Computer modelling of superconducting film type fault current limiters

Investigations are being carried out into the use of superconductors as fau lt current limiters. We are investigating devices constructed from various high T-c materials, Of particular interest are limiters constructed from su perconducting YBCO thick films on YSZ substrate. In order to predict the li miting characteristics of a fault current limiter, and to optimise the desi gn parameters, an accurate numerical simulation has been developed. This mo del includes measured data in the form of E-J characteristics, thermal prop erties, and R-T data, Data sets for different materials can be selected in order to compare the performance of candidate materials. A major concern during limiting is the way that heat is generated in the su perconducting film Our simulation treats the superconductor and substrate a s a number of small elements In order to determine the temperature distribu tion within the film and substrate. Further additions model the heat loss m echanisms to the surrounding environment, This thermal model is included in an overall FCL model, which includes voltage sources and line or load impe dances. We can use this model to accurately predict the current-time wavefo rms achievable with typical limiters, and to easily explore the effect of a change in operating conditions.