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Low-current grounding wire-selecting method

A technology of small current grounding and wire selection method, which is applied in the direction of measuring electricity, measuring electrical variables, measuring devices, etc., can solve problems such as difficult to accurately measure the fifth harmonic value, unsatisfactory practical effect, and low accuracy of wire selection , to achieve the effect of obvious line selection feature quantity, good practicability and reliable criterion

Active Publication Date: 2013-06-12
STATE GRID ELECTRIC POWER RES INST +1
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Problems solved by technology

The method described in this patent uses the fifth harmonic as the line selection feature quantity, but due to the compensation effect of the arc suppression coil, the zero-sequence current value of each line is very small, and the fifth harmonic value is even weaker. The electromagnetic interference is serious, and it is difficult to accurately measure the fifth harmonic value, which makes the practical effect of this method unsatisfactory, and the accuracy of line selection is not high

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Embodiment Construction

[0029] In the present invention, a method for selecting the grounding line by changing the operating state of the arc suppression coil is disclosed. figure 1 It is a system model in which the neutral point of the distribution network is grounded through the arc suppression coil. When the distribution network is in normal operation, the switch mechanism K is closed, and the arc suppression coil is connected to the grid. When a single-phase ground fault occurs in the distribution network, after the fault state is confirmed, the switch structure K is disconnected, so that the arc suppression coil is out of operation. This will produce an obvious zero-sequence current characteristic quantity, which is beneficial to accurately select the fault line.

[0030] figure 2 It is the equivalent circuit of the distribution network connected to the arc suppression coil when a single-phase ground fault occurs. U in the picture 0 is the neutral point displacement voltage; U ψ is the phas...

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Abstract

The invention discloses a low-current grounding wire-selecting method, which is characterized by comprising the following steps: 1) distribution network neutral point displacement voltage is used as a characteristic parameter to correctly identify whether a single-phase grounding fault happens in the distribution network; 2) if the grounding fault happens, grounding current at the fault point is compensated by an arc-suppression coil so as to reduce grounding current and extinguish grounding arc light; 3) a switch mechanism between the neutral point and the arc-suppression coil is switched off to make the arc-suppression coil out of operation in a short time; 4) circuits with single-phase grounding faults are selected by analyzing the change value of zero-sequence current of each circuit before and after the arc-suppression coil exits; and 5) the arc-suppression coil is added again after the fault circuits are selected so as to ensure the arc-suppression coil to play a role of compensation. Circuits with single-phase grounding faults can be accurately selected in the method disclosed by the invention.

Description

technical field [0001] The invention belongs to the field of electric power system automation. The invention is mainly applicable to the grounding system of the neutral point of the distribution network through the arc suppressing coil, and more precisely, it is a method for selecting a single-phase grounding fault line. Background technique [0002] During the operation of my country's distribution network, single-phase short-circuit grounding faults frequently occur. At the same time, with the transformation of urban distribution network, the number of cable outlets is increasing day by day, and the capacitive current of the system to ground increases sharply. If effective measures are not taken, it is very easy to cause phase-to-phase short circuit, expand the accident, and affect the quality of power supply. Therefore, the grounding method through the arc suppression coil is gradually recognized and widely used in medium and low voltage distribution networks. [0003] How...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R31/08G01R31/02
Inventor 吴维宁朱金大王长宝阙连元于海波范志刚杨锐姜铁卫
Owner STATE GRID ELECTRIC POWER RES INST
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