ABSTRACT
The power system is a highly dynamic system, and the system reliability changes due to energy situation, capacity utilization and operating conditions. The vulnerability of the power transmission will vary over the year. The consumption and production vary within a day, from day to day, and over the seasons, as illustrated in ??. In wintertime, during peak load periods, the consumption is large due to the need of warmingup. During spring the consumption may still be large, but the power production may be reduced due to low water reservoir levels. During the summer the consumption is low, but some parts of the grid will be out for maintenance.
