A Comparison of PD Detection Techniques for Complete Assemblies of Air-Insulated Switchgear
Mathieu Lachance; Francis Rosa
This publication presents a comparison between conventional PD measurements, TEV PD detection and ultrasonic PD detection applied on medium-voltage air-insulated switchgear. Several types of anomalies which generated PD were introduced in a 15 kV rated metal-clad distribution switchgear and in a 35 kV rated metal-enclosed distribution switchgear. PD measurements were then performed in a factory environment to verify the sensitivity of each technique using commercially available instruments. Additional measurements were performed by combining stand-alone TEV sensors with an advance PD instrument, which allows freely configurable digital filters to be applied to the acquired signals.It was found that ultrasonic detection using a camera is very useful at localizing external PD with a clear line of sight. The wideband handheld TEV instrument used in those experiments detected a variety of defects but was limited to PD sources that generated relatively high levels of apparent charge, as measured by conventional measurements. The combination of the advanced PD instrument with the stand-alone TEV sensors greatly improved the sensitivity of PD detection by allowing a configurable digital filter to be tailored according to the actual test environment. It is also important to mention that all defects were detected when using conventional PD measurements.