Site:           Super-GM Test Facility
                Engineering Research Association for Superconductive Generation Equipment and Materials (Super-GM)
                Kansai Electric Power Company
                Umeda UN Bldg. 2F
                5-14-10 Nishi-Tenma, Kita-Ku
                Osaka 530, Japan
Date Visited:   6 June 1996
WTEC Attendees: R.D. Blaugher (report author), 
                J. Daley, 
                G. Gamota, 
                P.M. Grant, 
                H. Morishita, 
                R. Schwall, 
                R. Sokolowski
Hosts:          Takasuke Ageta, Managing Director
                Makoto Kusuma, Senior Manager, System Department
                Tatsumi Ichikawa, Senior Manager, Engineering Department
                Hiroshi Kayama, Manager, Testing Center
                Katsuyoshi Toyada
                Noriyuki Yoshida
                Akio Katagiri
                Kouichi Ezaki
                Koichi Inoue
                Masamichi Chiba

BACKGROUND

In 1996 the Engineering Research Association for Superconductive Generation Equipment and Materials (Super-GM) entered the final installation, testing, and verification phase for the 70 MW-class superconducting generator model machine development. This program has been aimed at establishing technologies for the design and manufacture 200 MW-class pilot machines. This program, started in 1988, is administered by the New Energy and Industrial Technology Development Organization (NEDO) as part of the New Sunshine Program of AIST (Agency of Industrial Science and Technology) of MITI (Ministry of International Trade and Industry). The Super-GM program (Fig. Super-GM.1) involves 16 member organizations with representation from the electric utilities; manufacturers of electric power equipment; companies involved in both LTS and HTS research and manufacturing of wire and tape; refrigeration and cryogenic suppliers; and independent research institutes such as CRIEPI, which has assisted Super-GM with benefit and system analysis and electrical analysis for the stator and rotor.

Additional support on collaborative research and consulting is provided by universities and national research organizations such as the Electrotechnical Laboratory (ETL), which has provided basic research and technology assessment. NEDO provides direct funding to Super-GM in support of the generator design, construction, and test; conductor research on both LTS and HTS; the refrigeration system; and the total system integration and test. The 1996 budget of approximately $26 million was down from a peak in 1995 of $39 million. The manpower for the total effort averaged approximately 250 people/year from 1991-1996. MITI/AIST provided nearly $254 million in funding between 1988 and 1996. This figure has been complemented by additional support from member companies in what amounts to cost sharing of 20-50% of the contracted amount. The salaries for the technical staff assigned to the Super-GM organization in Osaka, for the most part, are directly paid by the individual companies (at approximately 250 people/year, the salaries alone would be $30-40 million). These staff members are rotated from the member companies on a two- to three-year basis, except for three persons, including Takasuke Ageta, the managing director.

Fig. Super-GM.1. Organization of the Super-GM program.

VISIT TO THE SUPER-GM TEST FACILITY

Team B of the WTEC panel visited the Super-GM test facility under final construction at the Osaka Power Station of the Kansai Electric Power Company (KEPCO). The team was hosted by the managing director, Takasuke Ageta, and key members of the Super-GM organization involved in the construction and generator testing. Figure Super-GM.2 shows the test facility for the model machines, and Fig. 2.2 (page 16) shows its schematic layout. The construction work, started in June 1994, was nearly complete at the time of the WTEC team's visit. The first rotor (designated "slow-response excitation type A") and the "common" stator, both constructed by Hitachi, were delivered and installed in early 1997, with plans for five months of testing starting in June 1997. The schedule planned on testing all three rotors through 1998. Following the Hitachi rotor, the Mitsubishi rotor ("slow response B") and the final ("quick response") rotor from Toshiba will be installed and tested. The Nb-Ti conductor for these three rotors was supplied, respectively, by Hitachi Cable (slow-response A), Sumitomo (slow response B), and Furukawa (quick response). The schedule called for testing of all three rotors through 1998.

As shown schematically in Fig. 2.2, the Osaka verification test facility uses a back-to-back motor-generator (M-G) test method, with the addition of an induction motor that is used to bring the M-G up to synchronous speed. The helium refrigeration system constructed by Mayekawa is a 100 l/hour closed cycle turbine-expander, screw compressor system. External LN₂ is used for additional precooling in the high temperature cold box heat exchanger. A preconditioning liquid He Dewar is used as a buffer to supply liquid to the generator. The first rotor and stator from Hitachi were factory tested at Hitachi prior to shipment to the test site. The second rotor from Mitsubishi likewise was also undergoing final testing at Mitsubishi's Kobe Works.

Fig. Super-GM.2. Schematic of the Super-GM test facility located at Osaka Power Station.

SC GENERATOR BENEFITS AND MARKET PROJECTIONS (PER SUPER-GM AND NEDO)

The 70 MW-class Super-GM effort is considered a "model" machine to establish technologies for design and manufacture of a 200 MW-class pilot generator. If the 70 MW class is successful, a future program targeted at 200-300 MW will be considered. The latter program would not provide 100% government support for manufacture. It is anticipated that the cost for a SC and a conventional machine would be nearly identical, at a 200-300 MW rating, using a 20-year lifetime. At present, the major advantage for SC generators is thought to be related to performance advantages for the power system, specifically with respect to steady state and transient stability, improved reactive power capability, and improved ability to tolerate negative sequence fields. It is also estimated that SC generators would lead to a ~30% increase in the power transfer limits for the transmission system. Additional benefits are the typical increase in efficiency of 0.5 - 1% and reduction in size and weight of ~50%. SC generators would also provide environmental advantages due to reduced oil consumption and reduction of CO₂ emissions. The forecast for sale of SC generators, with introduction expected by 2005, using only the national market for Japan, was estimated at $440 million/year for 20-30 units in the 200-600 MW range and ~2 units at 1 GW.

LTS AND HTS WIRE AND TAPE RESEARCH

The Super-GM research on superconducting wire and tape in support of power apparatus development has been conducted in parallel with the generator research since 1988 on both LTS and HTS conductors. The LTS effort has primarily focused on the development of low ac loss conductors for three different applications; an armature winding (Furukawa), a shunt reactor (Sumitomo), and a fault-current limiter (Hitachi). Three different types of Nb-Ti stranded wires with ~0.1 µm filaments and Cu-Ni matrix were developed by the identified manufacturers for the respective applications. The conductors showed reduced ac losses with acceptable current-carrying capacity of 2-3 kA.

APPROACHES FOR OBTAINING LOW AC LOSS

Approaches for obtaining low ac loss Nb₃Sn were also followed involving six different manufacturing processes: (1) the bronze process (Furukawa), (2) internal Sn (Sumitomo), (3) in-situ (Fujikura), (4) tube (Showa), (5) external diffusion (Hitachi Cable), and (6) powder metallurgy (Kobe Steel). The Nb₃Sn processed conductor, in general, was not as good as the Nb-Ti, having nearly one order of magnitude higher hysteresis loss than the Nb-Ti. The transport current was also lower than Nb-Ti at 1-2 kA. The normalized ac quench current at 50 Hz under a dc magnetic field of 0.5 T versus the cross-sectional area of the stranded wire (A_rms/mm²) was roughly equivalent at 200-500 for both Nb-Ti and Nb₃Sn conductors. The Nb-Ti in general showed a lower ac loss than the Nb₃Sn at 50 Hz, ± 0.5 T. The Super-GM HTS research on oxide wire and tape development is oriented primarily at the future ability to apply HTS conductor to power apparatuses, including SC generators. The realization of an HTS conductor would simplify the cryogenic design. The basic design approach for an HTS rotor would be nearly identical to an LTS design.

The HTS wire effort, which also started in 1988, was at the time of the team's visit following 6 approaches:

1. Under long wire progress, Furukawa using a "multipipe" method for fabricating Bi-2223 has produced 300 m, I_c = 4.4 A, with a low Ag ratio of 1.3.
2. A Bi-2212 tape of 250 m was fabricated by rolling using Bi-2212 laser pedestal rods and silver matrix, a 100 m test length showed ~5A at 77 K.
3. Hitachi produced 100 m, thallium-free precursor on 50 µm Ag tape. Subsequent thallination produced a Tl-1223 thick film with I_c of ~5 A at 77 K for a 10-meter length.
4. The large current progress produced a Bi-2212 laser pedestal rod fabricated by Sumitomo with an I_c value of 4.1 kA at 77 K.
5. High current density progress was reported by Fujikura using laser deposition on a polycrystalline metal tape with a biaxial aligned YSZ buffer layer. J_c of ~1.1 x 10⁶ A/cm² was observed at 77 K and just over 10⁵ A/cm² at 5 T.
6. A long length of ~1 m also showed 10⁵ A/cm² at 77 K.

Large area deposition progress for fault-current limiters reported two techniques: ionized cluster beam deposition (Toshiba) of Y-123 on SrTiO₃, which showed I_c of 60 A, and CVD (Mitsubishi) of Y-123.

Additional information on the Super-GM project can be obtained from several related publications presented at the ICEC 16/ICMC in Kitakyushu, Japan (May 20-24, 1996).