Service Group repairs a Federal Pacific transformer allowing for a full return to service

Posted: July 10, 2018

Earlier this year, one of our Southern customers de-energized a Federal Pacific 30 MVA 134/34.5 kV transformer for minor external repairs. Following repair completion and re-energization, the transformer immediately tripped off-line, indicating a serious event had occurred. SPX Transformer Solutions’ Service Group was contracted to test the unit, complete an internal inspection and present an actionable list of repairs. Following the internal inspection and review of oil quality reports, indicators pointed toward an LTC failure, which caused substantial internal damage. The customer, not having a spare and unable to locate a suitable replacement, requested our team repair the unit so it was ready for service until a suitable replacement could be obtained.

Items in need of immediate repair were the bridging regulating winding leads. Several of these leads showed signs of insulation flaking off as a result of flashing over and burning through. The destruction of these leads also resulted in extensive cracking damage to two LTC phase moldings. Once the LTC leads were isolated, further testing indicated localized damage only, leaving the core and coils suitable for future use.

Preparation services included:

  1. Removing all damaged materials and foreign debris from the main tank
  2. Removing all damaged leads and broken lead supports
  3. Removing the LTC completely, both selector and diverter assemblies and associated drive mechanism

Enlisting support from the other two groups within SPX Transformer Solutions, our Southern field service transformer specialist crew proceeded to make all required repairs. Support included obtaining leads, cable splices, cable lugs, dried blocking and wood supports from the Wisconsin transformer plant, as well as information and materials from our LTC specialist and engineering support team in Dallas.

This extensive project encompassed full internal lead repairs:

  • Re-insulating and insulation repair
  • Lead support structure rebuilding
  • Addition of lead support structures in critical areas
  • Securing and routing all lead bundles
  • Additional rebuilding of the complete LTC with new tap head assemblies, diverter assemblies, drive mechanism and associated chains, seals and gaskets

The unit was then fully regasketed, vacuum and oil processed, allowing for a full return to service.