The Mathematical Model of Contact Resistance and Injected Current in DRM Tests of SF6 Circuit Breaker

Dynamic contact resistance measurement (DRM) has been widely used in evaluating the contact condition of circuit breakers from 20 years ago. With the increasing of the injected current, the contact resistance is lower than it was. It is considered that the contact hardness, contact force, and specific resistivity are affected by the injected current. SF
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circuit breaker with self-elastic contact is studied in this paper because of its widely used in high-voltage power system. First, the parameters of the dynamic curves are discussed, and the contact resistance in arcing contact part is concerned because of its susceptibility. Second, the mathematical model of contact force is discussed and calculated, and the change of contact force under a different injected current can be ignored. Finally, the mathematical model of contact resistance and injected current is established, when the breaker contact speed is stable. The mathematical model is proven effective by DRM tests.