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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
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
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:
The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 4
Physical Background and Modelling (I)
SingleFCL
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/~tac1000 5
Physical Background and Modelling (II)
EXISTING PROPRIETARY MODEL
From Experiment: - Spread in Ic 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/~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
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
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 mm3, takes ~ 1 minute on P-IV, 2.4 GHz, 512 MGb RAM
T = 275.24-275.3 K T = 260.24-260.27 K
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-5m Ni-25m Ni-50m
FCLSimu2003D
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 KScaled 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
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 T = 80.8-81.9 K T = 80.8-81.9 K
FCLSimu2003D
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 m3 each
YBCO: T = 150.1-150.7 K
N-gas
YBCO
YBCO
Layout
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 m3 each
YBCO: T = 106.7-106.8 K
N-gas
YBCO
YBCO
YBCO: T = 175.1-176.1 K
Layout
FCLSimu2003D
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
YBCO tape, dc IV-characteristics, 7/03/2006
I, A
0 20 40 60 80 100 120 140 160
U,
V
0.0
5.0e-6
1.0e-5
1.5e-5
2.0e-5
2.5e-5
1st run2nd run3rd run4th run
DC in-phase Voltage vs. Current for LANL YBCO tape No.1, 7.03.06
I, A
0 20 40 60 80 100 120 140 160
DC
Vo
ltag
e (V
)
-5.0e-6
0.0
5.0e-6
1.0e-5
1.5e-5
2.0e-5
2.5e-5
Vc*(I/Ic)^nVdc
Fitting dc Current-Voltage Characteristic with EJ-model
The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 15
Experiments, AC Pulses (II)
AC Pulse measurements, 25% Vmains
Pulse measurements (2 pulses, 25% V_mains) on YBCO tape No.1, 7.03.06
time, sec
0.07 0.08 0.09 0.10 0.11 0.12
I ac, A
-0.08
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
Ua
c, V
-0.04
-0.02
0.00
0.02
0.04CurrentVoltage
Pulse measurements (2 pulses, 30% V_mains) on YBCO tape No.1, 7.03.06
time, sec
0.07 0.08 0.09 0.10 0.11 0.12
Ia
c,
A
-0.08
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
Ua
c, V
-0.08
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
CurrentVoltage
AC Pulse measurements, 30% Vmains
The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 16
Experiments, AC Pulses (III)
AC Pulse measurements, 6 pulses45% Vmains, expanded
Pulse measurements (2 pulses, 45% V_mains) on YBCO tape
time, sec
0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20
Ia
c,
A
-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
Ua
c,
V
-3
-2
-1
0
1
2
3
CurrentVoltage
Pulse measurements (2 pulses, 45% V_mains) on YBCO tape, expanded
time, sec
0.04 0.05 0.06 0.07 0.08
I ac, A
-0.10
-0.05
0.00
0.05
0.10
Ua
c, V
-2
-1
0
1
2
CurrentVoltage
AC Pulse measurements, 6 pulses45% Vmains, full scale
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
The EPEC Superconductivity Group –Engineering Department - University of Cambridge www2.eng.cam.ac.uk/~tac1000 18
Project Schedule (original)Activity Year 1 Year 2 Year 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 modelCreated 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/~tac1000 19
Project Schedule (reviewed)Activity Year 1 Year 2 Year 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 effectSolved high aspect-ratio problemVerified Existing model in Femlab & Built multi-element model
Setting up Experiments& Making Measurements
Building & verifying Structural Model