Power distribution network neutral point grounding system with controllable small resistance

Abstract

The invention provides a power distribution network neutral point grounding system with controllable small resistance, which comprises a current detection unit, a processing control unit and a grounding unit, wherein the current detection unit is used for detecting the current of the neutral point, the processing control unit is connected with the output end of the current detection unit, and thegrounding unit is used for receiving the processing control unit and executing a control command; the grounding unit comprises two sets of grounding circuits with the same structure; the grounding circuit comprises a bidirectional silicon controlled rectifier SCR, a normally-closed relay J, a grounding resistor RL and a silicon controlled drive circuit; one end of the bidirectional silicon controlled rectifier SCR is connected to the neutral point, the other end of the bidirectional silicon controlled rectifier SCR is connected with one end of the grounding resistor RL through a normally-closed switch K of the normally-closed relay J, and the other end of the grounding resistor RL is grounded; the control output end of the silicon controlled drive circuit is connected with the control electrode of the silicon controlled rectifier SCR1, the control input end of the silicon controlled drive circuit is connected with the control output end of the processing control unit; and the resistance value of the grounding resistor can be adjusted according to the real-time over-current size, so that the resistance heat is effectively reduced.

Description

technical field [0001] The invention relates to a grounding system, in particular to a controllable small resistance distribution network neutral point grounding system. Background technique [0002] In order to improve the reliability of power supply, the 35kV and 10kV distribution network systems in my country usually adopt the neutral point non-direct grounding method, including neutral point non-grounding and arc-suppression coil grounding. With the continuous development of the distribution network, some urban power grids mainly use cables as power transmission lines, and use compact fully enclosed switchgear and zinc oxide arresters. The characteristics of this system: a) The capacitive current of the system is large, and a high internal overvoltage will be generated after a single-phase ground fault; b) The probability of a single-phase ground fault is much less than that of an overhead line; After grounding, it will continue to operate under the overvoltage of about...

AI Technical Summary

Problems solved by technology

[0003] However, when the distribution network adopts the grounding method of the neutral point through a small resistance, there are also some problems, such as: excessive fault current is easy to expand the accident; Personal safety is harmful; the passage of high current requires a large resistance heat capacity, which brings difficulties to manufacturing, etc.

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