Current-opposition-influence-resistant composite differential protection method for power transmission line

Abstract

The invention discloses a current-opposition-influence-resistant composite differential protection method for a power transmission line. The method is characterized in that an imaginary portion of a ratio of each phase voltage obtained during normal running of the power transmission line to a corresponding phase current obtained after the power transmission line fails is computed at first, and phase currents at two ends of the power transmission line and the imaginary portion of the ratio of each phase voltage obtained during normal running of the power transmission line to the corresponding phase current obtained after the power transmission line fails form current differential protection criteria. The current-opposition-influence-resistant composite differential protection method has the advantages that the problem of influence of current reversal to the performance of differential protection actions for the currents is eliminated in principle, and the current-opposition-influence-resistant composite differential protection method is applicable to power transmission lines with series compensation capacitors; accurate and reliable actions can be performed by the method when faults occur on the inside of the power transmission line with series compensation capacitors, and correct and reliable locking can be performed by the method when faults occur on the outside of the power transmission line with the series compensation capacitors.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a composite differential protection method for transmission lines against the influence of current reverse phase. Background technique [0002] Because it is not affected by the power system operation mode and grid structure and has a natural phase selection function, the current differential protection has always been the main protection of various voltage levels of transmission lines. Series compensation capacitors are often installed on transmission lines with voltage levels of 500kV and above to compensate for the inductance of transmission lines to increase transmission capacity, shorten electrical connections, and improve power system stability. Since the inductance of the transmission line is compensated by installing the series compensation capacitor, after a fault occurs inside the transmission line, the current phase of the fault phase wil...

AI Technical Summary

Problems solved by technology

Since the inductance of the transmission line is compensated by the installation of series compensation capacitors, after a fault occurs inside the transmission line, the current phase of the fault phase will lead the phase of the voltage phase of the fault phase, that is, the current phase will be reversed, resulting in a decrease in the differential current and an increase in the braking current. If the current differential protection criterion is not satisfied, the current differential protection cannot operate correctly to jump off the fault line, and cannot isolate the fault line from the grid in time, resulting in a large current passing through the transmission line and power equipment for a long time, causing transmission line failure. Overheating fuse, overheating and burning of electrical equipment or damage to insulation

Images