Medium voltage direct current (MVDC) distribution networks have been considered for various applications, such as offshore wind farm collector systems, all-electric naval vessels, and aircraft. MVDC circuit breakers are a critical technology to directly manage faults in multi-terminal DC (MTDC) networks. However, DC current breaking is much more challenging than in AC systems because there is no natural zero-crossing of the current waveform to aid fault isolation. This paper reviews existing MVDC circuit breaker technologies and also discusses their advantages and disadvantages. This paper also introduces new topologies that can be applied in MVDC applications. The operation of several hybrid DC circuit breaker topologies with aided commutation is included. The paper illustrates that a hybrid DC circuit breaker with aided commutation can clear a fault within 2-5 msecs with low losses, this shows great potential for future MVDC applications. The implications for the practical design of commercial MVDC circuit breakers are also 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 sub-assemblies. Its goal is to provide a comprehensive overview of the field.

Direct current (DC) circuit breakers are a key enabling technology for fault management in multiterminal high-voltage DC (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 that 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 multistrand magnesium diboride (MgB₂) coil, a vacuum interrupter, and an insulated-gate bipolar transistor module. This prototype successfully demonstrated interruption of 500 A DC within 4.4 ms. This paper presents 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 the high-voltage and high-current applications.

High-voltage direct current (HVDC) transmission systems using Voltage-Source Converters (VSC) are widely recognized as offering significant potential for long distance high power delivery, particularly for offshore wind farm connections. One of the barriers for the development of multi-terminal HVDC systems is the lack of technologies which enable direct fault isolation. This paper will investigate DC fault current limiting technology to reduce fault currents to acceptable levels allowing DC circuit breakers to operate quickly and reliably. Superconducting fault current limiters (SFCL) are a promising candidate, satisfying most of the ideal fault current limitation requirements. This paper shows the potential for reducing the fault current to more acceptable levels using SFCLs in VSC-HVDC systems. A summary of the advantages and disadvantages of resistive and inductive SFCLs is also given. An SFCL limits DC fault current very effectively, reducing the fault current the HVDC circuit breaker would have to interrupt. The paper includes a detailed analysis of resistive and inductive SFCLs including aspects of practical design for use in commercial VSC-HVDC systems. Finally, key issues such as cryogenic cooling and superconducting material costs are highlighted

It is crucial to achieve a high safety and reliability standard in future Electric Propulsion Aircraft (EPA). Due to low short-circuit 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.