Friday, July 27, 2012

Routine Power Transformer Inspection

The routine service inspection should include the following tests. Unless specific problems have been noted then the appropriate installation tests may also need to be included:

  • Inspect the control cabinet, indicators, control relays, contactors, and operating mechanism.
  • Check oil level in the tanks, bushings, and tap-changer compartments.
  • Check for loose terminals, oil leaks, and contaminated or damaged bushings.
  • Inspect the inert gas system for leakage and proper pressure.
  • Check, read, and record the operation-counter indicator reading associated with the load tap changer.
  • Check the oil temperature, which should not exceed the sum of maximum winding temperature (as stated on the nameplate) plus the ambient temperature (not to exceed 40°C) plus 10°C. Oil temperature does not exceed 95°C and 105°C for 55°C and 65°C winding-temperature-rise units, respectively.

Internal Inspection of Transformer

Open-type transformers that have not been inspected for at least three years should, if time permits, be given an internal inspection consisting of the following:
  • Check for evidence of corrosion of tank walls and other metal parts.
  • Verify connections for secureness.
  • Lower the oil level to expose the top of the core coil assembly.
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