UK’s blackout first-responders included 475MW of batteries

Image: National Grid.

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.

“In this instance, 5% of Britain’s electricity supply was turned off to protect the other 95%. This had not happened in over a decade and is an extremely rare event,” National Grid said.

Editor Liam Stoker blogged over at Current± yesterday on the specific role that battery energy storage played on that Friday, looking also at how it can do more.

  • Referring to that previous event, Stoker writes that the two minutes and 22 seconds taken to restore frequency by a combination of load shedding and frequency response - a considerable amount provided by batteries - was four times faster this time around than the response to that prior event, in 2008, when there were no grid-connected batteries.
  • Within four minutes - 3:47 to be precise - grid frequency had been restored to its usual operating limits, significantly quicker than the 11 minutes it took a decade ago.
  • Social Energy, an aggregator of domestic batteries, said that its fleet all detected the incident within 200 milliseconds of it occurring; between 16:52:34.600 (shown in red) and 16:52:34.800 (shown in green). 

You can read the full blog over at Current±, which also features comments from other energy services providers including Limejump and Kiwi Power.

Coincidentally, reported yesterday that North Carolina's Clean Energy Plan, which is at the draft stages, could include ways to value the backup power capabilities of solar-plus-storage for communities often hit by storms. While this focused on backing up loads at individual rather than network level, the draft's authors at North Carolina's State Energy Office said the technologies could offer cost-effective energy resilience to customers as well as boosting adoption of solar and batteries at residential level. 

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