Superconducting Fault Current Limiters CRYOGENIC CLUSTER DAY PROGRAMME SEP 28 2011 Superconducting Fault Current Limiters Chris Waller Current Solutions for Future Networks

The John Vandore Challenge Squeeze my normal 110 slides which takes an hour into 15 minutes! So here goes. Current Solutions for Future Networks

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 Current Solutions for Future Networks

The fault current challenge - 2 Image © Palm Harbor Fire Department Current Solutions for Future Networks

The fault current challenge – 3 Climbing fault current G Current Solutions for Future Networks

The fault current challenge - 4 Upgrade Circuit Breakers Install high resistance Transformers G G Split the network Install Reactors Current Solutions for Future Networks

The fault current challenge - 5 Zero resistance G Instant rise in resistance limits fault current G Circuit breaker can operate safely Current Solutions for Future Networks

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 Current Solutions for Future Networks

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

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

Early Projects Project 1 & 2 Resistive Type utilising Bulk BSCCO Nexans Superconductors Project 3 & 4 Pre Saturated Core Type utilising BSCCO Tape Zenergy Power Current Solutions for Future Networks

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 Current Solutions for Future Networks

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)

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

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

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: 1250A Prospective fault current – 50kApk (20kArms) reduced to less than 7kApk

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

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

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!

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 Current Solutions for Future Networks