Use of transmission protection technology in distribution relays

Transmission level protection functions are increasingly being looked at for Distribution systems. This can be attributed mainly to the enhancements being planned for by the Operating Companies, to increase the system efficiency, and also to ensure reliable power supply to the end Consumers. Slowly, the catch word "Smart Grid" is being consciously and progressively transformed to practical implementations to reap operational benefits, and to increase the system reliability. There is also increased regulatory pressure on the Operating Companies to revamp the Distribution systems to prevent major catastrophes, given that the nature of these Distribution systems is also changing. One such change could be the birth of "micro-grids", where the lower fault levels could necessitate application of differential or distance protection. Given all these demands, though it seems straightforward to use the existing Transmission protection relays in Distribution as well, practical benefits need to be weighed. Also, considerations need to be given to the physical limitations and the operational demands. This paper will attempt to capture the emerging trend of the use of Transmission Protection Technology in Distribution systems, by elucidating the needed balance between the practical benefits that could be enjoyed, and the constraints that could be posed.