A phase selection method for single-phase ground fault in distribution network

Abstract

The invention provides a single-phase earth fault phase selection method for a power distribution network. The method comprises the following steps: sampling three-phase currents on the low-voltage side of a bus transformer before and after a fault occurrence moment after the single-phase earth fault occurence; subtracting the current sampling data before the fault moment from current sampling data after the fault moment of each phase to obtain current fault break variable data of each phase; normalizing the measured current break variable of each phase, and calculating an inter-phase currentbreak variable similarity coefficient by using a Hausdorff algorithm; calculating the phase average similarity; calculating a phase fault evaluation index that is specifically the sum of absolute values of difference values of the average similarity of the phase and the average similarity of the other two phases; and finally, determining a fault phase judgment threshold. The feeder with the faultevaluation index higher than the fault phase judgment threshold is a fault phase. According to the method, the rapidity and accuracy of single-phase earth fault phase selection of the power distribution network are improved.

Description

technical field [0001] The invention belongs to the technical field of distribution networks, and in particular relates to a phase selection method for single-phase grounding faults in a distribution network. Background technique [0002] Existing single-phase-to-ground fault phase selection methods in distribution network can be roughly divided into two categories according to their utilization information: one is the phase selection method based on the fault voltage steady-state quantity; the other is the phase selection method based on the fault current transient quantity . The phase selection method based on the fault voltage steady-state quantity has the following two problems: First, if there is a grounding arc, the system voltage information will always be doped with more transient voltage components, and the accuracy of the method will be greatly affected at this time. Second, even if the grounding resistance remains constant and no arc occurs, it still takes some t...

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Problems solved by technology

The phase selection method based on the fault voltage steady-state quantity has the following two problems: First, if there is a grounding arc, the system voltage information will always be doped with more transient voltage components, and the accuracy of the method will be greatly affected at this time. Second, even if the grounding resistance remains constant and no arc occurs, it still takes some time for the system to transition to a steady state after the ground fault, so there is usually a large gap between the fault occurrence and the accurate selection of the fault phase in this method. Time difference

Phase selection methods based on fault current transients include fault phase selection methods based on wavelet transform, etc. Although these methods can select the fault phase in one cycle after the fault occurs, the amount of calculation is too large, and there are "missing judgments" and " The risk of misjudgment is difficult to be directly applied in actual engineering

[0003] Since there is a certain difference in the current mutation of the fault phase and the non-fault phase of the distribution network in the case of a single-phase ground fault, the difference can be reflected in the difference or dissimilarity of the waveform, and it is possible to use the image similarity algorithm to identify the fault phase

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