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Newsletter "SEI NEWS" 2012

Home > Company Information > SEI WORLD > Back number > Vol.423

[Newsletter "SEI NEWS" Vol.423]

Japan’s First High-Temperature Superconducting Cables Interconnected with Power Grid

Three-cores-in-one-cryostat (3-in-One) type superconducting cable

On October 29, Japan’s first demonstration of a high-temperature superconducting cable interconnection with the power grid began at Tokyo Electric Power Company (TEPCO)’s Asahi Substation (Yokohama City), using Sumitomo Electric’s high-temperature superconducting cables.

This demonstration is part of NEDO’s ※1 joint research High-Temperature Superconductor Cable Verification Project implemented as a seven-year plan, which commenced in 2007. In this project, high-temperature superconducting cables approximately 240 m in total length are installed at TEPCO’s Asahi Substation and interconnected with the power grid to test the performance, reliability and stability of high-temperature superconducting cables in an existing electricity transmission grid.

The demonstration uses high-temperature superconducting cables of the world’s highest capacity (200,000 kVA class) among three-cores-in-one-cryostat type ※2 superconducting cables. The wires are made of improved bismuth-based high-temperature superconductor DI-BSCCO ※3, which was originally developed in 2004 by Sumitomo Electric.

※1. NEDO:
New Energy and Industrial Technology Development Organization

※2. Three-cores-in-one-cryostat type:
Three high-temperature superconducting cable cores are placed in a single thermal insulation pipe.

※3. Improved bismuth-based high-temperature superconductor DI-BSCCO:
Sumitomo Electric improved its original bismuth-based high-temperature superconductor Dynamically Innovative (DI)-BSCCO in 2004 on the basis of NEDO project results. Its slim wire construction reduces AC loss. BSCCO stands for oxide superconductor Bi2Sr2Ca2Cu3O10, a compound of bismuth (Bi), strontium (Sr), calcium (Ca), copper (Cu) and oxygen (O).

■Overview

Electricity supply systems serve as an important social infrastructure. To use superconducting cables in the electricity supply system, in this project, a superconducting cable system has been built, integrated with cooling technology. Used as a basis for the design are existing superconducting cable development results achieved through NEDO’s development of technology. The demonstration that tests interconnection with the actual grid is intended to verify the overall reliability of a total system comprising cable installation, operation and maintenance as well as of discrete superconducting cables. The project also aims to develop and test innovative high-efficiency power transmission technology.

The goal of the project is to create an initial market for superconducting cables and develop new industries through development of technology for stable and high-efficiency electricity supply.

Superconducting cable installation

■Project Results

Terminal connections

Using Sumitomo Electric’s low-AC loss bismuth wires, the project tested AC loss in short cables and the soundness of the power grid in an accident. Moreover, based on the test results, a 30 m class three-cores-in-one-cryostat type superconducting cable was designed and produced, technology was developed for high current carrying terminal and intermediate connections, and the performance of these products was assessed.

In a joint effort with TEPCO, we designed and built superconducting cable, operation and monitoring systems and constructed a protection/shutoff system connecting the superconducting system to the existing grid at the test location, TEPCO’s Asahi Substation. Mayekawa Manufacturing Company designed and built a cooling system and conducted a methodological analysis for maintenance of the cooling system while power is being transmitted. These were incorporated into the demonstration superconducting cable system.

After implementing these plans, we constructed a 66 kV, 200 MVA class three-cores-in-one-cryostat type superconducting cable, designed and built intermediate and terminal connections, and built a liquid nitrogen circulation system for cooling this equipment. These were combined into the demonstration cable system at the Asahi Substation.

■Topics

Graph represents present operation.

We have posted a page on the High-Temperature Superconducting Cable Demonstration Project on our superconductivity website. For an outline of the project, the installed systems and statuses of the present and yesterday’s operation, visit the following website.

Superconductivity website (English) http://global-sei.com/super/cable_e/ingridj.html
 

Superconductivity Review

What is superconductivity?

When cooled to ultra-low temperatures, specific materials exhibit zero electrical resistance. This phenomenon is generally referred to as superconductivity. Zero electrical resistance translates to low energy loss and high current density. Hence expectations are high for the use of superconductivity in energy-saving technology.

 
Development of Superconductivity Technology at Sumitomo Electric

We began to develop superconductivity technology in the early 1960s, starting with investigation of low-temperature superconductors; we began investigating high-temperature superconductors in 1986, immediately after their discovery.
Our R&D efforts are now focused on bismuth-based superconductors (critical temperature: -163°C/110 K) and rare-earth-based superconductors (critical temperature: -183°C/90 K) as promising candidates for practical industrial applications.

 
■Features of Bismuth-Based Superconductor DI-BSCCO

In 2004 Sumitomo Electric achieved success in the mass-production of bismuth-based superconducting wire “DI-BSCCO,” by adopting a new processing technique for superconducting wire. Since then, we have mass-produced and marketed several types of DI-BSCCO to meet customer needs.

 
Point1:Low Cost

DI-BSCCO, a high-temperature superconductor, enables use of inexpensive liquid nitrogen (approximately ¥50/liter) as a refrigerant, whereas conventionally dominant low-temperature superconductors require liquid helium (approximately ¥1,500/liter).

Point2:High-Capacity Power Transmission

Comparison of cross-sectional area (for carrying same magnitude of current)

DI-BSCCO can carry approximately 200 times more electric current than copper wire.

 
■Features of Superconducting Cable Using Bismuth-Based Superconducting Wire DI-BSCCO
Point1:Ecological Performance

Electricity produced at a power plant is transmitted and distributed through electric cables to factories and households. During transmission, 5% of the electricity is lost, mainly due to cable resistance. Superconducting cable, consisting of superconducting wires, provides zero resistance. Superconducting cable can carry electricity efficiently, and is therefore eco-friendly.

Point2:Space-Saving and Economical

Comparison of conventional and superconducting cables

Since superconducting wire can carry approximately 200 times as much current as copper wire of the same cross-sectional area, a cable composed of superconducting wires can be compact in size. Superconducting cable occupies little space and does not require extensive construction work for installation. Use of superconducting cables reduces construction costs, and is therefore economical.

・DI-BSCCO is a trademark or registered trademark of Sumitomo Electric Industries, Ltd.

 
 
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