Quantitative transmission system reliability assessment

Quantitative transmission system reliability is a prerequisite in transmission system planning and operating that supplying industrial and commercial customer loads. A utility industry traditionally has relied on a set of deterministic criteria such as the widely used N-1 criterion to guide transmission planning supplying all customer types, e. g., residential, agricultural, commercial, industrial and sensitive high tech electronic customers. The conventional deterministic planning criteria are based on system planner´s experience and intuition lacking a formal and consistent framework for their development. Though easy to use and understand, due to inherent limitations, the deterministic criteria can not realistically model the probabilistic nature of power system behavior. Moreover, the application of deterministic criteria possesses the inherent risk of over/under investment in transmission system facility additions to meet the system load growth. Over the past two decades different quantitative transmission system reliability techniques have been developed to accurately reflect stochastic nature of a power system behavior and assess its reliability performance. This paper illustrates applications of reliability models used to compute the reliability performance of a practical transmission system supplying industrial, commercial and other customer types.