Today’s LiveWire Spotlight assesses a new NERC’s Lesson Learned recounting two incidents at the same facility touched off by the failure of newly installed hermetically sealed metering current transformers (CTs).  Both caused service to be interrupted on the main 138 kV feed to the utility’s transmission system five days apart – affecting the entire transmission footprint.  A post-incident analysis showed that the moisture content of the oil surrounding the CTs’ coils was elevated above acceptable levels

Wide-area electric system outages that result from substation failures are among NERC’s top reliability concerns.  Severe penalties may be levied if a CT failure causes BES instability or Cascading, and it is found that an Operator did not act upon these Lessons Learned.