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

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

The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac 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:

The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac 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

The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac 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

The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac Physical Background and Modelling (III) 3D model Accounts for Inhomogeneities Proper thermal boundary conditions Linked Electrical and Thermal Properties External Elements Nitrogen boil-off

The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac 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

The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac 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 = K  T = K

The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac 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

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

The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac 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 to 6*5*0.5 mm3  T = K FCLSimu2003D

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

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

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

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

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

The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac 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

The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac Project Schedule (original) ActivityYear 1Year 2Year 3 Multi-Element Model Structural Failure Modelling of Complete Electrical System Measurement Validation Project months 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

The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac Project Schedule (reviewed) ActivityYear 1Year 2Year 3 Multi-Element Model Structural Failure Modelling of Complete Electrical System Measurement Validation Project months 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