Managing regional security of supply : a case study from Scotland

Securing the supply of electricity to a region of a power system requires either generation capacity within that region, or transmission import capability coupled with generation elsewhere in the power system. The problem is one of co-optimising generation and transmission infrastructure. This paper begins by discussing changes in Great Britain (GB) regulator environment affecting the provision of regional security of supply: changes to the transmission charging regime; new regulatory arrangements including enhancements to the System Operator’s role, and the opening up of major new transmission projects to competition; and some limitations of the existing standard defining the methodology for calculating secure transmission capabilities. Scotland, as a region of the GB power system, provides an interesting case study in which to investigate the allocation of contributions to regional security of supply between transmission and various categories of generation. In particular, intermittent generation is currently ignored when calculating the level of transmission import capability required to maintain security of supply in a region, whilst it is considered in overall generation adequacy calculations at a system level. Whilst wind generation is not dispatchable, it is shown here that it does provide an additional source of generation availability that should be considered in studies into transmission import requirements. This paper uses historical data for Scottish generation availability from recent winters to investigate the likely impact of changes to the Scottish generation fleet on the need for secure transmission import capability into Scotland. It calculates transmission requirements based on the risk of requiring demand reduction within a region. Scenarios representing possible generation backgrounds in Scotland over the coming decade show that, measured in this way, wind generation can offset transmission import requirements by up to 25% of its installed capacity. The key conclusions of the paper are that a risk-based analysis of regional security of supply and transmission requirements can help allocate the true impact of different generators on the transmission import capability needed to secure supply to a region. Such a method can therefore be useful in informing the allocation of charges between parties and in developing planning standards to shape future investment in the system