A novel method of fault line selection by transient component for single-phase to ground fault in distribution networks

Key words:  distribution network  wavelet pocket  instantaneous zero sequence power  single-phase to ground fault

Abstract:

The methods of fault line selection by wavelet transform wore summarized for single-phase to ground fault in distribution networks. Then a novel method of fault line selection was presented based on minimum instantaneous zero sequence power. By analyzing the transient process of single-phase to ground fault in distributiai networks, the expressiai of zero sequence voltage and zero sequence current was given. And instantaneous zero sequence power was defined and taken as characteristic quantity of fault line selection. The instantaneous zero sequence vdtage and currmt is deocmposed into many frequent bands by wavelet packet. The character frequent band is obtained by corr^)aring the value and the regulaticsn of instantaneous zero sequence voltage and current in each frequent band. The zero sequence instantaneous power of each line is calculated within first period of character frequent band. The fault line selection is implemented by comparing the minimum instantaneous ziero sequence power of each line. If its minimum instantaneous zero sequence power is least among all lines, the line is fault line It is avdded to corrpare the polarity of each line between zero sequence voltage and zero current. The new criteriai is adaptive to any type of neutral node oonnectiai in distribution networks. Smulation indicates that this novel selection fault line method exactly selects fault line in any time of short circuit with high value arc-resistance and with different length line.