BANGLADESH POWER DEVELOPMENT BOARD TENDER ... - BPDB

Non segregated bus duct between low tension terminals of auxiliary transformerand power centre terminals instead of cables may be acceptable.5.4 STATION TRANSFORMERS5.4.1 TYPE AND RATIOThe transformers shall be of three (3) phase, oil immersed, self air cooled (ONAN)type. Nominal no load ratio of delta star connection shall be 6.6 kV to 415 VThe connection shall be arrangement in vector symbol Dyn11 according to IEC76-4 and neutral of star connected low tension winding shall be earthed solidly.The off circuit tap changer shall be provided on the high tension winding, andtheir ratio shall be as follows:6.6 kV (5%) /415V -240 V5.4.2 OutputEach auxiliary transformer shall enable to supply 120% of required power on 415V for the gas turbine generating unit.5.4.3 IMPEDENCE VOLTAGEThe impedance voltage shall not less than 5%, but not more than 7.5% on therated tapping (6.6 KV /415V) and shall be guaranteed by the Contractor.5.4.4 WINDING AND INSULATIONThe requirements shall be in accordance with section 5.2.4, except voltage rating.5.4.5 OFF CIRCUIT TAP CHANGERThe requirements shall be in accordance with Section 5.3.5.5.4.6 CABLE BOXThe requirements shall be in accordance with Section 5.3.6.5.5 ACCESSORIESThe following accessories shall be furnished for each transformer:a. Name plateb. Valves for oil filtering and samplingc. Air vent valved. Manhole and hand-hole including blind coverse. Ladder fixed to the transformer tank for inspection of the upper part of thetransformer.f. Hanging hookg. Grounding terminalsGhorasal 200 MW to 300 MW Gas Turbine Peaking Power Plant Project (Vol-2 of 3)53