Interrupting characteristics of a DC combined apparatus for rail transit systems

Abstract

The short-circuit fault current of the urban rail transit systems is hard to interrupt due to the high amplitude and the high rising rate. The existing air DC circuit breakers applied in the rail transit DC traction system are difficult to interrupt the short-circuit fault current quickly and reliably, and cannot meet the increasing demand of the system capacity. The objective of this paper is to design a novel DC combined apparatus including a DC fuse module and an artificial zero crossing module series-connected to solve the problem of rapid isolation of short-circuit fault current in DC traction systems. The DC fuse module consists of a DC fuse and a transfer switch with additional auxiliary coils. Experimental results show that the DC combined apparatus can interrupt the rated current, overload current, and short-circuit current effectively within 6 ms. It can interrupt a 20 kA overload current within 5.12 ms, and the interrupting time of a prospective short-circuit current of 100 kA is less than 5.08 ms. The designed DC combined apparatus has the full range of current interrupting capacity and has the advantages of low on-state loss and low cost, which can significantly improve the reliability and stability of rail transit systems.