谐波导致复合绝缘子不明闪络机理研究

Unexplained Flashover of Composite Insulator Caused by Harmonic Wave

复合绝缘子耐污闪性能优异而广泛应用于电力系统中,但其不明原因闪络问题却日益严重。研究谐波与不明闪络之间的关联尤为重要。通过分析绝缘子串的等值电路,确定流过绝缘子串的电流大小与电压幅值和频率有关;针对处于谐波环境下的复合绝缘子不明闪络案例展开研究,计算发现10次谐波频率为线路的串联谐振频率,故障时刻电流频谱图也显示各谐波分量中10次谐波电流幅值最大;对故障电流进行测量,发现流过绝缘子的电流值已经超过危险区进入闪络范围;仿真验证了绝缘子串端部确实产生了谐振过电压,且由此计算得到绝缘子上的电流与测量结果一致。结果表明,谐波电流引发高频谐振过电压,导致流过绝缘子串的电流剧增,是复合绝缘子不明闪络的原因之一。

Composite insulators are widely used in power system due to their excellent pollution flashover resistance,but their unexplained flashover problem is becoming more and more serious.It is especially important to study the relationship between harmonics and unknown flashover.By analyzing the equivalent circuit of the insulator string,it is determined that the current flowing through the insulator string is related to voltage amplitude and frequency.Based on the unknown flashover case of composite insulator in harmonic environment,it is found that the 10 th harmonic frequency is the series resonance frequency of the line.The current spectrum diagram at the time of failure also shows that the 10 th harmonic current has the largest amplitude among all harmonic components.By measuring the fault current,it is found that the current value through the insulator has exceeded the danger zone and entered the flashover range.The simulation verifies that the resonant overvoltage is generated at the end of the insulator string,and the calculated current on the insulator is consistent with the measured result.The results show that the harmonic current causes the high frequency resonant overvoltage,which leads to the surge of the current flowing through the insulator string,and is one of the reasons for the unknown flashover of the composite insulator.