Judging method for current changing saturation based on differential current difference value

Abstract

This invention relates to method for judging saturation of current transformation based on difference value of difference current. Said method comprises steps of: sampling phase current according preset sampling rate, storing said sampling results in storage zone, processing said results, calculating difference value of the phase difference current, comparing said calculated difference value with preset valve valve. If said difference value is greater than valve value with an amount, current transformation is judged, if not, there must be fault in the zone. This invention has advantages of: decreased calculation for judging saturation of current transformation, high safety for bus bar protection.

Description

technical field [0001] The invention relates to the field of relay protection of electric power systems, and more particularly relates to a method for judging saturation of a current transformer (CT) based on a differential current differential value. Background technique [0002] In recent years, the voltage level of my country's power system has gradually increased, the power supply capacity has increased rapidly, and long-distance power transmission and large-area grid interconnection are also developing rapidly, so the probability of CT saturation caused by power system failures is increasing, and the depth of CT saturation It is also increasing, and the 750kV system to be built in the Northwest Power Grid of my country also puts forward higher requirements for CT saturation discrimination. Power CT saturation may cause misoperation of bus differential protection. If it cannot be judged quickly and appropriate measures are taken, it will cause large-scale power outages an...

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Problems solved by technology

[0004] In particular, for phase transition faults with different names, the current sudden change criterion may be misjudged and affect the action performance of the protection. When a fault occurs, due to the system impedance, the B-phase current also feels a sudden change at this time. After 10ms, the fault in the area begins, and the B-phase feels the emergence of a differential current. Press figure 1 According to the principle of synchronous identification, there is a sudden change of current first, and then there is a differential current. It is judged that the CT is saturated and the differential protection is blocked. Although the existing technology can reopen the bus differential, it has seriously affected the operating speed of the protection.

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