GB Power Outage - AUGUST 2019

A widespread power outage affecting apparently random areas of the UK occurred on 20th August when Little Barford power station disconnected from the grid at 16:58 due to a lightning strike followed two minutes later by some units at the Hornsea One wind farm becoming disconnected. The outage affected train services where passengers were stranded, traffic lights, homes, Ipswich Hospital, Newcastle Airport, etc.

During the day, strong winds led to more than expected renewable power being available and so there were fewer thermal stations generating. With fewer thermal stations providing inertia in the grid, there was insufficient capacity to manage the outages and so grid frequency dropped to 48.9Hz, which is well below the permitted tolerance. This website showed that there were 183 seconds where the frequency was below 49.7Hz.

It is unusual for two generating sources to go off-line at the same time; the last occasion was in 2008. When generating capacity is lost, the grid frequency drops as the remaining sources try to adapt to the increase in load. At this point the network detects the drop in frequency and compensates by shedding load. Large users of electricity have conditions written in to their contracts that they can be disconnected automatically from the grid in the event of a severe imbalance between supply and demand. However, those large users are usually aluminium refiners and steelworks, data centres with their own backup systems, cold storage warehouses and gas plants. In this incident, essential services suffered but possibly because their own systems detected the frequency drop, pre-empted a power cut and fell back to backup systems.

This incident will have provided businesses and those managing critical infrastructure services with a clear picture of how well their backup systems worked, or didn’t in the case of Ipswich Hospital whose backup generators failed to start.

More Information

Little Barford power station is owned by RWE npower and is a CCGT gas-fired power station producing 482MWe from two GE 9FA+e gas turbines and 265MWe from the heat recovery steam generator and Alstom steam turbine.

Ørsted’s Hornsea One wind farm in the North Sea is still being developed and will be the largest in the world. There will be 174 Siemens 7MW turbines connected to shore using the longest AC offshore wind export cable at 467km. Total capacity will be 1.2GW.

There are various articles and interviews at: