Method for distinguishing transformer magnetizing rush current based on weight mathematical morphology

Abstract

The invention discloses a method for distinguishing a transformer magnetizing rush current based on weight mathematical morphology. The method comprises the following steps: (1) collecting a difference current signal of current transformers on two sides of a transformer differential protection according to a certain sample frequency, (2) judging whether a break variable among a plurality of continuous sampling values is larger a preset break variable limit value, if yes, collecting data of a half circle in a delayed mode and carrying out a step (3), or, continuing sampling, (3) selecting a data widow as a difference current signal value with the length of a half fundamental frequency, carrying out processing on the weight mathematical morphology and obtaining a processed signal waveform, and (4) obtaining a wave-shaped correlation coefficient, judging whether the wave-shaped correlation coefficient is smaller than a preset setting value of the wave-shaped correlation coefficient, if yes, judging that the interior of a transformer breaks, or, distinguishing the transformer magnetizing rush current. The method has the advantages of being simple in steps, small in calculated quantity, short in delayed time, easy to implement, strong in generality and the like.

Description

technical field [0001] The invention relates to the technical field of transformer relay protection, in particular to a transformer excitation inrush current identification method based on weight mathematical morphology. Background technique [0002] Transformer is an important electrical equipment for power transmission and voltage conversion, and its operating status directly affects the safety and stability of power supply. At the same time, the cost of the transformer is high. Once it is damaged due to a fault, it will be difficult to repair and take a long time, which will cause serious economic losses. Therefore, it is of great engineering and theoretical value to study new transformer protection schemes with reliable performance and advanced technology. [0003] Differential protection is used as the main protection of transformers because of its high sensitivity and good selectivity. However, the differential protection of transformers has always been troubled by t...

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Problems solved by technology

But this method is not reliable in some cases, such as when the fault occurs not at the 0 degree closing angle, the first half wave of the current will not be reliably identified

[0009] The Chinese invention patent with the notification number CN101567552A discloses a power transformer excitation inrush current and internal fault identification method using morphological structure. The consistency between the original signal and the waveform of the morphological analysis results is essentially to reflect the similarity between the original waveform signal and the sine wave. By comparing the waveform consistency coefficient, the identification of the excitation inrush current and the internal fault current of the power transformer is realized; although this method overcomes the However, its sampling data window is as long as 25ms, which causes a long time delay and cannot meet the requirements of fast action of high voltage transformers, and the long action time also aggravates the damage of internal fault current to the transformer

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