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It is crucial to achieve a high safety and reliability standard in future Electric Propulsion Aircraft (EPA). Due to low shortcircuit impedance and high rate of fault current rise in EPA systems, the superconducting fault current limiter (SFCL) plays a promising role, with advantages of light weight, high efficiency and compact size, compared to conventional FCL. A novel helical bifilar coil is proposed which is composed of two windings wound in opposite directions on the same bobbin, these are connected in series to achieve equal current sharing and a non-inductive circuit. 12 mm-wide stainless steel reinforced superconducting tape from AMSC was used for the windings. To characterize the proposed helical bifilar coil connected in series (BCS), AC loss tests under three frequencies and quench tests under prospective fault current up to 2223 A were carried out. They were compared with the results measured from a conventional helical bifilar coil connected in parallel (BCP) which had an identical specification to the BCS. It was concluded that AC losses measured in the BCP is dependent on current and frequency. The fault current was suppressed effectively by the BCS at the first half peak from 2223 A to 495 A, corresponding to 22.3% of the prospective fault current. Quench performance of BCP was also tested and discussed.

HVDC circuit breakers are of increasing importance, as multi-terminal high voltage DC (HVDC) transmission becomes a commercial reality. Multiple HVDC breaker technologies have been developed, and are starting to appear as proof-of-concept installations on real networks. Information about them is however distributed widely in the literature. This paper describes the underlying challenges, the leading candidate solutions, and discusses the requirements and construction of the component subassemblies. Its goal is to provide a comprehensive overview of the field.

Abstract-Direct current (DC) circuit breakers are a key enabling technology for fault management in multi-terminal high voltage direct current (HVDC) systems. DC fault isolation is challenging 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 superconductor 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 Magnesium 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 voltage and high current applications.  Index Terms-DC circuit breaker, hybrid circuit breaker, Magnesium Diboride, MgB2, mechanical switch, semiconductor switch, and superconducting coil.

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