistance of electrical
insulating
Method of test for power factor and
dielectric constant of electrical insulating
liquids
Determination of electrical strength of
insulating oil
Installation and maintenance of transformers.
Revised Guidelines of Bureau of Energy
Efficiency
IS-104
IS 1271
IS-2099
IS-649
IS-457
IS-7421
IS-.347
IS-5484
IS-9335
IS- 576
IS-6600
I S-2362
IS-6162
IS-6160
IS-5561
IS-6103
IS-6262
IS-6792
IS-10028
International and
Internationally
recognized standards
IEC 76
ASTM 8-49
BS 148, 0-1473, D-15331934, IEC Pub296
DIN 42531 to 33
ASTM B – 233
IEC554
IEC 641
IEC76
Material conforming to other internationally accepted standards which ensure equal or better quality
than the standards mentioned above would also be acceptable. In case the bidders who wish to utilize
material conforming to other standard, the bidder shall clearly bring out the salient points of
difference between the standards adopted and the specific standards in relevant schedule. Four copies
of such standards with authentic English translation shall be furnished along with the offer.
2
4. DESIGN AND STANDARDIZATION:
a.
b.
c.
d.
e.
f.
g.
h.
The reclaimed
transformers and accessories shall be reclaimed to facilitate operation,
inspection, maintenance and repairs. All apparatus shall also be reclaimed
to ensure
satisfactory operation under such sudden variations of load and voltage as may be met with
under working conditions on the system, including those due to short circuits.
The reclamation 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
requirement of Indian Electricity Rules and Acts.
All material including bought out items like bushings, oil, conductor and insulating materials
used shall be of the best quality and of the class most suitable for working under the
conditions specified and shall withstand the variation of temperature and atmospheric
conditions arising under working conditions without undue distortion or deterioration or
setting up of undue stresses in any part and also without affecting the strength and suitability
of the various parts for the work which they have to perform.
Corresponding parts liable to replacement shall be interchangeable.
All outdoor apparatus, including bushing insulators with their mounting shall be replaced so
as to avoid external pockets in which water can collect and internally air could trap.
All taper pins used in any mechanism shall be of the split type complying with IS: 2593 or
any equivalent International Standards for these items.
All connections and contacts shall be of ample section and surface for carrying continuously
them specified currents without heating and fixed connection shall be secured by bolts or set
screw of common size adequately locked against vibration. Lock nuts shall be used on stud
connections carrying current.
All apparatus shall be replaced to minimize the risk of accidental short circuit caused by
animals, birds or vermin.
5. SERVICE CONDITIONS
a) The distribution transformers to be reclaimed against this Specification shall be suitable for
satisfactory continuous operation under the following climatic conditions as per IS- 2026
(Part-I)
i)
Location
ii)
Maximum ambient air temperature
Minimum average daily ambient air temperature
(°C)
Maximum average daily ambient air
Temperature (°C)
Maximum yearly weighted average
Ambient temperature (°C)
iii)
iv)
v)
vi)
At various locations in
Jammu Division.
45
10
40
32
95% (Sometimes
approaches saturation
point).
Maximum relative humidity
6. PRINCIPAL PERAMETERS
a) The reclaimed transformers shall be suitable for outdoor installation with three phase 50 Hz
11 KV or 6.6 KV system in which the neutral is effectively earthed and they should be for
service with fluctuations in supply voltage upto plus 12.5% to minus 12.5%.
b) The reclaimed transformers shall conform to the following specific parameters:
3
S.No
Item
01.
02.
03.
04.
05.
06.
07.
08.
09.
System voltage (max.)
Rated Voltage HV
Rated Voltage LV
Frequency
No. of Phase
Connection HV
Connection LV
Vector group
Type of Cooling
11 KV Distribution
Transformers
12 KV
11 KV
433-250 V*
50 Hz +/-5%
Three
Delta
Star(neutral brought out)
Dyn-11
ONAN
6.6 KV Distribution
Transformers
7 KV
6.6 KV
433-250 V*
50 Hz +/-5%
Three
Delta
Star(neutral brought out)
Dyn-11
ONAN
*The voltage level can be specified as 415-240 V/400-230 V volts as per the requirements of
the Department / Division. Audible sound level (decibels) at rated voltage and frequency for
liquid immersed distribution transformers shall be below (NEMA Standards):
KVA Rating
Audible sound Levels(Decibels)
0-50
51-100
101-300
301-500
45
50
55
60
7. CONTINUOUS MAXIMUM RATING:
The reclaimed transformers shall have a continuous maximum rating at the specified normal
ratio, frequency and temperature rise.
a.) Reclaimed transformers shall be capable of operation continuously in accordance with IS
loading guide at their continuous maximum rating and at any ratio without exceeding
temperature rise.
b.) Reclaimed Transformers with tapping ranges extending more than 9% below normal voltage
shall meet the temperature rise limits specified in IS: 2026 or any International Standard. On
other tapings, they shall operate continuously without injurious heating. The loading of the
transformers is to be in accordance with IS: 6600 - guide for loading of oil immersed
transformers natural cooled units or any international standards.
c.) The reclaimed transformers shall be capable of operation without danger at other than rated
voltage and frequency in accordance with clause 4.3 and 4.4 of IS: 2026 (Part I) 1977 or any
international standards.
8. MAXIMUM TEMPERATURE RISE:
The maximum temperature rise in reclaimed transformer tested at its continuous maximum
rating shall not exceed the following limit with reference to ambient air temperature.
a.) Temperature of oil by thermometer: 45 degree C +50 degree C ambient.
b.) Temperature of winding by test resistance: 50 degree C +50 degree C ambient.
9. NO LOAD VOLTAGE RATIO:
The No load voltage ratio corresponding to the principal tapping shall be
11,000/440Volts,6,600/440volts as the case may be (in case of Distribution Transformers).
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10. MAXIMUMCURRENT DENSITY:
The current density for HV and LV winding should not exceed 2.5 Amps/mm2. KVA Rating
Audible sound Levels (Decibels)
0-50 45
51-100 50
101-300 55
3301-500 60
11. MAXIMUM GUARANTEED NO LOAD AND LOAD LOSSES:
a.) Not withstanding anything, the department / division reserves the right to reject the
transformers for the losses exceeding guaranteed losses beyond tolerance limit losses as well
as in case of temperature rise of oil and winding exceed nameplate value and or impedance
value differ from nameplate value including tolerance, the manufacturer / repair agency shall
have to reclaim the transformer afresh within a reasonable period, as decided by the
department / division at no extra cost.
b.) While the Tenderers may offer their own design for reclamation it may be noted that the
transformer losses at 75ºC should not exceed the prescribed limit as already specified in
foregoing para.
12. WINDING CONNECTION VECTORS:
a.) The primary winding shall be connected delta and secondary winding star as per vector
symbol Dy.11 (IS: 2026) so as to produce positive displacement of 30o from the primary to
the secondary vector of the same phase (vector rotation assumed counter-clock wise).
b.) The neutral point of the secondary (LV winding) is intended for solidly earthed system and
should be brought out to a separate insulated terminal.
c.) All windings of reclaimed transformers shall have uniform insulation when tested in
accordance with ISS: 2026/1977 or any equivalent international standards. The minimum
basic impulse withstands level of windings for 1.2/50 micro sec. Full wave shall be as given
below: i) 11 KV - 75 KV Peak
13. TECHNICAL REQUIRMENTS:
a) CORE MATERIAL – CRGO / AMORPHOUS METAL (Wherever to be utilized to
replace the damaged/Burnt core) The shortfall of core shall be constructed from high
grade, non-ageing, low loss cold rolled super grain oriented silicon steel lamination of HI-B
grade steel or better. All stipulations under clause-8 be considered while selecting material of
core.
b) CRGO Material
c) The core shall be stack / wound type of high grade cold rolled grain oriented annealed steel
lamination, as per applicable Indian/ International standards, having low loss and good grain
properties, coated with hot oil proof insulation, bolted together and to the frames firmly to
prevent vibration or noise.
d) No-load current shall not exceed 3% of full load current and will be measured by energizing
the transformer at 433 volts, 50 Hz on the secondary. Increase of voltage of 433 volts by
12.5% shall not increase the no-load current by 6% (maximum) of full load current.
5
14. WINDINGS:
a.) Material:
b.) HV and LV windings shall be wound from Super Enamel covered / Double Paper covered.
Aluminum conductor for 250 KVA and below.
c.) HV and LV windings shall be wound from Super Enamel covered / Double Paper covered
copper conductor for winding for ratings above 250 KVA.
d.) Inter layer insulation shall be Nomex / Epoxy dotted Kraft Paper
e.) Proper bonding of Inter layer insulation with the conductor shall be ensured. Test or bonding
strength shall be conducted.
f.) Dimensions of winding coils are very critical. Dimensional tolerances for winding coils shall
be within limits.
g.) Current density for HV and LV winding should not be more than 2.8 Ampere per sq mm for
copper and 1.6 Ampere per sq mm for Aluminium Conductor.
h.) Joints in the winding shall be avoided. However, if jointing is necessary the Joints shall be
properly brazed and the resistance of the joints shall be less than that of parent conductor. In
case of foil windings, welding of leads to foil can be done within the winding.
15. TAPS:
a.) No tapping shall be provided for transformers up to 100 KVA rating
b.) For ratings above 100 KVA and up to 200 KVA, tapping shall be provided. if required by
the Department / Division, on the higher voltage winding for variation of HV voltage.
c.) For ratings higher than 200 KVA, tapping shall be provided on the higher voltage winding
for variation of HV voltage if required by the division.
16. TERMINAL ARRANGEMENT:
a.) The reclaimed transformers shall be fitted with shaded porcelain bushings of outdoor type
suitable for solder less connectors on HV as well as LV side if need be. The HV/LV bushing
shall not be provided with arcing horns. Aluminum bushing stems and aluminum metal parts
will not be accepted. The HV/LV bushings shall have the characteristics as per IS: 2099
(latest issue). LV neutral bushing requirement is identical to LV line bushing in all respect.
The electrical characteristics of bushing insulators shall be in accordance with IS: 2099 as
amended from time to time. All routine tests shall be carried out in accordance with IS: 20991986.
b.) Bushing studs of 11KV should be of copper and conforming to IS: 3347 with latest
amendment.
17. VIBRATIONS AND NOISE:
Every care shall be taken to ensure that the refitting and manufacture of all transformers and
accessories shall be such as to reduce noise and vibration to the level obtained in good
modern practice.
18. INTERNAL EARTHING ARRANGEMENT:
a.) General: - All metal parts of the transformer to be reclaimed with the exception of the
individual core laminations, core bolts and associated individual clamping plates shall be
maintained at some fixed potential.
b.) Earthing of core clamping structure: - The top main core clamping structure shall be
connected to the tank body by a copper strip. The bottom clamping structure shall be earthed
y one or more of the following methods.
1. By connection through vertical tie rods to the top structures.
2. By direct metal-to-metal contact with the tank base maintained by the weight of the core and
the windings.
3. By a connection to the top structures on the same side of the core as the main earth
connection to the tank.
6
c.) Earthing of magnetic circuit: The magnetic circuit shall be earthed to the clamping
structure at one point only through a disconnectable link placed in an accessible position
beneath an inspection opening in the tank cover plate. The connection to the link shall be on
the same side of that core and the main earth connection.
d.) Size of earthing connections: All earthing connections with the exception of those from the
individual cell clamping rings shall have a cross sectional area of not less than 0.8 sq.mm.
e.) Leads from winding to bushing and intercake connection: The leads from winding to
bushing and intercake connection should be rigid enough to withstand normal vibration and
transportation shocks and short circuit stresses. They should be spaced in such a way that
necessary clearances are maintained not only in air but also with oil medium at the lowest
permissive electrical strength as per relevant ISS over the period of normal service.
19. OVER LOAD CAPACITY:
a.) Reclaimed transformer shall be capable of carrying sustained over loads as stated in
ISS:6600.
b.) Type of load: - The Re c l a ime d transformer will supply a mixed power and lighting load
within varying power factor from 0.6 lag to 0.8 lead due to capacitors.
20. INSULATION LEVELS:
S.No.
Voltage (KV)
Impluse Voltage (KV
Peak)
Power frequency
Voltage (KV)
01.
0.433
--
3
02.
11/6.6
95
28
21. OIL:
a.) The Insulating oil shall comply with the requirements of IS 335 or BS 148 Use of recycled
oil is not acceptable. The specific resistance of the oil shall not be less than 2.5 X 1012 ohmcm at 27°C when tested as per IS 6103.
b.) Oil shall be filtered and tested for break down voltage (BDV) and moisture content before
filling.
c.) The oil shall be filled under vacuum.
d.) The design and all materials and processes used in the repair of the transformer shall be such
as to reduce to a minimum the risk of the development of acidity in the oil.
22. LOSSES :
a.) The bidder shall guarantee individually the no-load loss and load loss without any positive
tolerance.
b.) For transformers of other rating the following maximum allowable losses at rated voltage and
frequency and 75°C shall be taken:
Distribution Transformers:
Voltage
Rating KVA
Max. losses at 50%
loading (Watts)
Max. losses at 100%
loading (Watts)
11000/433-250 V
250
1050
3320
11000/433-250 V
400
1450
4630
11000/433-250 V
500
1600
5500
7
23. TOLERANCES:
a.) No positive tolerance shall be allowed on the maximum losses displayed on the label for both
50% and 100%, loading values.
24. PERCENTAGE IMPEDANCE.
a.) The value of impedance of transformers at 75°C shall be 4.5% for transformers up to and 200
KVA and ,for ratings above 200 KVA shall be in accordance with IS 2026.
25. TEMPERATURE RISE:
The temperatures rise over ambient shall not exceed the limits given below:
a.) Top oil temperature rise measured by thermometer : 35 °C
b.) Winding temperature rise measured by resistance method : 40 °C
Bids not meeting the above limits of temperature rise will be treated as nonresponsive.
c.) The reclaimed transformer shall be capable of giving continuous rated output without
exceeding the specified temperature rise. Bidder shall submit the calculation sheet in this
regard.
26. INSULATION MATERIAL:
a.) Electrical grade insulation epoxy dotted Kraft Paper / Nomex and pressboard shall be of
standard make or any other superior material.
b.) All spacers, axial wedges / runners used in windings shall be made of pre- compressed
Pressboard-solid, conforming to type 8 3.1 of: EC 641 -3-2. In case of cross-over coil
winding of HV all spacers shall be properly sheared and dovetail punched to ensure proper
locking. All axial wedges/ runners shall be properly milled to dovetail shape so that they pass
through the designed spacers freely. Insulation shearing, cutting, milling and punching
operations shall be carried out in such a way, that there should not be any burr and
dimensional variations.
27. SURFACE PREPARATION AND PAINTING:
GENERAL
a.) All paints, when applied in a normal full coat, shall be free from runs. sags, wrinkles,
patchiness. Brush marks or other defects,
b.) All primers shall be well marked into the surface. Particularity in areas where painting is
evident and the first priming coat shall be applied as soon as possible after cleaning.
c.) Inner paintings shall be made of highly zinc chromite.
28. PROTECTIVE COATING:
As soon as all items have been cleaned and within four hours of the subsequent drying they
shall be given suitable anti-corrosion protection.
29. FASTENERS:
a.) All bolts studs, screw threads, pipe threads, bolt heads and nuts shall comply with the
appropriate Indian Standards for metric threads or the technical equivalent.
b.) Bolts or studs shall not be less than 6 mm in diameter except when used for small wiring
terminals.
c.) All nuts and pins shall be adequately locked.
d.) Wherever possible bolts shall be fitted in such a manner that in the event of failure of locking
resulting in the nuts working loose and falling off, the bolt will remain in position.
30. TESTS:
a.) Before dispatch each of the completely assembled transformer shall be subjected to the
routine tests at the manufacturer's works as listed in IS 2026.
8
31.
a.)
b.)
c.)
d.)
e.)
f.)
g.)
h.)
i.)
ROUTINE TESTS:
Ratio, polarity, phase sequence and vector group.
No Load current and losses at service voltage and normal frequency.
Load losses at rated current and normal frequency. 34.4 Impedance voltage test.
Insulation resistance.
Neutral current measurement-The value of zero sequence current in the neutral of the star
winding shall not be more than 2% of the full load current.
Oil samples (one sample per lot) to comply with IS 1866.
Measurement of no load losses and magnetizing current at rated frequency and 90%, 100%
and 110% rated voltage.
The repaired transformer shall be accepted only after routine tests are done successfully.
It may also be noted that the Department / Division reserves the right to conduct short
Circuits lest and impulse voltage withstand test in accordance with the IS.
32. TESTS AT SITE:
a.) The Department reserves the right to conduct all tests on transformer after arrival at site and
the repairing agency shall guarantee test certificate figures under actual service conditions.
b.) The stage inspection shall be carried out once the coils (HV & LV) are ready for assembling,
in the premises of the manufacturer / repair agency.
c.) In case of any defective workmanship observed at any stage by the Inspecting Officer, the
same shall be pointed out to the firm in writing for taking remedial measures. Further
processing should only be done after clearance from the Inspecting Officer.
d.) All tests and inspection shall be carried out at the place of site of the bidder, unless otherwise
specifically agreed upon by the bidder and the Department / Division at the time of dispatch.
The repairing agency / bidder shall offer the Inspector representing the Department /Division
all reasonable facilities, without charges, to satisfy him that the material is being supplied in
accordance with this specification. This will include Stage Inspection during
manufacturing/repairing stage.
e.) The manufacturer/ bidder shall provide all services to establish and maintain Quality of
workman ship in his works and that of his sub-contractors to ensure the mechanical/electrical
performance of components, identification and acceptability of all materials, parts and
equipment as per latest quality standards.
f.) The Department / Division shall have every right to appoint a third party inspection to
carryout the Inspection process.
g.) The Department / Division has the right to have the test carried out at his own cost by
independent agency wherever there is a dispute regarding the quality.
33. ACCEPTANCE TEST:
T he D e p a r t m e n t a l / D i v i s i o n a l /Representative at the firm’s works shall witness
the following tests:
a.) All the routine tests as mentioned in above on each and every reclaimed transformer.
b.) Further, the department / Division Inspector reserves the right to carry out any other test for
acceptance of reclaimed transformers as per relevant specifications.
34. INSPECTION:
All tests and inspection shall be carried out at the place of manufacture unless otherwise
specifically agreed upon by the manufacturer and department / Division at the time of
delivery. The manufacturer shall offer the Inspection representative of the department /
Division with all reasonable facilities without charges to satisfy him that the material is being
supplied in accordance with this specification. This will include Stage Inspection during
manufacturing stage as well as Active Part Inspection during acceptance tests. The
department / Division has all the rights to conduct the test including type tests at his own cost
by an independent agency whenever there is dispute regarding the quality of supply or
9
interpretation of test results. In the event of failure of reclaimed transformer in such tests, the
expenses incurred in testing and cost of reclamation r etc. shall be to the manufacturer’s/
repair agencies account.
35. QUALITY ASSURANCE PLAN:
a.) In order to ensure use of quality material as per specified/ applicable standards, the
department reserves the right to inspect the quality and quantity of material at works of the
bidder firm before or during the reclamation process.
b.) The bidder shall invariably furnish following information along with his bid, failing which
'his bid shall be liable for rejection.
c.) Statement giving list of important raw materials, names of sub-suppliers for the raw
materials, list of standards according to which the raw materials are tested, list of tests
normally carried out on raw materials in the presence of bidder's representative, copies of test
certificates.
d.) Information and copies of test certificates as above in respect of bought out accessories.
e.) List of manufacturing facilities available.
f.) Level of automation achieved and list of areas where manual processing exists
g.) List of areas in manufacturing process, where stage inspections are normally carried out for
quality control and details of such tests and inspection,
h.) List of testing equipment available with the bidder for final testing of equipment along with
valid calibration reports. These shall be furnished with the bid. Manufacturer shall posses 0.1
accuracy class instruments for measurement of losses.
36. GUARANTEE:
The manufacturer / Repair Agency shall among other things warranty the following: a.) Quality and strength of material used, both electrical and mechanical.
b.) Satisfactory operation during the guarantee period of 12 months from the date of final
Inspection( On successful completion of all routine tests for the delivery of Reclaimed
Transformer) or 09 months from the date of commissioning. This period will be
reckoned from the day all accessories are received enabling assembly testing,
commissioning and commercial operation of transformers.
37. DEVIATIONS:
The bidders are not allowed to deviate from the principal requirements of the Specifications
and conditions as laid in the e-NIT.
-SdExecutive Engineer,
Electric Workshop Division
Jammu
Accepted
Signature with Stamp/seal
of Firm/Tenderer/Contractor
10