The high-temperature superconducting (HTS) ac and dc cables are gradually finding their way toward commercialization due to their ability to transfer bulk electric power with negligible dielectric loss. In this context, this article critically reviews the different aspects of HTS cables used in various applications and related accessories. The operational, laboratory-scale, and prototype HTS cable projects are discussed in detail. Different dielectrics, electrical insulations, superconductors, cooling systems, cryogens, and upcoming projects of HTS cables are reviewed. The underlying challenges and future directions in ac and dc cables, electric aircraft and ships, associated costs, cryogenic insulation materials, cooling technologies, superconductors, and electrical insulations of HTS cables are discussed in detail. The space charge performance of presently used polypropylene laminated paper insulation and future insulation, i.e., Kapton material, is experimentally analyzed, to show the future challenges in the insulation design. The technology readiness level, market trends, and relevant test standards are explored. The research and market trends suggest that HTS cables can replace conventional transmission methods. However, their consistent growth and adaptation of HTS cables will depend on the design of cryocoolers, raw material cost of superconductors, and large-scale production.

The objective of this paper is to propose a dc current interruption technology for railway dc traction systems, consisting of a dc vacuum circuit breaker with a superconducting fault-current limiter (SFCL). To this end, a 1.5-kV dc circuit breaker prototype is designed, involving a dc vacuum circuit breaker and a resistive-type SFCL serially connected. The dc vacuum circuit breaker is developed with a commutation circuit to generate a reverse injection current, and the resistive-type SFCL is composed of yttrium barium copper oxide superconducting tape. An LC current source tested the 1.5-kV prototype, showing that, when the precharged capacitor voltage is 1.5 kV, the prospective current is 47 kA increasing at a rate of 9.4 A/μs. The SFCL limits this current to ∼3 kA (peak value), and then, decreases the current to 2 kA after 6 ms, followed by successful clearance via the dc vacuum circuit breaker. The proposed 1.5-kV circuit breaker will successfully clear short-circuit faults up to 47 kA by first limiting the prospective current and then interrupting it.

Short circuit currents show an upward trend in Multi-Terminal High Voltage (MTHV) DC systems. DC resistive type Supercon-ducting Fault Current Limiters (SFCLs) can limit short circuit currents to a much lower level to improve the stability of MTHV DC system. Superconducting tapes used for DC SFCL will quench after a short circuit current attack. Then temperature and voltage of the tapes will increase. The objective of this paper is to obtain the effects of short circuit currents on quench and re-covery properties of the superconducting tapes of DC resistive type SFCLs. YBCO tapes was chosen as investigation samples. This paper concluded that for higher short circuit currents, the temperature and the voltage of the tape was higher. The highest temperature was 379.2 K for YBCO tapes when a short circuit current of 10 kA applied for 50 ms. Recovery time of short circuit current of 10 kA was 240 ms longer than the recovery time of the short circuit current of 500 A. Quenched resistance curves gotten by experiments and analysis were similar, which proved the accu-racy of the analysis.

Quench and recovery characteristics are the most important characteristics of DC resistive type Superconducting Fault Cur-rent Limiters (SFCLs). In the normal state, the superconducting tapes of SFCLs stays in superconducting state without power loss. However, if there is a thermal disturbance energy impacts to the superconducting tapes, the tapes may be quenched, some-times even break once its temperature is too high. After the ther-mal disturbance, the tapes may recover to superconducting state again. A numerical analysis method was proposed to analyze quench propagation and recovery characteristics of the YBCO tapes based on thermal conduction theory. The objective of this paper is to obtain the influencing factors such as magnitude of thermal disturbance, transport current, material of stabilized lay-er and cooling on quench and recovery properties of DC resistive type SFCL. Numerical analysis results show that the temperature and voltage of the tape increased while the transport current through the tape and the magnitude of thermal disturbance in-creased. The quench propagation velocity was higher and the re-covery time was shorter for copper stabilized layer than stainless steel stabilized layer.

With an impressive dielectric constant of 1.43 at 77.3 K, liquid nitrogen (LN ₂ ) has the potential to be used as a promising insulation medium for next-generation power switchgear protection systems. It can potentially replace the conventionally used SF ₆ gas. We have the privilege of having firsthand knowledge of the arc conditions in LN ₂ . This paper deals with the experimental approach of first limiting the fault current using an SFCL, and then, interrupting it using the LN ₂ switch and a controlled magnetic field. This is a series of totally R&D based tests to show that the limited fault currents can be interrupted using LN ₂ as an arc quenching medium. The experiments were conducted on 50 Hz, 500 VAC. Nine-meter superconducting tapes were used to limit the prospective current of 15.7 kA into 800 Amps. The 800 Amps were tested to be interrupted using the LN ₂ switch. The electrode gaps were taken to be 35 mm for all the cases. Pure copper and aluminum alloy (Al6061) made electrodes were employed. NdFeB (N35 type) magnets were used to control the shape, size, and direction of the arc plasma. Total circuit voltages, arc voltages, SFCL voltages, arc currents, and arcing times were measured. The optical observations were done using a high-speed camera. Some very important and preliminary results were achieved. All the interruption tests were successful. The results show that the prospective currents were limited by the SFCL within 1 ms and the LN ₂ switch extinguished arcs in 2.1 ms.

With the development of a distributed generation, direct current (DC) load and energy‐storage equipment, voltage‐source‐converter‐based medium‐voltage DC systems (VSC‐MVDC) have attracted more attention due to its low power consumption, high reliability, independent power control and so on. However, VSC‐MVDC has the problem of DC fault isolation, which requires the fast‐acting DC circuit‐breakers to isolate faulty lines and ensure low cost. This problem can be solved by coordinating resistive type superconducting‐fault‐current‐limiter (R‐SFCL) and integrated‐gate‐commutated‐thyristor (IGCT) based hybrid circuit breaker. Based on this, IGCT based superconducting DC circuit breaker (SDCCB) is proposed and analysed. Combining R‐SFCL with IGCT could realise large current limiting and interruption and ensure low cost. In addition, the IGCT based hybrid DC circuit breaker (IGCT‐HDCCB) is compared with the traditional insulated gate bipolar transistor (IGBT) based hybrid DC circuit breaker (IGBT‐HDCCB) to evaluate which circuit breaker is more suitable for VSC‐MVDC. The results show that, coordination based on R‐SFCL and SDCCB, the fault current is successfully limited from 17.6 to 2.1 kA, and then interrupted within 3.8 ms. In addition, IGCT‐HDCCB overcomes the disadvantage that IGCT has less interrupting capacity than IGBT, retains the advantage of low cost of IGCT and is more suitable for MVDC system.