AN INVESTIGATIVE STUDY FOR CALIBRATION OF EXTERNAL PD SENSORS IN GAS INSULATED SWITCHGEAR

Mandava M. Rao∗ and Mritunjay Kumar∗

Keywords

Calibration, earthing switch, external sensors, gasinsulated switchgear, insulated ports, partial discharge

Abstract

Partial discharge (PD) measurement is one of the important checks in gas-insulated switchgear (GIS) to ensure its reliability and also to limit outages against operation initiated discharges. In the present paper, the measurement of PD is carried out on site-deployable 420kV GIS modules using the ultra-high-frequency (UHF) technique. The design of fixing arrangements for external PD sensors on a support insulator is discussed as part of the study. A GIS module with this set-up is energized at a laboratory, and a discharge pattern is measured and compared with the data simultaneously obtained through a straight detection method. One more objective of the study is to develop a novel on-site sensitivity verification technique for external PD sensors employed in GIS. This technique is further extended to establish the location of the sensors across the GIS bay for optimal coverage. The suitability of novel insulated ports employed in earthing switches and composite insulators of gas-toair bushing of the GIS bay for the injection of PD signals and for sensitivity verification of external sensors has been analysed. The developed technique has been further extended to verify and quantify the accuracy of PD measurements and discharge location. Finally, calibrated external sensors are effectively implemented to identify discharge location in a 420-kV GIS bay being commissioned at the site.

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