Condition Monitoring to Detect Insulation Deterioration in Bushings

Bushings are key to the performance of the power transformer – much like the wheels on a car: the wheels are not why we have a car, but without the wheels the car doesn’t do what it is supposed to do. The detection and diagnosis of insulation deterioration in power system assets such as bushings is of great concern to system owners/operators. Asset failure may lead to not only asset replacement but costs to cover collateral damage, environmental clean up and so on. But targeting insulation related failure modes can be difficult where multiple failure modes may be in operation, with numerous parameters indicating several different diagnoses, each with different timescales. In this paper we look at some of the standard techniques used to detect bushing insulation deterioration, offline and online, and some cases where unexpected situations contributed to the analyses.