Consideration of multi-state weather models in reliability evaluation of transmission and distribution systems

The physical environment in which transmission and distribution networks operate can have a significant impact on the resulting reliability of the power system. Extreme weather conditions can create an excessive physical stress on overhead lines resulting in sharp increases in the failure rate. This significantly increases the chance of overlapping failures during this period. This paper briefly illustrates the conventional two weather state model used to incorporate the effect of fluctuating weather in reliability assessment. The failures that can occur in extreme adverse weather are incorporated by utilizing a three weather state model. A multi-state weather modeling concept is introduced to reflect the effect of continuously varying stress created by the weather. A series of weather models are developed and used to assess the reliability indices associated with a two line parallel redundant circuit. This paper clearly shows that assessments without recognizing the weather can be very optimistic. The studies presented in this paper show that the inclusion of additional adverse weather severity levels can be important in certain situations and impact the accuracy of the analysis