1. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 1 Superconducting Fault Current Limiters A. V. Velichko, T. A. Coombs Department of Engineering, Cambridge University, UK. Funded by EPSRC

2. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 2 Outline Overview of the work done Physical Background and Modelling Simulation and Experiment Summary and Future Plans

3. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 3 Overview 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. Problems to be solved within the project:

4. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 4 Physical Background and Modelling (I) Single FCL Structural ThermalElectrical All Properties are NONLINEAR and INTERDEPENDENT! If done consistently & simultaneously – very time-consuming and could be fallible

5. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 5 Physical Background and Modelling (II) EXISTING PROPRIETARY MODEL From Experiment: - Spread in I c and n; Strain and Stress; Model takes into account: Thermal and Electrical; Need to incorporate: Structural, Multi-element

6. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 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. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 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. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 8 Simulation: verifying our model (II) FCLSimu2003D & FEMLAB Cu-block, 1*0.5*0.25 mm 3, takes ~ 1 minute on P-IV, 2.4 GHz, 512 MGb RAM  T = 275.24-275.3 K  T = 260.24-260.27 K

9. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 9 Simulation: effect of substrate (III) Ni (5-50  m)-CeO2(0.5  m)-YBCO(1.0  m)-Ag (10  m) over 1 sec, Q= 10*(1+2*t), (2D, 3554 cells, 372 boundary elements) Multilayer Ni/CeO2/YBCO/Ag, ~ 2 minutes on P-IV, 2.4 GHz, 512 MGb RAM Ni-5  mNi-25  mNi-50  m FCLSimu2003D

10. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 10 Simulation: size-multipliers (IV)  T = 266.62-266.64 K Scaled Up by 10  T = 266.67-266.68 K Unscaled, Cu, 1*0.5*0.1 mm3  T = 265.5-267.5 K Scaled Down by 10 FCLSimu2003D

11. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 11 Simulation: size-multipliers (V) 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  T = 80.8-81.9 K FCLSimu2003D

12. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 12 Simulation: multi-element (VI) FCLSimu2003D Two uniform elements in parallel, YBCO, 200*40*25  m 3 each YBCO:  T = 150.1-150.7 K N-gas YBCO Layout

13. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 13 Simulation: multi-element + defect (VII) Two elements in parallel, one with defect YBCO, 200*40*25  m 3 each YBCO:  T = 106.7-106.8 K N-gas YBCO YBCO:  T = 175.1-176.1 K Layout FCLSimu2003D

14. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 14 Experiments – DC VACH (I) dc Current-Voltage characteristics, 4 consecutive runs Fitting dc Current-Voltage Characteristic with EJ-model

15. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 15 Experiments, AC Pulses (II) AC Pulse measurements, 25% V mains AC Pulse measurements, 30% V mains

16. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 16 Experiments, AC Pulses (III) AC Pulse measurements, 6 pulses 45% V mains, expanded AC Pulse measurements, 6 pulses 45% V mains, full scale

17. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 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 with multi-element model (target - YBCO tape) Simulate Structural Modifications Complete Electrical Network Further experiments: IV-characteristics, stress & strain

18. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 18 Project Schedule (original) ActivityYear 1Year 2Year 3 Multi-Element Model Structural Failure Modelling of Complete Electrical System Measurement Validation Project months 3 6 9 15 18 21 27 30 33 Mastered existing FCL model Created 2D Thermal model in FEMLAB Repeat Existing model in Femlab & Built multi-element model Setting up Experiments & Making Measurements Building Structural Model

19. The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 19 Project Schedule (reviewed) ActivityYear 1Year 2Year 3 Multi-Element Model Structural Failure Modelling of Complete Electrical System Measurement Validation Project months 3 6 9 15 18 21 27 30 33 Estimated Substrate effect Solved high aspect-ratio problem Verified Existing model in Femlab & Built multi-element model Setting up Experiments & Making Measurements Building & verifying Structural Model