Symmetrical components and digital signal processors for smart grid protection

The paper presents a study on asymmetric faults with explicit reference to smart grids. The kinds of faults examined are: single phase ground fault, double phase ground fault, phase-phase short circuit, three-phase short circuit and single phase interruption. As a matter of fact, the complexity of smart grids requires new targets for protective systems in terms of reliability, timeliness and security. In comparison with traditional methods, the digital protections of the latest generation are very effective, versatile and programmable, allowing to simulate all network components effortlessly and therefore exactly. This new scenario also requires a revisitation of the theories underlying power system protection, so as to target them to the latest requirements. The results of a case study concerning a single-phase fault clearing and subsequent, automatic network reconfiguration are reported and illustrated.