500kV SF_(6)瓷质套管多工况仿真与故障分析

Simulation and Failure Analysis of 500kV SF_(6) Porcelain Bushing under Complicated Working Conditions

SF_(6)填充式瓷质高压套管的炸裂事故对电力系统的稳定运行十分不利,同时也给相关工作人员的人身安全造成了极大威胁。近年来,我国北方发生了多起SF_(6)瓷质套管炸裂事件,但事故原因尚未明确。因此,该类套管在多种工况下的运行特性还需要更加深入的分析。针对这一问题,该文对500kV电压等级的SF_(6)填充式瓷质高压套管在电场、电热耦合场中的运行特性进行仿真,考虑了积污、雨雪环境等外绝缘因素,以及套管内温度分布、低温下套管内壁SF_(6)气体液化等因素对于套管内部气体主绝缘特性的影响。仿真计算结果表明,雨雪、积污等外绝缘因素以及温度分布对于套管内电场分布的影响较小,因此基本不会成为套管炸裂事故的诱因;但在低温环境下,SF_(6)气体在套管内壁上的液化现象会引起液膜端部电场激增,甚至可能导致局部电场高于SF_(6)气体的击穿场强,从而致使绝缘失效、气体放电等情况发生,最终引发瓷质套管炸裂事故。

Explosive failure of high voltage porcelain bushings with SF_(6) gas is a great threaten to the safe operation of the power system as well as to the security of the neighboring staff and apparatus.Recently,this kind of failure has been reported to occur several times but the reason has not been thoroughly worked out.Thus the operation of the bushing considering various possible occasions under different working conditions requires further investigation.In this paper,the simulation of electric and thermal distribution for the 500kV porcelain bushing with SF_(6) has been done.During the simulation process,the influence of many factors on the gas insulation characteristics inside the bushing is considered,which includes the interior temperature distribution,low temperature liquefaction of SF_(6)gas and external insulation factors such as pollution,rain and snow.The simulation result shows that the temperature distribution as well as external insulation factors such as the pollution and the environment has minor effect on the internal electric field in the bushing.But the liquidation of the SF_(6)on the inner wall of the bushing greatly enhances the maximum field strength and may result in insulation failure under specific working condition.