Single-phase grounding fault protection method for small-resistance grounding system

Abstract

The invention provides a single-phase grounding fault protection method for a small-resistance grounding system. Multi-stage cooperation among protection to an outlet circuit breaker, a branch switch,a boundary switch and a distribution transformer is achieved through cooperation of a time stage difference and a setting value, and a fault line is cut off selectively. For a high-resistance grounding fault, fault line selection is carried out by utilizing fault current traveling wave signals detected at the head ends of outgoing lines of a transformer substation, the situation that a high unbalanced current is generated due to other reasons is eliminated, the grounding protection constant value is reduced, the sensitivity is greatly improved, and the grounding protection can still reliablyact under a high-resistance grounding fault. After a grounding fault occurs, the fault can be quickly and selectively removed. The method is still effective when the transition resistance is up to 1500 ohms. An obvious effect is achieved for reducing the range and time of outage of a power distribution network due to a fault.

Description

technical field [0001] The invention relates to the field of distribution network fault processing, in particular to a single-phase ground fault protection method for a small resistance grounding system. Background technique [0002] The neutral point adopts a small resistance grounding method to limit the overvoltage level of the non-faulted phase after a single-phase ground fault, overcome the ferromagnetic resonance of the ungrounded system and the series resonance overvoltage of the grounded system through the arc suppression coil, and the relay protection configuration is simple. In my country, with the development of the economy, in the densely populated central urban area, the distribution network structure is perfect to ensure the reliability of the power supply. faulty line. Based on this, the urban distribution networks in Shanghai, Beijing, Guangzhou, Shenzhen, Suzhou and other places in China have successively changed the grounding mode of non-grounding or arc-su...

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Problems solved by technology

[0004] At present, for feeder single-phase ground faults, the staged zero-sequence current protection scheme is mainly adopted, considering the influence of avoiding the downstream capacitive current of the protected line and the maximum unbalanced current during normal operation, the setting value of the zero-sequence current protection is too high, which can withstand The value of the transition resistance is generally only about 100Ω; and the ground fault in the actual distribution network is usually accompanied by tree barriers, incomplete breakdown of lightning arresters, and wires falling on the ground, ponds, etc., resulting in small current to ground and zero sequence overshoot. Flow protection often refuses to move

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