Efficacy Study of a Pilot Installation of an On-Line Partial Discharge Measurement Sensor at KHP Unit 2 Generator

Partial Discharge (PD) is a slow-progressing phenomenon in electrical equipment whichdeteriorates the insulation system over time. Monitoring the PD activities has become avital method to prevent major failures of the electrical equipment (Yue et al., 2006). Thispaper presents a comprehensive study of the installation & efficacy of an on-line PDcoupling capacitors on the unit 2 generator of the Kurichhu Hydropower Plant (KHP),which had been in operation since August 15, 2001, without any form of monitoring ormeasurement system to assess the insulation system of the stators. A comprehensive siteassessment identified the necessity of three PD coupling capacitors (CCs) and associatedaccessories suitable for real-time monitoring of the generator stator, under electrical,thermal, ambient, and mechanical stresses. Following installation, a commissioning testwas conducted, and initial PD measurements were recorded as baseline data. To evaluatethe system’s effectiveness, a trend analysis was performed on four sets of measurementstaken from 2022 to 2024, also covering seasonal variations in 2024. Key parameters suchas PD magnitude, NQS values, and level counts were analyzed along with Phase-ResolvedPartial Discharge (PRPD) patterns to assess PD activity and severity. This study has doneoriginally for the installed PD measurement system, which can be used for the similar studyfor the same measurement system on the generators. The results demonstrated that theonline PD monitoring system effectively detected the integrity of the insulation system,with insulation resistance tests serving as a complementary validation method. Thecorresponding recommendations were made to KHP based on the findings.