The impact of reduced system inertia on system planning and HVDC interconnection

Over the past decade, significant levels of wind and solar generation have been built in Great Britain (GB). These represent non-synchronous sources of power with little or no contribution to system inertia. Further such developments are expected along with increases in HVDC interconnection capacity with mainland Europe. This paper presents a modelling framework to study the economic impact of operating a low inertia system. It is used to study a range of scenarios for the years 2020 and 2025 and provides an assessment of economic impacts of increasing GB interconnection for two sets of limits to the rate of change of frequency (RoCoF) that would arise after a loss of infeed event. The study shows that savings of between £44 million and £247 million in 2020 and up to £539 million in 2025 can be made by increasing the maximum RoCoF settings from 0.125 Hz/s to 0.5 Hz/s and the volume of curtailment of operation of renewables and interconnector imports is much reduced.