Ofgem has published the Technical Report on the events of 9 August 2019 with technical appendices covering responses from the affected parties. This can be viewed by following the link: https://www.ofgem.gov.uk/publications-and-updates/investigation-9-august-2019-power-outage
This was updated on the 10th September 2019 and forms part of the formal investigation into the power cuts experienced on 9th August 2019.
The report points to a lightning strike on the Eaton Socon-Wymondley double circuit, shortly followed by the loss of c.500MW of embedded generation due to their Loss of Mains Protection. Following the lightning strike Hornsea offshore wind farm de-loaded 737MW and Little Barford CCGT tripped with a loss of 641MW. In little over a minute the system frequency dropped to critical levels triggering the Low Frequency Demand Disconnection (LFDD) operation, 931MW of demand was disconnected from the system by DNOs. No more than 4 minutes later the system frequency was restored to 50Hz and stabilised following 1000MW of frequency response and 1240MW of system control room actions. Approximately 40 minutes later all DNOs confirmed that demand had been restored and customers were reconnected.
Wider travel disruption appears to have resulted from Govia Thameslink Railway Class 700 and 717 trains reacting unexpectedly to the system frequency drop. No track supplies were lost due to the LFDD operation. Approximately 30 trains required technicians to attend the trains and reset them, which impacted upon hundreds of other trains. Newcastle airport was not classed as a Protected Site under the Electricity Supply Emergency Code (ESEC) and as such was disconnected by Northern Power Grid (NPG) as a result of the LFDD operation. Newcastle International Airport have requested and been accepted to be categorised as a Protected Site under ESEC so will no longer be part of the LFDD scheme.
A recommended action from the Ofgem Technical Report is a review of the timescales for delivery of the Accelerated Loss of Mains Programme which is an industry-led project, upgrading older protection settings to accelerate compliance with new Distribution-Code requirements. Information on this can be found here: http://www.energynetworks.org/electricity/engineering/loss-of-mains.html.
