Weather effect considerations in reliability evaluation of electrical transmission and distribution systems

Abstract

The weather environment has a significant impact on the reliability of a power system due to its effect on the system failure mechanisms of overhead circuits and on the operational ability of an electric power utility. The physical stresses created by weather increase the failure rates of transmission or distribution lines operating in adverse weather conditions, resulting in increased coincident failures of multiple circuits. Exceptionally severe weather can cause immense system damages and significantly impact the reliability performance. Recognition of the pertinent weather impacts clearly indicates the need to develop appropriate models and techniques that incorporate variable weather conditions for realistic estimation of reliability indices. This thesis illustrates a series of multi-state weather models that can be utilized for predictive reliability assessment incorporating adverse and extremely adverse weather conditions. The studies described in this thesis are mainly focused on the analyses using the three state weather model. A series of multi-state weather models are developed and utilized to assess reliability performance of parallel redundant configurations. The application of weather modeling in reliability evaluation is illustrated using a practical transmission system. The thesis presents an approach to identify weather specific contributions to system reliability indices and illustrates the technique by utilizing a test distribution system. The analysis of a range of reliability distributions with regard to major event day segmentation is presented.The research work illustrated in this thesis clearly illustrates that reliability indices estimated without recognition of weather situations are unrealistic and that at minimum the three state weather model should be applied in reliability evaluation of systems residing in varying weather environments. The conclusions, concepts and techniques presented in this thesis should prove useful in practical application.