Tender Document Volume - 2 - BPDB

e allowed.
b. The tank shall be of the welded steel plate structure and shall withstand
and hold continuously a vacuum of 760 mm Hg.
e. The sealed joint part of the tank shall be designed to prevent oil and gas
leakage and shall be water light even after long term use, and careful attention
shall be paid to fastening methods of packing of bushing, bursting tube, cooling
radiator, connecting pipes and other accessories.
d. Looseness of core, yoke, coil and other parts shall not happen during
transportation and long term use.
e. The transformer shall be provided with a bursting tube to discharge the
pressure in case of abnormal rise of the inner pressure. The tube shall be
equipped with alarm contact. The tube shall be extended up to tile oil pit which
will be constructed around the transformer.
f. No corona shall be discharged inside and outside of the tank under the
imposed primary voltage of 230√3 KV x 130%.
g. All generated gas and oil flow under fault conditions shall be concentrated
to the Buchholz or similar type relay so as to ensure the relay action.
h. The transformer shall be provided with skid type base.
i. Anti-vibration rubber or the equivalent shall be provided under the base so
as to prevent propagation of transformer's vibration to the other Equipment, if
installed in the power house.
j. Winding of coils shall be designed so as to make the initial potential
distribution caused by impulsive travelling waves as uniform as possible, to avoid
potential oscillation and to withstand abnormal voltage due to switching.
k. The ground terminals of the transformer shall be copper faced steel
ground pad, and shall be welded on the tank wall near the base. The ground
terminal shall be of the bolt fastened type, suitable for 100-200 sq. mm hard or
annealed copper stranded conductors.
l. In designing the transformers, the Contractor shall refer to the general
arrangement of the transformer and shall consider the location of the lightning
arrester.
(2) Bushing and Connection
230 KV line and neutral bushings of the generator step-up transformer shall be oil
filled nitrogen sealed draw lead type with an oil level gauge, and 15 kV bushings
shall be of the solid type. The glazing colour shall be of brown.
The lighting impulse (1.2/ 50 micro see.) insulation level of bushings
shall be as follows:
- 230 KV line bushings :1050 kV peak
- 230 KV line neutral bushing :1050 kV peak
Ghorasal 200 MW to 300 MW Gas Turbine Peaking Power Plant Project (Vol-2 of 3)
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