Risk Assessment of Electrical Defects in MV Switchgear Using Partial Discharge Diagnostics

Partial discharge (PD) diagnostic is regarded as a powerful method for diagnosing the potential electrical insulation defects in a medium voltage (MV) and high voltage (HV) switchgear. This paper proposes a method, termed as a risk-based approach, to identify the severity of several critical electrical defects in MVI HV switchgear based on partial discharge testing. To accomplish this, several defects have been artificially created in a MV switchgear. Testing was carried out to investigate the characteristics of PD signals using nonintrusive sensors. Accordingly, the specific PD intensity of the discharge pulse has been considered as stress parameters and then statistically modelled by suitable probability distribution. In this way, the probability of dielectric failure has been quantified. The consequences of dielectric failure, and hence the failure of the switchgear are given by the power outage cost and repair expenditures. The risk assessment is made by combing both of these factors. The estimated risk is an indication of the criticality of the fault and can be specified as low, medium, high, or maximum. In this way, the proposed approach can be easily adopted by asset manager for risk assessment of switchgear in the petroleum and chemical industries.