supply of 500kva, 11kv / 415v , 3 phase, 50hz, outdoor type, plinth mounted, oil immersed, non- sealed type ( transformer tank body and cover are bolted ) distribution transformer, primary winding in delta and secondary winding instar ( vector symbol - dyn11 ) , onan cooled transformer, energy efficiency level-2 or above confirming to is 1180 ( part 1 ) : 2014 with amendments nos. 1, 2, 3 & 4 and supplied with all standard fittings mentioned in clause 20.1 of is 1180 ( part 1 ) along with oil temperature indicator & winding temperature indicators. drain-cum sampling valve ( 3 / 4 inch nominal size thread, is :554 ) of steel with plug. terminal arrangement: - the transformer shallbe fitted on high voltage and low voltage sides with bushings of appropriate voltage and current ratings. suitable cable end box is to be provided in lt side. tap changer: off load tap changer for variation of hv voltage from +5% to -10% in steps of 2.5% [ warranty period: 30 months after the date of delivery ]