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.

Traditional electrical method for measuring AC loss in superconducting coil can perform well only when the high temperature superconducting (HTS) coils work with sinusoidal current. But due to the existence of harmonics, the working currents of some HTS power devices are not pure sinusoidal wave but periodic non-sinusoidal current. In order to obtain the AC loss under various periodic currents, integral method is applied in this paper. Experiments for measuring the AC loss in a coil wound from SCS4050 coated conductors are performed. AC loss measurements under sinusoidal currents, triangular currents and two highly distorted currents are investigated to explore advanced techniques for measuring the AC loss under periodic currents. The measurement results with integral method are compared with those by lock-in amplifier and those calculated by finite element model (FEM) to prove that the integral method has a high reliability. The results also show that the measured losses are dependent on the current frequency and waveform. This study widens the measuring range of electrical method. It can be employed to measure the AC loss of HTS devices under various periodic current.

Traditional electrical method for measuring AC loss in superconducting coil can perform well only when the high temperature superconducting (HTS) coils work with sinusoidal current. But due to the existence of harmonics, the working currents of some HTS power devices are not pure sinusoidal wave but periodic non-sinusoidal current. In order to obtain the AC loss under various periodic currents, integral method is applied in this paper. Experiments for measuring the AC loss in a coil wound from SCS4050 coated conductors are performed. AC loss measurements under sinusoidal currents, triangular currents and two highly distorted currents are investigated to explore advanced techniques for measuring the AC loss under periodic currents. The measurement results with integral method are compared with those by lock-in amplifier and those calculated by finite element model (FEM) to prove that the integral method has a high reliability. The results also show that the measured losses are dependent on the current frequency and waveform. This study widens the measuring range of electrical method. It can be employed to measure the AC loss of HTS devices under various periodic current.