Small current grounding line selection method based on residual current variable

Abstract

The invention discloses a low current grounding wire selection method based on residual current variable, and the method comprises the following steps of: (1) correctly identifying whether an electric distribution network has a single-phase ground fault by adopting the neutral point displacement voltage of the electric distribution network as characteristic quantity; (2) after the ground fault happens, compensating the grounding current of a fault point by virtue of an arc-suppression coil to achieve the effects of reducing the grounding current and extinguishing grounding arc light; (3) adjusting the tap position of a first tap arc-suppression coil on the premise of ensuring that the grounding residual current meets the standard request; (4) because the neutral point displacement voltagebefore and after the tap position adjustment of the arc-suppression coil changes, converting the zero-sequence current of each outgoing line subjected to the tap position adjustment to be below the voltage level before the top position adjustment by utilizing a voltage translation method so as to prevent the wire selection characteristic quantity from being influenced by the neutral point displacement voltage; and (5) selecting the line with the single-phase ground fault according to the change values of the zero-sequence current of each outgoing line after voltage translation before and after the tap position adjustment. The low current grounding wire selection method based on residual current variable can be used for improving the accuracy of wire selection.

Description

technical field [0001] The invention belongs to the field of electric power system automation. The invention is mainly applicable to the grounding system of the neutral point of the distribution network through the arc suppressing coil, and more precisely, it is a method for selecting a single-phase grounding fault line. Background technique [0002] During the operation of my country's distribution network, single-phase short-circuit grounding faults frequently occur. At the same time, with the transformation of urban distribution network, the number of cable outlets is increasing day by day, and the capacitive current of the system to ground increases sharply. If effective measures are not taken, it is very easy to cause phase-to-phase short circuit, expand the accident, and affect the quality of power supply. Therefore, the grounding method through the arc suppression coil is gradually recognized and widely used in medium and low voltage distribution networks. [0003] How...

AI Technical Summary

Problems solved by technology

The method described in this patent uses the fifth harmonic as the line selection feature quantity, but due to the compensation effect of the arc suppression coil, the zero-sequence current value of each line is very small, and the fifth harmonic value is even weaker. The electromagnetic interference is serious, and it is difficult to accurately measure the fifth harmonic value, which makes the practical effect of this method unsatisfactory, and the accuracy of line selection is not high

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