dc Superconducting Power Transmission Line in Chubu University

1. dc Superconducting Power Transmission Linein Chubu University Presented by S. Yamaguchi yamax@isc.chubu.ac.jp

2. Contents Introduction of HTS Power cable Present status of ac power cable system DC Power Transmission System Proposal of dc superconducting power transmission system

3. Start of ac Power Transmission Started by Sumitomo in Japan Replace of Copper cable High current density of HTS cable Low Cost of civil engineering Good for Metropolitan Area, like New York & Tokyo

4. Present System of ac Power Transmission superconducting ac cable

5. Goal of ac Power Transmission normalized loss Low Loss Cable Main loss is due to AC losses! Power is consumed by Cryo-cooler goal copper cable HTS cable 4 times Higher @present time From memo of Sumitomo in 1990’s

6. ac Power Transmission Projects From memo of Sumitomo

7. NEDO 500m Cable Project 2001 2005 Fiscal Year Project is terminated March, 2005!

8. Present Cable Projects in the World US several projects in NY and Long Island Korea KEPRI, now installing by Sumitomo China InnoST & Universities These are all ac cable projects!

9. Present Summary of ac HTS Cables Reduce ac Losses ~ 1/4 is required Reduce the Cost ~ 1/10 is required Reduce heat leak ~ 1/3 is required Reduce Pressure Drop How to re-start the National Project in Japan! Review and Check Basic Ideas

10. Proposal of dc SC transmission line y0: Initial cost of ac Cu cable system y1: Initial cost of dc Cu cable system High Inverter Cost x0 ~ 300 km for present system y2: Initial cost of dc SC cable system Inverter, Cryo-cooler Costs for long distance, ac Cu cable < dc Cu cable < dc SC Cable

11. dc Power Transmission in World Gotland 98km 260MW Quebec-NewEngland 1486km 2250MW Nelsonriver 240km 500MW Vancouver Ekibasutsuusu-centa 2400km 6000MW Vienna 600MW Ninamifukumitsu 300MW Inter-mountain 785km 1920MW Shyanghai 1046km 1200MW Pacific intertie 1361km 1100MW Crosschannel 70km 1000MW Ultra high Voltage system Long distance system Many system in all over the world Newzealand 617km 1240MW 総合電気雑誌 OHM 1999 / 1 p.45 図１より引用

12. Development of Electric Power US - GRID2030 300GW until 2020 dc transmission for long distance China 150GW is underconstruction now. 18GW/year until 2020

13. dc transmission system Merit & demerit Advantage for long distance High utilization factor Available for different frequency High cost by Inverter

14. Low cost Inverter(1) Development of low cost inverter - Application of Hybrid car’s Inverter Battery- dc Motor -ac in Toyota Prius VVVF inverter Low Cost ! Less than 1/10

15. Low Cost Inverter(2) Inverters of Electric Vehicle and Power Cables dc power transmission: High Voltage/series connection EV : Low Voltage / series and parallel connection High switching freq. ⇨ low higher harmonics 　　　　　　　　　　 ⇨ high efficiency & low loss ⇨ hard serial connection

16. Low Cost Inverter(3) Inverter for SC Cable & connection • Thyrister is used for power transmission line, and its voltage and current are ~ 4 kV and ~3 kA • IGBT is used for EV, and its voltage and current are 1.7 kV and ~ 100 A • Ic of Bi-2223 tape is ~100A in the present time • Insulated and individual connection of the tape and the inverter is better to avoid the current imbalance and for the control and monitor. EV’s inverter is better for the parallel connection of Inverter and HTS Tape, But higher voltage is better now.

17. dc Copper cable Honshu-Hokkaido Power Cable, Japan Ultra High Voltage: ±250kV Relative Low current: 1kA Single Phase cable Oil Cooling Cable Structure is similar to SC cable!

18. Subjects of dc SC cable system Keep low temperature for long distance ↓ High Thermal Insulation Low Pressure Drop & Low Cost Cable ! No ac Losses! High current density is achieved!

19. Criticism of Sumitomo’s SC cable Electric Insulation isolate the SC from coolant Low Thermal Insulation High Pressure Drop

20. Criticism of Furukawa’s SC cable No transport current in shield layer (high cost) Low Thermal Insulation High Pressure Drop Hard to reduce the cost!

21. Our design of SC cable No Shield Layer (low cost) High Thermal Insulation (electric and thermal insulator) Lowest Pressure Drop (Gas and oil pipe line structure)

22. Connections of Current Lead, HTS tape and Inverter Management of Cable System Contorl of Strand Current(Insulated HTS tape) Small inverter connects insulated strand Monitor the individual voltage of Strand

23. Connection of dc SC cable system dc Single Phase connection for SC cable and Low Cost!

24. dc SC cable connection Management of Cable System Contorl of Strand Current(Insulated HTS tape) Small inverter connects insulated strand Monitor the individual voltage of Strand

25. Electric Power Storage Power Grid can Store Electric Power! High current for Superconducting cable high current and high inductance is better to store the electric power

26. Low Cost & SMES Pipe Line Iron Core Pipe ↓ Magnetic Shield High Inductance Low Cost High Mechanical Strength Storage Energy ~ 230MJ for 20kA, 100km

27. PCL application High Current, but High heat Leak Peltier Current Lead Heat leak for 77K unit(mW/A) We plan not to use liquid N2 to reduce the heat leak at current lead.

28. Reality of dc SC cable system • Many dc Power Transmission Projects and Plan in US, China, Russia and Middle East • Low cost Inverter is developed in Japan • Enough high current density for Bi-2223 tape conductor • Need to develop cable cooling for long distance • Electric Power Storage function

29. Present Experimental Plan Length < 15 -20 m Current > 2 - 4 kA 40 HTS Tapes of Sumitomo Ic > 130 A @ 77K Voltage > 10 - 30 kV Temp. < 77K (sub-cool N2 & slush N2) From 2005.4 to 2010.3 Layout in the experimental room

30. Present Collaborations & Goal Japanese several Universities materials, design, basic test & experiment calculation Two Private Companies in Japan Cryo-cooler system, cryostat for cable goal Re-start the National Project in Japan

31. Back to Edison ! Use dc power ! Realize a Realistic SC System through Collaboration from all over the world!