Global-and-local-feature-combined current transformer saturation detection method

Abstract

The invention discloses a global-and-local-feature-combined current transformer saturation detection method, which comprises the following steps: if meeting emergency variable startup judging criteria, entering the saturation detection step immediately; calculating harmonic ratio alpha of secondary current waveform within a period starting from an extreme point; calculating integral areas of equal four sections of waveforms of secondary current of a current transformer within the period starting from the extreme point after fault starts and calculating the ratio Sc of the maximum area and the minimum area; comparing the obtained ratio Sc and the harmonic ratio alpha with corresponding preset threshold values respectively, and when both the ratio Sc and the harmonic ratio alpha are larger than the preset threshold values, judging that the current transformer enters a saturation state; and when detecting saturation, carrying out comprehensive analysis on the calculating results of the waveform area ratio and the harmonic ratio immediately to obtain exact saturation degree. The method retains the sensitivity of harmonic ratio to mild saturation, and meanwhile, can also use the ratio of sectional integrals to better reflect the degree of saturation; and through combination of the two modes, the method is allowed to be high in sensitivity and improves identification efficiency.

Description

technical field [0001] The invention relates to the technical field of electric power automation, in particular to a current transformer saturation detection method combining global and local features. Background technique [0002] The current transformer, as the hub connecting the primary side and the secondary side, is an important component for the relay protection and monitoring system to perceive the operating status of the system. At present, most of the current transformers configured in the power system are ferromagnetic transformers based on electromagnetic induction. Due to the nonlinear excitation characteristics of the iron core, the current transformer will be saturated when a large current flows, which will cause defects and distortions in the secondary side current, resulting in the failure of the primary current to change normally. misjudgment. In actual engineering, this situation happens from time to time, for example, due to the saturation of the current...

AI Technical Summary

Problems solved by technology

[0003] Existing current transformer saturation detection methods often fail to meet the needs in engineering applications due to difficulties in obtaining data sources, low sensitivity, and poor anti-interference ability.

In particular, the single-principle detection method is difficult to take into account the various complex situations of current transformer saturation, which affects the accuracy and reliability of saturation identification

At the same time, the conventional detection method is only a single real-time identification of saturation, so as to block or open various protections in time; it is often impossible to accurately analyze the degree of saturation

This makes it impossible for us to further reveal the law of protection maloperation affected by the degree of saturation of the current transformer and the law of the relationship between the health status of the current transformer and the probability of saturation, and misses the need to make full use of the saturation information of the current transformer for relay protection analysis and equipment status evaluation, which is not conducive to timely early warning of potential safety hazards in the future

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