This month’s Featured Technical Paper is from the Proceedings of the 2020 International Conference of Doble Clients. The paper is titled: Online Monitoring and Investigation Examples for ABB O+C Bushings.
The value of online condition monitoring at electric transmission utilities is often focused on preventing failures through early fault detection. Another valuable benefit of online condition monitoring is risk management with improved asset condition visibility and additional data related to potential causal factors prior to an incipient fault.
Active partial discharge and an increasing power factor trend were detected with online monitors on relatively new 138kV O+C bushings. By analyzing the partial discharge (PD) pattern and comparing it with available literature [2-3] it was speculated that the presence of PD was likely due to floating particles in oil. The presence of oil contamination may not affect the C1 capacitance readings but can affect the power factor results with additional conductive current. Also, the presence of partial discharge generates abnormal levels of dissolved gases which were confirmed through DGA. This paper will discuss the monitoring results, factory testing, as well as the subsequent bushing investigation.
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