Selectivity and coordination of protection systems for an effective smart grid reconfiguration

The complexity of smart grids requires timely, fast and selective protection systems, in order to improve reliability, quality and efficiency so as to reach the new targets required in electric energy distribution and management. On the other hand, any automatic reclosing may involve switching surges, delays in the identification of faulted line segments, unacceptable overheating of line conductors, etc. This paper examines protection methods based on logic selectivity and digital new generation relays for an effective protection of smart grids. The main protections examined are overcurrent and directional relays adopted to face three and double phase-to-ground faults, as well as single-phase groud fault for both compensated and non-compensated neutral. The aim is to minimize the area of an outage as much as possible. The techniques proposed can be suitably applied to protect smart grids with large, complex configurations and massive distributed generation. Finally, an algorithm useful for network reconfiguration is also proposed and illustrated.