A method of reverse start and line selection suitable for high-resistance grounding faults in asymmetric power grids

Abstract

The invention provides a reverse starting and line selecting method suitable for a high-resistance grounding fault of an asymmetric power grid. In operation of a power distribution network, neutral point displacement voltage UN of a power distribution network and zero sequence current In0 of each feed line are detected in real time. If a stable change of the neutral point voltage UN of the power distribution network occurs in a time period deltaT, and continuous increment of the neutral point voltage UN of the power distribution network reaches a certain value, deltaUN can be a forward increment (deltaUN>0) or a reverse increment (deltaUN<0), but when the change amplitude satisfies |deltaUN| >=Udelta and the zero sequence current increment in a random feed line in the power distribution network satisfies deltaI0>Idelta and imax0>=i0B, the single-phase high-resistance grounding fault of the power distribution network is determined. Hereon, a grounding fault processing device performs fault starting and processes the single-phase grounding fault. Hereon the feed line with highest zero-sequence current increment in the lines is the line in which single-phase grounding occurs.

Description

technical field [0001] The invention belongs to the field of single-phase grounding fault processing of distribution networks, and is mainly used for starting processing and grounding line selection of a grounding fault processing device when a neutral point displacement voltage decreases when a high-resistance grounding fault occurs in an asymmetrical power grid. Background technique [0002] Different single-phase ground fault processing devices have different fault start methods and fault start values, but most of them use the grid neutral point displacement voltage as the fault start value of single-phase ground fault. However, due to the different ground parameters of the power grid, the degree of asymmetry of the power grid is also different, and the displacement voltage of the neutral point of the power grid is also different. The neutral point of the power grid is not grounded, and the value range of the asymmetry coefficient is 0-5%. The test found that when a high-...

AI Technical Summary

Problems solved by technology

[0003] In order to solve the problem of reverse start-up processing and line selection of neutral point displacement in the case of high-impedance ground faults in asymmetric power grids, a reverse start-up processing and line selection method suitable for high-impedance ground faults in asymmetric power grids was invented. real-time detection of the distribution network neutral point displacement voltage U N and the zero-sequence current I of each feeder n0 , if within the time period ΔT, the neutral point displacement voltage U of the distribution network N There is a steady change, the neutral point displacement voltage U of the distribution network N The continuous increment reaches a certain value at ΔU N It is a reverse increment, that is, when ΔU when U δ is the fixed value of neutral point displacement voltage fault startup voltage, and the zero-sequence current increment in any feeder in the distribution network satisfies ΔI 0 ≥I δ , I δ is the fixed value of the zero-sequence current increment, and the maximum zero-sequence current I in the feeder MAX0 ≥I 0B , I 0B is the maximum zero-sequence current value caused by the asymmetry of the power grid, it is judged that a single-phase high-resistance ground fault has occurred in the distribution network, and it is judged that a single-phase high-resistance ground fault has occurred in the distribution network, at this time the ground fault processing device enters Fault start to deal with single-phase grounding faults; at this time, the feeder with the largest zero-sequence current increment in each line is the line where single-phase grounding occurs; ΔT is the time period during which the grid parameters continue to increase; U δ Set value for neutral point displacement voltage fault startup voltage