Reliability-based Derating Approach for Interconnectors

This Masters project work has its genesis in the preliminary findings of a research collaboration in 2016 between the Department of Electric Power Engineering, NTNU, and Statnett (the Norwegian Transmission System Operator). As its overarching goal, the research proposition centred on developing a foundation for a suitable theoretical framework for one issue related to cross-border capacity auctions: interconnector adequacy. The motivation itself for such an undertaking stemmed from the divergent recommended approaches for estimating the capacity that the prospective Norway-GB interconnector (North-Sea Link) is allowed to bid into the GB Capacity Market. Capacity made available through an interconnector for an area with a capacity mechanism in place, should be eligible to participate in the auctions to prevent market distortion and to ensure that correct investment signals are sent. There is also a need for a transparent and robust method to calculate the proportion of the rated interconnector capacity allowed to participate in market auctions. Such a methodology should consider and remunerate the interconnector’s contribution to improved system adequacy in the importing area. In the NTNU-Statnett project, a unique reliability metric – Interconnector Effective Load Carrying Capability (IELCC) was conceptualized for the purpose of probabilistic interconnector derating; preliminary results were demonstrated on a very simple interconnected test system with a simple load profile. IELCC was founded on Loss-of-Load Expectation (LOLE) quantification in the interconnected system, addressing the need for a reliability-based de-rating procedure, as opposed to other existing approaches that focused on empirical considerations such as price differentials.