Modelling of Ice Storms and their Impact Applied to a Part of the Swedish Transmission Network

In this paper a technique of modelling severe weather for power system reliability calculations is developed. The model is based on geographically moving winds and precipitation and is suitable for transmission network. A scenario represents a weather situation with given parameters. Besides the weather model a stochastic vulnerability model for the components is required for each scenario that connects the risk of failure to the weather situation. In order to mitigate severe consequences of future ice storms in an efficient way it is essential to be able to estimate the consequences based on assumptions of the technical system and the severity of possible storms. It is assumed that the probability of a failure due to a given weather depends on load functions for wind and ice together with the component vulnerability model which is based on the design of the components. The wind load is direct and the ice load is given by a known ice accretion model. Conclusions about the reliability of the studied lines under ice storms are presented as well as a graph of the critical conditions for the studied lines with ice thickness on the x-axis and gust wind on the y-axis. The numerical examples show the impact of different weather situations on a part of the Swedish Transmission network using data both from real weather situations in Sweden and the weather model.