Case Study: KEPCO prevents in-service failure of a 345kV bushing with TOTUS online monitoring

Evidence: Online monitoring showing capacitance increase and arcing events.

Action: KEPCO planned offline Capacitance and DGA test confirming online data and issues replacement, thus preventing an in-service failure.

Background

Bushing Power Factor and Partial Discharge (PD) online monitoring was installed on a single-phase transformer bank in Ulsan, South Korea in 2015. The installed device monitors leakage current from the bushings and detects PD activity from the main tank and bushings using tap adaptors installed on the bushing test taps. The monitor acquires leakage current and PD information continuously and simultaneously in all phases with a summary of the data stored hourly.

The transformer bushings were in operation for more than 30 years, and were an OIP type, rated 345 kV, and approximately 430 pF capacitance.