Power distribution network single-phase earth fault identification method and system based on grounding transformer tapping tap grounding

Abstract

The invention discloses a power distribution network single-phase earth fault identification method and system based on grounding transformer tapping tap grounding. According to the method, a grounding branch switch is arranged at a winding tap of a grounding transformer; by continuously measuring the neutral point voltage and the neutral point voltage variable quantity of the grounding transformer, when the neutral point voltage and the neutral point voltage variable quantity exceed set values, the tap of the grounding transformer at the head end of the line is grounded, tap gears are adjusted step by step, and finally whether a grounding fault exists or not is judged by judging whether the zero-sequence current of the line is in linear change or not. Compared with a traditional method for measuring the neutral point voltage deviation and the neutral point voltage variation, the method has the advantages that the fault characteristic quantity of the power distribution network can be actively adjusted, the fault identification accuracy is higher, and the method is not affected by three-phase grounding parameter asymmetry, three-phase load imbalance and load fluctuation.

Description

technical field [0001] The invention belongs to the field of distribution network fault identification, and in particular relates to a single-phase ground fault identification method and system of a distribution network based on grounding transformer tap tap grounding. Background technique [0002] The distribution network is deep into the user terminal, and it is very prone to faults. Among the fault types, the single-phase ground fault has the highest probability of occurrence. If the fault is not found and cleared in time, the insulation medium of the line may be damaged, and the single-phase ground fault develops into a phase-to-phase short circuit fault, resulting in Damage to electrical equipment and reduce power supply reliability. Rapid detection of ground faults is of great significance to the safe and reliable operation of distribution networks. [0003] In the prior art, there are mainly two methods for identifying single-phase-to-ground faults in distribution ne...

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Problems solved by technology

However, when the parameters of the three-phase line to ground are not equal, the three-phase load is unbalanced or the load fluctuates, etc., the neutral point voltage or voltage variation may exceed the set value, which may easily lead to misjudgment of faults.

[0005] 2. Measure the damping rate. For low-resistance ground faults, the fault current is large, and the damping rate changes greatly before and after the fault. At this time, it is easy to judge the fault by measuring the damping rate, but for high-resistance ground faults, the fault current is very small, and the line The change of the active current to the ground is also very small, the damping rate basically does not change, it is difficult to distinguish whether a fault occurs, and the protection sensitivity is low

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