Fault Line Selection And Fault Section Location For Single-phase Earth In Distribution Network

With the development of society, the growing power consumption, power qualityalso put forward higher requirements. The distribution network is a high incidence offailure of the power system, mainly single phase to ground fault. Timely and effective todetect fault lines and fault section, troubleshooting to restore power, has greatsignificance for the maintenance of network security, improving reliability of powersupply. Distribution network in China is mainly small current grounding fault. The faultfeature is not obvious in single-phase ground fault and arc suppression coil changes thezero-sequence current distribution. The impact of unstable arc and the difficult of lagredata transmission increase the difficulty of the fault line selection and positioning.This article first analyzes the steady-state current-voltage characteristics of smallcurrent grounding fault, a ground capacitance measurement method is proposed whichis usful for neutral point ungrounded system and resonant grounded system. A methodto calculate the transition resistance based on the capacitance measurement methodfurther. The transition resistance tends to infinity for the fault line, and tends to the realvalue for the non-fault line in theory. Secondly, a method to calculate the equivalentcapacitance through least square method based on the zero-squence network bandfeatures of the transient. The capacitance is positive for non-fault lines, and is negativefor the fault line, whose die is the maximum. The difference between the fault line andnon-fault lines is enlarged by subtraction and addition. Again, the zeros current sectioncharacteristics for small current grounding is researched according to the distributionfeeder automation. The transient zero sequence current are different on both sides of thefault point, have different energy distribution at different frequencies. Wavelet packetenergy relative entropy is defined, and its effectiveness to recognition the difference ofdiffent signals is analysised. A new fault section location method is proposed basded onthe wavelet packet energy relative entropy, and the entropy is the largest of fault section.Another method to dectect the fault section is proposed based on wavelet transformmodulus maxima in consideration the ability to recognize the singular point. On bothends of the fault section the modulus maximas are opposite polarity, and of the healthysection arê the same polarity.Most of the small current grounding faults are arc faults. An arc model is buildedbased on energy banlance theory. These methods are effective proved by large number of simulation for metal grounding, across transition resistance grounding, arc groundingat different location and time.