Superconducting fault-current limiters:New tools in the box for handling
high short-circuit power
Power grids of the future
An increasingly decentralised supply of
power, higher power flows and the present
backlog of investment in equipment will
require stronger adaptations to the power
network in the coming years. In this context,
high short-circuit currents play an essential
role. For example, in power networks short
circuits can arise due to lightning strikes or
failures of system components and of power
lines, resulting in high fault currents. These
cause extremely high dynamic and thermal
loads which all system components of the
power network must resist.
Due to their modular construction, superconducting fault-current
limiters can be used for various nominal voltages and currents
and can be adapted to particular limiting characteristics in case
of short circuits.
Innovation superconducting
fault-current limiters
Electrical equipment that controls high fault
currents can increase the security of the network
and allow power equipment to be designed
more cost-effectively. The superconducting
fault-current limiter is such a device.
In contrast to a high-voltage fuse it does not
disconnect the line in case of a short circuit
but limits the very high currents to defined
values. In addition, it allows electrical interconnections
of existing systems, which would
not be possible without limiters.
Functional and inherently safe
During operation, the superconductors of the
limiter are cooled to a temperature of around
-200 °C, which is easily and cost-effectively
accomplished by means of liquid nitrogen. At
these temperatures, the materials used have
virtually no electrical resistance – even at
nominal power loads. However, if the socalled
"critical current" (above the nominal
current) is exceeded, the material suddenly
loses its superconducting properties and behaves
like a "normal" resistor. This relatively
high resistance limits the current to a predefined
value. These material properties only
make superconductors ideal self-actuating
current limiting elements.

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