The sudden loss of nearly 2GW of generation triggered a stress event and power cuts experienced up and down the country on Friday evening (9 August 2019).

The incident, which caused significant disruption up and down the UK, was triggered by failures at two large generators, specifically Orsted’s 1.2GW Hornsea offshore wind farm and the 727MW Little Barford gas-fired power station in Bedfordshire, operated by RWE.

Those failures triggered a stress event which saw the transmission grid’s frequency drop to 48.91Hz, far below the 49.5Hz threshold, causing the power cuts experienced by consumers.

Commenting on the incident, National Grid ESO described the simultaneous loss of two large generators as “rare and unusual”, and said the system operator was working with the parties involved to understand its causes.

Other generators responded to the event by ramping up their own output, but National Grid ESO said that due to the scale of generation lost – just shy of 2GW – the response was not sufficient to cover it and as a result, selected demand across the country was disconnected to protect the system itself.

Read more: Current