Current transverse differential protection method of double-branch AC filter

Abstract

The present invention discloses a current transverse differential protection method of a double-branch AC filter. The AC filter has two branches which are a first branch and a second branch. The method comprises the steps of detecting the first branch end tail end current and the second branch end tail end current of the AC filter in real time, and emitting a transverse differential current alarm signal or a trip command according to the sizes of the differential current deviation of the first branch end tail end current and the second branch end tail end current from a normal value. When the any phase differential current of transverse differential protection differential current is larger than a transverse differential overcurrent detection action threshold value, a transverse differential overcurrent detection criterion acts. When the transverse differential overcurrent detection acts, tail end large current lock detection and tail end CT abnormality detection do not act, and a transverse differential current trip delay is reached, transverse differential current trip acts. According to the current transverse differential protection method, the sensitivity and mobility of the AC filter in a grounding failure or high end capacitance breakdown failure can be improved, and the wrong actions in various external short circuit failures and various non-normal operating conditions can be prevented.

Description

technical field [0001] The invention relates to the electrical quantity protection technology of a double-branch type AC filter used in a high-voltage direct current transmission project in the field of electric power system, in particular to a current transverse difference protection method of a double-branch type AC filter. Background technique [0002] Wiring mode of double-branch AC filter, such as figure 1 As shown, the high-side capacitor ( figure 1 shown in C1. The same below) breakdown is the most common internal fault of the AC filter. For this reason, high-end capacitors often use H-type or π-type wiring to facilitate the installation of special capacitor unbalance protection to deal with high-end capacitor breakdown faults and prevent accidents from expanding. If the high-end capacitors do not use the above wiring method, there is no special protection against capacitor breakdown faults. Because the differential current protection cannot reflect the high-end c...

AI Technical Summary

Problems solved by technology

Because the differential current protection cannot reflect the high-end capacitor breakdown fault in principle; moreover, when a non-metallic grounding short circuit fault occurs at the end of the AC filter, the sensitivity of the differential current protection is often insufficient

In addition, whether it is a high-end capacitor breakdown fault or a ground fault, the overcurrent protection or zero-sequence overcurrent protection in the backup protection of the AC filter has shortcomings such as low sensitivity and poor quick action, which cannot meet the needs of the internal fault of the AC filter. , Reliable failure removal requirements

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