A New Method of Fault Transient Components Leakage Line Selection Based on Wavelet Transform

摘要

For 6～10kV high-voltage distribution networks in China coal mine, the zero sequence power direction leakage protection can be only used in neutral point ungrounded system, whose selectivity and sensitivity are greatly affected by the distribution networks running conditions. The fifth harmonic direction leakage protection can be used in neutral point ungrounded system and neutral point resonant grounded system, which only approximately responds single-phase grounding leakage fault, and the reliable leakage resistance detecting value only ranges from 0Ω to 200Ω. But it has poor anti-interference and low sensitivity. A new method of leakage protection is put forward. When zero sequence voltage and zero sequence voltage transient components go beyond the fixed value leakage protection is started. Wavelet transform is used to decompose zero sequence voltage transient components and detect the leakage signal singularity to locate the leakage time, and line selection is carried out via line selection criterion composed of wavelet packet coefficients. Leakage fault simulation and equivalent low-voltage model experiment indicate that the new method of leakage protection possesses exact line selection and high sensitivity (the reliable resistance detecting value ranges from 0Ω to 10kΩ); besides neutral point grounded modes have no effect on this method.