A probabilistic method of grid security assessment in transmission grid planning

Electrical transmission grids are planned to be in compliance with redundancy specifications, such as the deterministic (N-1) criterion. Due to increasing power transmission, the grid components experience a higher utilization rate. One essential issue of transmission grid planning is the necessity of the grid enforcement and the dimensioning of its components. Considering a similar level of grid security in case of failures, the level of grid security should not change after significant changes in grid structure and power flow. The (N-1) criterion can neither be used for comparison nor for assessing the severity of stochastic failures in grid assets. Therefore, probabilistic indices based on failure probabilities are introduced to complement the deterministic assessment of grid security. This paper presents a method for calculating indices based on a set of power flow situations with an appropriate simulation of failures.