Bushings replaced on Laramie River Station transformer


Raymond Fitzwater, Basin Electric substation electrician in Wyoming, changing
out a bushing inside the GSU.

 A 345-kilovolt (kV) bushing on Laramie River Station’s Unit 1 generator step-up (GSU) transformer has been replaced after a fault occurred on July 30. 

According to Basin Electric Substation Superintendent Nathan Helbling, a late night call-out and visual inspection showed oil leaking from the GSU at the base of one of the high side 345kV bushings, and when the transformer's insulating oil was drained, large shards of porcelain glass showed that a bushing had exploded inside the transformer. The insulating oil was processed, the glass was cleaned up, and the bushing, along with six additional bushings, were replaced with spares Laramie River Station and the transmission system maintenance department had in its warehouses.

“Significant testing was conducted on the GSU before Unit 1 was put back in service,” said Helbling. “We had the plant operators run the generator at a lower power output then ramp up the unit slowly to ensure there wouldn’t be a catastrophic failure that would affect reliability. This was successful and the Laramie River Station Unit 1 generator was back at full load on Aug. 24.”  

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