Design and Experimental Tests of a Superconducting Hybrid DC Circuit Breaker

Direct current (DC) circuit breakers are a key ena-bling technology for fault management in multi-terminal high voltage direct current (HVDC) systems. DC fault isolation is chal-lenging due to the high rate of rise of the fault current and the lack of natural current zero-crossings found in AC systems. In this paper we present a novel superconducting hybrid DC circuit breaker which utilizes the intrinsic characteristics of the super-conductor material. The automatic quench of the superconductor coil as a result of a high fault current transfers the current from the mechanical switch to the semiconductor switch. The isolating mechanical switch is able therefore to open at low current and recover its dielectric capability rapidly. A low voltage DC circuit breaker prototype has been built using a multi-strand Magnesi-um Diboride (MgB2) coil, a vacuum interrupter and an IGBT module. This prototype successfully demonstrated interruption of 500 A DC within 4.4 ms. This paper includes the design of the superconducting hybrid breaker prototype and a detailed analysis of the experimental results. This superconducting hybrid DC circuit breaker has significant potential for scaling-up to high volt-age and high current applications.