A distribution network line selection method based on time-frequency domain traveling wave information

Abstract

The invention discloses a distribution network line selection method based on time-frequency domain traveling wave information, the steps of which are: S1: installing a traveling wave sensor at the exit of each line busbar to extract current traveling wave signals at the exit of each line; S2 : Carry out Karen Bell transform on the current traveling wave signal of each line to obtain the zero-mode component of the current traveling wave; S3: use the S-transform to analyze the time-frequency domain component of the current traveling wave zero-mode component of each line, and obtain the corresponding time-frequency domain of each line Waveform and time-frequency domain matrix; S4: Perform pairwise correlation analysis on the time-frequency domain matrix of each line to obtain the correlation coefficient matrix R, and calculate the sum R of the correlation coefficients of each line i , wherein i=1, 2, ..., n represents the line number; S5: compare the sum R of the minimum correlation coefficient of each line min , if R min When it is negative, judge R min The corresponding line is the faulty line; if R min When it is a positive number, it is judged that the bus is faulty. A large number of simulation results show that the invention has the advantages of simple principle, easy realization and high reliability.

Description

technical field [0001] The invention mainly relates to the technical field of distribution network grounding, in particular to a distribution network line selection method based on time-frequency domain traveling wave information. Background technique [0002] my country's distribution network widely adopts neutral point non-effective grounding mode. This operation mode can effectively improve the reliability of power supply. Most of the faults in the distribution system are single-phase grounding faults, and the fault current amplitude is small during single-phase grounding faults. , the fault characteristics are not obvious, affected by interference and other factors, the accuracy and reliability of ground fault protection are poor, and it is very difficult to correctly select the fault line. [0003] In recent years, some experts and scholars have proposed the method of line selection, which provides valuable ideas for correct line selection. According to the frequency ba...

AI Technical Summary

Problems solved by technology

Among them, the main difficulty of the power frequency method is that the power frequency information of the fault is weak, and it is easily affected by factors such as the size of the transition resistance, the center point grounding method, and the overcompensation of the arc suppression coil. The reliability of the measured signal is not high, and the accuracy of line selection is generally biased. Low

The existing transient ground fault line selection methods have some research on the analysis of transient characteristics of faults, and some transient line selection methods have been proposed, such as zero-sequence current line selection method, transient energy method, and transient power method. The transient method is a model-based method, which has a great relationship with the structural parameters of the distribution network feeder, and has difficulties such as being sensitive to transition resistance and the "first capacitive" frequency band at the busbar is not fixed.

After a single-phase ground fault occurs in the small-current grounding system of the distribution network, a fault traveling wave that can be analyzed, measured, and with clear physical meaning is generated. Some literatures propose a line selection method based on two-phase and single-phase current traveling waves. Although the principle is simple to use The wave velocity of traveling wave line-mode component and zero-mode component is different, and the polarity discrimination is carried out within the time difference of arriving at the bus to distinguish the faulty line from the sound line, but there is a line selection dead zone at the exit of the bus, the effective time is short, and the sampling rate is too high , it is difficult to achieve on-site

Images