The Moyle Interconnector is a High Voltage Direct Current (HVDC) connection between Northern Ireland and Scotland. It is made up of two 250MW cables and can operate in either direction, providing a total connection of 500MW between the all-Ireland Single Electricity Market and the GB market. Since 1 st October 2018, with the arrival of the new I-SEM market on the island of Ireland, the SEM and GB markets are coupled, meaning the physical interconnector flows are determined by the relative prices in the two connected markets. Previously, long-term transmission rights were allocated in the form of Financial Transmission Rights (FTRs) which paid out the positive day-ahead price difference between the SEM and GB markets to holders. These arrangements were underpinned by the UK’s participation in the EU’s Single Day Ahead Coupling (“SDAC”). Interconnectors to GB, including Moyle, are no longer able to participate in SDAC as of 1st January 2021, and therefore FTRs are not currently offered. Now Moyle interconnector capacity will be made solely available for allocation in two coupled intraday auctions between the SEM and GB. Market parties in the SEM may access these auctions via SEMOpx whilst GB market parties can access them via either the EPEX SPOT or Nord Pool power exchanges. More information on these coupled intraday auctions can be found on the SEMOpx website.

While Moyle is technically able to transport 500MW between the two markets, due to constraints on the transmission networks at either end of the interconnector, the commercial capacity of the interconnector is lower than this.

The maximum available capacity in each direction varies throughout the year, and is given in the table below:

Further documentation detailing the rules underpinning capacity calculation and FTR allocation and compensation can be found on the Publication’s Page