Identification method of ground fault phases in three-phase ungrounded system and identification device thereof

Abstract

The invention relates to an identification method of ground fault phases in a three-phase ungrounded system and an identification device thereof. The identification method comprises the following steps: firstly selecting any line voltage in the three-phase ungrounded system as reference voltage, determining value domains of phase difference between theoretical zero-sequence voltage of the fault phases and the reference voltage when a ground fault occurs on each phase aiming at the reference voltage, and carrying out real-time online acquisition of the actually measured zero-sequence voltage; if the actually measured zero-sequence voltage is zero, judging no ground fault occurs; and if the actually measured zero-sequence voltage is not zero, calculating the phase difference between the actually measured zero-sequence voltage and the reference voltage, and judging which value domain the phase difference falls into so as to judge that the ground fault occurs on the phase corresponding to the value domain. The identification method can rapidly judge the ground fault occurs on A phase or B phase or C phase in the three-phase ungrounded system and directly point out the ground fault phases while finding out the fault, thus reducing troubleshooting time, being beneficial to eliminate faults timely, and guaranteeing safe operation of the system.

Description

technical field [0001] The invention relates to a method and a device for discriminating phases with grounding faults in an operation mode in which a neutral point is not grounded in a power system and a special power distribution system. Background technique [0002] There are many power systems and special power distribution systems that use the distribution transformer neutral point ungrounded operation mode. When a single-phase ground (rigid or arc ground) fault occurs, the line voltage remains unchanged, so it will affect the user's continued work. It is not large, so it is stipulated in the power regulations to allow short-term operation with faults (usually a maximum of two hours), thus greatly improving the power supply reliability of the system. [0003] However, when a single-phase ground fault occurs in the neutral point ungrounded system (such as figure 1 As shown, the fault phase is phase C), and the ground voltage of the non-fault phase can be increased from t...

AI Technical Summary

Problems solved by technology

Therefore, this technology can only detect and identify the branch circuit where the ground fault occurs, but it is impossible to further find out the fault phase.

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