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Main >> Applications >> Sample problems >> Fault current controller

Fault current controller

QuickField simulation example

This simulation example is prepared by Professor James R. Claycomb as a part of the webinar Fault Current Limiter Simulations using QuickField.
The model setup is based on Moriconi, F., Singh, A., Rosa, F. D, & Koshnick, N. (2010). Modeling and Test Validation of a 15kV 24MVA Superconducting Fault Current Limiter. UC Berkeley: California Institute for Energy and Environment (CIEE).
DC current running through the superconducting coil saturates the cores. The field of the fault current opposes the DC flux and drives the core out of saturation. Unsaturated core presents a higher impedance to the fault current which limits its magnitude.
Fault current controller consists of 2 cores and 2 AC windings. During the positive half-wave of AC current the left winding creates the flux opposing the DC flux, during the negative half-wave of AC current the right winding creates the flux opposing the DC flux.

Problem Type
Plane-parallel problem of AC magnetics.

Geometry
Z-direction size of the limiter is 10 mm.
Fault current limiter Dual iron cores saturated by an HTS DC coil in a single phase FCL DC V Fault DC flux AC flux Core Core 336 turns 336 turns Symmetry line

Given
AC winding number of turns is 336 per each leg, wire diameter is 0.5 mm, copper conductivity σ = 56 MS/m.
Voltage source V = 10 V, frequency 60 Hz.
DC current I = 900 A*turns.

Task
Calculate the fault current when the source voltage is directly applied to the limiter without the resistive load.

Solution
The geometry model includes only parts of the coil that are perpendicular to the screen. These parts have the conductor length of 10 mm each. The geometry model does not include front and back sides of the coil, that have the length of 14 mm each. To take into account the resistance of missing parts, electrical conductivity of the AC coil is attenuated: σ * (10 + 10) / (10 + 10 + 14 + 14) = 23.3 MS/m.
DC coil is made of superconductor, it has zero electrical resistivity, so there is no need to attenuate it. DC coil is modelled as a thin current carrying layer. The coil height is 18 mm, so the layer current linear density is Ht = I / 0.018 = 5000 A/m.
The geometry model features symmetry, so we can cut off the bottom half to reduce the simulation time. The voltage source magnitude should be halved too in this case, so AC voltage source will have the 10/2 magnitude. The winding connection scheme and the voltage source are specified in the external electric circuit.

Results

Magnetic flux density variation in time in the core. During the positive half-period of the current wave the left core is driven out of saturation, during the negative half-period of the current wave the right core is driven out of saturation.
Fault current controller