Ultra-High Frequency (UHF) Based Partial Discharge Measurement in Gas Insulated Switchgear (GIS)

Gas Insulated Substations (GIS) offer significant advantages over conventional Air Insulated Substations (AIS) on account of reduced space and operational efficiency. Partial discharge (PD) measurement is one of the important test in GIS to ensure its reliability during service and also to reveal defects at incipient levels. One of the methods employed for partial discharge (PD) measurement is by capturing the Ultra high frequency (UHF) signals that emanate from the partial discharge sites. The present paper discusses the measurement of partial discharges and also localization of PD source in a gas insulated bus duct assembly of EHV (Extra high voltage) class, using UHF PD detector. The corresponding PD magnitude obtained through conventional electrical method has also been reported. The study has been aimed to monitor PD during service (on-line) using the UHF method so that defects can be detected at premature levels. Necessary set-up for measurement is also discussed in the paper. This process of evaluation helps utility to make appropriate plans for maintenance schedules and ensure reliable operation of GIS.