Off Line Partial Discharge as an essential Condition Based Monitoring (CBM) Tool for busbar insulation monitoring on Air Insulated Switchgear (AIS)

Abstract

This paper investigates the effectiveness of current test methods and procedures associated with insulation testing on the busbar of Air Insulated Switchgear (AIS) during scheduled planned maintenance. An improved test method proposes combining traditional AC voltage withstand test with Partial Discharge (PD) measurement. Three PD sensors were considered, namely Airborne Acoustic (AA), Transient Earth Voltage (TEV) and High Frequency Current Transformer (HFCT). The results confirm that HFCT is most sensitive and revealed significant difference at higher voltages between the six AIS samples. The TEV results produced consistent readings with smaller differences at higher voltages. The Ultra-sound instrument was found to be extremely sensitive but lack the capability to produce reliable measurement readings. Peak TEV measurements indicate a noticeable difference between older and newer samples