Analysis by Cornwall Insight reveals that inertia* levels have been falling over time as the proportion of synchronous generation has declined. The below graph highlights the drop in inertia and shows 2020 levels are significantly lower.
While we are not even halfway through the year the shape of the curve and frequency of half-hours where inertia is below 150GVA.s is particularly pronounced.
Joe Camish analyst at Cornwall Insight, said:
“COVID-19 demand changes and reductions have brought about lower levels of inertia on the system sooner than previously forecast. As a result of the demand changes, more expensive coal and gas plants are being pushed out of merit and renewables penetration is consequently rising substantially as a proportion of demand.
“The problems of falling levels of inertia are not new or solely related to COVID-19. Instead, this is an acceleration of something that was already on the horizon. In January 2020 National Grid announced the results of its Stability Pathfinder tender to address these long-term stability concerns.
“The ESO is dealing with unprecedented issues, and the short-term measures currently utilised perhaps provide a signal of the future market. These changes to inertia are likely to lead National Grid ESO to rethink how they balance the system and procure services.”
Notes to Editors
*Inertia – is an attribute of the system related to the energy stored in the rotating motors of synchronous generators (e.g. conventional thermal generation). It prevents system frequency from falling too quickly after a frequency disturbance (e.g. a generator trip).