Online monitoring and line selecting method for single-phase earth faults of small current grounding system

Abstract

The invention discloses an online monitoring and line selecting method for single-phase earth faults of a small current grounding system. Precise fault line judgment is achieved through the steps of online monitoring power grid zero sequence voltages, measuring and recording zero sequence currents of all feeder lines before and after the single-phase earth faults of a power grid happen, calculating zero sequence insulation admittance of all feeder lines according to the measured zero sequence voltages and feeder line zero sequence current data and utilizing the characteristics of the zero sequence insulation admittance of all feeder lines. The method is not affected by grounding modes, the influence of the asymmetry degree of parameters of the power grid and transition resistance is eliminated, and the problem of line selection when high-resistance earth faults of a power grid with large asymmetry degree happen is solved. The realizing mode is simple, normal operation of the system is not affected, and the sensitivity of judging whether a power grid has single-phase earth faults can be improved.

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...

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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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