Small current fault line selection protection system of power grid isolated neutral system

Abstract

The invention discloses a small current fault line selection protection system of a power grid isolated neutral system. In a typical system which adopts a post-set arc suppression coil controller and a small current fault line selection device which are separate from each other, the system is additionally provided with a grounding overvoltage relay and a time relay. The coil of the grounding overvoltage relay is connected with an open delta voltage signal output end of a busbar potential transformer. The normally open contact of the grounding overvoltage relay is serially connected with the coil of the time relay and then is powered by an external power supply. The normally open contact of the time relay is serially connected between a signal input end of the small current fault line selection device and the open delta voltage signal output end of the busbar potential transformer. The system staggers the dynamic compensation process of a post-set arc suppression coil and process of the small current fault line selection capturing a ground fault, so that the small current fault line selection device is enabled to carry out fault line selection after arc suppression coil compensation residual current is stable, the motion correctness of the small current fault line selection device is improved further, and wrong selection and selection leakage are avoided.

Description

technical field [0001] The invention relates to a small current grounding line selection protection system for a grid neutral point ungrounded system. Background technique [0002] In my country's urban power grids and medium-voltage systems of factories and mines, most of them are neutral point ungrounded (that is, small current grounded) systems. When single-phase grounding occurs in this system, the power grid can still run with a fault for 1 to 2 hours. The operating cost is greatly reduced and the reliability of the power supply system is improved. However, this power supply method is prone to arc overvoltage and phase-to-phase short circuit when the single-phase ground current is large, which causes great harm to the power supply and consumption equipment. In order to avoid accident expansion caused by arc overvoltage after single-phase grounding, my country's electric power regulations stipulate that when the capacitive current of 10kV system is greater than 30A, and ...

AI Technical Summary

Problems solved by technology

[0013] It can be seen from the above that in the arc suppression coil compensation system with adjustment, when a single-phase ground fault occurs, the selection of the small current grounding line selection device is often in the transient process of the arc suppression coil dynamic compensation. Stability leads to false alarms and false alarms in small current grounding line selection devices

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