An improved model for protective-system reliability

A Markov model extends and improves previous models for determining the unreadiness probability and unavailability of a protective system, such as those found on electric-power transmission and distribution systems. Improved definitions of unreadiness probability and other relevant measures are proposed, based on a new Markov model of the system. This new model provides a more direct and physically important definition of unreadiness, and can be computed based on typical system-transition rates. Using this model, it is possible to estimate the optimal value of the protection inspection interval, viz, the time between inspections of the protective system. The model accounts for the operation of backup protection, the removal of protection for inspection, the occurrence of common-cause failures, and the usual clearing of faults