Probabilistic assessment of grid security for different scenarios of power system development

In transmission system planning, deterministic criteria like the (N-1) security criterion have to be fulfilled for predefined contingencies. The main drawback of the (N-1) security criterion is that it only gives information about whether it is fulfilled or not, making a comparison between possible candidates for power system expansion or a deeper analysis regarding network security rather difficult. This paper presents a method for probabilistic assessment of the grid security based on the stress level of the power system, e. g. the proximity of violating the technical restrictions. The method quantifies the network security using probabilistic risk indexes. Throughout the information obtained by the method, a comparison of the stress level for different scenarios or power system configurations can be done. This method also helps identifying prone regions as well as those situations that lead the power system to higher stress levels. This methodology is intended to be used as a complement to the (N-1) security criterion in the transmission network expansion planning process. The method was implemented in the Northern Chilean Transmission System (SING) for different possible generation scenarios in the year 2025.