OMICRON Magazine

Magazine | Issue 2 2023 Optimizing sensitivity for on-site PD measurements In GIS systems with SF6 insulation, PD generates electromagnetic waves in a broad frequency spectrum due to their short rise time. Protrusions and particles or voids inside insulators may generate low-level partial discharges, which require a sensitive PD measurement, especially for testing GIS on site. Compared with performing PD measurements in optimized factory and laboratory test environments, on-site PD measurements are often compromised by significantly higher interference signal levels, namely external noise. For on-site commissioning testing and troubleshooting on GIS, the ultra-high frequency (UHF) method has established itself as the standard method for PD measurements to ensure the required sensitivity. The common bandwidth of the UHF PD measurement method is typically from 100 MHz to 2 GHz. In a sensitive UHF PD measurement, even minor defects generating low-level partial discharges can be detected in GIS, and it’s a reasonable alternative to expensive on-site tests being used for low-level PD detection, such as the lightning impulse test. Different UHF PD measurement modes There are different approaches to performing UHF PD measurements. Wideband measurements are appropriate for «PD activity is a reliable indicator for the insulation condition in electrical equipment, as it is often a sign of developing insulation defects that can potentially cause dielectric failure.» Stefan Hoek, Product Manager, OMICRON 21