EPRI SCDC Cable Review Meeting Palo Alto 24 th October 2006 Meeting May 22-26th Sevenoaks UK Progress since

Sevenoaks Meeting: th May 2006 Agreed cable types: – 2 x monopoles –100% redundancy Agreed target ratings: –10 GW (2x10 GW) –2 GW (2 x 1 GW) Developed cable design spread sheet –Add BSCCO PIT characteristic: I, H, T Actions: (See Bill’s slides) –Method to determine Magnetic field and PIT current/wire at outer surface of inner conductor –Circulate spreadsheet –In parallel prepare vacuum and cryogenic info to add –In parallel to add cable losses –In parallel to add circuit parameters

Progress Since May Spread sheet: –Added magnetic field and PIT current/wire at outer surface of inner conductor –Circulated Spreadsheet and ‘instructions’ Patent proposals submitted to EPRI: ‘contraction compensation’ Produced draft DC cable ‘design primer’ Performed preliminary sensitivity study to identify limiting boundaries (to present later) Performed outline search for extrudable insulation materials

DC Cable Configuration

Bi-Pole’s Advantages: Simplest Construction, Half-Insulation Thickness and Smaller Diameter and Longer Cable Conventional Bi-Pole Designs are Unsuitable No ground return, so lose one cable, lose circuit. Mutual magnetic field is perpendicular to PIT conductor Ground conductor is added to give N+1 security No outer HTSC shield: field is not contained Mutual magnetic field is perpendicular to PIT conductors

Selected Design: Two Monopoles Ground Returns Must be Current Carriers Half insulation thickness of one monopole One third insulation thickness of a single integrated bi-pole Ground conductors are added to give N+1 security Concentric HTSC conductor: field is parallel to PIT: OK No mutual magnetic field +ve pole -ve pole Integrated HTSC Ground return conductor Integrated HTSC Ground return conductor Does this cause problems to the bridge design and control? Opposite or same polarity poles?

DC Cable Sensitivity Study: Boundary Limitations Dry cable construction, extruded insulation, can be factory HV tested, joints are simplest. Voltage and current: no restriction Fault circuit current: 2 x rated current for 1 sec and 1K rise Maximum number of tapes in one pass on present stranding machines is 150. Perhaps extend to 250? (Need to ask manufacturers). See video of cable factory. Reel: –outer diameter: 4.2m –hub diameter: 20D (D is cable OD) –Width:2.4m (could increase) –Cable net weight: 30ton (could increase). Installation: See video of cable factory – Tensile load: F=COF x Unit Mass x Length –Maximum safe load on cable= 50N/mm 2 of stranded conductor area. PIT tape: –Present BSCCO minimum bend diameter: 70mm –Will tape width conform to circumference?

Present Spread Sheet Limits for 75mm OD Conductor Show: We need more tapes than present strander machine limit of 150 tapes Optimum voltage is ~ kV

For 75mm OD Conductor: 1 GW rating is OK 2 GW: too many tapes needed

No Duct Case: 1GW Cable is OK at 70kV and above with <150 tapes Optimum voltage for min OD is 120kV Max cable length on reel is 6.2kM, but reel weight is high at 38.4t Power per poleGW 1.00 CurrentA20,00016,66614,28012,50011,11110,0008,3336,6665,000 Pole voltagekV Duct internal diameter (target)mm Area inner quench conductormm Conductor OD (entered into sheet)mm Max current per tape inner conductorA Number of PIT wires-inner conductorNumber Number of PIT layers inner conductorNumber Insulation thicknessmm Number of PIT wires outer conductorNumber Number of PIT layers outer conductorNumber Cable outer diametermm Cable unit weightkg/m Cable weight on reelT54,75153,55048,15844,82142,99642,73038,37731,82824,489 Cable length on reelm4,1074,6964,9065,1725,4825,8666,1925,7955,199

Power per poleGW 1.00 CurrentA20,00016,66614,28012,50011,11110,0008,3336,6665,000 Pole voltagekV Duct internal diameter (target)mm Area inner quench conductormm Conductor OD (entered into sheet)mm Max current per tape inner conductorA Number of PIT wires-inner conductor Numb er Number of PIT layers inner conductor Numb er Insulation thicknessmm Number of PIT wires outer conductor Numb er Number of PIT layers outer conductor Numb er Cable outer diametermm Cable unit weightkg/m Cable weight on reelkg46,91943,60741,73939,47636,19433,80531,79927,14721,942 Cable length on reelm3,3363,5783,9554,1394,2014,1774,4114,4123,837 20mm Duct Case: 1GW Cable is OK at 70kV and above with <150 tapes Optimum voltage for min OD is kV Max cable length on reel is 4.4kM, but reel weight is OK at 27-32t

Power per poleGW1.0 CurrentA Pole voltagekV Duct internal diameter (target)mm Area inner quench conductormm Conductor OD (entered into sheet)mm Max current per tape inner conductorA Number of PIT wires-inner conductorNumber Number of PIT layers inner conductorNumber Insulation thicknessmm Number of PIT wires outer conductorNumber Number of PIT layers outer conductorNumber Cable outer diametermm Cable unit weightkg/m Cable weight on reelkg Cable length on reelm mm Duct Case: 1GW Cable is OK at 70kV and above with <150 tapes Optimum voltage for min OD is kV Max cable length on reel is 2.8kM and reel weight is OK at 22-25t

1 GW with no central duct: Optimum voltage is 120kV

Minimum voltage is 70kV, OK for <150 wires

At optimum 120kV only need 76 wires, so can double current and power to 2GW?

1GW Study Conclusions: To achieve 5 GW need: 5 x Increase in current per tape, or a very long factory strander, or a multi- pass application?

1GW: Unit weight falls with voltage

1GW with no central duct: very long length is possible

120kV Constant Voltage and Increment Current and Power with BSCCO 125A: Duct ID0mm120kV300-TapesIncrease Current Power per poleGW Current (A)A8,33010,00015,00020,00025,00030,00035,00040,00045,000 Pole voltage (kV)kV120 Duct internal diameter (target)mm Area inner quench conductormm ,0891,225 Conductor OD (entered into sheet)mm Max current per tape inner conductorA Number of PIT wires-inner conductorNumber Number of PIT layers inner conductorNumber Insulation thicknessmm Number of PIT wires outer conductorNumber Number of PIT layers outer conductorNumber Cable outer diametermm Cable unit weightkg/m Cable weight on reelT38,24639,32944,77550,32550,30250,70253,62855,97956,995 Cable length on reelm6,1875,2964,1873,6282,9342,4652,2782,0861,888 Rings on reelNumber Flakes on reelNumber Reel hub ODmm Reel external widthm2.4 Reel Flange ODm4.2 At 150 tape limit can achieve 1.8GW At 316 tape limit can achieve 3.6GW At 450 tape limit can achieve 5GW At 5GW, reel length falls to 2km At 5GW, reel weight is high at 56.5t