Method for detecting voltage zero cross near fault in travelling wave protection

A voltage zero-crossing, traveling wave protection technology, applied in emergency protection circuit devices, fault locations, measuring electricity and other directions, can solve the problems of difficult detection of weak traveling wave signals, protection refusal or misoperation, etc., to achieve reliable and detection methods. handy effect

Inactive Publication Date: 2008-09-03
KUNMING UNIV OF SCI & TECH
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Problems solved by technology

When the fault occurs near the voltage zero-crossing point, the traveling wave generated by the fault will be very small. Although some traveling wave protection claims to be effective when the voltage is zero-crossing fault, the traveling wave signal is very weak at this time and superimposed on the powerful On the power frequency signal, considering various interference factors, the weak traveling wave signal may be difficult to detect in practice, and the traveling wave protection cannot correctly detect the head of the traveling wave, which may cause the protection to refuse to operate or malfunction, and the consequences are very serious (Reference 4 )

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  • Method for detecting voltage zero cross near fault in travelling wave protection
  • Method for detecting voltage zero cross near fault in travelling wave protection
  • Method for detecting voltage zero cross near fault in travelling wave protection

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Embodiment Construction

[0027] The research shows that: when the fault is near the voltage zero crossing, most of the wavelet transform waveforms of the current traveling wave are far away from the time axis, and when the fault is not near the voltage zero crossing, most of the wavelet transform waveforms of the current traveling wave are near the time axis, Therefore, the identification of faults near the voltage zero crossing should be judged as a whole, not just based on some points in the waveform. The concrete implementation steps of this method are as follows:

[0028] (1) When the traveling wave protection detects the threshold traveling wave, it starts and records the three-phase current traveling waves;

[0029] (2) Use the phase-mode transformation matrix T formula to calculate three linear-mode traveling waves and their energy, and select a linear-mode traveling wave with the largest energy for the following calculation; the phase-mode transformation matrix is T = ...

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Abstract

The present invention belongs to the field of relay protection technology for electric power system. Based on the characteristic that the small scale wavelet conversion waveform of current traveling wave has its main part far from the time axis while voltage zero-cross failure and near to the time axis normally, phase-analog conversion matrix T is used in calculating three line mode traveling waves and their energy, one line mode traveling wave with maximum energy is selected for wavelet conversion, and the number of the points with values exceeding the maximum Kw is calculated to judge whither to have zero-cross failure. The present invention provides reliable and effective method capable of separating zero-cross failure from other failures.

Description

Technical field: [0001] The invention relates to a detection method for faults near voltage zero crossing in traveling wave protection, which belongs to the technical field of electric power system relay protection. Background technique: [0002] Most of the existing protection devices are based on the protection principle of power frequency quantity. It regards the traveling wave (transient state) process after the fault as interference, tries to filter it out, and only uses the steady state quantity after the fault (reference 1 , 2), and the steady-state quantity after the fault is almost not affected by the fault closing angle, so the power frequency quantity protection is almost not affected by the fault closing angle. Different from the power frequency protection, the traveling wave protection is formed according to the propagation, refraction and reflection of the traveling wave caused by the fault on the line. It uses the high frequency signal caused by the fault and ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02H7/26G01R31/08G01R31/00
Inventor 束洪春司大军董俊邱革非唐岚刘志坚孙向飞
Owner KUNMING UNIV OF SCI & TECH
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