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NEXANS Superconducting fault current limiter lowers CO2 emissions
Hürth, Germany, 25 April
2007:
Nexans
SuperConductors
GmbH (NSC), Hürth, and RWE Energy AG, Essen, are working together with partners
from industry and research to develop and test a superconducting fault current
limiter (FCL) for 110 kV. The intention is to protect the high-voltage network
from negative effects of short circuit currents. Using it, it will be possible
to couple hitherto separately operated 110 kV subnetworks. This means that the
400 kV transformer currently required at the respective coupling points to
supply the separated networks can be abandoned.
The
European Union is sponsoring the "INES-110" project with over 1 million euros as
part of the LIFE environmental programme, as the abolition of a transformer will
also mean the drop out of the physical open-circuit losses caused by it. This
produces a reduction in CO2 emissions.
The project is set to run
for almost three years. During this period the developers will work through the
various stages towards creating a prototype. Firstly, the preliminary stages
will be tested in a laboratory, followed by use of a demonstrator in a European
12 kV network and finally the prototype will be installed for an extended field
test in the RWE 110 kV network.
Each
transformer saved means 2,000 t/a less CO2
Around 60%
of net power generation in Germany comes from fossil fuels. "Based on this power
mix, each network coupling point and transformer dispensed with means about
2,000 tons less of carbon dioxide in the atmosphere. This saving equals the CO2
output caused by the energy consumption of a small village community", explained
Dr. Joachim Bock, CEO at NSC. The use of current limiters also reduces the
emissions of nitrogen oxide and sulphur dioxide.
The reduction in the
number of 400 kV transformers has further potential for the protection of the
environment: dispensing with such transformers also means saving on resources
such as steel, copper and oil used in their manufacture and operation. Each
transformer on its own contains around 90,000 litres of insulating oil, so the
production and disposal of these resources would be unnecessary.
No conflict:
environmental protection and operating efficiency
In addition to the
environmental aspects, a reduction in investment and operating costs represent
further incentives for utilities to rely on modern superconductivity.
According to Professor
Claus Neumann, who is responsible for Operative Asset Management for RWE
Transportnetz Strom GmbH, "The opportunity to design more flexible network
structures, and the environmental aspects, make superconducting short circuit
current limiters an extremely attractive resource. We look forward to testing,
from 2009, the three-phase prototype of the INES 110 project in the highvoltage
network."
Superconducting fault
current limiter acts like a quick, wireless switch
Superconducting BSCCO
2212 components form the core of the current limiter. The material is
superconducting at temperatures below -180°C (its "critical temperature") and
behaves like a loss-free electric conductor. If the ceramic metallic oxide heats
up above the critical temperature or the current density becomes too high, it
immediately loses its superconductivity. The same happens if the superconductor
is exposed to a powerful electromagnetic field. The current limiter exploits the
following characteristics: as soon as the current density exceeds the critical
value at one point on the superconductor, and this point loses its
superconductivity locally, the current flows through a spool connected in
parallel. This current causes a magnetic field to develop, which immediately
forces the superconductor to adopt its non-superconducting ("quenched") state
over its entire length and so the current limitation is accelerated even more.
This effect is called magnetic field triggering. The system is intrinsically
safe, so that no damage will occur even if the superconductor fails. The
superconducting state is resumed a few seconds after the network failure and the
system is ready to be used again.
Nexans SuperConductors is
displaying a functional model of the superconducting limiter element and the
trigger spool at the Hanover Fair (April 16 to April 20) in hall 2 on stand
D26).
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