Self-adaption route selection method for single-phase ground fault of power distribution network based on transient zero sequence current

Abstract

The invention relates to the relay protection field of a distribution network, in particular to a single-phase earth fault self-adapting selection method of a double-phase TA distribution network based on transient state zero sequence current frequency distribution. The invention is characterized in that: firstly zero sequence currents before and after failure are decomposed into wavelets and character frequency ranges of each line are reconstructed by single branches; then zero sequence current instantaneous values in reconstructed signals of each line are compared with corresponding instantaneous values of other lines through symbols; if the symbols of the zero sequence current instantaneous values are different from that of other lines, 1 is added to a counter; after all the sampling points are compared, a line with largest counter value is obtained; symbol comparison of respective reconstructed data is performed again to lines with the character frequency range of (4,0), and if points with uniform symbols account for over 60 percent and the values of the points are larger than counter values of other lines by five, then the line is estimated as a fault line; otherwise the line with largest counter value verified is estimated as a fault line. The invention can effectively utilize information included in the fault transient state process and greatly improve the reliability of fault selection.

Description

technical field [0001] The invention relates to the field of distribution network relay protection, in particular to an adaptive line selection method for distribution network single-phase grounding faults based on transient zero-sequence current frequency distribution. Background technique [0002] my country's 3-66kV distribution network adopts the non-direct grounding method of the neutral point. Because the current flowing through the grounding point is small when a grounding fault occurs, it is called a small current grounding system (NUGS). It includes the neutral point ungrounded system (NUS), the neutral point through the arc suppression coil grounding system (NES, also known as the resonant grounding system) and the neutral point through the resistance grounding system (NRS). [0003] After a single-phase ground fault occurs in a small-current grounding system and reaches a steady state, the non-fault line only flows through its own ground capacitance current, which...

AI Technical Summary

Problems solved by technology

Although this solves the problem of inaccurate wavelet frequency division, the frequency distribution of transient quantities of different lines is not always completely consistent because the frequency components and size of transient quantities are affected by various factors such as network parameters and fault times. Therefore, in some cases, it is very difficult to select a frequency segment where the transient quantities of each line are relatively concentrated for line selection

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