A method for on-line monitoring and line selection of single-phase grounding fault in small current grounding system

Abstract

The invention discloses an on-line monitoring and line selection method for a single-phase grounding fault in a small current grounding system. Through online monitoring of the zero-sequence voltage of the power grid, the zero-sequence current of all feeders before and after the occurrence of a single-phase grounding fault in the power grid is measured and recorded. Calculate the zero-sequence "insulation admittance" of each feeder based on the sequence voltage and feeder zero-sequence current data, and use the characteristics of the zero-sequence "insulation admittance" of the feeder to realize accurate judgment of the fault line. This method is not affected by the grounding mode, eliminates the influence of the asymmetry of the power grid parameters and the transition resistance, and solves the problem of line selection for high-resistance grounding faults in the power grid with a large asymmetry. The implementation method is simple, does not affect the normal operation of the system, and can improve the sensitivity of judging whether the power grid has a single-phase ground fault.

Description

technical field [0001] The invention relates to a measurement and control method of electrical technology, in particular to the technology of on-line monitoring and fault line identification of single-phase grounding faults in small current grounding systems. Background technique [0002] my country's distribution network is mainly based on the low-current grounding method. After a single-phase ground fault occurs, the grid line voltage is symmetrical and can still provide sustainable power supply. The small-current grounding system (non-effective grounding system) includes ungrounded neutral point, high-impedance grounding and arc-suppression coil grounding, and 80% of distribution network faults are single-phase grounding faults. It is the domestic problems of long-term concern. [0003] The traditional method of fault line selection in the neutral point ungrounded system is realized by comparing the zero-sequence power frequency current or power of the feeder; in the res...

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Problems solved by technology

[0003] The traditional method of fault line selection in the neutral point ungrounded system is realized by comparing the zero-sequence power frequency current or power of the feeder; in the resonant grounding system, due to the introduction of the arc suppression coil, the zero-sequence current characteristics of the fault line become complicated, so there are Scholars have proposed a line selection method for zero-sequence active components

However, the above line selection methods are all based on the strict symmetry of the line parameters of the power grid. In reality, the asymmetry of the line-to-ground parameters of the power grid is ubiquitous, and the power grid with strict symmetric line parameters hardly exists; and the size of the transition resistance is also random. , especially when high-impedance grounding occurs in the power grid, the accuracy of the above line selection method will be greatly reduced

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