Asymmetric power grid single-phase high-resistance grounding fault phase identification method considering line impedance

Abstract

The invention provides an asymmetric power grid single-phase high-resistance grounding fault phase identification method considering line impedance, wherein the method comprises the steps: step 1, the neutral point voltage of a power distribution network, the voltage to ground of each phase, and the phase angle of each phase during the operation of a power distribution network system are measured; and step 2, 15% of the rated phase voltage is set to be a single-phase grounding fault threshold value, and whether the measured neutral point voltage exceeds 15% of the rated phase voltage or not is judged. According to the method, a resonance under-compensation grounding system is analyzed, the situation that misjudgment is prone to occurring when voltage amplitudes are approximately equal before and after a fault is made up, according to the change rule of the voltage amplitudes and phases before and after the fault, the reliability of the criterion is higher, the influence of line impedance is considered, and the method is not influenced by factors such as the line unbalance degree, fault resistance and line impedance; and the fault phase can be accurately identified in both an over-compensation grounding system and an under-compensation grounding system.

Description

Technical field [0001] Technical Field The present invention relates to electric power system protection, particularly to a consideration grid line impedance high impedance single-phase asymmetric phase to earth fault identification method. Background technique [0002] Traditional small current ground fault Consider the phase identification system asymmetrical only for ungrounded systems, and the situation is not under compensation of the resonance line grounding system to analyze the case of the asymmetry parameter, when the voltage on a phase fault misjudgment may occur when approximately equal magnitude before the fault, when the imbalance is located in a phase angle value of each boundary region, the track zero-sequence voltage difference is not obvious, the criterion may not avoid the misjudgment resulting, and this criterion is dependent on accurate measurement of imbalance parameters and the like. Inventive content [0003] The present invention provides an asymmetric po...

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Problems solved by technology

[0003] The present invention provides a single-phase high-resistance grounding fault phase identification method for asymmetric power grids considering the line impedance, and its purpose is to solve the problem that the traditional fault phase identification method does not undercompensate the resonant grounding system and the line-to-ground parameter asymmetry If the situation is analyzed, it is easy to misjudgment when the amplitude after the fault is approximately equal to that before the fault, and the criterion depends on the accurate measurement of parameters such as unbalance

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