Neutral point non-effective earthing system single-phase earthing fault identification method

A single-phase ground fault and non-effective grounding technology, which is applied to fault locations, measuring devices, instruments, etc., can solve problems such as single-phase high-resistance ground faults cannot be identified, and achieve the effect of ensuring reliability

Active Publication Date: 2013-03-06
ZIYANG POWER SUPPLY COMPANY STATE GRID SICHUAN ELECTRIC POWER +2
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Problems solved by technology

[0005] The purpose of the present invention is to provide a sensitive and reliable single-phase ground fault identification method to overcome the shortcomings of traditional methods that cannot be identified when a single-phase high-resistance ground fault occurs

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  • Neutral point non-effective earthing system single-phase earthing fault identification method
  • Neutral point non-effective earthing system single-phase earthing fault identification method
  • Neutral point non-effective earthing system single-phase earthing fault identification method

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Embodiment Construction

[0019] When a single-phase ground fault occurs in a neutral point non-effectively grounded system, such as figure 1 , when considering the influence of fault resistance, assuming that a single-phase ground fault occurs on phase C, Z C is the capacitive reactance of each phase of the system to ground, and there is Z C =-jX C , R f is the fault resistance, U ph is the phase voltage rating, and the system voltage (bus zero-sequence voltage and three-phase voltage) has the following rules:

[0020] When the fault resistance is zero, the fault phase (C phase) voltage decreases to zero, and the non-fault phase (A, B) voltage rises to 1.732U ph , the zero-sequence voltage rises to the phase voltage U ph .

[0021] When the system is a neutral point ungrounded system, the characteristics of each phase voltage changing with the fault resistance are as follows: figure 2 , the bus zero-sequence voltage decreases with the increase of the fault resistance, but it is still greater t...

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Abstract

The invention discloses a neutral point non-effective earthing system single-phase earthing fault identification method which includes the steps that a zero sequence voltage instantaneous value and a instantaneous saltation value are taken as the startup criteria of an identification scheme; when any of the above values is out of the limit, an identification process is started, a saltation moment is determined according to a signal saltation point, and the effective values of the zero sequence voltages and the three-phase voltages in cycles before and after the signal saltation point and the variations of the effective values are calculated; and a single-phase earthing fault is judged to have happened only when the variation of the zero sequence voltage and the variations of all phases of voltage all satisfy all the criteria. The method takes voltage variation for identification, and the saltation of the state of the system can be reflected; a low threshold value scheme is adopted in the method, so the system can be started sensitively under a high impedance fault; and the multiple criteria scheme of zero sequence voltage and three-phase voltage are adopted, so the method has high reliability. The method is simple and easy to realize.

Description

technical field [0001] The invention relates to a single-phase ground fault discrimination method of a power system distribution network, in particular to a "low threshold, multi-criteria" single-phase ground fault identification and detection method established by the voltage change before and after the fault in the power system distribution network. Background technique [0002] my country's distribution network mainly adopts neutral point non-effective grounding methods, including neutral point non-grounding and resonance grounding. It is found in actual operation that single-phase grounding faults account for about 80% of the total faults in this type of system. After a single-phase ground fault occurs, the fault phase voltage decreases, the non-fault phase voltage increases, the system line voltage remains unchanged, and the power supply is not affected. The system is allowed to continue to run for 2 hours, but long-term operation may cause the accident to expand or caus...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R31/02G01R31/08
Inventor 庄琳肖先勇张文海李长松马超
Owner ZIYANG POWER SUPPLY COMPANY STATE GRID SICHUAN ELECTRIC POWER
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