A new algorithm for smart grid protection based on synchronized sampling

Conventional distribution systems are usually radially operated, supplied at one end through a main source. The presence of a massive Distributed Generation (DG) from renewable sources radically changes the radial operation of these systems. Indeed, from passive the network becomes active, and bidirectional power flows can appear in the distribution system, which causes a number of problems related both to normal and fault conditions. In this paper, a new protection procedure is proposed, based on distance protection concepts and synchronization of the voltage and current samples coming from the two terminals of the faulted MV line segment. The fault identification algorithm suitably exploits the model equations of the lumped parameter circuit by applying the Recursive Least Square approach. A thorough set of simulations are carried out in order to validate the proposed algorithm, which is able to estimate the fault distance with good performances and great speed, even in case of high distortion of the acquired voltage and current waveforms. Moreover, the algorithm provides a very good estimate of the fault resistance, which means it works correctly also whenever high fault resistances appear in the distribution systems herein examined