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Method for judging single-phase grounding fault of low-current grounding system

A single-phase grounding fault, small current grounding technology, applied in the fault location, detecting faults according to conductor types, measuring electricity and other directions, can solve the problems of high sampling rate requirements of equipment, error-prone fault determination, and difficult application, etc. Verify difficult effects

Pending Publication Date: 2021-04-13
NR ELECTRIC CO LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

At present, most of the commonly used ground fault judgment methods use the zero-sequence steady-state electrical quantity after the fault. Since the amplitude of the zero-sequence steady-state electric quantity is small when the single-phase is grounded, it is difficult to measure accurately, so it is difficult to apply in practice.
The injection method is limited by the capacity of the voltage transformer, and the injection signal is small. When there is a transition resistance grounding, the fault judgment is easy to make mistakes
Transient method requires high sampling rate of equipment, and is easily affected by zero-sequence CT polarity

Method used

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  • Method for judging single-phase grounding fault of low-current grounding system

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Effect test

Embodiment 1

[0034] Embodiment 1 of a method for judging a single-phase ground fault in a small current grounding system, as shown in figure 1 shown, including:

[0035] Collect zero-sequence voltage on the bus, three-phase current and zero-sequence current in this interval;

[0036] Compare the direction of transient three-phase current and transient zero-sequence current at the moment of grounding, and the direction of transient zero-sequence voltage and transient zero-sequence current;

[0037] When the directions of the three-phase current and zero-sequence current and the directions of zero-sequence voltage and zero-sequence current are both positive or negative, it is determined that a ground fault occurs in this bay.

Embodiment 2

[0039] Embodiment 2 of a method for judging a single-phase ground fault in a small current grounding system, as shown in figure 2 Shown include the following steps:

[0040] Step (1): Collect the zero-sequence voltage of the bus, the three-phase current and zero-sequence current of this interval, and calculate the zero-sequence voltage amplitude in real time;

[0041] Step (2): Comparing the zero-sequence voltage amplitude with the zero-sequence starting voltage, when the zero-sequence voltage amplitude exceeds the zero-sequence starting voltage, start the ground fault judgment procedure and enter step (3), otherwise return to step (1);

[0042] Step (3): Intercept the data of the three-phase current, zero-sequence current and zero-sequence voltage of the first cycle before starting and the half cycle after starting, perform wavelet packet transformation on the data, select the frequency band with the largest energy as the characteristic frequency band, and obtain the charact...

Embodiment 3

[0046] Embodiment 3 of a method for judging a single-phase ground fault in a small current grounding system includes the following steps:

[0047] Step (1): Collect the zero-sequence voltage of the bus, the three-phase current and zero-sequence current of this interval, and calculate the zero-sequence voltage amplitude in real time;

[0048] Step (2): Comparing the zero-sequence voltage amplitude with the zero-sequence starting voltage, when the zero-sequence voltage amplitude exceeds the zero-sequence starting voltage, start the ground fault judgment procedure and enter step (3), otherwise return to step (1);

[0049]Step (3): Intercept the data of the three-phase current, zero-sequence current and zero-sequence voltage of the first cycle before starting and the half cycle after starting, perform wavelet packet transformation on the data, select the frequency band with the largest energy as the characteristic frequency band, and obtain the characteristic frequency band The th...

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Abstract

The invention discloses a method for judging a single-phase grounding fault of a low-current grounding system. According to the method, bus zero-sequence voltage, interval three-phase current and zero-sequence current need to be accessed, and whether a grounding fault exists or not is judged according to the zero-sequence voltage; wavelet packet transformation is carried out on the transient three-phase current, the transient zero-sequence current and the transient zero-sequence voltage of the length of the data window of the previous cycle and the latter half cycle of the fault at the grounding occurrence moment; and the directions of the zero-sequence current and the phase current of the characteristic frequency band and the directions of the zero-sequence current and the zero-sequence voltage of the characteristic frequency band, which are obtained after conversion are comprehensively compared so as to identify the grounding fault. The method can be applied to a system of which the neutral point is not grounded and which is grounded through an arc suppression coil.

Description

technical field [0001] The invention relates to the field of relay protection of power systems, in particular to a method for judging single-phase ground faults in small current grounding systems. Background technique [0002] In my country's 3-66kV power supply and distribution network, most of them adopt a small current grounding system. In such a system, when a single-phase ground fault occurs at any point, the entire system will sense zero-sequence current and zero-sequence voltage, and enter failure state. At present, most of the commonly used ground fault judgment methods use the zero-sequence steady-state electrical quantity after the fault. Since the amplitude of the zero-sequence steady-state electric quantity is small when the single-phase is grounded, it is difficult to measure accurately, so it is difficult to apply in practice. The injection method is limited by the capacity of the voltage transformer, and the injection signal is small. When there is a transitio...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R31/08G01R31/52
CPCG01R31/086G01R31/088Y04S10/52
Inventor 倪群辉侯炜石勇赵健龙陈俊李宇琦
Owner NR ELECTRIC CO LTD
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