Research of Fault Line Selection Method of Distribution Network Based on Transient Zero-sequence Energy

For problem of ineffectiveness of traditional line selection methods by use of single feature value caused by complex and random fault borderline, small steady component of fault and reverse phase of instantaneous zero-sequence power when single-phase grounding fault happens in power system connected to earth through an arc suppression coil, the paper proposed a new method of line selection based on transient zero-sequence energy. The method filters nonsymmetrical component and steady component of transient zero-sequence current through a digital filter and gets zero-sequence current of each line and pure transient fault component of zero-sequence voltage of bus in order to get transient zero-sequence energy. Then the method judges fault type and line according to the value and direction of transient zero-sequence energy. When single-phase grounding fault happens, the direction of transient zero-sequence energy of non-fault line is positive, the direction of transient zero-sequence energy of fault line is negative, and absolute value of transient zero-sequence energy of fault line is the sum of the ones of other lines. When the bus grounding fault happens, the value of transient zero-sequence energy of the bus is the sum of the ones of other lines. Meanwhile, in order to solve the problem of low sensitivity of line selection caused by influence of noise on transient zero-sequence energy of the bus, the paper proposed a scheme of usting auto-reclosing technique in the line selection method. The Matlab simulation result showed that the line selection method has high accuracy and reliability.