High Tc superconducting (HTS) Cables are expected as a new technology to transmit large amount of electricity in a compact size with lower loss. There are many projects to demonstrate their performance and reliability in the grid around the world. Demonstrations of the cables include those with up to 275 kV in voltage and up to DC 10 kA in current. Maximum capacity is more than 1 GVA and length is in the km order. Therefore, their commercialization is expected to occur in the near future. This report shows the present development status of HTS cables outside Japan in the USA, Europe, Korea and China.
There are expectations for high-temperature superconducting (HTS) power cables as compact cables with large capacity and low-loss power transmission. Recently, the stable manufacture of many long REBCO (RE = rare-earth element) tapes has been achieved. REBCO tapes have a high critical-current density, and the AC loss resulting from the parallel magnetic field is extremely small because of the thin-film structure of the superconducting layer. The basis of the Materials & Power Applications of Coated Conductors (M-PACC) project is to develop a process technology for fabricating REBCO tapes and promote development aiming toward the commercialization of superconducting cables using REBCO tapes. Two types of HTS cables are being developing as part of this project. These cables have superior transmission efficiency, lower loss and larger capacity than existing power cables. One is a 66 kV/5 kArms three-core large-current cable and the other is a 275 kV/3 kArms single-core high-voltage cable. There are several development targets. We examined factors such as AC loss, thermal characteristics of the cables under overcurrent and the optimum cable design. The cable systems of the above mentioned two kinds of cables were developed by combining the above elemental technologies and verifying the performance. This paper provides an overview of the project and describes its results.
The high-temperature superconducting (HTS) cable demonstration project is now underway at Asahi substation in Yokohama city. This project aims to operate a 66 kV, 200 MVA HTS cable system in a real power network of the Tokyo Electric Power Company in order to verify its reliability and stable operation. A 240-meter-long HTS cable was successfully installed and other system components-such as a cable-to-cable joint, terminations and a cooling system-were also constructed at the substation. After several completion tests and performance tests of the system, the cable was connected to a real grid, and the ingrid demonstration began on October 29, 2012. So far, the cable system has been operating quite well despite the fluctuations of the transport current or the climate change.
DC electric railway systems are widely used in Japan, including in metropolitan areas. However, they have some problems, such as limited use of regenerative brakes and energy losses. In order to solve these problems, and to attain the essential energy savings for next-generation electric railway systems, we have been studying the feasibility of applying superconducting power cables to DC electric feeder systems. In this study, investigations regarding effective use of regenerative brakes, loss reduction, etc., have been carried out on the assumption that the substations concerned are connected with each other by superconducting power cables placed in parallel with the feeder line. This research was supported by the Japan Science and Technology Agency, JST, under the strategic promotion of innovative research and development.