Photon counting technique as a potential tool in micro‐defect detection of epoxy insulation pull rod in gas‐insulated switchgears

The micro‐defects in epoxy‐based insulation materials generate a local high electric field which results in continuous degradation, seriously endangering the insulation system of gas‐insulated switchgears. A highly sensitive detection technique is reported for micro‐defects of insulation pull rods based on the photon counting (PC) technique. The results demonstrated that for an epoxy‐based insulation pull rod, the photons released during electroluminescence and ionisation at 2 kV, which is less than the partial discharge inception voltage, can be clearly detected. The findings presented a strong correlation between photon counts and defect severity. Discourse has been conducted to elucidate the mechanism behind defect‐induced PC, employing the amplification of ionising luminescence through electric field distortion induced by micro defects and the augmentation of electroluminescence through the aggregation of trap charge. In this regard, the authors verified that PC can serve as a potential tool in the detection of micro‐insulation defects, which also has huge potential in online insulation condition monitoring.