Medium-voltage switchgear is the most widely used core equipment in power distribution systems. It operates in complex indoor and outdoor environments for a long time, and is prone to partial discharge defects caused by insulation aging, dampness, dust pollution and mechanical looseness. Switchgear partial discharge is the main cause of distribution network faults. Scientific and standardized PD testing is the key to ensuring the safe and stable operation of switchgear.
Typical PD Defects Found in Medium‑Voltage Switchgear
Common partial discharge defects of MV switchgears mainly include four categories: internal void discharge of insulation parts, surface creeping discharge caused by damp and dirt, floating potential discharge of loose metal parts, and corona discharge of sharp metal burrs. These defects develop slowly in the early stage and have no obvious failure phenomenon, but will rapidly deteriorate under overload and lightning surge conditions, leading to switchgear breakdown and tripping faults.
TEV and AA Ultrasonic Testing for Switchgear
TEV testing is the most efficient screening method for metal-clad switchgear. It can capture transient earth voltage pulses generated by internal discharge without opening the cabinet, realizing rapid non-intrusive screening of hidden defects. AA air-coupled ultrasonic testing is used for auxiliary detection of open discharge and surface defects of switchgears, which can remotely capture ultrasonic discharge signals outside the cabinet. The combination of TEV and ultrasonic dual detection covers all common switchgear PD defects.
Field Live‑line Testing Tips for Switchgear PD Inspection
First, carry out overall TEV scanning for all switchgear cabinets to quickly screen abnormal discharge points; second, use AA ultrasonic probe to perform directional detection on abnormal cabinets to judge discharge positions; finally, use AE contact sensor for close verification to confirm defect types. During the test, avoid strong electromagnetic interference sources nearby, conduct multiple sampling comparisons, and eliminate environmental noise interference to ensure test accuracy.
MOEORW‑Wi900PD comes with built‑in TEV and AA sensors for fast switchgear partial discharge inspection without extra accessories.
