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Recognition method of magnetizing inrush current and internal short circuit of power transformer by utilizing morphological structure

A power transformer and excitation inrush technology, which is applied in the direction of emergency protection circuit devices, electrical components, etc., can solve the problems of transformer differential protection malfunction, inability to identify transformer internal fault excitation inrush current, delayed action, etc.

Active Publication Date: 2009-10-28
KUNMING UNIV OF SCI & TECH
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Problems solved by technology

At present, the main protection of the transformer mostly adopts the differential protection based on the second harmonic braking principle. Due to the defects of the second harmonic braking principle, it may not be possible to identify the internal fault of the transformer and the excitation inrush current in some cases, resulting in the transformer Differential protection misoperation or delayed operation, so it is necessary to study a new identification method of excitation inrush current

Method used

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  • Recognition method of magnetizing inrush current and internal short circuit of power transformer by utilizing morphological structure
  • Recognition method of magnetizing inrush current and internal short circuit of power transformer by utilizing morphological structure
  • Recognition method of magnetizing inrush current and internal short circuit of power transformer by utilizing morphological structure

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Embodiment

[0103] by Figure 12 Take the inrush current waveform as an example when the transformer is switched on with no load, and identify it according to the following steps.

[0104] 1. The length of the data window is 5ms before and 20ms after the start of the transformer differential protection. According to the formula (5) respectively for the transformer A phase difference flow i A , B phase difference flow i B and C difference flow i C , that is, the amplitude of the three-phase differential current is calculated for its sine half-wave structural elements, and the results are 10.30, 9.08, and 13.09 respectively;

[0105] 2. Take ρ=0.9, sampling frequency f s is 5kHz, according to the formula (6) to find the length of the structural elements, N = 45;

[0106] 3. Taking the transformer A-phase differential current as an example, construct the three-phase differential current structural element s(n) according to the formula (6), and the A-phase structural element is as follow...

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Abstract

The invention relates to a recognition method of magnetizing inrush current and internal short circuit of a power transformer by utilizing a morphological structure. The method comprises the following steps of: constructing a sine half-sinusoid discrete series with the amplitude of A and the frequency of 50Hz by utilizing the maximum value and the minimum value of sample data of a power frequency cycle, and reducing the series by 10 percent so as to be used as a structural element; carrying out morphological analysis to three-phase differential currents respectively by utilizing a sine half-sinusoid structural element; obtaining a waveform consistency coefficient of an original signal and a morphological analysis result so as to reflect the similarity degree of the comparison between the original signal and a sine wave; and realizing the recognition of the magnetizing inrush current and the internal short circuit of the power transformer by comparing the size of the waveform consistency coefficient. By theoretical analysis and stimulation verification, the method is proved to be effective.

Description

technical field [0001] The invention relates to the technical field of power system relay protection, in particular to a method for identifying inrush current and internal short circuit of a power transformer using a morphological structure. Background technique [0002] Power transformers are the main electrical equipment in power plants and substations, and their safe operation is directly related to whether the power system can work continuously and stably. Due to the high cost of the transformer itself, once it is damaged due to a fault, its maintenance is difficult, the maintenance time is long, and the economic loss is also quite heavy. Therefore, seeking a safe, reliable and sensitive transformer protection scheme has always been a hot topic of research by domestic and foreign power system scholars. For a long time, differential protection has been the main protection in transformer power protection. The key issue of transformer differential protection is how to ide...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02H7/045
Inventor 束洪春朱子钊彭仕欣张广斌朱盛强陈豪何兆林刘凤龙高晖宋庆林夏琦杨栋张晓辉
Owner KUNMING UNIV OF SCI & TECH
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