Ofgem, the UK’s electricity industry regulator, has launched an investigation into the causes of the power cuts on 9 August that left around a million people without power for several hours and disrupted the rail network for more than 24 hours.
An initial report from National Grid Electricity System Operator (NGESO) stated that at 4.52 pm there was a lightning strike on a transmission circuit (the Eaton Socon – Wymondley Main). The protection systems operated and cleared the lightning in under 0.1 seconds. The line then returned to normal operation after about 20 seconds. However, immediately following the lightning strike and within seconds of each other the Hornsea off-shore windfarm and Little Barford gas power station, total capacity 1.3 GW, both reduced their energy supply to the grid.
The investigation will seek to establish what lessons can be drawn from the power cut to ensure that steps can be taken to further improve the resilience of Britain’s energy network.
It will also seek to establish whether any of the parties involved National Grid ESO, National Grid Electricity Transmission, 12 distribution network operators in England and Wales, as well as generators RWE Generation (Little Barford Power station) and Orsted (Hornsea) - breached their licence conditions. ?
On receiving NGESO’s report the areas Ofgem’s investigation will initially focus on are:
• NGESO’s requirements to hold sufficient back-up power to manage the loss of generation supplies. This can take two forms: inertial response delivered by generators already running and connected to the system, and frequency response, which is when the system operator calls on rapid-sources of additional power like batteries to manage a generator dropping off the system.
• How generators met their obligations with respect to the transmission fault. Generators have rules to follow on how they should respond to these faults. The investigation will look at whether these were met.
• Whether distribution network operators complied with their Low Frequency Demand Disconnection obligations and the circumstances leading to the loss of power to critical infrastructure. Ofgem will be looking at whether the companies made the right decisions both in the numbers of customers disconnected and whether those customers disconnected were the right ones.
Ofgem is liaising with the rail regulator (Office of Rail and Road) and will be engaging with the rail authorities to understand better why the drop in frequency on the energy network led to disruption for passengers.
Ofgem is additionally supporting the government¹s Energy Executive Emergency Committee investigation into the power failure and its consequences.
Jonathan Brearley, Ofgem’s executive director of Systems and Networks said:
“The power cuts of Friday 9 August caused interruptions to consumers’ energy and significant disruption to commuters. It’s important that the industry takes all possible steps to prevent this happening again.
“Having now received National Grid ESO¹s interim report, we believe there are still areas where we need to use our statutory powers to investigate these outages. This will ensure the industry learns the relevant lessons and to clearly establish whether any firm breached their obligations to deliver secure power supplies to consumers.”