Online monitoring prevented catastrophic failure of a GSU transformer

Mirant Mid-Atlantic LLC experienced two generator step-up (GSU) transformer failures in 2001. Both failures occurred despite disciplined adherence to traditional regiments for electrical tests and dissolved gas analyses. In 2002, localized temperatures and accelerated hydrogen gas generation were the results of an active fault on the Morgantown Unit 02 GSU. In response, the frequency of dissolved gas analyses increased, and an on-line hydrogen and moisture analyzer was installed. The on-line analyzer provided advance warning of failure while the fault condition remained in the incipient stage. On-line monitoring of hydrogen generation prevented catastrophic failure, and enabled an inventive repair of the winding and expedited return to service of the step-up transformer.