Shoichi Honjo

A New HTS Cable Project in Japan

A new HTS cable project supported by Ministry of Economy, Trade and Industry (METI) and New Energy and Industrial Technology Development Organization (NEDO) has just started in Japan. Target of this project is to operate a 66 kV, 200 MVA HTS cable in a real grid in order to demonstrate its reliability and stable operation. Tokyo Electric Power Company (TEPCO) provides the real grid and studies the impact of connecting the HTS cable to the existing conventional facilities in Yokohama. Sumitomo Electric Industries, Ltd. (SEI) designs and manufactures the HTS cable, terminations and joint. Mayekawa Mfg. Co. Ltd. provides a cooling system. Total project period is planned to be 5 years. In 2007, components of HTS cable system were studied and designed. In 2008 and early 2009, the pre-system with a 30-meter cable will be installed in the factory to demonstrate basic performance of the HTS cable and its accessories. Then the 200 MVA HTS cable will be manufactured in 2009 and installed and operated at the site in 2010 and 2011. One of the technical targets in this project is to reduce the AC loss of HTS cable. For this purpose, a new type DI-BSCCO wire with twisted superconducting filaments is planned to be applied in the cable. A 1-meter cable core manufactured with the new wires shows its AC loss as less than 1 W/m/ph at 2 kArms, which is 1/4 of AC loss with normal DI-BSCCO.

Test Results of a 30 m HTS Cable for Yokohama Project

HTS cable demonstration project supported by Ministry of Economy, Trade and Industry (METI) and New Energy and Industrial Technology Development Organization (NEDO) has started in Japan. The target of this project is to operate a 66 kV, 200 MVA HTS cable in the live network of Tokyo Electric Power Company in order to demonstrate its reliability and stable operation. The design of the HTS cable with DI-BSCCO has been completed as well as those of a termination and a joint. A 30-meter HTS cable system with terminations, a joint and a cooling system was installed in SEI facility to confirm their design and performance. Various tests as voltage tests, nominal and over current tests, heat cycle tests, heat loss measurements and so on were conducted and it is verified that the cable has good performances as design. This paper describes the design and test results of a 30-meter HTS cable, and discusses required test items of HTS cables.

New HTS Cable Project in Japan: Basic Study on Ground Fault Characteristics of 66-kV Class Cables

In July 2014, a new high-temperature superconducting (HTS) cable project supported by the New Energy and Industrial Technology Development Organization began in Japan. The aim of this project is to verify and improve the safety and reliability of HTS cable systems. The main verification targets are system safety in the event of the following accidents: (1) ground fault; (2) short-circuit current; (3) cryostat failure; (4) a low heat loss cryostat; and (5) a high efficiency cooling system. If a ground fault occurs, it is a matter of concern that the pressure in the cryostat increases due to the arc energy. It is an additional concern if the arc penetrates the cryostat so that the liquid nitrogen leaks out of the cable. It is important to know the amount of energy in the arc in order to numerically predict the outcomes of a ground fault. We performed basic ground fault tests using sheet samples immersed in liquid nitrogen while measuring the arc energy and also examining the structure of a protection layer that can prevent arc penetration to the outside of the cable core.

Shield Current of 3-in-One High-Temperature Superconducting Cables

This paper discusses the shield current of 3-in-One high-temperature superconducting (HTS) cables. The cable core consists of the HTS conductor and the HTS shield, which is coaxially wound around the former. By short-circuiting the three-phase shields at both ends, electromagnetic induction makes it possible to pass a current through the shield that is nearly identical to the conductor current and opposite in phase. In the case of 3-in-One cables, in which the three cores are tightly wound, the inductivity of the shield current is heavily influenced by the winding direction and the spiral pitch of the shield. Reversing the winding direction of the multi-layer shield or designing the shield layer with long spiral pitch are both effective ways to keep inductivity high. The shield current of a 240 meter cable was measured, and the measured inductivity was comparable to the numerically simulated value.