Nexans has commissioned the world’s first installation of a superconducting fault current limiter at a power plant – Vattenfall’s Boxberg 1900 MW lignite plant in Saxony, Germany. The SFCL is essentially a very fast fault current limiter that uses superconductor technology to respond within a few milliseconds to limit short circuit currents that would otherwise damage switchgear and other power network components .

In this pilot project the SFCL, which utilises a passive characteristic of the superconductor, namely that its resistance rises very steeply at overcurrent and on reset returns to near-zero without damage, will provide short-circuit protection for the internal medium voltage power supply that feeds coal mills and crushers in the plant. Vattenfall anticipates that this technology will offer significant benefits and they are keen to gain practical experience on SFCL in collaboration with Nexans. “It could also help cut costs significantly by reducing the need to oversize substation equipment and cables to withstand even the most extreme short-circuit currents. … SFCL technology improves safety and cuts overall investment costs” said Dr Thomas Krüger, Vattenfall’s project manager.

“… a power plant is a highly challenging environment from a technological point of view,” said Dr Joachim Bock, CEO of Nexans SuperConductors. “It is particularly important for us that the systems are being implemented without public grants, which is also unprecedented”.

The device, designed for a rated current of 800 A, is undergoing live testing by daily routine operation in a feeder bar of the 12 kV power supply for rebound hammer mills (used for crushing coal).

Nexans designed and built the device according to specifications from Vattenfall and the Brandenburg Technical University in Cottbus, which is providing scientific support for the project. The device can limit a 63 kA prospective short circuit current to less than 30 kA immediately and to about 7 kA after 10 ms.