Current transformer tail current truncation method in failure protection

A technology of current transformers and trailing currents, applied in the direction of emergency protection circuit devices, electrical components, etc., can solve problems such as poor recognition ability of CT trailing currents, expansion of fault range, malfunction protection malfunctions, etc., to shorten the return time, Improve the sensitivity and avoid the effect of protection misoperation

Active Publication Date: 2017-02-22
CHINA ELECTRIC POWER RES INST +2
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  • Summary
  • Abstract
  • Description
  • Claims
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AI Technical Summary

Problems solved by technology

[0006] In the existing protection, 0.06A is usually used as the no-current setting value, and this single threshold criterion has a poor ability to identify CT tail current
When there is a CT tailing problem and the CT tailing current is not processed, the protection return time can reach 200ms, which is likely to cause malfunction protection and expand the fault range

Method used

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  • Current transformer tail current truncation method in failure protection
  • Current transformer tail current truncation method in failure protection
  • Current transformer tail current truncation method in failure protection

Examples

Experimental program
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Effect test

Embodiment 1

[0061] The invention of this example provides a method for cutting off the tail current of a current transformer in failure protection, which includes the following steps:

[0062] (1) Differential current: The sampling current at the protection installation is Calculate the differential current

[0063]

[0064] (2) Fourier transform: half-wave Fourier algorithm fundamental wave formula:

[0065]

[0066]

[0067] In the formula: N is the number of sampling points in a period of the fundamental signal; x k Is the kth sampling value of the differential current; a 1T / 2 Is the real part of the fundamental component after half-wave Fourier transform; b 1T / 2 Is the imaginary part of the fundamental component after half-wave Fourier transform.

[0068] The general formula of the full-wave Fourier algorithm:

[0069]

[0070]

[0071] Where: a nT Is the real part of the n-th harmonic (n=1 is the fundamental wave) component after full-wave Fourier transform; b nT It is the imaginary part of t...

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Abstract

The invention relates to a current transformer tail current truncation method in failure protection. The method comprises the following steps that differential current of a sampling value is calculated; Fourier transform is performed on the differential current so as to determine the fundamental wave and the harmonic wave of the differential current; differential amplitude restoration is performed on the fundamental wave and differential amplitude restoration is not performed on the harmonic wave; CT tail current and short circuit current are determined according to the fundamental wave, the harmonic wave and amplitude restoration; and the criterion for CT tail current truncation is constructed according to the CT tail current and the short circuit current, and the braking coefficient of the criterion is corrected. According to the technical scheme, misoperation of failure protection is enabled not to perform under the condition of the CT tail current.

Description

[0001] Technical field: [0002] The invention relates to the field of power system relay protection, and more particularly to a method for cutting off the tail current of a current transformer in failure protection. [0003] Background technique: [0004] Circuit breaker failure protection is a kind of backup protection widely used in power systems. It is mainly for the protection configuration when the main protection operates correctly, but the failure still exists due to the failure of the circuit breaker mechanism. According to the principle of circuit breaker failure protection, the delay of circuit breaker failure protection should be greater than the sum of circuit breaker action time and protection return time. [0005] When the system fails, the relay protection detects the failure and the action outlet trips. After the circuit breaker is opened, the CT current tailing phenomenon occurs in the current transformer (CT) due to the attenuated DC component. At this time, the CT ...

Claims

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Application Information

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IPC IPC(8): H02H7/22
Inventor 柳焕章郭雅蓉王兴国周泽昕谢俊
Owner CHINA ELECTRIC POWER RES INST
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