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

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 ...

AI Technical Summary

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 )

Images