Hiroyasu Yumura

Electric properties of a 66 kV 3-core superconducting power cable system

A 100 m-long, 66 kV, 3-core high temperature superconducting power cable system prototype has been developed and installed in order to verify its properties and performance for practical use. The cable is a cold dielectric type with three cable-cores placed in co-axial stainless corrugated pipes. After cooling the cable to LN/sub 2/ temperature, long duration tests, such as that for nominal current-voltage loading and that for load fluctuation, were performed for a one-year period. The cable was warmed to room temperature after each test to investigate the influence of the heat cycle. Critical current was more than 2.7 kA at 77.3 K, and AC loss was 0.7 W/m/phase at 1 kArms. The magnitude of shielding current was almost equal to the transport current. Capacitance, dielectric losses and other electric properties were also measured. All values showed no change during the tests, and were in good agreement with calculated expectations.

Design and experimental results for Albany HTS cable

The Albany Project plans to install a 350 m High Temperature Superconducting (HTS) cable in the power grid of the Niagara Mohawk Power Company to carry 800 Arms at 34.5 kV. The type of the cable has 3 HTS cores in one cryostat with Bi-2223 used for HTS conductor and shield layers. The three cores are housed within double SUS corrugated pipes which provides thermal insulation. The tapes are manufactured with a new innovative sintering method with controlled over pressure (CT-OP) technology. Polypropylene laminated paper (PPLP) is used as electrical insulation. The cable will be installed in long underground conduit. A cable joint will be made in an underground vault to connect a 30 m length of the cable with the remaining 320 m. The original Bi-2223 30 m cable will be replaced with a 30 m YBCO cable after long-term operation. The terminations at both ends of the cable will have three bushings in a cryogenic vessel. Typical performance evaluation experiments, such as cable bending tests, voltage tests, and fault current tests, have been conducted with sample cables to check the design. Voltage tests for 69 kV AC and 200 kV impulse were successfully applied to a 5 m cable in accordance with the Association of Edison Illuminating Companies (AEIC) code of 35 kV class cable. The cable will be manufactured and installed in 2004 and 2005, then, long-term operation will be started.

Phase II of the Albany HTS Cable Project

High-temperature superconducting (HTS) cable systems are expected to be a solution for improvement of the power grid and three demonstration projects in the real grid are underway in the United States. One of these is the Albany, NY HTS Cable Project, involving the installation and operation of a 350 meter HTS cable system with a capacity of 34.5 kV, 800 A, installed between two substations in National Grids electric utility system. A 320 meter and a 30 meter cable are installed in an underground conduit and connected together by a joint, or splice in a vault. In Phase I of this project, the cables were fabricated with DI-BSCCO wire in a 3-core-in-one cryostat structure. After the installation of the HTS cable system, the in-grid operation began on July 20, 2006 and operated successfully in unattended condition through May 1, 2007. In Phase II, the 30 meter section was replaced by a 2G (YBCO) cable. The 2G cable was fabricated with SuperPowers YBCO coated conductors in a 3-core-in-one cryostat. After replacement of the 30 meter section, the joint and one termination were reassembled and the commissioning tests that included initial cooling, critical current measurement and DC withstand voltage test were completed successfully. After the commissioning tests, the HTS cable system with a 30 meter YBCO cable and a 320 meter DI-BSCCO cable was re-energized on January 8, 2008 and started again to operate in a live utility network. This paper describes the latest status of the Albany HTS cable project.

Fabrication and Installation Results for Albany HTS Cable

The Albany project has installed a high temperature superconducting (HTS) cable with a 350 m length in 34.5 kV and 800 Arms in the real power grid of the National Grid Power Company. The type of the cable is a 3 cores in a cryostat. Bi-2223 wires manufactured with SEI new sintering method, CT-OP, is used as both superconducting conductor and shield. The Cable was manufactured and shipped to the Albany test site after passing various tests such as Ic measurement, voltage tests, pressurized tests, and so on. Cable installations into a 320 m long conduits and a 30 m long conduit under ground was completed successfully. The cable was pulled with 2.5 ton tension, which is within its allowable limit. A joint between the 320 m cable and the 30 m cable was assembled in an underground vault. Cable terminations were also assembled at both ends of the cable. After all of the installation, the initial cooling was conducted successfully and then in-grid operation was started on July 20th in 2006 after confirmation of cable performance.

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.

Status of Superconducting Cable Demonstration Project in Japan

The HTS cable demonstration project, called the Yokohama Project, supported by Ministry of Economy, Trade and Industry and the New Energy and Industrial Technology Development Organization, was initiated in Japan in 2007. The aim of this project is to operate a 66 kV, 200 MVA high-temperature superconducting (HTS) cable in a network of the Tokyo Electric Power Company to demonstrate cable reliability and stable operation. Total project period was changed from 5 years to 6 years. Chosen as the demonstration site was the Asahi substation in Yokohama. Based on the analysis of the network conditions of the demonstration site, specifications of the HTS cable system were determined. Element technologies were developed and various preliminary tests using short core samples were conducted to confirm the HTS cable design. A 30-meter HTS cable system was manufactured and tested prior to initial demonstration tests. Long-term demonstration tests of the HTS cable system in an actual grid at the Asahi substation are scheduled to be started in 2011.

Testing and Demonstration Results of the 350 m Long HTS Cable System Installed in Albany, NY

The Albany Cable Project team (BOC, National Grid, Sumitomo Electric, SuperPower) have built and tested a 350-m long HTS cable and cryogenic system rated at 48 MVA (800 Arms, 34.5-kV). The cable system included the worlds first demonstration of an HTS cable-to-cable joint (or splice) as well as some novel design aspects in both the cryogenic refrigeration system and the terminations. The cable was installed and began operation in July 2006. This paper will summarize the testing and operational aspects of the HTS cable system and its integration into the existing national grid 34.5-kV network.

Verification tests of a 66 kv HTSC cable system for practical use (first cooling tests)

Abstract Tokyo Electric Power Company and Sumitomo Electric Industries, Ltd. have been jointly developing elementary technologies for an high temperature superconducting (HTSC) cable system, such as conductor wound with HTSC wires, thermal insulation pipes, terminations and so on. Verification tests of a 100 m HTSC cable system integrating these elementary technologies have been conducted in collaboration with Central Research Institute of Electric Power Industry (CRIEPI) to verify its long term electric and cryogenic properties. The cable conductor is composed of four layers of Bi-2223 wires wound spirally around a former. Polypropylene laminated paper impregnated with liquid nitrogen is adopted as cable insulation for its properties of high insulation strength and low dielectric loss. HTSC wires are also wound around the electrical insulation to form an electrical and magnetic shield. To reduce heat invasion from ambient temperature part, multi-layer insulation is wound between the co-axial stainless corrugated pipes where high vacuum is maintained. The cable was partially installed into a ∅ 150 mm duct and formed in a U-shape. Each end has a splitter box and three terminations. The cable and the terminations are cooled using two separate sets of a pressurized and sub-cooled liquid nitrogen cooling system. The cable has been developed and laid at CRIEPIs test site and long-term tests have been under way since June, 2001. This paper presents the design of the cable and some results of the first cooling tests.

Update of YOKOHAMA HTS Cable Project

The high-temperature superconducting (HTS) cable demonstration project supported by Ministry of Economy, Trade and Industry and New Energy and Industrial Technology Development Organization 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-m HTS cable system with terminations, a splice, and a cooling system was installed in the SEI facility and confirmed the cable has good performances as design. The HTS cable, splice box, and termination vessels have been manufactured with the same design of a 30-m cable system. By now, the HTS cables have been installed into the conduit at the Asahi substation of Tokyo Electric Power Company. The constructions of splice and terminations have been completed. The HTS cable system at Asahi substation was cooled down in this spring. This paper describes the design and completion test results of the HTS cable system.

Scale up of applications-ready practical Y-Ba-Cu-O coated conductors

YBa/sub 2/Cu/sub 3/O/sub x/ (YBCO) coated conductors have been produced in 100 m lengths in pilot scale facilities established at SuperPower. In addition to scaling up coated conductors to long lengths with high critical current, we have modified the basic conductor for enhanced in-field performance and low ac losses. In addition, our coated conductors have been produced in practical configurations in 4 mm widths and with a surround copper stabilizer. The conductors were slit first to a 4 mm width and then subjected to electroplating to apply the copper stabilizer. Mechanical and electrical properties of the complete conductor have been elaborately tested. 61 m of 4 mm wide, surround copper stabilized conductor was provided to Sumitomo Electric Industries who fabricated a 1 m cable using the conductor. The cable exhibited the lowest ac losses reported with HTS conductors. SuperPower also fabricated a pancake coil with 7.4 m of coated conductor, which generated a maximum magnetic field of 0.28 T at 77 K.