Reliability optimization of PLC-integrated high-quality power supply protection systems

The authors deal with the analysis of some possibilities related to the adoption of the programmable logic controller (PLC) in a protection system for a medium-voltage electrical installation. A reliability evaluation of the entire protection system as obtained with PLC adoption is performed in order to point out every possible advantage of this promising technical solution. A correct reliability evaluation of PLC integrated solutions must analyze the entire system behavior if there is a PLC failure to indicate improved reliability indices of the whole system. On the basis of numerical evaluations, some design criteria on protection system logic are proposed, which allows achievement of a noticeable improvement of these indices, by means of an appropriate choice of tripping logic between positive and negativ