EPSRC Portfolio Research Area: Fault current limiting is an enabling technology for connection of mixed, renewable energy generation in modern smart power grids. As such it spans EPSRC 'Resource Efficiency' and 'Whole Energy Systems' and, beyond TRL3, is directly aligned to Innovate UK 'Energy & Infrastructure themes'.

Description:
The increasing connection of distributed power generation from conventional and alternative sources is pushing the limits of the capacity of existing grids, specifically in its ability to cope with fault currents that can cause disruptions in power supply, equipment damage and major power outages. Fault current limiters (FCL) are a technology designed to be added to a power grid to provide additional fault 'head-room' and negate the need for costly and time consuming network infrastructure upgrades. They extend the capacity and asset life of the existing power grid.

Research in Cardiff has led to the development by a Cardiff School of Engineering spin-out, Faultcurrent Ltd., of the world's first full-scale (11kV, 20MVA, 55 tonnes) permanent magnetic based fault current limiter (pmFCL) which addresses the shortcomings of previous generations of FCLs - a completely passive technology, featuring a pre-saturated core utilizing low-cost ferrite magnets. However, in some highly built-up areas, access to substations is difficult, requiring a more compact form of pmFCL than possible with a ferrite based structure.

This project aims to develop knowledge gained in the development of the pmFCL, together with understanding of non-linear, anisotropic magnetic materials, to develop novel compact FCL technologies. The project aims are:

- to investigate new FCL core concepts including (i) application of novel effective field sources (and their combination with permanent magnet biasing) and (ii) investigation of novel linear topologies for compact cores
- to investigate new material applications in FCL core including (i) mixed rare earth/ferrite bias sources, (ii) application of recycled rare earth magnets
- to develop FEM models for prediction of non-linear inductive behaviour of the FCL cores in response to a fault current including inductive response, voltage drop, robustness to over-fluxing, field leakage, power losses
and thermal control.
- to build bench-top prototype cores which will be tested in the magnetics laboratory to validate FEM model results