电涌保护器中漏电流阻性分量的监测及提取方法

Monitoring and extraction of resistive components of leakage current in surge protectors

电涌保护器漏电流的阻性分量是表征其老化的重要参数,监测阻性分量的变化趋势并提取其基波和三次谐波的峰值,对电涌保护器的老化监测具有重要意义。从等效模型出发,推导出利用漏电流计算电涌保护器相关系数k的表达式,分析验证了k值与阻性分量特别是三次谐波的峰值负相关,可通过k值监测阻性电流的变化。进一步,针对容性电流补偿法提取阻性分量受谐波干扰、移相电流法不适用于阻性分量较小的情况等问题,提出一种改进方法。将漏电流进行过零检测、低通滤波和相位测量,确定基波频率和移相角度,利用各分量的相位关系求解容性电流并提取阻性分量。将该方法应用到仿真和实际数据中,对提取的阻性电流进行快速傅里叶变换(FFT)分析比对,结果表明,阻性电流基波和谐波的提取精度得到改善。

The resistive component of the leakage current in surge protectors is an important parameter to characterize its aging.Monitoring the trend of resistive components and extracting the fundamental and third harmonic peaks is of great significance for monitoring the aging of surge protectors. Starting from the equivalent model,the expression of the correlation coefficient k of the surge protector is calculated by using the leakage current. The analysis verifies that the k value is negatively correlated with the resistive component,especially the third harmonic,and that the change of the resistive current can be monitored by the k value. Furthermore,an improved method is proposed to solve the problems,for example,capacitive current compensation method to extract resistive components by harmonic interference,phase-shift current method is not applicable to the case of small resistive components. The improved method determines the fundamental frequency and phase shift angle by performing zero-crossing detection,low-pass filtering,and phase measurement on the leakage current. The phase relationship among the components is used to solve for capacitive currents and to extract resistive components. This method is applied to the simulation and actual data,and FFT analysis of the extracted resistive currents is performed. The results show that the extraction accuracy of the fundamental and harmonic wave of the resistive current is improved.