Low current neutral grounding electric network single-phase earth fault diagnostic method

Abstract

The invention provides a low current grounding single phase earth fault diagnosis method, comprising: capturing A voltage to ground, B voltage to ground, C voltage to ground, neutral point current and entire waveform information of each zero sequence current from a steady state to a transient state then to steady state when neutral point voltage exceeds presupposed threshold; first diagnosing whether being single phase earth fault, PT fusing, ferro resonance, arc suppressing coil resonance overvoltage, or neutral point overvoltage disturbance caused by experiment; selecting lines for the earth fault. The inventive method makes full use of steady state information and transient information of electric network before and after fault, and judges the fault and selects lines according to the long term changing rule of the neutral point voltage, which is different from the traditional stable state line selecting method and the transient line selecting method, thereby being suitable for the neutral point unearth electric network and the neutral point arc suppressing coil earth electric network at the same time, and well adapts the condition of complex site, thereby ensuring fault diagnosis and correct line selection.

Description

technical field [0001] The invention relates to a fault diagnosis method, in particular to a single-phase ground fault diagnosis method which fully utilizes the complete transient state and steady state information of a small current grounded power grid. Background technique [0002] In the medium-voltage distribution network, single-phase ground faults account for more than 80% of the total faults. When a single-phase ground fault occurs, accurate selection of grounding lines is of great significance to the operation and management of the power grid. [0003] In the prior art, it is usually judged whether a ground fault has occurred based on the rise of the neutral point voltage of the power grid, but in fact there are many reasons for the rise of the neutral point voltage, not necessarily single-phase grounding, so the neutral point After the point voltage exceeds the limit, it is very important to identify the fault type first. Only when it is judged to be a single-phase ...

AI Technical Summary

Problems solved by technology

[0003] In the prior art, it is usually judged whether a ground fault has occurred based on the rise of the neutral point voltage of the power grid, but in fact there are many reasons for the rise of the neutral point voltage, not necessarily single-phase grounding, so the neutral point After the point voltage exceeds the limit, it is very important to identify the fault type first. Only when it is judged to be a single-phase ground fault can the line selection be meaningful; in addition, the current line selection method cannot adapt to the complexity of the single-phase ground fault. The correct results are obtained under specific circumstances, and the unsatisfactory application effect of these methods in the power grid is a proof; therefore, only the fault identification of the system is carried out layer by layer by category, and fully utilize the power grid from steady state to transient state and then to fault when a fault occurs. The complete process information of the steady state can ensure the accuracy of fault diagnosis and line selection

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