Managing regional security of supply: a case study from Scotland

Security of supply within a region of a power system can be achieved using generation within that region, or transmission import capability coupled with generation elsewhere. Great Britain, system planners cannot directly influence the location in which generators are built, and instead maintain regional security of supply by developing the transmission system via a deterministic standard which takes as inputs expected values of peak demand and generation fleet parameters in each region. This is in contrast to the probabilistic standard used to define system wide generation adequacy through a Loss of Load Expectation. This paper proposes a probabilistic standard for regional security which is used to determine the secure import required from the transmission network for a given level of security. The method is applied to Great Britain and Scotland using historical data for demand and generation availability from recent winters. The paper concludes that a probabilistic metric provides greater information on the level of regional security provided, and allows the impact of all types of generation, including intermittent renewables generators such as wind, to be properly accounted for.