Neutral point grounding device and its control method

Abstract

The present invention provides a neutral point grounding device and a control method thereof, wherein the neutral point grounding device comprises: an arc suppression coil, one end of which is connected to the neutral point, and the other end is grounded; a resistance unit connected with the arc suppression coil The parallel connection is used to provide a variable resistance resistance; the controller is used to control the resistance value of the resistance unit and the on-off of the resistance unit circuit. The neutral point grounding device and its control method provided by the present invention have the largest resistance value when the adjustable resistor is initially put into use, and it can be judged that the metallic grounding and medium and low resistance grounding faults of a large proportion of the line are faulty, and the fault current is small, ensuring Personal safety; for a very small number of ground faults with high transition resistance and no fault line is identified, the adjustable resistance is automatically adjusted to the minimum, which further increases the fault characteristics and improves the accuracy of fault selection.

Description

technical field [0001] The invention relates to the technical field of power transmission and distribution, in particular to a neutral point grounding device and a control method thereof. Background technique [0002] The neutral point grounding methods of the power grid include: non-grounding method, grounding through arc suppressing coil and low resistance grounding. Different grounding methods have their own advantages and disadvantages: the neutral point non-grounding method allows continuous operation for 2 hours when the single-phase is grounded, but when the grounding current exceeds a certain value, the arc cannot be self-extinguished, and it is easy to generate arc grounding overvoltage; neutral grounding The grounding method through the arc-suppression coil can compensate the large capacitive current generated by the power grid, but it may cause resonance overvoltage due to inaccurate measurement of the capacitive current and improper compensation. When the capacit...

AI Technical Summary

Problems solved by technology

Different grounding methods have their own advantages and disadvantages: the neutral point non-grounding method allows continuous operation for 2 hours when the single-phase is grounded, but when the grounding current exceeds a certain value, the arc cannot be self-extinguished, and it is easy to generate arc grounding overvoltage; neutral grounding The grounding method through the arc-suppression coil can compensate the large capacitive current generated by the power grid, but it may cause resonance overvoltage due to inaccurate measurement of the capacitive current and improper compensation. When the capacity of the arc-suppression coil does not meet the requirements, it needs to be upgraded. ;The grounding current is large when the neutral point is grounded by low resistance, which is beneficial to the fault line selection, but the tripping rate is high, the local resistance value is too small, and the grounding fault current is large, which brings safety hazards to equipment, communication lines and personal safety.

The resistors connected in parallel to the arc suppression coil are all fixed resistors. If the resistance value is large, the sensitivity will be low. If the resistance value is small, the fault current will be large, which is not conducive to personal safety.

In addition, the selection of fault characteristics is mainly based on the magnitude of the zero-sequence current, and when the transition resistance is large, only the magnitude of the zero-sequence current cannot effectively distinguish the fault line

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