Distribution network bus protection device and method with grounding mode automatic identification function

Abstract

The invention discloses a distribution network bus protection device with a grounding mode automatic identification function. The device comprises a collection circuit, a judgment circuit, and a zero sequence differential protection circuit. The collection circuit is used for collecting the electrical characteristics of a current bus line, wherein the electrical characteristics includes the zero sequence differential current of the current bus and the zero sequence voltage of the current bus. The judgment circuit is used for judging whether the current bus line is grounded at the neutral point via a small resistor according to the electrical characteristics of the current bus line. The zero sequence differential protection circuit is used for starting zero sequence differential protection and outputting a control signal to turn off the switch of the current bus line if the current bus line is grounded at the neutral point via a small resistor. The invention further discloses a distribution network bus protection method with a grounding mode automatic identification function. With the distribution network bus protection device with a grounding mode automatic identification function provided by the invention, the problem that the bus of a distribution network cannot be protected under change of the grounding mode is solved.

Description

technical field [0001] The invention relates to the field of relay protection of power systems, in particular to a distribution network bus protection device with self-identification grounding mode and a distribution network bus protection method with self-identification grounding mode. Background technique [0002] At present, the grounding method of the medium voltage distribution network usually adopts the neutral point ungrounded system, the neutral point grounded system through the arc suppression coil or the neutral point grounded system through a small resistance according to the difference in the grounding capacitance current. When a single-phase ground fault occurs in the distribution line, the neutral point ungrounded system or the arc suppression coil system does not need to remove the fault, and can continue to run for 1.5 to 2 hours, while the neutral point grounded system with a small resistance needs to remove the fault immediately, otherwise It will cause the...

AI Technical Summary

Problems solved by technology

[0004] (1) For the neutral point grounding system through a small resistance, due to the existence of the grounding resistor, the grounding current is usually limited to a low level. It is necessary to reduce the setting value of the phase-separated differential protection, which will bring risks to the reliable operation of the bus differential protection, and the disconnection of the current transformer (CT) of a heavy-duty line may cause protection malfunction

[0005] (2) The busbar protection cannot automatically identify the grounding method of the distribution network. If the grounding method is changed from a neutral point ungrounded system or an arc suppression coil grounded system to a small resistance grounded system, the setting value of the phase-separated differential protection cannot be automatically reduced. The busbar protection refuses to operate after single-phase grounding occurs on the busbar; if the grounding method is changed from the neutral point through the small resistance grounding system to the neutral point non-grounding system or the arc suppression coil grounding system, the setting value of the phase-separated differential protection cannot be automatically increased , reduce operational risk

[0006] (3) The two sections of busbars in a substation may be powered by two substations with different grounding methods. Usually, only one set of phase-separated differential action settings can be set for busbar protection, which is not conducive to the realization of different grounding methods for single-phase grounding. Differentiated relay protection methods

In this way, the fault can be removed quickly by the switch at station A. As a result, the switch of B1 needs to be delayed for a period of time to remove the fault, and the scope of power outage is also expanded. The bus fault in station A is usually the failure of the main equipment, and the removal time is significantly longer. It is important for equipment safety. very unfavorable

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