132-110/33-13.
8 kV, 67 MVA MULTI-WINDING TRANSFORMER
The transformer shall be designed, manufactured and tested in accordance with the relevant
clauses of NATIONAL GRID SA Materials Standard Specification 53-TMSS-1, unless
otherwise noted herein. The specific requirements shall be as given in 53-TMSS-1.
Mineral insulating oil for the transformers shall conform to the requirements of the
NATIONAL GRID SA Materials Standard Specification 54-TMSS-1.
The transformer shall be 60 Hz, three-phase, vector group YN0, yn0, yn0, d1, four-winding
type with 132-110 kV primary HV winding and the secondary windings of 33 and 13.8 kV
rated voltage.
The primary and secondary windings of the transformer shall be connected in star. The
secondary windings shall be suitable for operation with the neutral resistance grounded.
The HV side shall be provided with an DETC tap changer of 13 steps (3 above and 9 below
normal voltage) of 3.33% step voltage.
Bushing current transformers shall be provided as per the details given in Data Schedule of 53-
TMSS-2.
The impedance of the transformer shall be chosen such that the fault current at the 13.8 kV
system does not exceed the proposed switchgear ratings by assuming infinite bus source as
primary.
132-110/33-13.8 kV, YN0, yn0, yn0+d1, 67 MVA, ODAF Rated Transformer, oil immersed
type, multi-winding transformer along with its accessories for the mobile substation. The
transformer shall be provided with an off-circuit tap changer having a total of 13 steps, 3 above,
9 below, step voltage 3.33% (4.4 kV). The transformer impedances shall be as follows:
29.5% at 132/13.8 kV, 67 MVA Base winding. The transformer’s 132 kV shall be solidly
grounded while and 13.8 kV LV shall be grounded thru grounding resistances. The rating of
grounding resistances shall be as per SOW given hereunder.
The VENDOR shall be responsible for specifying and supplying the type of cooling on the
transformer. The VENDOR should indicate the transformer rating in percent of full rating, if
any, when operating under normal cooling conditions.
DESIGN CRITERIA
The VENDOR shall adopt the following design criteria as a minimum for this PURCHASE
ORDER:
1- ENVIRONMENTAL CONDITIONS
All equipment and devices, and their specified ratings furnished under this PURCHASE
ORDER shall be suitable for operation as outlined in the COMPANY Materials Specification
01-TMSS-01, GENERAL REQUIREMENT FOR ALL EQUIPMENT/MATERIALS,
Appendix B1.
The mobile substation and all its components shall be capable of withstanding the effects of
direct solar radiation at its installed location. The temperature of metal surfaces exposed to
direst solar radiation and the temperature inside unventilated metal enclosures should be
regarded as 75ºC, plus the effect of any internal heating.
The mobile substation location is subject to sand and dust storms, salt laden winds and fog, and
airborne chemical contaminants. All terminal enclosures shall be weatherproof and dust tight
and all metal parts shall be corrosion and/or abrasion resistant.
In case of a conflict between the requirements specified in 01-TMSS-01 and other COMPANY
Materials Specifications, the requirements specified in 01-TMSS-01 shall prevail.
2- Additional / Special Requirements
Following are the additional / special requirements that apply to this SOW.
1. Maximum Ambient Temperature 55 ºC
2. Minimum Ambient Temperature -5 ºC
3. Permissible Top Oil Temperature Rise 45 ºC
4. Permissible Average Winding Temperature Rise 50 ºC
5. Insulation level of HV-Neutral shall not be less than (170/70 kV).
6. The ratio of no-load currents at 110% and 100% of U0 (Rated Voltage at Nominal Tap)
shall be ≤ 2. This shall be proved by manufacturer thru measurement of no-load currents / no-
load losses during factory acceptance tests.
7. Core Steel shall be high grade silicone steel per 53-TMSS-01, Rev. 02 from renowned
source, proven service experience and already used in previously supplied power
transformers to National Grid / SEC. The make and type of steel to be used for core shall be
subject to prior approval by NG. The COMPANY has the right to ask for producing
documentary proof for the source of core material used by the manufacturer.
8. Enameled copper windings shall be provided.
9. Copper shall be from some renowned source, proven service experience and already used
in previously supplied power transformers to National Grid / SEC. The make and type of
steel to be used for core shall be subject to prior approval by NG. The COMPANY has the
right to ask for producing documentary proof for the source of copper/winding material used
by the manufacturer.
10. The transformers shall be provided with dry type / maintenance free type breathers.
11. Employing in transformer design, the Higher flux density (not complying to Company’s
applicable standard) and hybrid / composite insulation (NOMEX etc.) shall not be permitted.
12. Thermally up-graded paper from Western European Source shall be used. The make and
type of paper / insulation material shall be subject to prior approval by NG. The COMPANY
has the right to ask for producing documentary proof for the source of insulation material
used by the manufacturer.
13. Insulating oil shall be non-corrosive conforming to 54-TMSS-01, Rev. 01 from
COMPANY’s approved manufacturer. Any other make / designation of oil shall be subject to
prior approval by NG.
14. All factory tests on transformer shall be conducted in line with IEC 60076 Edition 2011,
53-TMSS-01, Rev. 01 and this Scope of Work.
15. All HV tests in factory shall be conducted with LV cable boxes mounted on the
transformer.
16. Station service transformer shall be located on HV (power transformer) trailer.
2- ELECTRICAL CHARACTERISTICS
3- STANDARDS, CODES AND SPECIFICATIONS
All WORK, equipment and materials covered by this document shall conform to the latest
edition of the COMPANY’s Material Standard Specification supplemented with the latest
applicable Industry Standards, Codes and Specifications.
The VENDOR shall strictly comply with the following Standards, Codes and Specifications,
and no deviation shall be accepted unless otherwise supported by a written waiver from the
COMPANY.
The VENDOR may propose “Equivalent” Standards and Specifications if such Standards and
Specifications are in fact equal to or better than those specified herein, and shall be subject to
prior approval of the COMPANY.
A. NATIONAL GRID GENERAL Appendix B1
SA Materials Standard REQUIREMENTS FOR
Specifications 01-TMSS- ALL
01 EQUIPMENT/MATERIAL
S (REV. 03)
35-TMSS-3 SURGE ARRESTERS, 11 Appendix B2
KV THROUGH 380 KV
(REV. 1)
53-TMSS-2 TRANSFORMER, Appendix B3
POWER, ABOVE 2.5
MVA (REV.2)
54-TMSS-1 MINERAL INSULATING Appendix B4
OIL FOR ELECTRICAL
APPARATUS (REV. 2)
30-TMSS-1 AIR BREAK Appendix B5
DISCONNECT AND
GROUND SWITCHES
(REV. 1)
37-TMSS-1 DEAD TANK CIRCUIT Appendix B6
BREAKERS (REV.1)
32-TMSS-1 METAL ENCLOSED MV Appendix B7
SWITCHGEAR (REV. 2)
32-TMSS-3 METAL CLAD GAS Appendix B8
INSULATED
SWITCHGEAR (REV. 0)
31-TMSS-1 RELAY AND CONTROL Appendix B9
PANEL (REV. 1)
31-TMSS-2 AUXILIARY AC/DC Appendix B10
PANELS (REV. 2)
40-TMSS-2 METERING DEVICES Appendix B11
51-TMSS-1 PAD-MOUNTED Appendix B12
STATION SERVICE
TRANSFORMER (REV. 1)
11-TMSS-10 POWER AND/OR Appendix B13
CONTROL CABLES,
COPPER OR ALUMINUM
CONDUCTOR, 600/100V
RATING (REV. 1)
46-TMSS-6 VENTED TYPE, NICKEL- Appendix B14
CADMIUM STATIONARY
BATTERY BANK (REV.
0)
46-TMSS-2 BATTERY CHARGER Appendix B15
(REV. 1)
37-TMSS-1 CIRCUIT BREAKERS Appendix B16
DEAD TANK 69 KV
THRU 380 KV (REV. 1)
53-TMSS-03 ONLINE GAS ANALYZER Appendix B17
(REV. 0)
