A lightning strike that caused two separate losses of generation – described by National Grid ESO as an “extremely rare and unexpected event” – has been revealed as the cause behind Britain’s power cut on 9 August 2019.

This morning the electricity system operator published its interim report into the incident, revealing that a lightning strike at around 4:52pm on Friday 9 August was the trigger for a cascade of events which resulted in around 1.1 million customers losing their power supply.

It states that lightning hit a transmission circuit – the Eaton Socon – Wymondley Main. But while the grid’s protection systems operated normally and cleared the lightning within 0.1 seconds, shortly after there was a near simultaneous loss of load from both the Little Barford CCGT power station and Hornsea One offshore wind farm.

Those trips, National Grid ESO has concluded, were entirely independent of each other – dispelling a previous theory that a trip at one plant caused the other to de-load – but both were connected to the lightning strike.

The lightning strike also caused some losses from embedded generators in the area of the lightning strike, equivalent to around 500MW, after the Loss of Mains protection system kicked in.

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