Fuzzy recognition method of magnetizing inrush currents in transformer differential protection

A technology of excitation inrush current and differential protection, which can be used in emergency protection circuit devices, instruments, measurement of electrical variables, etc., and can solve problems such as errors and inaccurate reliability.

Inactive Publication Date: 2014-01-29
JIANGSU UNIV OF SCI & TECH
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Problems solved by technology

[0005] The purpose of the present invention is to provide a fuzzy identification method for excitation inrush current in differential protection of transformers, so as to solve the problem that the existing general fuzzy theoretical method for transformer protection can only identify a single criterion, and when each criterion is used independently, there will be certain error, technical problem of inaccurate reliability

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  • Fuzzy recognition method of magnetizing inrush currents in transformer differential protection
  • Fuzzy recognition method of magnetizing inrush currents in transformer differential protection
  • Fuzzy recognition method of magnetizing inrush currents in transformer differential protection

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Embodiment Construction

[0043] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0044] First, some basic concepts and formulas that need to be used are given to facilitate understanding later.

[0045] The definition of fuzzy set: a fuzzy set A on the universe U means: for any element x∈U in the universe U, a number f in the closed interval [0,1] is specified A (x)∈[0,1] corresponds to it, f A (x) is called the degree of membership of x to A. That is, a mapping f is defined A :

[0046] f A : U→[0,1],

[0047] f A (x)

[0048] Definition of membership function: It is used to describe the characteristic function of fuzzy set and can take values ​​continuously in the closed interval [0,1]. The membership function uses f A (x) where A represents a fuzzy set and x is an element of A. The membership function satisfies: 0≤f A (x)≤1. f A The larger the value of (x), the more likely x belongs to A. if f A The value ...

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Abstract

The invention discloses a fuzzy recognition method of magnetizing inrush currents in transformer differential protection. By 2-additive fuzzy measurement based on the fuzzy theory, advantages of various inrush current criteria can be complemented; waveform dead angle criterion, waveform symmetry criterion and low voltage criterion are integrated into a criterion set; the influence of each criterion on magnetizing inrush current criteria can be adjusted through weighting coefficient; even if the certain one criterion is imperfect and errs, not the error of final results but fuzzy quantity membership function deviation occurs only; the problem that high-frequent occurrence of malfunctions due to singleness of criteria is solved, and transformer protecting performance is improved.

Description

technical field [0001] The invention relates to a fuzzy theory-based method for identifying excitation inrush current of differential protection of transformers, belonging to the technical field of relay protection for power system equipment. Background technique [0002] At present, transformer protection is realized by differential protection, but this method has certain defects. The reason is that when the transformer is closed with no load or the external fault is removed, the terminal voltage suddenly rises and the iron core is quickly saturated, and the excitation circuit will generate a peak value of up to The excitation inrush current of 6 to 8 times the rated current will become a source of differential protection unbalanced current, so auxiliary criteria are needed to help distinguish. [0003] Functionally speaking, transformer differential protection should have the following two functions: one is to distinguish the excitation inrush current and internal fault cu...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02H7/045G01R19/00
Inventor 曾庆军卢梦宁王彪
Owner JIANGSU UNIV OF SCI & TECH
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