Power distribution network fault line selection method based on optimal FIR (finite impulse response) filter and hierarchical clustering

Abstract

The invention discloses a power distribution network fault line selection method based on an optimal FIR (finite impulse response) filter and hierarchical clustering. The power distribution network fault line selection method includes design of the optimal FIR filter, a hierarchical clustering algorithm and a fault line selection method based on the optimal FIR filter and hierarchical clustering; single-phase earth fault line selection in a small current grounding system is achieved according to the hierarchical clustering algorithm by the designed optimal FIR filter. The power distribution network fault line selection method has the advantages that the FIR filter is used for signal processing, data sampling frequency only needs to reach above 6kHz and is lower than sampling frequency required by a wavelet analysis based fault line selection method, and system resource is saved; the clustering algorithm is adopted, fault feeder lines are determined according to pedigree clustering evaluation indexes, and reliability of line selection results is guaranteed; faulty lines can be detected effectively under various fault conditions by the power distribution network fault line selection method, so that the power distribution network fault line selection method has higher reliability than a wavelet algorithm.

Description

technical field [0001] The invention relates to the field of high-voltage distribution network robustness estimation, in particular to a distribution network fault line selection method based on optimal FIR filters and hierarchical clustering. Background technique [0002] my country's distribution network mostly adopts a small current grounding method, and one of them is a single-phase grounding fault. Since the neutral point is not directly grounded, the impedance value of the fault path formed by a single-phase ground fault is relatively large, and the fault symptoms caused by it are not obvious. Although the single-phase-to-ground fault line selection method has been studied extensively for a long time, there are still deficiencies in reliability and universality. [0003] Based on different characteristic quantities, at present, single-phase ground fault line selection methods can be divided into three categories: signal injection method, steady state line selectio...

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Problems solved by technology

Since the neutral point is not directly grounded, the impedance value of the fault path formed by a single-phase ground fault is relatively large, and the fault symptoms caused by it are not obvious. Although the single-phase-to-ground fault line selection method has undergone long-term and extensive research, there are still deficiencies in reliability and universality.

[0003] Based on different characteristic quantities, at present, single-phase ground fault line selection methods can be divided into three categories: signal injection method, steady state line selection method and transient line selection method, among which, signal injection method requires additional signal The installation and engineering are complex, and the steady-state line selection method has weak characteristic signals and unreliable line selection results.

However, the transient characteristics based on the transient quantity line selection method are several times or even dozens of times larger than the steady state value, and are not affected by the arc suppression coil, without adding additional equipment. However, in the transient quantity, except for the fault signal , but also mixed with multiple types of signals, direct use is easy to cause misjudgment, therefore, the effective extraction and full use of fault transient features have become an urgent problem to be solved

As a powerful tool for time-frequency localization and multi-resolution analysis, wavelet transform is widely used in the extraction of transient feature quantities of single-phase-to-ground faults in simulation experiments, which effectively improves the reliability of fault line selection, but there are still deficiencies : First, the characteristic frequency band is agreed on the basis of the principle of maximum energy. Under severe noise interference or unbalanced operation of the power grid, the generated characteristic frequency band may not be an effective fault transient characteristic frequency band, which will lead to misjudgment; in addition, the characteristic frequency band The frequency band is determined based on the analysis of the collected signals and cannot be known in advance. At the same time, a large number of layer-by-layer extraction and separation of the sampled data requires a huge amount of multiplication operations, which is not conducive to engineering implementation. In addition, faulty and non-faulty lines can be qualitatively distinguished according to signal polarity. Only relying on human judgment without quantitative scientific description will also lead to misjudgment

Therefore, at present, the practical degree of single-phase ground fault line selection method based on wavelet transform is not high

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