An investigation has been launched into a significant power cut that affected the UK on 9 August 2019, after two sources of power generation failed nearly simultaneously
The incident started with when the Little Barford gas-fired power station owned by RWE went offline, followed minutes later by the Hornsea One offshore windfarm owned by Ørsted.
UK Secretary of State for Business, Energy and Industrial Strategy, Andrea Leadsom said the power outages “caused enormous disruption.” She said National Grid, the electricity system operator in the UK, should “urgently review and report to Ofgem” on the causes of the incident. She said she would also be commissioning the government’s Energy Emergencies Executive Committee to consider the incident.
EnAppSys Ltd director Phil Hewitt told OWJ, “What happened was a trip at Little Barford and Hornsea One shortly afterwards. This caused a large frequency drop. The frequency went down to less than 49 Hz so certain parts of the network started to disconnect automatically causing the power cuts until the system came back into balance and the frequency stabilised. We would have expected the system to cope with this size of loss of generation but the double hit may have destabilised it.”
The image used here from EnAppSys shows the frequency literally dropping off the chart, the reduction in gas and wind generation from Little Barford and Hornsea One, and the upward response of pumped storage to try and arrest the event.
A National Grid spokesperson said, “We appreciate the disruption caused by the power outage and investigations have continued to better understand the situation.
“As the electricity system operator, we do not generate power directly, but use the power made available by the industry to manage the system and balance supply and demand. The root cause of the issue was not with our system but was a rare and unusual event, the almost simultaneous loss of two large generators, one gas and one offshore wind. We are still working with the generators to understand what caused the generation to be lost.
“Following the event, the other generators on the network responded to the loss by increasing their output as expected. However due to the scale of the generation losses this was not sufficient, and to protect the network and ensure restoration to normal operation could be completed as quickly as possible, a backup protection system was triggered which disconnects selected demand across Great Britain.”
The electricity regulator in the UK, Ofgem, said it had asked for an urgent, detailed report from National Grid so it can understand what went wrong and decide what further steps need to be taken. “This could include enforcement action,” said Ofgem.
Ørsted said, “Hornsea One lost load on 9 August, around the same time as another generation source lost load. We are investigating the cause, working closely with National Grid, which balances the UK’s electricity system.”
Although well-known critics of renewables and wind power have been quick to seize on the fact that a windfarm was involved, the incident is similar to one that took place in the UK in May 2008 in which windfarms were not involved, when the Sizewell B nuclear plant and Longannet coal-fired station went offline within minutes of one another.