Differential Protection Method Based on Inflection Point Tracking with Hyperbolic Braking Characteristics

Abstract

The invention discloses a hyperbolic braking characteristic differential protection method based on inflection point tracking. The motion equations and the motion characteristics are listed in the specification. In the expression (3) and the expression (4), I<d> is motion current, I<z> is braking current, I<q> is starting current, I<g> is inflection current, I<s> is quick break current and K<z> is the ratio braking coefficient; and I<gn> and I<qn> are actual inflection current and actual starting current of a hyperbolic braking characteristic curve based on inflection point tracking. Inflection current is introduced to the curve motion equations again so that the starting threshold can be adaptively enhanced, the problem of CT transient saturation can be effectively prevented, and the possible false action of differential protection in the CT desaturation process can also be effectively prevented; besides, the characteristic of ratio braking can still be guaranteed under the condition of high braking current so that the sensitivity of differential protection can be ensured.

Description

technical field [0001] The invention relates to a hyperbolic braking characteristic differential protection method based on inflection point tracking, and belongs to the technical field of electric power system relay protection. Background technique [0002] Differential protection is used as the main protection for internal short-circuit faults of electrical main equipment such as generators and transformers. At present, the principle of ratio braking is generally used. see figure 1 , its action equation and action characteristics are as follows: [0003] [0004] In formula (1), I d is the operating current, I z is the braking current, I q is the starting current, I g is the knee current, I s is the quick breaking current, K z is the ratio braking coefficient. [0005] The protection action characteristic consists of two parts: no braking part and ratio braking part. The advantage of this action characteristic is that it has high action sensitivity when the fau...

AI Technical Summary

Problems solved by technology

[0011] Aiming at the deficiencies in the prior art, the purpose of the present invention is to provide a hyperbolic braking characteristic differential protection method based on inflection point tracking, which reintroduces the inflection point current into the curve action equation. On the one hand, it can self-adaptively raise the starting The threshold can effectively prevent the CT transient saturation problem, and can also effectively prevent the possible misoperation of the differential protection when the CT exits the saturation process; on the other hand, the ratio braking is still guaranteed under the condition of large braking current The characteristics ensure the sensitivity of differential protection

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