Component ranking in Great Britain transmission system based on either equipment failures or sabotage

In the long-term and operational planning of the power transmission system (PTS), one challenge is to identify components critical to system reliability. In this paper, the importance of each component for system reliability and vulnerability are quantified for two scenarios in a model of the Great Britain (GB) PTS. The scenarios are: (1) technical failures based on statistical data and (2) sabotage where the attacker has the ability to immobilize two contiguous components. In a novel method approach, the total importance of each component is based on three separate indices that include the system impact on (i) security margin, (ii) load, and (iii) generation. The final result of the GB system screening, including nearly 7000 components and 50 million outage events, is a ranking list indicating the 30 most critical components for each of the two scenarios. The results show that a component ranking that only includes risks of technical failures cannot be used to describe critical sabotage threats. Based on the results, the system operator can perform further and more detailed analysis on a few components and then make the necessary investments to improve the system reliability for equipment failures and strengthen the system vulnerability against sabotage.