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

Abstract

Partial Discharge (PD) is a slow-progressing phenomenon in electrical equipment which
deteriorates the insulation system over time. Monitoring the PD activities has become a
vital method to prevent major failures of the electrical equipment (Yue et al., 2006). This
paper presents a comprehensive study of the installation & efficacy of an on-line PD
coupling 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 or
measurement system to assess the insulation system of the stators. A comprehensive site
assessment identified the necessity of three PD coupling capacitors (CCs) and associated
accessories suitable for real-time monitoring of the generator stator, under electrical,
thermal, ambient, and mechanical stresses. Following installation, a commissioning test
was conducted, and initial PD measurements were recorded as baseline data. To evaluate
the system’s effectiveness, a trend analysis was performed on four sets of measurements
taken from 2022 to 2024, also covering seasonal variations in 2024. Key parameters such
as PD magnitude, NQS values, and level counts were analyzed along with Phase-Resolved
Partial Discharge (PRPD) patterns to assess PD activity and severity. This study has done
originally for the installed PD measurement system, which can be used for the similar study
for the same measurement system on the generators. The results demonstrated that the
online PD monitoring system effectively detected the integrity of the insulation system,
with insulation resistance tests serving as a complementary validation method. The
corresponding recommendations were made to KHP based on the findings.