Arc suppression method and device for ground fault in neutral point ungrounded system

Abstract

The invention discloses an arc-suppression method of a ground fault in a neutral non-grounding system and an apparatus thereof. A power supply apparatus is connected to a neutral line in the neutral non-grounding system. Through the power supply apparatus, a compensation voltage is output so as to compensate a fault current of the system so that an arc-suppression purpose is reached. An output voltage of the power supply apparatus is defined in the description, wherein omega is a fundamental wave angular frequency; ic, iR and ih are capacitive, resistive and harmonic wave currents respectively; n is a harmonic order; a zero sequence voltage on a neutral point is defined in the description and L is an equivalent inductance of a power supply system. The arc-suppression method of the ground fault in the neutral non-grounding system and the apparatus are easy to carry out and arc suppression can be effectively enforced aiming at a single-phase ground fault.

Description

technical field [0001] The invention relates to the technical field of power system overvoltage protection and power supply reliability assurance, and relates to an arc suppression method and device for ground faults in a neutral point ungrounded system, which is used to eliminate a wide range of instantaneous or arc faults in a neutral point ungrounded system. Arcing from permanent single-phase-to-earth faults. Background technique [0002] my country's electric power industry standard DL / T620-1997 "Overvoltage and Insulation Coordination of AC Electrical Installations" stipulates that for 3kV ~ 10kV systems that are not directly connected to generators and 35kV and 66kV systems, when the single-phase ground fault capacitor current does not exceed the following values When it exceeds the following values ​​and needs to operate under ground fault conditions, the arc suppression coil grounding method should be used: [0003] A) 3kV~10kV reinforced concrete or metal tower over...

AI Technical Summary

Problems solved by technology

[0012] 1) The current adjustment range of the pre-adjusted arc suppressing coil is limited, it cannot be smooth, stepless adjustment, and cannot compensate harmonic current and active current

The residual current at the grounding point cannot be zero, the fault line selection is difficult, and it is not convenient for parallel operation

If the operation mode of the system changes again during the failure, it cannot be adjusted. If the regulation is improper, it will resonate with the system, so that the equipment will be damaged and the accident will expand.

[0013] 2) With the adjustment method, if it is the adjustment method of mechanical switch switching capacitors or inductors, there is a level difference in the residual current at the grounding point, which cannot achieve smooth and stepless adjustment; it cannot compensate harmonic currents and active currents

The problem is that all the problems of the arc suppression coil exist, and there are many equipments, complicated control, and difficult line selection for faults.

[0016] 1), the tripping rate is high, and the reliability of power supply is reduced

[0017] 2), increase the number of circuit breaker actions, shorten the operating life of the circuit breaker

[0018] 3) Frequent tripping affects the power supply to other users, especially for the case of multiple users on one line

cause adverse social impact

[0019] 4) The fault current at the grounding point is large, which can easily cause high ground potential, contact potential and step voltage, which can cause secondary injury accidents such as personal injury

[0020] 5) Large fault current at the grounding point may easily cause damage or interference to weak current equipment such as communication

However, with the increase of the power supply system, in addition to the large fundamental capacitive current in the fault current, its harmonic current and active current components are also increasing. According to the actual measurement, it can reach the level of tens of amperes, so it is possible Can not self-extinguish arc

The arc suppression coil can only compensate the capacitive current of the fundamental component, but cannot compensate the harmonic current and active current.

At the same time, because it is not convenient for stepless adjustment, in some operating modes, the residual current at the fault point will be too large, and the arc may not be extinguished effectively

According to statistics, if only ordinary arc suppressing coils (manual shifting) are installed, the failure rate is about 40%; after using automatic arc suppressing coils, the failure rate is about 20%.

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