Low-current grounding fault line selection method based on wide-area zero-sequence voltage distribution characteristics

Abstract

The invention discloses a low-current grounding fault line selection method based on wide-area zero-sequence voltage distribution characteristics and belongs to low-current grounding fault line selection methods. According to the method, based on a distributed parameter model, a fault line can be selected correctly only under the circumstance of obtaining zero-sequence voltage data in the conditions of different grounding modes, fault distance, transition resistance and small off-tuning degree; difference between a sound line and the fault line in zero-sequence voltage distribution along the lines after a fault occurs is taken as a line selection basis. The method includes: constructing fault measurement factors for each feeder line according to line lengths and zero-sequence voltages measured at tail ends of a bus position and all branches after the fault occurs; then, establishing a relative fault measurement matrix for representing the difference between the sound line and the fault line in zero-sequence voltage distribution along the lines and similarity between the sound line and another sound line in zero-sequence voltage distribution along the lines; selecting the fault line according to a maximum vote principle. The low-current grounding fault line selection method is high in line selection accuracy and insusceptible to the fault distance, the transition resistance and a neutral point grounding mode.

Description

technical field [0001] The invention relates to a line selection method for small current grounding faults, in particular to a line selection method for small current grounding faults with characteristics of wide-area zero-sequence distributed voltage. Background technique [0002] The neutral point operation mode of my country's distribution network is mostly a small current grounding operation mode. At present, for the small current grounding system, especially in the resonant grounding distribution network where the neutral point is grounded through the arc suppression coil, the reliability of fault line selection needs to be improved due to the small fault signal characteristics. Although a variety of line selection methods such as transient traveling wave method, wavelet singularity detection method, zero-sequence admittance method, and injection method have been proposed, the reliability of line selection has been greatly improved, but whether it is based on transient ...

AI Technical Summary

Problems solved by technology

In the actual power grid, the existence of iron core saturation, eddy current, hysteresis and excitation current can easily cause the saturation of the current transformer, causing its transmission characteristics to be nonlinear, thus reducing the accuracy of the measurement results or even distorting them.

At the same time, there are inconsistencies in parameters among multiple transformers, and these factors will affect the correct line selection; in addition, due to the asymmetry of power supply and three-phase load, the asymmetry of three-phase line parameters and the asymmetry of three-phase current transformers , there will be a large unbalanced current in the system, its magnitude may be much larger than the zero-sequence current at the fault, and the direction is uncertain, resulting in the wrong selection of the line selection device

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