Fault phase selection method for isolated neutral system

Abstract

The invention relates to a fault phase selection method for an isolated neutral system, which comprises the following steps: step one, grounding fault judgment, wherein the step further comprises the sub-steps of (1) grounding fault judgment, (2) single-phase grounding fault judgment and (3) two-phase grounding fault judgment; and step two, non-grounding fault judgment, wherein the step further comprises the sub-steps of (1) asymmetric fault judgment, (2) two-phase short circuit judgment and (3) three-phase short circuit judgment. According to the invention, algorithm improvement is performed on a current difference sudden change phase selection method, the current difference sudden change phase selection method is divided into a grounding short circuit fault phase selection method and a non-grounding fault phase selection method according to characteristics of a line after a fault occurs, and a set of complete fault phase selection method for the isolated neutral system is formed. The method has very high phase selection reliability for isolated neutral systems which are complicated in harmonic wave, strong in electromagnetic interference, instable in operating mode and high in grounding resistance, and can act as a common means for fault phase selection for the isolated neutral system.

Description

technical field [0001] The invention belongs to the technical field of power system fault analysis, in particular to a fault phase selection method for a neutral point ungrounded system. Background technique [0002] If the neutral point ungrounded system runs for a long time with a fault, the non-fault relative ground voltage will rise, which will accelerate the aging of the cable insulation, which may expand the fault and endanger the reliability of the power supply. Therefore, it is very necessary to find out the fault line in time and cut it off for the safe operation of the neutral point ungrounded system. [0003] In the accident analysis of power system and the calculation of fault point location, it is necessary to judge the fault type and phase difference. At present, the most widely used fault phase selection method is the current difference sudden change phase selection method. The current difference sudden change phase selection method uses the amplitude charact...

AI Technical Summary

Problems solved by technology

The phase selection method of sudden change in current difference is to distinguish various types of faults by using the amplitude characteristics of the two-phase current difference change when a fault occurs in the system. Its main features are: high sensitivity, less calculation data, and the ability to distinguish between two Three-phase short circuit, but the phase selection accuracy is very low for single-phase ground fault

[0004] Therefore, in the fault phase selection of the neutral point ungrounded power system, phase-to-phase faults and three-phase short-circuit faults use the current difference sudden change phase selection method, but the ground fault current difference sudden change phase selection method is no longer applicable, and it is necessary to find other options. phase method

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