Fault feature extraction method of weak transient zero-sequence current on background of strong noise

Abstract

The invention relates to a fault feature extraction method of weak transient zero-sequence current on the background of strong noise. The method comprises the following steps: firstly, transient frequency compression ratio CR is determined, compressive sampling frequency fsc is determined based on the CR, and compression numerical value is determined according to the fsc so as to calculate step length hsc, wherein numerical range of the CR is 1000-2000; secondly, transient zero-sequence current izy(t) under the background of strong noise is input into a bistable system, numerical calculation of the bistable system is carried out by a fourth-order Runge-Kutta method, and an output signal is is(t); thirdly, an initial period of the is(t) is extracted as a characteristic signal ic(t); and finally, a cross correlation coefficient pcz between the characteristic signal ic(t) and an initial period izo(t) of noise-free transient zero-sequence current is calculated, and fault feature extraction of the transient zero-sequence current is finished if the pcz is greater than or equal to 0.7; and if the pcz is less than 0.7, the CR is adjusted until the pcz is greater than or equal to 0.7, so as to finish fault feature extraction of the transient zero-sequence current.

Description

technical field [0001] The invention relates to a method for extracting weak transient zero-sequence current fault features under strong noise background, and belongs to the field of fault line selection of power system distribution network. Background technique [0002] The fault line selection of the distribution network has the following difficulties and problems: 1) The fault characteristics of the signal are not obvious: after a single-phase ground fault, the steady-state current is generally less than 30A or even only a few A. In addition, the complex structure of the distribution network sometimes leads to fault characteristics Not obvious, although the fault transient zero-sequence current signal is larger than the steady-state zero-sequence current signal, but the duration is short, and sometimes it is difficult to detect; It will also change frequently, and the harmonic current and distributed capacitance current of its line will also change accordingly. In additi...

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Problems solved by technology

[0002] The fault line selection of the distribution network has the following difficulties and problems: 1) The fault characteristics of the signal are not obvious: after a single-phase ground fault, the steady-state current is generally less than 30A or even only a few A. In addition, the complex structure of the distribution network sometimes leads to fault characteristics Not obvious, although the fault transient zero-sequence current signal is larger than the steady-state zero-sequence current signal, but the duration is short, and sometimes it is difficult to detect; It will also change frequently, and the harmonic current and distributed capacitive current of its line will also change accordingly.

In addition, factors such as the intensity of external noise, the influence of load, the fluctuation of bus voltage and the uncertainty of grounding resistance at the fault point will all affect the change of fault zero sequence current.

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