2018 08 Paper: McKay Creek Gen Step Up Transformer Failure

This paper reports a generator step up transformer failure event happened in Mckay Power Station. In the event, protection relay operated, transformer operated and high voltage circuit breaker isolated the failed transformer. Relay trip event was downloaded and high current waveform was recorded. Transformer was isolated for investigation and testing. Series of tests were performed, results revealed no insulation failure but one of the winding open circuit. Dissolved Gas Analysis (DGA) confirm present of acetylene which indicates arcing in the transformer and genuine transformer fault. Transformer was removed and replaced with a spare unit from another station. The Spare unit was recondition, bushing was replaced and oil was dehydrated. In the process of shifting the transformer, part of the road was reinforced. The spare transformer was put in service after 2 weeks; shifting, installation, reconditioning, testing and recommissioning. The failed transformer later was untank for inspection and investigation. It was found one of the winding is open
circuited and confirm the test result is valid. The cause of the failure was suspected due to moisture ingress.

• Author: Kaw Choen Low
• Exchange: 2018 - Albury AGL
• Company: AGL Energy
• Topic: Transformer
• Key Words: DGA, Fault, Testing, Transformer