A fast line selection method for single-phase grounding fault in small current grounding system

Abstract

The invention discloses a fast line selection method for a single-phase grounding fault in a small current grounding system. First, the instantaneous value of the three-phase current at the outlet of each feeder line in the substation is collected in real time; secondly, according to the instantaneous value of the current, the instantaneous value of the zero-sequence current of the line is calculated, and the second-order derivative of the instantaneous value of each zero-sequence current is obtained by interpolation method; then, Taking the fault occurrence time as the zero time, find out the maximum value and minimum point of the second order derivative of the zero-sequence current instantaneous value of each line within 3ms; finally, find out the characteristic quantity of the zero-sequence current change trend of each line, and find out the maximum characteristic quantity , that is, it is judged that the line is a faulty line. The method of the invention is less affected by line length, transition resistance and arc suppressing coil, and can quickly select a single-phase grounding fault line.

Description

technical field [0001] The invention belongs to the field of power systems, and relates to a line selection technology for a single-phase ground fault in a distribution network, in particular to a fast line selection method for a single-phase ground fault in a small current grounding system. Background technique [0002] my country's 10kV distribution network system generally adopts the neutral point indirect grounding method, including neutral point non-grounding, arc suppression coil grounding, and resistor grounding. In the neutral point indirect grounding system, when a single-phase grounding fault occurs, the current at the fault point is very small, so it is also called a small current grounding system. When a single-phase ground fault occurs, the neutral point voltage rises from zero to the phase voltage, and the line voltage between the three phases remains symmetrical, which does not affect the normal power supply. Therefore, the system is generally allowed to conti...

AI Technical Summary

Problems solved by technology

By comparing the 5th harmonic current of the faulty line and the non-faulty line, the 5th harmonic method is proposed, but the 5th harmonic is very small, and it is difficult to propose

The wavelet method analyzes the transient zero-sequence current signal through the wavelet transform theory, and can perform fault line selection, but it is very difficult to select a suitable wavelet base

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