Funded by EPSRC

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


Outline

Overview of the work done Physical Background and Modelling Simulation and Experiment Summary and Future Plans


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:


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


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


Physical Background and Modelling (III)

• 3D model• Accounts for Inhomogeneities • Proper thermal boundary conditions• Linked Electrical and Thermal Properties• External Elements

Nitrogen boil-off


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


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


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


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


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


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


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


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


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


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


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


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


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

Funded by EPSRC

Documents

Transcript of Funded by EPSRC