Furukawa Electric Develops the World's Highest Standard for High-Temperature Superconducting Cables

As part of the NEDO project related to the technological development of superconductivity, Furukawa Electric's research team and others have developed high-temperature superconducting cables^{(Note 1)} that enable power transmission at 275kV and 1.5 million kVA, which is the highest level of superconducting power transmission in the world. They have also developed an aerial terminal connector and an intermediate connector^{(Note 2)} for connecting with electrical equipment, and conducted demonstration tests at Shenyang Furukawa Cable Co., Ltd.^{(Note 3)} in Shenyang, China. In the demonstration test, a long-term current load was conducted in an acceleration test equivalent to 30 years,^{(Note 4)} which successfully confirmed the soundness of the cable and connectors.

Technological development of superconducting power transmission cables has mainly focused on 66kV so far. However, demand has increased, mainly overseas, for cables capable of power transmission at even higher voltages. The establishment of these technologies is expected to lead to the adoption of these cables and connectors as a new infrastructure, not only in Japan, but also in other countries.

Overview

In order to realize a stable and efficient power supply system, which forms the basis of economies and societies, it is necessary to establish technologies to control power systems appropriately and stabilize the power supply, as well as highly efficient power transmission technologies to transport generated power without loss. In the Technological Development Project for Yttrium Superconducting Electrical Systems (project leader: Yu Shiohara, Director of the International Superconductivity Technology Center), NEDO has been working on developing superconducting cables, superconducting transformers, and other electrical equipment that uses high-temperature superconducting wires from rare earth oxides—of which a typical example is yttrium (generally referred to as yttrium superconducting wires)—which are expected to result in compact large-capacity power supply by utilizing the global cutting-edge superconductivity technologies that have been derived from the past technological development.

Current load tests are conducted as part of the project. For the 275kV high-temperature superconducting cable system, Furukawa Electric created high-temperature superconducting cables based on the following design specifications, utilizing the yttrium superconducting wires^{(Note 5)} developed for the project: a diameter of 150mm, a transmission loss of 0.8W/m, and a voltage of 275kV. A system measuring 30m in total length was built in Shenyang, China.

After confirming the cable's initial performance in mid-October 2012, the cable was loaded with a 3kA current at a voltage of 200kV, completing the monthlong test at the end of December of that year. The cable was then loaded with a voltage of 310kV to confirm that no partial discharge could be seen from the deterioration of the cables. The results confirmed the soundness of the cable, aerial terminal connector, and intermediate connector.

Future prospects

Based on the results of this technological development, NEDO intends to continue striving to put these superconducting cable systems to practical use in the hopes of helping to resolve global environmental issues.

Furukawa Electric plans to obtain a number of detailed design data necessary for this practical application by conducting further tests under different conditions and long-term current load tests, as part of its efforts to put superconducting cables to practical use.