Method and device for monitoring line defects in bus differential protective current analog quantity of transformer substation

Abstract

The invention provides a device for monitoring line defects in bus differential protective current analog quantity of a transformer substation. The device is matched with a system including N branch neutral lines which are connected to a public N terminal and then commonly grounded. (N+1) monitoring devices are respectively arranged on N branch neutral lines and a common ground wire. Each monitoring device comprises a current transformer, a middle relay and an alarm module, wherein the first end and the second end of the current transformer are positioned on the existing connected circuit to induct current; one end of the middle relay is connected to a normally open contact point of the current transformer and used for controlling the existing working state of the normally open contact point after comparing the inducted current value with the preset current threshold value; and the alarm module is connected to the other end of the normally open contact point and started to emit an alarm signal when the normally open contact point is closed. According to the embodiment of the invention, the device can be used for timely finding that multiple points of the bus differential protective current secondary loop of the transformer substation are grounded, and is beneficial to the maintaining staff to quickly maintain, so that a phenomenon that the transformer substation bus differential protection is wrongly started while having external faults or not started while having internal faults is avoided.

Description

technical field [0001] The invention relates to the technical field of electric power systems, in particular to a method and device for monitoring neutral line defects of substation bus differential protection current analog quantities. Background technique [0002] Substation bus differential protection is an important system equipment to ensure the safe and stable operation of the power grid. Its safety, reliability, sensitivity and rapidity are of decisive significance to ensure the safety of the entire regional power grid. Substation bus differential protection consists of large bus differential and several small differential bus sections. The large differential busbar is a differential element composed of the sum of the current phasors of all branches on the busbar except the busbar and the section circuit breaker, and is used to distinguish short circuits inside or outside the busbar area. The small differential of the busbar is a differential element composed of the ...

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Problems solved by technology

It should be pointed out that it is not advisable to ground the secondary circuit of the bus differential protection current at one point in the early stage by connecting the grounding points of each branch circuit in series and fixing the secondary grounding grid grounding copper plate in the screen with a grounding wire, because when When the intermediate serial link or the general grounding point is loose, it may cause part or all of the secondary current circuit to lose grounding or have no good grounding point

[0005] when using as figure 1 In the correct grounding method shown, although the disadvantage of one-point grounding after series connection is avoided, its disadvantage is that when the secondary circuit of the current is damaged due to insulation damage of the control cable, water entering the secondary junction box of the current transformer, etc. When there is another grounding point outside the grounding point, there may be interference with the secondary circuit of the substation bus differential protection current due to the large ground potential difference in the substation ground network (such as shunting, neutralization, etc. Extra differential current on the neutral line, aggravating the secondary saturation of the current transformer, etc.), which makes the substation bus differential protection malfunction when an external fault occurs and refuses to operate when an internal fault occurs, causing serious consequences

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