overhauling of 42 . 5 mva , 11/139 kv , bhel make overhauling of 42 . 5 mva , 11/139 kv , bhel maketransformer of chilla power house . , draining transformer oil to the drums & transportation of transformer and its accessories from chilla power house to workshop including packing . , sampling & dga ( dissolved gas analysis ) of oil as per is 10593-2006 . , removal of top cover plate of transformer and other accessories . , inspection and testing of core assembly . , inspection and testing of 3- phase lv & hv windings . , replacement of all 3-phase lv windings including insulation etc . , replacement of all 3-phase hv windings ( if , required ) including insulation etc . , drying out of complete core- coil assembly to achieve proper ir values and tan delta values and tanking of core coil assembly . , overhauling of transformer along with replacement of oti , wti , lv bushing , neutral bushing & breather with silica gel . , replacement of all gasket alongwith one new hv bushing . , filtration ( centrifuging ) & filling of testing oil & complete testing of transformer . , painting of complete transformer as per is 631 . , draining the transformer oil ( testing oil ) . , transportation of repaired transformer to chilla power house with filling of required inert gas . , refilling of transformer oil to the repaired transformer at site . , erection , testing of the repaired transformer complete in all respect at chilla power house including dga according to is: 10593-2006 after dismantling one of the connected transformers as per availability of shutdown .