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

Abstract

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.

Photon Count Technique as a Potential Tool for Insulation Micro-Defect Detection: Principles and Primary Results

“…EL is an important indicator of the health of insulating materials used in high-voltage applications, but photon release from air ionization and PD can interfere with its accurate measurement. A previous study demonstrated a sharp increase in photon counting results under PD, highlighting its potential impact on EL measurements [16] . To circumvent this issue, this study investigates the photon response characteristics of defect-free specimens under AC 3 kV and different pressures (0.1 to 0.3 MPa) in air, N 2 , and SF 6 gases.…”

“…The surplus energy within systems can be dissipated through degradation pathways, thereby paving the way for chemical degradation processes [15] . Thus, the EL phenomenon activation preceding the initial occurrence of PD is considered a significant hallmark of the onset of insulation degradation [16] . In the previous work [17] , the insulation pull rods used in GIS with surface scratches were utilized to verify the sensitivity and feasibility of the photon counting (PC) technique for mico-defect detection.…”

Simulation and Characterization of Micro-Discharge Phenomena Induced by Glitch Micro-Defects on an Insulated Pull Rod Surface

“…The insulated pull rod is a crucial insulating component in gas-insulated, metaleclosed switchgears (GISs) characterized by its slender, elongated structure and frequent involvement in disconnection scenarios [1][2][3][4][5]. In operational conditions, it is subjected to significant mechanical stress and impact vibrations, necessitating superior electrical insulation and mechanical strength [2,[6][7][8][9]. The resin-impregnated fiberglass (RIF) process is instrumental in achieving these properties [1,[10][11][12].…”

“…The resin-impregnated fiberglass (RIF) process is instrumental in achieving these properties [1,[10][11][12]. However, inadequacies in the design of the process or its parameters can lead to micro-defects, such as white spots, burrs, and poor surface infiltration, compromising the rod's integrity [2,13,14]. The presence of these micro-defects can distort the electric field, initiating micro-discharges and potentially leading to breakdown incidents.…”

“…The presence of these micro-defects can distort the electric field, initiating micro-discharges and potentially leading to breakdown incidents. While various methods, including X-ray, non-destructive microwave, and ultrasonic tests, have been proposed for defect detection in insulation rods, comprehensive studies on the micro-discharge phenomena induced by these defects remain scarce [2,13,14].…”