Takaharu Mitsuhashi

Experimental Results of 275-kV 3-kA REBCO HTS Power Cable

A 30-m-long 275-kV 3-kA high-temperature superconducting (HTS) cable had been developed in a national project of the Materials and Power Applications of Coated Conductors project in Japan. The design of the cable was based on the design values obtained from ac loss properties, thermal behavior under short-circuit tests, and electrical properties, such as partial discharge properties, impulse withstand properties, and dielectric properties. Through the development, the material of the cable insulation was determined and designed on the basis of its design stresses and test conditions based on the IEC, JEC (Japan electrical standards), and other HTS demonstrations. This cable was also designed to withstand a short-circuit test of 63 kA for 0.6 s and to have low losses of 0.8 W/m at 3 kA, 275 kV, including ac loss and dielectric loss. Based on these designs, a 50-m cable was manufactured and tested. The short samples obtained from 50 m were confirmed to have the designed characteristics. Furukawa Electric constructed a demonstration system of a 30-m cable with two terminations and a cable joint. The demonstration had started since November 2012 at Shenyang in China. In this demonstration, a 30-day long-term test was conducted and monitored at a current of 3 kA and at a test voltage selected to verify a 30-year operational lifetime. Removal tests revealed the superior reliability of the 275-kV HTS cable system.

Status of a 275 kV Class REBCO Superconducting Cable Development

The REBCO high-temperature superconducting cable, rated at 275 kV and 3 kA, was developed in the Materials and Power Applications of Coated Conductors project in 2008. The cable is expected to be put to practical use as a backbone power line in the future because the transmission capacity is about the same as the UHV overhead transmission line. Transmission loss is significantly reduced by using superconducting wires instead of Cu or Al conductors. Furukawa Electric plans a demonstration of the 275 kV high-temperature superconducting cable. The cable system consists of a 30-m cable, terminations, a cable joint, and a cooling system. The 30-m cable has already been manufactured and installed on a test site. In this demonstration, various electrical evaluations will be conducted, such as a long-term test under a current of 3 kA, and the test voltage will be determined assuming 30 years of insulation degradation.