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Funded by EPSRC

Superconducting Fault Current Limiters A. V. Velichko, T. A. Coombs Department of Engineering, Cambridge University, UK. Funded by EPSRC. Outline. Overview of the work done Physical Background and Modelling Simulation and Experiment Summary and Future Plans. Overview.

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Funded by EPSRC

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  1. Superconducting Fault Current Limiters A. V. Velichko, T. A. Coombs Department of Engineering, Cambridge University, UK. Funded by EPSRC

  2. Outline • Overview of the work done • Physical Background and Modelling • Simulation and Experiment • Summary and Future Plans

  3. Overview • Problems to be solved within the project: • FCLs are highly nonlinear devices, extensive simulation is required: • So far we have addressed: • - High-aspect ratio • - Multi-element configuration • - First Experiments(DC VACH, AC loss and Pulse Measurements) • Problems remaining to solve: • - Structural deformations (simulation and experiment) • - Overall contribution to the power network.

  4. Thermal Electrical Single FCL Structural Physical Background and Modelling (I) All Properties are NONLINEAR and INTERDEPENDENT! If done consistently & simultaneously – very time-consuming andcould befallible

  5. Physical Background and Modelling (II) EXISTINGPROPRIETARY MODEL Model takes into account: Thermal and Electrical; Need to incorporate: Structural, Multi-element • From Experiment: - Spread in Ic and n; • Strain and Stress;

  6. Physical Background and Modelling (III) • 3D model • Accounts for Inhomogeneities • Proper thermal boundary conditions • Linked Electrical and • Thermal Properties • External Elements Nitrogen boil-off

  7. Simulation (I) • We also use commercial FEM software (FEMLAB) to: • Verify the proprietary model • Simulate other features (Structural modelling) • Quick test for new geometries • So far we have used Femlab to: • Verify T and I –distribution for metals • Estimate importance of metallic substrate • Check the concept of the length scaling

  8. Simulation: verifying our model (II) FCLSimu2003D & FEMLAB Cu-block, 1*0.5*0.25 mm3, takes ~ 1 minute on P-IV, 2.4 GHz, 512 MGb RAM DT = 275.24-275.3 K DT = 260.24-260.27 K

  9. Simulation: effect of substrate (III) FCLSimu2003D Multilayer Ni/CeO2/YBCO/Ag, ~ 2 minutes on P-IV, 2.4 GHz, 512 MGb RAM Ni-5mm Ni-25mm Ni-50mm Ni (5-50 mm)-CeO2(0.5 mm)-YBCO(1.0 mm)-Ag (10 mm)over 1 sec, Q=10*(1+2*t),(2D, 3554 cells, 372 boundary elements)

  10. Simulation: size-multipliers (IV) Unscaled, Cu, 1*0.5*0.1 mm3 FCLSimu2003D Scaled Up by 10 DT = 266.62-266.64 K DT = 266.67-266.68 K Scaled Down by 10 DT = 265.5-267.5 K

  11. Simulation: size-multipliers (V) FCLSimu2003D BSCCO, Unscaled, 6*5*0.5 mm3 BSCCO, Scaled Up by 1000 to 6*5*0.5 mm3 BSCCO, Scaled down by 0.001 to 6*5*0.5 mm3 DT = 80.8-81.9 K DT = 80.8-81.9 K DT = 80.8-81.9 K

  12. Simulation: multi-element (VI) FCLSimu2003D Two uniform elements in parallel, YBCO, 200*40*25 mm3 each YBCO N-gas YBCO Layout YBCO: DT = 150.1-150.7 K

  13. Simulation: multi-element + defect (VII) FCLSimu2003D Two elements in parallel, one with defect YBCO, 200*40*25 mm3 each YBCO N-gas YBCO YBCO: DT = 106.7-106.8 K Layout YBCO: DT = 175.1-176.1 K

  14. Experiments – DC VACH (I) Fitting dc Current-Voltage Characteristic with EJ-model dc Current-Voltage characteristics, 4 consecutive runs

  15. Experiments, AC Pulses (II) AC Pulse measurements, 30% Vmains AC Pulse measurements, 25% Vmains

  16. Experiments, AC Pulses (III) AC Pulse measurements, 6 pulses 45% Vmains, expanded AC Pulse measurements, 6 pulses 45% Vmains, full scale

  17. Summary and Future Plans • So far we have: • Estimated Substrate effect • Verified proprietary software in FEMLAB • Solved high-aspect ratio problem • Attempted simulation of multi-element geometry • Performed first experiments: DC, AC loss & pulse • In the near future we plan to: • Input realistic parameters (n and Jc) into the EJ-model • Continue withmulti-element model (target - YBCO tape) • Simulate Structural Modifications • Complete Electrical Network • Further experiments: IV-characteristics, stress & strain

  18. Project Schedule (original) Mastered existing FCL model Created 2D Thermal modelin FEMLAB Repeat Existing model in Femlab & Built multi-element model Building Structural Model Setting up Experiments & Making Measurements

  19. Project Schedule (reviewed) Estimated Substrate effect Solved high aspect-ratio problem Verified Existing model in Femlab & Built multi-element model Building & verifying Structural Model Setting up Experiments & Making Measurements

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