May 18, 2012
Furukawa Electric Co., Ltd. is conducting long-term loading cycle tests of superconducting power cables with the world’s highest voltage class of 275 kV at Shenyang Furukawa Cable Co., Ltd. in Shenyang City, China. The tests are conducted within the framework of the Project for Technological Development of Yttrium-based Superconducting Power Equipment (Project leader: Yuh Shiohara, Director General, Superconductivity Research Laboratory) commissioned by the New Energy and Industrial Technology Development Organization (NEDO). We have laid a high-temperature superconducting power cable with outdoor termination and intermediate joints, and verified the required performance for high-temperature superconducting power cables. The 30 m superconducting power cable was manufactured at the VISCAS Corporation’s Ichihara plant. After confirmation of initial performance, we plan to start testing in October this year.
275 kV superconducting power cable
Testing layout for 275 kV superconducting power cable
Background
Since high-temperature superconducting power cables(note 1) are capable of carrying massive amounts of electricity with low loss, the expectation is that they will make significant contributions to energy conservation and the reduction of CO2 emissions while allowing for innovative cabling that cannot be achieved with conventional technologies. Based on the premise that the energy-saving effect is greater the larger the transmission capacity, Furukawa Electric has been working since 2008 on developing ultra-high voltage superconducting power cables within the framework of the Project for Technological Development of Yttrium-based Superconducting Power Equipment, allowing for transmission of 1.5 million kW, or three times the power carried by non-superconducting power cables. Until now, the highest voltage for superconducting power cables developed in Japan and overseas was 66 kV and 154 kV respectively, so the key has been to develop a superconducting power cable and joints that could withstand high voltages. Last year we aimed to raise the voltage and we successfully developed a 275 kV superconducting power cable and its outdoor termination(note 2). To confirm long-term performance, we decided to manufacture a model cable with termination and intermediate joints, lay it at the test site to conduct long-term loading cycle tests.
Aim of Conducting Tests in China
When transmitting electricity from power plants to the point of consumption through the power lines in the backbone grid, it is the general practice in Japan and overseas to raise the voltage in the underground power cables to transmit massive amounts of electricity. Since the superconducting cables have a compact cross-section size that allows the transmission of large current, it would be possible to lay the cables in pipes instead of in tunnels, as has been the general practice for ultra-high voltage cables in the past. This is expected to reduce construction costs and shorten the construction period. Going forward, we aim to develop ultra-high voltage superconducting power cables that can be adapted to the construction of new power transmission grids. We believe that verifying the superconducting power cable in China where the infrastructure for electricity transmission is rapidly progressing will highlight the predominance of Japanese technology for superconducting power cables and boost competitive strength for the industry in international terms. This is why Furukawa Electric is verifying long-term performance by simultaneously conducting long-term load and distribution tests for superconducting power cables at Shenyang Furukawa Cable Co., Ltd., a wholly owned subsidiary(note 3).
(Note 1)Superconducting power cables
By using high-temperature superconducting wires that reach a state of superconductivity at the temperature of liquid nitrogen (minus 196ºC) in the conductor that carries the electric current, superconducting power cables can conduct large current at low loss via small cross-section areas. Compared with the transmission cables currently in use, these cables are lightweight, compact and capable of delivering large capacity transmission lines without heating. The superconducting power cable has a core called a former, which is severally wound with Yttrium-based superconducting wire tape in a spiral shape overlaid with electric insulation layers, superconductive shielding layers and protective layers to form the core of the cable. The cable core is packed into insulated tubing.
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(Note 2)Outdoor termination, intermediate joints
The termination and intermediate joints are required fittings for connecting superconducting power cables. The termination is a terminal that is installed at the cable end to connect with electric equipment installed at room temperature. The intermediate joint connects superconducting power cables to each other and is necessary when laying cables over long distances. Since the superconducting power cable is cooled by liquid nitrogen and the conductor is exposed to high voltages, the joints must feature heat insulation for liquid nitrogen temperatures and room temperatures, as well as electric insulation for earth and high voltage.
(Note 3)Shenyang Furukawa Cable Co., Ltd.
Established as a joint venture between Furukawa Electric Co., Ltd., Shenyang Cable Co., Ltd., and Itochu Corporation in 1995. Became a wholly owned subsidiary of Furukawa Electric in 2003, taking us to the present. The company owns a plant in Shenyang City, China, and manufactures, sells and installs ultra-high voltage power cables ranging from 66 kV to 500 kV as well as joints and other equipment. Furukawa Electric has transferred product designs, manufacturing and quality control technologies to the company, making it China’s No. 1 manufacturer of ultra-high voltage power cables.
