EHV substations reliability improvement by means of circuit breakers autodiagnostic

The use of advanced autodiagnostic systems is becoming a common practice for HV circuit breakers, as well for their auxiliary systems, such as protections, control circuits, etc. Their main advantages are the possibility to reduce the frequency of heavy damages and the mitigation of the relevant outages, and the possibility to avoid up-stream severe outages, such as the out-of-service of the main busbars of a substation. This paper covers a reliability analysis of a large EHV S/S, carried out by means of the adaptation of the classical Endrenyi models, both of the HV circuit breakers and of the three-state switching sequences; a dependability analysis by means of frequency and duration reward models has been developed, in order to take into account the importance of the different rewards of the faults consequences.