High-voltage direct current transmission line internal fault and external fault identification method based on backward traveling waves

Abstract

The invention discloses a high-voltage direct current transmission line internal fault and external fault identification method based on backward traveling waves. The high-voltage direct current transmission line internal fault and external fault identification method comprises the following steps that firstly, a voltage transformer and a current transformer installed on the rectification station line side and an inversion station line side of a direct current transmission system collect voltage and current across the two ends of a positive electrode line and voltage and current across the two ends of a negative electrode line respectively; secondly, the voltage leap amount and current leap amount of the two ends of the positive electrode line and the voltage leap amount and current leap amount of the two ends of the negative electrode line are calculated; thirdly, the voltage leap amount and current leap amount of each electrode line are transformed into corresponding line mode voltage component and line mode current component; fourthly, the voltage backward waves at the two ends of the direct current line are worked out according to the line mode voltage component and the line mode current component, and integration of backward wave amplitude values is conducted in specific time; fifthly, a specific value of the backward wave amplitude value integral on the rectification side of the direct current line to the backward wave amplitude value integral on the inversion side of the direct current line is calculated, and faults are judged according to the specific value. By means of the method, the internal faults and the external faults can be quickly and accurately recognized, correct actions can still be conducted under the high-resistance faults at the line tail end and the noise interferences, and reliability and sensitivity are high.

Description

technical field [0001] The invention relates to the field of electric power systems, in particular to a method for identifying internal and external faults of high-voltage direct current transmission lines based on reverse traveling waves. Background technique [0002] At present, traveling wave protection is used as the main protection for DC lines, and differential undervoltage protection, current longitudinal differential protection, etc. are used as backup protection to identify whether a fault occurs on the DC line. Among them, traveling wave protection and differential undervoltage protection constitute the protection criterion based on the voltage change rate. When a high-impedance fault occurs on the line, the voltage change rate cannot reach a fixed value and it is easy to refuse to operate. [0003] Current longitudinal differential protection, as the backup protection of traveling wave protection and differential undervoltage protection, can effectively detect hig...

AI Technical Summary

Problems solved by technology

[0003] The current longitudinal differential protection, as the backup protection of traveling wave protection and differential undervoltage protection, can effectively detect high-impedance faults, but the differential protection is to avoid the circuit distributed capacitor charging and discharging current and sampling value fluctuations caused by faults on the AC side outside the zone. It is possible that before the differential protection operates, the low-voltage protection or the maximum trigger angle protection action in the rectifier side pole control will block the fault pole, so that the differential protection often occurs. Less than the backup protection effect on the line

At the same time, in order to ensure reliability, current differential protection requires precise synchronization of data at both ends of the line, which requires high communication equipment

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