采样电阻值对泄漏电流中脉冲分量采集结果的影响及机理初步分析

Influence of Sampling Resistance on Acquired Impulse Component of Insulator Leakage Current and Its Preliminary Mechanism Analysis

为研究采样电阻值对绝缘子泄漏电流采集结果的影响,采集了9 kV和25 kV工频电压下,单片干燥洁净及表面有分离水珠的瓷绝缘子的泄漏电流,并使用大容量工频试验变压器以及人工气候室开展了绝缘子人工污秽试验。试验中分别使用了5个不同阻值的无感电阻采集泄漏电流信号。提取并统计了脉冲幅值的最大值及幅值大于1/2最大脉冲幅值的脉冲均值。结果表明:采样电阻值对泄漏电流中的脉冲分量有显著影响;绝缘子在干燥洁净状态下施加电压25 kV时,采样电阻取1?与10 k?时测得的泄漏电流中脉冲幅值比大致为200;绝缘子污湿状态下施加工频额定9 kV电压,采样电阻取1?和100?时,脉冲幅值比亦可达到10左右。通过最小二乘法拟合发现随着串入阻值的增加脉冲信号幅值呈幂函数规律下降,必须考虑采样电阻值的影响,而基于该规律有望校正泄漏电流采集结果。初步分析认为采样电阻阻值对泄漏电流中脉冲分量采集结果产生影响的原因是电阻值会影响放电时的暂态过程。

To study the influences of sampling resistances on measurement of insulators＇ leakage current, the leakage current waveforms of a dry clean porcelain insulator and water drops attached porcelain insulator under 9 kV and 25 kV power frequency voltages acquired. The experiments of the insulator under contaminated and humid condition were conducted in the artificial climate chamber with the high-capacity power frequency test transformer. Five non-inductive resistors with different resistances were used in the experiments to obtain the leakage current. We extracted the impulse components from the acquired leakage current signal, and obtained the maximum impulse amplitude and the mean am- plitude of the impulses which possess amplitudes more than half of the maximum. The results indicate that the sampling resistance obviously affects the impulse components of the obtained leakage currents. When a dry and clean insulator is applied with voltage of 25 kV, the amplitude of impulse component of the leakage current acquired using a 1 f~ sampling resistor is about 200 times as much as that acquired using a 10 k~ sampling resistor. When a humid contaminated insula- tor is applied with the rated power-frequency voltage of 9 kV, the amplitude of impulse component of the acquired leakage current acquired using the 1 fl sampling resistor is about 10 times as much as that acquired using a 100 ~ sam- pling resistor. Through a least-square fitting.analysis, it is concluded that the impulse amplitude decreases with increasing resistance in a manner of power function. Hence, sampling resistance should be taken into consideration in the measure- ment of leakage current, and the measurement can be corrected based on the correlation between the impulse amplitude and resistance. From a preliminary analysis, we believe that the influence of sampling resistance on the impulse compo- nents comes from the influence on the discharge transient process.