A nugs single-phase-to-ground fault location method based on harmonic difference discrimination

Abstract

Provided is an NUGS single-phase grounding fault location method based on harmonic difference distinguishing. When a fault occurs, a sampling request is sent to all fault indicators, current signals in a period before the occurrence of the fault and in a period after the occurrence of the fault are recorded, and the recorded current signals are decomposed into direct-current components, fundamental harmonics and higher harmonics through FFT transform. The higher harmonics are retained, and subtraction operation is carried out on the content value of harmonic acquired by each fault indicator and the content value of harmonic of the same order acquired by the following fault indicator to form a matrix deltaU of operation results corresponding to all harmonics. The maximum values of all lines of the matrix deltaU are selected line by line to form a difference matrix deltaUmax. A line section which goes out the most in the deltaUmax is judged as a faulty section. The fault location method provided by the invention is simple in structure and easy to implement, and the deployment cost of complete equipment can be reduced greatly. The original grounding property of a distribution network is not changed, and the reliability of a distribution network of a small-current grounding system is not reduced. Moreover, injection of additional non-stationary signals is not needed, and the risk to safe and stable operation of the distribution network is not increased.

Description

technical field [0001] The invention belongs to the technical field of distribution network fault location, and in particular designs a single-phase ground fault location method for a small current grounding system (NUGS) based on a harmonic discrimination method. Background technique [0002] The neutral point not directly grounded system is widely used in the distribution network below 66kV. The advantage of this form of distribution network lies in its high reliability of power supply, especially in the case of a single-phase ground fault, it can operate with faults in a short period of time . However, the current characteristics of single-phase faults are not obvious in this type of distribution network, and the fault cannot be eliminated by means of protection trips. The fault point can only be checked along the fault line by using the fault indicator on the premise of selecting the fault line. [0003] At present, the implementation methods of fault indicators with re...

AI Technical Summary

Problems solved by technology

However, the realization of the former requires additional high-voltage coupling equipment, which requires high hardware investment and is not sensitive to high-resistance and arc instability faults; the latter also has high requirements for auxiliary hardware equipment, and its implementation destroys the original distribution network sex point grounding

Both belong to the active positioning method, which needs to actively inject non-stationary signals into the power grid, which is harmful to the safe and stable operation of the distribution network.

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