Rapid detection method of tail current of current transformer

Abstract

The invention discloses a rapid detection method of a tail current of a current transformer so that a technical problem of increasing the detection speed of the tail current of the current transformer is solved. The method comprises: acquiring a transmission line parameter; calculating an impedance angle and a decay time constant of a secondary loop; collecting a parameter of a transmission line power voltage before a fault moment; calculating an effective value of a fault current fundamental wave; and comparing the effective value of the fault current fundamental wave with a constant current value of failure protection. Compared with the prior art, the rapid detection method has the following beneficial effects: two-time differential filtering is carried out, the effective value of the fundamental component in the tail current is obtained by means of quarter-cycle absolute value integration, and the effective value is compared with a constant current return value of failure protection to determine whether the effective value is lower than the constant current return value, and the normal operation state is recovered when the fault state is eliminated or the protection action condition is not met, so that the tail current determination time is reduced to be within 10ms, the failure protection action delay is reduced while high reliability is ensured, and the operation risk of the power system is reduced.

Description

technical field [0001] The invention relates to a relay protection method, in particular to a method for detecting tailing current of a current transformer. Background technique [0002] my country's current power grid backbone network is a large AC-DC hybrid power grid. With the massive access of DC power grid systems, the power electronic characteristics of the power grid are becoming more and more obvious. In order to solve the problem of DC blocking caused by the failure of the circuit breaker, the State Grid Corporation of China proposed a solution through the failure of the station domain, requiring the AC grid system to fail. When the circuit breaker fails, all adjacent switches are cut off within 200ms from the moment of the failure. , to prevent multiple commutation failures in the DC grid system. In order to remove the fault within 200ms, it is necessary to compress the action delay of the failure protection. The inherent time of the switching action cannot be com...

AI Technical Summary

Problems solved by technology

However, this method has poor filtering effect on low-frequency DC components.

Based on the detection method of the CT tailing current mentioned above, some literatures propose an improved full-cycle Fourier algorithm, which uses the Mann-Morrison algorithm to improve the calculation of the imaginary part. This algorithm can basically ensure that the DC component is completely filtered within 25ms after the fault is removed. However, there is still the disadvantage that the detection speed of CT tail current is not ideal

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