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Magnetic Simulations of Single-Core, HighTemperature Superconducting, Fault Current Limiter
Yasha Nikulshin
Institute of Superconductivity, Department of Physics Bar-Ilan University, Israel
Sponsored by the Israeli Ministry of National Infrastructures
We present here the results of static and transient magnetic simulations of a single core Fault Current Limiter (FCL), saturated by a
High-Tc Superconducting (HTS) bias coil . Simulations are performed for a 120 kVA model designed and built by Bar-Ilan
University and Ricor Ltd. Results show that the magnetic core is saturated by the DC bias and that counter core limbs are desaturated alternately by the two halves of the AC fault current cycle contributing to the device impedance. Current and voltage
waveforms are calculated and present about 40% clipping ratio.
Introduction: The research group at BIU and Ricor
developed a concept for a single core FCL where
the AC open magnetic circuit is superimposed on a
DC closed magnetic circuit resulting with the
following key features:
Compact Design – The FCL is single core based
design, hence offering a compact design relative to
designs that require two cores per phase.
Coupling Free – The unique orthogonal and
superimposed closed DC and open AC magnetic
circuits of this design reduces coupling between AC
and DC coils, hence enabling high clipping,
extended current limiting holding time, zero-time
recovery and most important, the possibility to up
scale the design to significantly higher voltage
levels.
Variable Impedance – Due to its coupling free
design, the limiter can operate at any level of
saturation rather than deep. The FCL may therefore
be used as a variable and controllable impedance
device, providing grid operator with impedance
level complying with momentary needs.
(1)
BIU-Ricor 120 kVA HTS FCL
Static magnetic simulations: Vector Field
simulations of the distribution of the magnetic
induction in the core are shown below. The short
limb to the left is the DC bias limb, showing full
magnetic saturation of ≈ 2.1 T.
During a half cycle of the fault current, one limb
remains saturated while the other is de-saturated.
The color code figures represent the situation
obtained at the peak current of both half-cycles.
Current and Voltage waveforms are calculated
and exhibited above. While the current remain
sinusoidal, voltage exhibits a nonlinear behavior
resulting from the change in the core state. An
impedance of Z ≈ 80 mΩ is obtained, which
results in 154 V voltage drop across the FCL
terminals. In our 400 V single phase grid, this
implies 38.5% fault current clipping.
Research Group
Alex Friedman, Shuki Wolfus, Faina Kopansky
and Yosef Yeshurun
Magnetic induction distribution is extremely nonhomogenous along the long limb of the core.
Web: http://www.biu.ac.il/ESC/htslab/
Email: [email protected]