Repairing of 400 KVA damaged Transformer

Handling and dragging of transformer from stacking yard to repairing hall including opening of top cover plate.

Opening of tap changer connection detanking of core and coil assembly, checking of transformer winding to assess the extent of damage.

Cleaning, removing the rust of tank etc of the repairable transformer and painting of inside of transformer tank with zinc chromate (Yellow) in two coats with spray painting machine. Zinc chromate (Yellow) shall be supplied by the contractor.

Dismantling of core and coil assembly, opening of top yoke core, lamination. Removing of HV and LV Leg coils for assessing its reuse, reuse of major insulating material if possible, checking and recording of physical dimensions of coil.

Reconditioning of the damaged LV leg coils (3 Nos) of T/f old and damage DPC insulation is to removed and new DPC insulation confirming to IS: 1271/53 is to be provided on LV strips after cleaning of strip LV coil should be made of same size.

‘‘Making of complete LV leg cu Leg coils identical to original one with same number of turns, weight etc providing DPC Strip confirming to IS 1971 /53 in place of old and damage coil. Copper. coil, wire strip will be provided by the department. All coil assembly of identical voltage shall be interchangeable without requiring any special equipment. Coil shall be supported between adjacent sections by insulations, spacers, beamers and other insulations.

‘‘Making of complete HV leg coils for 11/.4 KV 400 KVA copper wounded Transformers from old and damaged copper coil/strip. The work will involve removing complete old insulation and cleaning of wire/strips and covering the wire/strips with new DPC insulation and rewinding of coil identical to original one with same number of turns, size, dimension and weight etc including, providing, insulating varnish and baking to develop full electrical strength of new winding as per original design.

Assembly of core and coils and fitting of top yoke and other parts. Replacement of insulation such as press board, craft paper, making support between adjacent section by insulating spacers and wrapping etc. shifting of repaired core coil assembly and placement inside the oven for proper dry out.

Taking out the core coil assembly from oven and shifting the same in assembly yard. Connection of HV Coils and its delta formation, LV connection and its star formation. Fixation of insulating material wherever necessary. Tanking out leads fortap changer contact surface between movable and fixed contacts, tap changer should operate smoothly and there should be no gap between fixed and moving contacts. Retightening of core, coil assembly to match with tank dimension. Clearance between coils, core and tank body to be as per design so that unnecessary losses are avoided. Retanking of core and coil assembly, refitting of tap changer assembly in operating condition and electrical connection of the tap changer.

Dragging out empty tank form yard to repairing hall

Fitting of complete accessories of H.T. & L.V. Bushing and Bushing Rod on H.V. & L.V. side of transformer.

Refilling of reclaimed transformer oil having sufficient dielectric strength and IR Value. Shifting the transformer to testing yard. Refitting of top cover plate, and fixing of rubberized cork sheet, breather assembly after filling of dry silicagel.

Testing the correctness of connection, DVDF, No load, load loss test (where available), High Voltage, impedance voltage, Short Circuit and open circuit test, Voltage ratio on various tap position.

Painting outside of the tank by synthetic enamel paint of smoke grey shade in two coats after providing red oxide primer. Red oxide primer and synthetic enamel paint shall be provided by the contractor.

LALJEE YADAV

M/S jai ambey traders