1. Superconducting Fault Current Limiters
CRYOGENIC CLUSTER DAY PROGRAMME SEP
Superconducting Fault Current Limiters
Chris Waller
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2. The John Vandore Challenge
Squeeze my normal 110 slides which takes an hour into 15 minutes!
So here goes.
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3. The fault current challenge - 1
Generator
Circuit breaker
Load
Copper line G
Short circuit:
Fault Current unrestricted by load G
Circuit breaker interrupts fault current
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4. The fault current challenge - 2
Image © Palm Harbor Fire Department
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5. The fault current challenge – 3
Climbing fault current G
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6. The fault current challenge - 4
Upgrade Circuit Breakers
Install high resistance Transformers G G
Split the network
Install Reactors
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7. The fault current challenge - 5
Zero resistance G
Instant rise in resistance limits fault current G
Circuit breaker can operate safely
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8. The fault current challenge - 6
132kV
fault prone network
Rural Semi-Urban Urban
Sensitive
Load
Too Much Load
Plenty of capacity
33kV
11kV
40MW
Wind farm
sharing
Security
of supply
Generator
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9. The fault current challenge – eureka
Key characteristics of Fault Current Limiters based on superconducting materials
Under normal operation a fault current limiter inserts negligible impedance into the network
When a fault occurs the limiter‘s impedance rises rapidly, reducing the current flowing through it

10. Some types of Superconducting Fault Current Limiters
Fault Current Limitation
Some types of Superconducting Fault Current Limiters
Superconductor quenches under excessive fault current reverting to a normal conductor, inserting resistance.
Resistive
Shielded core
Induced current in the Superconducting tube shields the iron core until excessive current causes quench.
Pre-saturated
Core
Iron core driven into saturation by superconducting DC winding. Fault current opposes the saturation and increased impedance switched into the circuit. DC

11. Early Projects Project 1 & 2 Resistive Type utilising Bulk BSCCO
Nexans Superconductors
Project 3 & 4
Pre Saturated Core Type utilising BSCCO Tape
Zenergy Power
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12. Early Projects 2009 2010 2011 2012 2013 1st in commercial network
11kV / 100A
operation
1st in commercial network
11kV/400A
11kV/1250A
33kV / 800A
11kV/ 1250A
MgB2 demonstrator
2009
2010
2011
2012
2013
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13. Resistive Limiters Critical Characteristics Superconducting properties
T (Temperature)
Normal
conducting
properties
Normal
conducting
properties
J (current density)
Too much current, magnetic field or temperature leads to a “quench” and the loss of superconducting properties.
Superconducting
properties
Superconductors remain in the superconducting state as long as the current, temperature and flux density remain below the critical values.
Normal
conducting
properties
B (magnetic field)

14. Resistive Limiters
Superconducting Characteristics – Resistive Fault Current Limiters
High
Resistance
Low
Superconducting range
Normal range
Equivalent circuit
Critical Value

15. Resistive FCL – Limiting Behaviour
Up to 90% clamping
Clamps within 1.5 ms
Removes DC component
fault current
limited fault current

16. Resistive MgB2 SFCL Development
ETI Commissioned Project secured in June 2011 to develop a MgB2 type SFCL with a view to targeting the future mass market.
The prototype will be installed in substation on Western Power Distribution’s network in Summer 2013.
Key parameters
Nominal operational voltage and frequency: 11kV, 50Hz
Maximum normal load current: A
Prospective fault current – 50kApk (20kArms) reduced to less than 7kApk

17. Resistive FCL – Key Components
HV Bushings
Current Limiting Modules
Heat Exchanger
Helium Compressors

18. Resistive MgB2 SFCL - Challenges
Using the quench: Even quenching, no hot spots, material homogeneity
Wire heating: Removal of the heat (0.96MJ in 120ms) reset within 3 minute
Low thermal losses Current leads
AC losses in superconductor/sheath
Induced losses in cooling systems
Enclosed volume & thermal radiation

19. Resistive MgB2 SFCL - Challenges
Customer driven issues Fail safe
No maintenance.
Low carbon footprint
Competitive with alternative options
Low noise.
Suppliers: Limited MgB2 wire suppliers. All interested in MRI as mass market.
Cryogenic components suppliers needed.
This is why we are here!

20. Thank you ! Superconducting Fault Current Limiters
are a bottleneck component in the rise of Clean Technologies and Smart Grids
and critical to meet Low Carbon targets
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