基于馈线零序阻抗特性的谐振接地故障选线方法

谐振接地配电网发生单相接地故障后,健全线路的零序阻抗在最小串联谐振频率以下的各频段呈电容特性;故障线路的零序阻抗在高频段呈电容特性,在低频段呈电感特性。依据这一现象,提出一种基于馈线零序阻抗特性的故障选线方法。通过低通和带通数字滤波器提取母线零序电压和各馈线零序电流的高频分量和低频分量,并分别对母线零序电压的高频分量和低频分量求导。由于容性线路的电压导数与电流的比值为定值,故母线零序电压导数与健全线路零序电流的比值在高频段与低频段相等,其实际差值近似为0;母线零序电压导数与故障线路零序电流的比值在高频段与低频段不等,其差值较大,据此构成故障选线判据。理论分析和仿真结果表明,该方法选线准确、可靠且适应性强。

A Method of Fault Line Selection in Resonant Earthed System Based on Zero Sequence Impedance Characteristic of Lines

AbstractAfter the single phase ground fault occurred in the resonant ground distribution network, the zero sequence impedance of the sound line shows capacitance characteristic under the circumstance that the frequency is below the minimum series resonant frequency. However, the zero sequence impedance of the faulty line presents capacitance characteristic in the high frequency and inductance characteristic in the low frequency. In terms of the phenomena above, a faulty line selection method based on zero sequence impedance characteristics of lines is proposed. The high and low frequency components of the bus zero sequence voltage and each feeder zero sequence current are extracted through low-pass and band-pass digital filters. And then the high and low frequency components of the bus zero sequence voltage are derived separately. Since the ratio between the voltage derivative and the current in the capacitive circuit is constant, the ratios between the bus zero sequence voltage derivative and the zero current of the sound line are same both in the high and the low frequencies theoretically. The actual difference of these two ratios is almost zero. Whereas, the ratios between the bus zero sequence voltage derivative and the zero current of the faulty line are different both in the high and the low frequencies, and the difference is greater. Therefore, a faulty line selection criterion is proposed. The method is proved to be accurate, reliable and adaptable through the theory and simulations.