Faulty line selection in non-solid earthed network based on zero sequence frequency characteristic of transmission line

According to the frequency characteristic of an even transmission line, when the frequency is lower than fm, the input impedance of an unloaded even transmission line is capacitive, and the line maybe modeled as a capacitor. The healthy line is unloaded for zero-sequence component when a single-phase fault occurs in a non-solid earthed network. The zero-sequence angle -frequency characteristic of the lines are studied based on it and the characteristics of transient zero-sequence current in different frequency bands when a single-phase fault occurs in a non-solid earthed network are found. In SFB (Selected Frequency Band), the polarity of transient zero-sequence current in faulty line is opposite to that in healthy ones. The wavelet packet is used to decompose transient zero-sequence current and the coefficients represent the polarity of the current. Comparison of coefficient signs can find out the faulty line. The EMTDC simulations indicate that the method can find out the faulty line correctly and prove that the analysis of the angle-frequency characteristic of zero impedance of the line is correct.