Neutral-point grounding control equipment medium-voltage power grid

Abstract

The invention discloses neutral-point grounding control equipment of a medium-voltage power grid. The neutral-point grounding control equipment comprises a bus voltage transformer, a grounding transformer, a circuit zero-sequence current transformer and a controller, wherein the bus voltage transformer is connected with a bus and the controller, the grounding transformer is connected with the busand an arc extinguishing coil, a neutral point current transformer and a neutral point voltage transformer are arranged between the grounding transformer and the arc extinguishing coil and are connected with the controller, a branch is arranged between the neutral voltage transformer and the arc extinguishing coil and is connected with a resistor by a switch connected with the controller, the controller is connected with at least two branch lines by the circuit zero-sequence current transformer, and the branch lies are connected with the bus. The advantages of two grounding modes of neutral-point resonant grounding and resistance grounding are combined, the advantage that a line can be accurately selected by resistance grounding is maintained, residual current of a grounding point also canbe reduced, an arc light grounding overvoltage is limited, an appropriate working mode can be selected according to different conditions of a short-term grounding fault or a permanent grounding fault, the safety running of the line is guaranteed, and the power supply reliability is also improved.

Description

Technical field: [0001] The invention relates to the field of power transmission and transformation, in particular to a neutral point grounding control device for a medium-voltage power grid. Background technique: [0002] The neutral point grounding method of urban distribution network is a complex comprehensive problem, which is related to power supply reliability, personal safety, equipment safety and so on. However, the current neutral point grounding method has the following problems: the overvoltage limit of the arc suppression coil grounding method is insufficient, and the detection of ground fault lines is difficult. , leading to an increase in the residual current of the ground fault; series resonance overvoltage that may occur in disconnection; the small resistance grounding method, the system will trip quickly when a single-phase grounding occurs, which will affect the reliability of power supply, distribution network structure, mutual supply capacity, equipment a...

AI Technical Summary

Problems solved by technology

However, because it cannot distinguish the instantaneous single-phase ground fault from the permanent single-phase ground fault, the instantaneous single-phase ground fault also trips, which affects the reliability of power supply

Using a small resistance for grounding causes the instantaneous grounding that accounts for most of the grounding to also trip, causing a power outage and seriously affecting the reliability of the grounding

At the same time, in this way, it is necessary to have good switching equipment and a backup power supply, otherwise trips and power outages are frequent, power supply reliability is poor, and the maintenance workload of the switch is increased.

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