Comparison of different methods to limit short circuit currents in DC traction networks

In this paper, different methods to limit short circuit currents in DC traction networks are compared. Typically, DC traction networks are supplied by the AC grid by means of an uncontrolled diode bridge rectifier. In case of a low-impedance short circuit fault between catenary and rail, the fault current reaches a large value. For densely meshed networks the mechanical circuit breakers can become too slow. The methods studied are applying fault current limiters, faster interruption of fault currents and adding controlled rectifiers. The fault current limiters considered are a reactor and a superconducting fault current limiter (SFCL). For faster interruption of fault currents, a hybrid circuit breaker is investigated. Simulations show that the short circuit current can be limited considerably by installing limitation devices after the rectifiers, when the short circuit occurs close to a substation. Fast interruption of the fault or application of the SFCL results in the strongest reduction of the short circuit current.