Repairing of Damage Transformers

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 core and coil assembly and cleaning of dust and dirt from the core assembly and checking of LV and HV leg coils for assessing its reuse, rechecking and recording of physical dimensions of coil and cleaning of core and their components etc.

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 Alu. Leg coils identical to original one with same number of turns, weight etc providing super enameled / DPC conductor/ Strip confirming to IS 1971 /53 in place of old and damage coil. Alu. 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.Rewinding shall be arranged to ensure free circulation of oil to reduced hot spots in winding. The insulation of coil shall be treated with suitable insulating, varnish or equivalent compound to develop the full electrical strength of winding as per original design.

‘‘Making of complete HV leg Alu. Leg coils identical to original one with same number of turns, weight etc providing super enameled / DPC conductor/ Strip confirming to IS 1971 /53 in place of old and damage coil. Alu. 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.Rewinding shall be arranged to ensure free circulation of oil to reduced hot spots in winding. The insulation of coil shall be treated with suitable insulating, varnish or equivalent compound to develop the full electrical strength of winding as per original design.

Assembly of core and coils and fitting of other parts requiring replacement such as press board, making supports between adjacent sections by insulating spares and rapping etc & tapping etc. (Breezing/soldering) required, shall be arrange by the contractor.

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 from 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.

ganga electrical industries

Engineers India