Automatic control device for neutral point grounding resistor

Abstract

The invention discloses an automatic control device for a neutral point grounding resistor, and relates to the technical field of electric power. The device is connected between a power distribution network neutral point and the ground, and comprises a small resistor, a silicon controlled rectifier overvoltage automatic fling-cut switch, a contactor and a controller, wherein the controller is connected with the contactor in series, the contactor is connected with the silicon controlled rectifier overvoltage automatic fling-cut switch in parallel; one ends of the contactor and the silicon controlled rectifier overvoltage automatic fling-cut switch which are connected in parallel are connected with a neutral point of a power distribution network, the other ends of the contactor and the silicon controlled rectifier overvoltage automatic fling-cut switch are connected to the small resistor, and the other end of the small resistor is directly grounded. When a power grid operates normally, asilicon controlled rectifier is not conducted, the neutral point is grounded through the voltage-sharing resistor, the resistance value of the voltage-sharing resistor is selected according to a high-resistance grounding mode, the power grid operates in the high-resistance grounding mode at the moment, so that the ferromagnetic resonance can be avoided, the relay protection sensitivity is high ina small-resistance grounding manner, and the protection algorithm is simple.

Description

technical field [0001] The invention relates to the field of electric power technology, in particular to an automatic control device for a neutral point grounding resistor. Background technique [0002] The neutral point grounding mode of the medium voltage distribution network is closely related to the safety, economy and reliability of the distribution network operation. At present, there are mainly the following neutral point grounding modes in my country: neutral point ungrounded mode, neutral Point via arc suppressing coil grounding mode, neutral point via small resistance grounding mode, these grounding modes are suitable for different occasions, and each has its own advantages and disadvantages. [0003] The neutral point is not grounded to save investment, and the power grid can operate with faults, but arc overvoltage is prone to occur in places with large capacitive currents, and ferromagnetic resonance overvoltages are prone to occur in places with small capacitive...

AI Technical Summary

Problems solved by technology

[0003] The neutral point is not grounded to save investment, and the power grid can operate with faults, but arc overvoltage is prone to occur in places with large capacitive currents, and ferromagnetic resonance overvoltages are prone to occur in places with small capacitive currents, causing equipment insulation breakdown and causing Major safety accidents cause major economic losses. Therefore, this method is only suitable for power grids with small capacitive currents equipped with means of eliminating associations; the neutral point is grounded through the arc suppression coil to reduce grounding residual current and effectively suppress arc overvoltage. , Ferromagnetic resonance overvoltage, which can be applied to occasions with large capacitive currents, but there are also problems in the selection of grounding lines and insufficient compensation capacity with the development of the power grid; the neutral point grounding method through a small resistance can effectively suppress the overvoltage of the power grid , the use of zero-sequence overcurrent protection can cut off the fault and other advantages, but there are also large ground fault currents, and the relay protection equipment needs to cut off the fault immediately, which leads to a large number of instantaneous ground faults that will also cause tripping, which greatly reduces The power supply reliability of the power grid, so this grounding method is generally used in power grids with high insulation rate, that is, power grids dominated by cable lines

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