Testing Methods for Medium Voltage GIS Switchgear

This case study outlines the testing methods for partial discharge (PD) in medium voltage gas insulated switchgear (GIS). Partial discharge can lead to significant failures in switchgear operating above 2500V, and traditional ultrasonic and TEV techniques may not be effective for GIS due to its unique construction. EA Technology conducted a series of tests to determine the best approach for PD testing in GIS, utilizing real PD sources embedded in a popular brand of 24KV switchgear. The study details the test plan, which involved a custom-built device generating internal PD and recording TEV and HFCT readings. Results indicated that GIS switchgear produces a significant PD signature detectable by both TEV and HFCT sensors, while ultrasonic testing may not be sufficient. The findings emphasize the importance of effective PD detection methods to prevent catastrophic failures without the need for de-energizing the equipment. The study concludes with recommendations for periodic PD surveys using appropriate sensor technology.