220 kV玻璃绝缘子并联间隙雷电冲击放电路径研究

绝缘子并联间隙可以保护绝缘子不受电弧损伤，提高供电可靠性，但试点应用中发现并联间隙存在失效情况。为获取并联间隙结构参数对保护效果的影响，对220 kV玻璃绝缘子不同结构尺寸并联间隙开展了雷电冲击闪络特性试验，获取各间隙试品的雷电冲击50%放电电压与保护效果，并对电弧路径进行了分析，给出了并联间隙失效的可能解释。试验结果表明：Z/Z0值越小、Xc与Xp值越大，并联间隙保护效果越好，所选220 kV并联间隙Z/Z0小于0.875后保护效果趋于稳定。雷电冲击电压作用下，并联间隙两侧电极均会出现先导，先导发展过程受径向电场作用向绝缘子串弯曲，可能是U50电压下发生沿面闪络的主要原因。

Lightning Discharge Character of Shunt Gap Used for 220 kV Glass Insulator String

Shunt gap for insulators is beneficial for protecting insulators and improving power supply reliability. However, there exist failure examples during shunt gap application. Lightning discharge test of shunt gap with typical geometry parameters for 220 kV glass insulators is performed to investigate relationship between geometry size and protection effect. The U50 discharge voltage of the gap is found and the arc path is analyzed. Possible explanation of protection failure is proposed. Test results indicate that shunt gap protection effect could be improved with smaller value of Z/Z0 and with larger value of Xc and Xp. Protection effect stabilizes when the value of Z/Z0 is smaller than 0.875. Arc exists at both sides of the gap under the lightning voltage. The arc bends to the insulator by the radial electrical field, which might be the main reason of protection failure under U50.