Multipoint earth fault detection method, device and system for secondary current circuit

Abstract

The invention provides a multipoint earth fault detection method, device and system for a secondary current circuit. The method includes the steps that N-phase currents of an N-phase line of a three-phase current circuit and ground line currents of a ground line are collected in real time through a current mutual inductor, and the amplitude and the phase of the 1-kth harmonic of the N-phase currents and the amplitude and the phase of the 1-kth harmonic of the ground line currents are respectively calculated, wherein whether the amplitude of any harmonic, lager than a fault threshold, exists in the amplitude of the 1-kth harmonic of the N-phase currents is judged; if the harmonic exists, whether the amplitude of the harmonic is equal to the amplitude of the corresponding harmonic of the ground line currents and whether the difference between the phase of the harmonic and the phase of the corresponding harmonic of the ground line currents is 180 degrees are further judged; if the amplitude of the harmonic is equal to the amplitude of the corresponding harmonic of the ground line currents and the difference between the phase of the harmonic and the phase of the corresponding harmonic of the ground line currents is 180 degrees, it is judged that multipoint earth faults exist in the secondary current circuit.

Description

technical field [0001] The invention relates to the field of electric power technology, in particular to a method, device and system for detecting a multiple-point grounding fault in a secondary current loop. Background technique [0002] The substation grounding grid is not the actual equipotential surface, and there will be a potential difference between two different grounding points. When the secondary circuit of the current transformer in the substation is grounded at multiple points, the potential difference between the fault ground point and the protective ground point will generate an inrush current in the secondary circuit of the transformer. [0003] When an equipment grounding fault occurs, the potential difference between the two grounding points will change significantly, which will affect the correct transmission of the current transformer. At the same time, the fault grounding point and the protective grounding point will generate a shunt current to the curre...

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Problems solved by technology

[0004] Therefore, under the dual effects of the shunt current and the potential difference of the grounding point, the amplitude and phase of the current detected by the current transformer may change, which affects the correct judgment, thereby affecting the operation result of the fault detection

However, when there is no fault, the multi-point grounding of the secondary current loop is difficult to be found, which is a hidden fault. At present, there is no good way to quickly detect the fault when a multi-point grounding fault occurs in the secondary current loop, and the current cannot be guaranteed. Accuracy of secondary circuit grounding

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