This paper presents a software tool, named INCA, for the assessment and improvement of supply reliability indices. Based on statistical failure rates associated to each individual component, and other recorded information, such as restoration and reparation times, INCA obtains expected reliability indices related with the number and duration of interruptions, for a feeder or set of feeders. INCA then allows the user to improve the resulting indices so that they are within permisible limits. This is carried out, either automatically or assisted by the user, by means of systematic procedures such as the addition of protecting devices or the modification of the feeder topology.