Fault current limiters for transmission & distribution networks

Abstract

In the liberalised electricity market, with strong emphasis on renewable energy as an increasing part of the generation mix, much of the geographically distributed new generation is more economically fed into local distribution network operators' (DNO's) networks rather than the primary transmission grid. Continuing growth in power demand, the use of intelligent/active networks and the addition of distributed generation, (DG) which allows multi-directional power flow, all require tighter interconnections. All of these tend to raise the fault current level of existing networks. Fault Current Limiters (FCL) can help networks to limit this rise, particularly of asymmetrical fault current when X/R ratios are also increased by local addition of generators, transformers or series inductors. A suitably priced reliable FCL that could be introduced into existing power grids without excessively costly network analysis would be welcomed by utilities if it minimised costs of upgrading or reinforcing components to handle fault conditions while allowing increased normal power transmission. The FCL may also become attractive at transmission level voltages, 132 kV and higher.