A report out today on the causes of the UK’s recent blackout, where electricity supply to 5% of National Grid’s customers was cut off “to protect the other 95%”, highlighted that 475MW of batteries were used to help bring the network back online.
A timeline of events produced by National Grid ESO, based on interim findings conducted by the Electricity System Operator and submitted to regulator Ofgem on Friday evening, shows that a lightning strike the previous Friday evening had triggered events that led to loss of power for around 1.1 million customers and reportedly causing chaos on transport networks.
Our sister site Current± reported today 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. All in all, close to 1.4GW of load was lost from the system, which is prepared for the loss of capacity equivalent to its biggest generator, a 1.2GW nuclear reactor, Sizewell B.
What National Grid described as an “extremely rare” event – the ESO deals with more than 1,000 lightning strikes a year – then occurred as frequency continued to fall even as 1,000MW of backup power was called on, including 475MW of battery energy storage.
Customers on the distribution network had to be automatically disconnected to “ensure the safety of the network in a controlled way and in line with parameters pre-set by the UK’s distribution network operators (DNOs), which feed power from the grid into peoples’ homes and businesses.
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