偏置电容法测量中压电网电容电流的误差分析

ANALYSIS ON MEASURING ERROR OF CAPACITANCE CURRENT IN MEDIUM-VOLTGAE POWER NETWORK BY BIASED CAPACITANCE METHOD

中压电网的系统电容电流是一个非常重要的参数,消弧线圈的安装、铁磁谐振的研究以及分析电压互感器高压侧保险熔断原因等都需要这个参数。文章介绍了中压电网电容电流间接测量方法(偏置电容法)的原理;详细分析了偏置电容法产生测量误差的原因,并给出了测量结果相对误差值与三相电压不平衡度以及偏置电容取值关系的定量表达式,同时指出了现场应用时为减小误差需注意的方面;误差分析表明,偏置电容法在三相电压不平衡度较小时可以满足测量精度的要求。

The system capacitance current in medium voltage (MV) power networks is a very important parameter, which is required in arc suppression coil installation, ferromagnetic resonance research and analysis of the reason causing fuse-blown in the high voltage (HV) side of PT. Here, the principle of indirect measurement of capacitance current in MV power network, i.e., biased capacitor method, is presented and the reason of measuring error caused by biased capacitor method is analyzed in detail. The quantitative expression for the relation between the relative error in measured result and both unbalance of three phase voltages and the value of biased capacitor given. At the same time, to reduce the measuring error, the items that should be paid attention to in on-site application of this method are pointed out. Error analysis result shows that biased capacitor method can meet the need of measurement accuracy while the unbalance of three phase voltages is relatively small.