With the increase in the voltage and capacitance of gas-insulated transmission lines (GILs), the insulation failure of GIL has attracted more and more attention. Further understanding of the partial discharge (PD) and flashover characteristics of metal particles on the insulator surface, as well as the flashover mechanism, is necessary to reduce the failure rate and improve the reliability of the equipment. In this study, an ultra-high voltage (UHV) AC insulator PD test and measurement system based on the cross-reference pulse current (PC) and ultra-high frequency (UHF) methods were established. The PD development and flashover characteristics of 5 mm-long metal particles at different positions on the surface of a UHV AC insulator, as well as the surface charge accumulation, were studied. The results show that the discharge of millimetre-scale metal particles on the insulator surface under PD test conditions is relatively low (generally lower than 2PC), and it is difficult to be detected by the conventional PC and UHF methods due to their insufficient sensitivity. Moreover, it is found that the weak PDs of the millimetre-scale metal particles will result in a charge accumulation on the insulator surface under AC voltage, which eventually will lead to the insulator flashover. The PDs of the UHV AC insulator before flashover are generally small, which will make it difficult for online monitoring systems to give an effective alarm before flashover.

中文翻译：

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交流电压下1100kV GIL绝缘子后表面金属颗粒引起的表面电荷积累和预闪络特性

随着气体绝缘传输线（GIL）的电压和电容的增加，GIL的绝缘故障引起了越来越多的关注。需要进一步了解绝缘子表面上的金属颗粒的局部放电（PD）和闪络特性，以及闪络机理，以降低故障率并提高设备的可靠性。本研究建立了基于交叉参考脉冲电流（PC）和超高频（UHF）方法的超高压交流绝缘子局部放电测试测量系统。研究了特高压交流绝缘子表面不同位置的5 mm长金属颗粒的PD展开和闪络特性，以及表面电荷的积累。结果表明，在PD测试条件下，毫米级金属颗粒在绝缘子表面的放电相对较低（通常低于2PC），并且由于其灵敏度不足而难以通过常规PC和UHF方法进行检测。而且，发现毫米级金属颗粒的弱PD将导致在交流电压下绝缘子表面上的电荷积聚，最终将导致绝缘子闪络。特高压交流绝缘子的闪络前的局部放电通常很小，这将使在线监控系统难以在闪络前发出有效的警报。并且由于其灵敏度不足，难以通过常规的PC和UHF方法进行检测。而且，发现毫米级金属颗粒的弱PD将导致在交流电压下绝缘子表面上的电荷积聚，最终将导致绝缘子闪络。特高压交流绝缘子的闪络前的局部放电通常很小，这将使在线监控系统难以在闪络前发出有效的警报。并且由于其灵敏度不足，难以通过常规的PC和UHF方法进行检测。而且，发现毫米级金属颗粒的弱PD将导致在交流电压下绝缘子表面上的电荷累积，最终将导致绝缘子闪络。特高压交流绝缘子的闪络前的局部放电通常很小，这将使在线监控系统难以在闪络前发出有效的警报。