Method for realizing theoretical criterion protection of distribution network feed line single phase earth fault

Abstract

This invention discloses a method for protecting distributing network feed line single-phase grounding fault for providing a protection method applying three-phase transient current component orthogonal wavelength resolution or improved wavelet packet resolution algorithm to extract the character value of single or combined character frequency bands of phase transient components, utilizing the judgement principle of fixed theory between frequency band character values of fault or unfault phases to distinguish the two phases. Combined start mode is applied to protection.

Description

technical field [0001] The invention relates to a protection method for a distribution network feeder, and more specifically, relates to a protection method for a single-phase ground fault of a distribution network feeder. Background technique [0002] In systems where the neutral point is not effectively grounded (including grounded through the arc suppressing coil, the neutral point is grounded through high resistance, or the neutral point is not grounded), the detection of the single-phase ground fault of the feeder is mostly based on the line selection method. , the basic principle is the steady-state zero-sequence power direction or zero-sequence direction, that is, it is required that all feeders connected to the busbar should collect steady-state zero-sequence current and zero-sequence direction (referring to the steady-state zero-sequence current of each feeder and the busbar zero-sequence voltage direction of formation). There are two speci...

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Problems solved by technology

Because this type of principle is easily affected by factors such as system operation mode and fault status, the faulty feeder cannot be accurately selected, and the reliability of field operation is very low, and the accuracy rate is poor. About 50% of the devices have retreated.

In view of the existing problems, they are all working on related research, but the grounding protection principle proposed is still a steady-state component or a sequence component, so it is still a partial improvement and cannot fundamentally eliminate the substantive problems [1-2] , also useful protection principle based on wavelet or wavelet packet of transient components [3] and line selection principle [4-5] They basically overcome the limitations of the steady-state component. Literature [3] uses a fixed characteristic frequency band, and there will be uncertain factors in the judgment of different fault characteristics; Literature [4-5] implements the line selection mode in principle , so there is complexity of the device and it is not conducive to the realization of automation

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