13 /EE ( M-33kV )/2025-26

50MVA 66/33kV Power Transformer OLTC Dismantling, Repair & Replacement: Draining of oil from OLTC vessel & safe storage in drums, Opening of OLTC head cover, dismantling of gear system, Lifting OLTC insert with mobile crane, Replacement of damaged moving & fixed contacts of R-phase changeover switch, Replacement of top cover & inspection window gaskets, Fixing & alignment of drive shaft, operation check on tap positions 1 to 17 and 17 to 1.

50MVA 66/33kV Power Transformer overhauling including Transformer Drying & Oil Processing – Dismantling of conservator / Buchholz relay pipeline, Fixing of dummy plates on radiator bank header pipe, replacement of all gasket, Transformer dry-out using vacuum pump & dry-air generator (dew point ≤ -60°C), Two cycles of vacuum drying & dew point monitoring (12 hrs each), Oil filtration, degassing & moisture removal, Filling of tested oil under vacuum, refilling conservator & radiator, Circulation of oil (4 cycles) maintaining ≥ 60°C temp. Painting of 50 MVA power transformer with glossy paint.

Testing & Commissioning of 50 MVA power Transformer Pre-commissioning electrical tests: i) Tan Delta, Capacitance on bushings & windings, ii) Turns ratio test on all taps, iii) Magnetic balance at normal tap, iv) Vector group verification, v) Short circuit impedance test, vi) IR/PI measurement (15 sec, 60 sec, 600 sec), vii) Winding resistance measurement (tap 1–9B), viii) Oil quality tests: BDV, Moisture (ppm), Resistivity, DGA, ix) Final inspection & report for energization of Power Transformer.

ADD: GST @ 18%