Quantitative Transmission-System-Reliability Assessment

Quantitative transmission-system reliability is a prerequisite in transmission-system planning and operation 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 the system planner's experience and intuition which are lacking a formal and consistent framework for their development. Although easy to use and understand, due to inherent limitations, the deterministic criteria cannot 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 the 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.