Tender Document Volume - 2 - BPDB

on the transformer.
The wiring shall be connected at the terminal blocks terminating the outgoing
control cable. The flexible tube of the vapour tension thermometer shall be
covered by a protective tube.
(8) Insulating oil
The insulating oil shall have a sufficient insulation strength, and shall be excellent
in heat conductivity, low in viscosity and pour point, and high in flash point. The
oil shall not cause any corrosion to insulating materials and structured materials of
electrical equipment and shall be chemically stable for long years of use.
Delivery shall be made to Site partly contained in the transformers and partly in
steel drums, according to the method of packing employed. An excess of 10% of
the quantity of oil required for filling transformers shall also be supplied and its
cost shall be included in the price of each transformer.
(9) Skid Base
The transformer shall be provided with a skid base with four (4) steel wheels and
necessary jacks for setting and appropriate devices for locking in position of its
foundation.
5.2 GENERATOR STEP-UP TRANSFORMERS
5.2.1 TYPE AND RATIO
The transformer shall be of single phase, oil immersed, self cooled / forced air
cooled (ONAN/ONAF) by cooling fans, outdoor use type. Ratio of delta star
connection shall be 11 KV to 230 KV on full load condition.
The connection of the three phase bank shall be arranged in vector symbol Ynd11
according to IEC 74-4 and neutral of star connected high tension winding shall be
solidly grounded.
The on load tap changer shall be provided on the high tension winding, and their
ratio shall be as follows:
230 kV(±1.25% x 8)
5.2.2 OUTPUT AND REQUIRED NUMBERS
The maximum continuous rating of the transformer shall met at any taps a total
output of the generator which is connected with the transformer in series as
shown in the attached single line diagram.
The self cooled capacity shall not be less than 75 % of forced air cooled capacity.
5.2.3 IMPEDENCE VOLTAGE
Impedance voltage (+ve seq.) shall be within the range of 15% to 18% on the
forced air cooled rating on the rated tapping (11/230 KV ) and shall be
guaranteed by the Contractor.
Ghorasal 200 MW to 300 MW Gas Turbine Peaking Power Plant Project (Vol-2 of 3)
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