A reliability approach to transmission expansion planning using minimal cut theory

This paper presents a minimal cut set based approach for the reliability evaluation of an optimally planned transmission system (Part I) and obtains a configuration of transmission lines to achieve a desired failure rate set by the planner (Part II). In Part I an algorithm is developed to find minimal cuts which contain the system components. Overall system reliability indices are then calculated by considering that any bus failure causes system failure. In Part II the system failure rate and other reliability indices are calculated using system first-order minimal cuts based on the criteria that (a) the system fails if overload occurs in a line or the bus voltage variation is greater than ± 11% and (b) the system fails if overload in a line and bus voltage variation greater than ±11% occur simultaneously. Part II excludes components in the system and shows how to decrease the failure rate by adding lines and subsequently to achieve a network configuration for a desired failure rate set by the planner for each of the above criteria. A six-bus transmission network is considered to study the applications of the algorithm developed.