A Fault Line Selection Method of Distribution Network Based on Time-Frequency Eigenvector of Transient Zero-Sequence Current

Abstract

The invention relates to a power distribution network fault circuit selection method based on transient zero-sequence current time-frequency characteristic vectors, and belongs to the technical field of power system relay protection. When a power distribution network runs into a single-phase earth fault via an arc suppression coil grounding system, a transient zero-sequence current component detected by a measuring end is a nonlinear non-stationary signal formed by different frequency components. By taking the fault component as a study object, time-frequency characteristics of a fault transient current of the fault component are analyzed by utilizing the wavelet packet theory, time-frequency distribution regularities among all feeder lines under different fault conditions are described according to similarity of the time-frequency characteristics, and consequently line selection criteria based on transient zero-sequence current time-frequency characteristics can be obtained. The method is simple in principle, only utilizes short-time window zero-sequence current data of 5ms after the fault, can identify faulty feeders under the conditions of small fault angle and high resistance ground fault, has excellent timeliness and robustness, is free from influence of an arc fault or a resistance ground fault, requires a low sampling rate for hardware, and is highly practical.

Description

technical field [0001] The invention relates to the technical field of power system relay protection, which is based on the time-frequency feature vector of transient zero-sequence current, uses the wavelet packet theory to analyze the time-frequency feature of the time-frequency fault transient current, and uses the time-frequency feature similarity to describe different According to the time-frequency distribution law of each feeder under the fault condition, a new fault line selection method of distribution network based on the line selection criterion based on the time-frequency characteristics of transient zero-sequence current is obtained. Background technique [0002] When a single-phase ground fault occurs in a distribution network whose neutral point is grounded through an arc-suppression coil, the fault transient current amplitude is much larger than the steady-state current and is not affected by the arc-suppression coil. Compared with the steady-state component, ...

AI Technical Summary

Problems solved by technology

Distribution network faults are mostly single-phase ground faults, and the problem of line selection has been difficult to solve. The main reasons are: 1. The fault boundary is complex and random, such as the initial phase angle of the fault, the fault distance, and the size of the transition resistance

Different fault conditions, transient zero-sequence signal frequency components, attenuation characteristics, and spectrum energy distribution are quite different; 2. When a single-phase ground fault occurs near the voltage zero-crossing point, the high-frequency components caused are very small, and the high-frequency transient quantity is selected The sensitivity of the line method is greatly reduced; 3. The electrical characteristics of the cable line and the overhead line and the length of each line are quite different, and the similarity between the zero-sequence current waveforms of the sound line becomes worse; 4. When the traveling wave detection method is used, due to the traveling wave propagation The speed is fast, but the distribution network line is short, and the signal interference of the distribution network is more, so it is difficult to capture the first wave head of the traveling wave reliably

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