Rapid line selection method for single-phase earth fault of low-current grounding system

Abstract

The invention discloses a rapid line selection method for a single-phase earth fault of a low-current grounding system. The method comprises the steps of firstly collecting the three-phase current instantaneous values at all feeder outlets of a substation in real time; secondly, calculating zero-sequence current instantaneous values of lines according to the current instantaneous values, and solving a second derivative of each zero-sequence current instantaneous value by utilizing an interpolation method; then, finding out the maximum value and minimum value points of the second derivative ofthe instantaneous value of each zero-sequence current instantaneous value of each line within 3ms by taking the fault occurrence moment as a zero moment; and finally, solving the zero-sequence currentchange trend characteristic quantity of each line, and finding out the line with the maximum characteristic quantity, i.e., judging the line as a fault line. The method is slightly influenced by theline length, the transition resistance and an arc suppression coil, and the single-phase earth fault line selection can be rapidly carried out.

Description

Technical field[0001]The invention belongs to the field of electric power systems, and relates to a single-phase grounding fault line selection technology of a power distribution network, in particular to a single-phase grounding fault fast line selection method for a small current grounding system.Background technique[0002]The 10kV distribution network system in my country generally adopts the neutral point indirect grounding method, which includes the neutral point is not grounded, the arc suppression coil is grounded, and the resistance is grounded. In a neutral point indirectly grounded system, when a single-phase grounding fault occurs, the fault point current 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 and does not affect the normal power supply. Therefore, the system is generally al...

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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