Case study: Asia Pacific Utility replaces two 69 kV bushings thanks to TOTUS online monitoring

Evidence: Increase of Power Factor and Partial Discharges in the bushing

Action: Both bushings replaced after offline tests confirmed the online results

Background

Due to federal PCB regulations in Canada, the utility has a targeted transformer bushing replacement program to meet end of use dates in 2025. Typical practice at the company is to install bushing monitors on new transformer HV oil filled bushings and to target older suspect bushings as a retrofit. In this instance the utility was applying a new approach, by adopting a more advanced online monitor, TOTUS, that could measure DGA in main tank as well as Partial Discharge (PD) in both main tank and bushings. The unit was installed to investigate a suspected source of PD in the transformer with the transformer bushings replaced at the same time.

The choice of TOTUS was driven by its unique ability to separate the PD in the tank from those in the bushings, as well as automatically rejecting the noise.