Circuit Breaker Emergency Trip Scheme for the Outage of Auxiliary DC Power System

The outage of auxiliary DC power system in the substation will lead to the power loss of all the circuit breakers, relay protection devices and other important equipment. In the event of fault, the failure of quick primary protection in the local substation would not only expand the scope of the accident, but also cause serious harm to the substation equipment. In this paper, a new circuit breaker emergency tripping system based on supercapacitor and Buchholz relay or pressure relief valve is proposed, which can quickly clear the fault and isolate the faulty equipment when a fault occurs to the transformer in the case of DC power outage in the substation. The required capacity of the supercapacitor is calculated considering the cable length, cross-sectional area and other factors. A simulation is conducted to verify the feasibility of the method.