The electricity system operator has also recommended:
- A review to determine if it is worth beefing up security of supply standards (which if implemented may require procuring more frequency response)
- Potentially expediting plans to change of loss of mains protection for embedded generators so that they do not trip as easily
- Reviewing who gets automatically disconnected from the distribution network
- Assessing whether critical infrastructure providers should have a standard their internal systems should be designed to handle
The review provides more detail on the sequence of events that led Hornsea offshore wind farm, Little Barford CCGT and swathes of distributed generators to trip.
It confirms National Grid ESO had sufficient reserve power to react to a frequency loss equivalent to the largest single infeed loss, and was managing to restore frequency after the initial trips at Hornsea, Little Barford and distributed generation when a second unit at Little Barford tripped. At that point there was not enough frequency response left and frequency dropped to 48.8Hz, resulting in around 1GW of demand disconnection to keep the rest of the system running.
Citing Ørsted’s incident report, the ESO states that the configuration of Hornsea’s network was a “contributory factor” to its deloading and that its turbine controllers “reacted incorrectly”. Ørsted has since updated its systems.
RWE’s report is less conclusive. The firm continues to investigate the conditions under which its steam turbine initially tripped and why “for reasons presently unknown” its first gas turbine tripped a minute later. The second gas turbine was manually shut down due to high steam pressure. RWE has planned a shutdown this month and will investigate further.
See the report here.
Colm Murphy, of National Grid ESO, will speak at The Energyst’s DSR Event, taking place tomorrow at One Moorgate Place. Details here.