A small current grounding line selection device and single-phase grounding detection method

Abstract

The invention discloses a small-current grounding line selection device and a single-phase grounding detection method. According to the single-phase grounding detection method, through simultaneously sampling a three-phase bus voltage and a three-phase line current and calculation of a least square filter, the magnitude and phase of each of the voltage and the current can be obtained, and furthermore a phase difference between the time before a fault and the time after the fault can be obtained. Furthermore through real-time calculation for the complex impedance of a line, an impedance change in the fault is detected. Through the two characteristics of the phase difference and the impedance change, the single-phase grounding fault characteristic of the line can be accurately determined and is not affected by direction of a loop power flow. The single-phase grounding detection method is a new solution for detecting a small-current grounding fault.

Description

technical field [0001] The invention relates to a small current grounding line selection device and a single-phase grounding detection method. Background technique [0002] As we all know, the transmission lines of the power grid are divided into direct grounding systems and indirect grounding systems according to the different grounding methods of the neutral point of substation transformers. High-voltage transmission lines (220kV and above) belong to direct grounding systems, also known as high-current grounding systems. Low-voltage lines (110kV and below) belong to the transformer neutral point indirect grounding system, also known as the small current grounding system. Since the small current grounding system is responsible for delivering power to end users, it is also called distribution network, or distribution network for short. However, since the distribution network is located in a densely populated area, and the lines are close to buildings and residential areas, ...

AI Technical Summary

Problems solved by technology

[0008] The above four methods, the steady-state component method and the wavelet method need to analyze the transient characteristics of all lines synchronously, and the amount of calculation is very large. The harmonic method cannot be effectively detected because the harmonic content is too small. The transient line selection method is based on Hypothetical premise, not very useful in practice

[0009] To sum up, from the detection principle, there is still a lack of reliable and effective methods for small current grounding line selection.

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