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Chaos caused by last week’s power cuts leaves industry chiefs facing big questions
When lightning struck part of Britain’s national electricity grid near Bedford shortly before 5pm on Friday last week, it should have been a routine event. Lightning strikes hit the grid more than 1,000 times every year, usually with no discernible impact.
Yet on this occasion it triggered an unexpected chain of events that less than two minutes later had resulted in power being cut to more than a million homes around Britain and chaos being unleashed on the rail networks. Passengers spent hours trapped on immobile trains, while in Ipswich part of a hospital ended up in the dark.
The blackout, the most serious in Britain in more than a decade, has raised searching questions for National Grid, the FTSE 100 company that is entrusted with keeping the lights on, as well as for other organisations responsible for Britain’s energy and transport infrastructure.
National Grid yesterday submitted a preliminary technical report to Ofgem, the regulator, early details of which were obtained by The Times. Here, we document what is thought to have happened and the key questions that will need to be answered.
The initial failure [4:52pm]
The lightning strike caused a temporary trip to the circuit, resulting in a brief electrical disturbance to the national grid.
More than 150 miles away off the coast of Yorkshire, Orsted is commissioning Hornsea One, the world’s biggest offshore wind farm. Though still under construction, it was generating 800 megawatts of power. Preliminary analysis suggests that this output dropped almost instantly after the lightning strike. Nearer to the strike, at least part of RWE’s Little Barford 730MW gas plant in Bedfordshire also tripped off almost instantaneously. It appears that smaller power plants connected to the distribution network may also have tripped at this point. Either way, there was a sizeable, sudden drop in supply.
Key questions
Why did the plants trip?
Orsted has confirmed a “technical fault”, but has given no details; RWE is still investigating, but suggests an automatic safety shutdown after an “abnormality”. Initial National Grid analysis suggests that both should have withstood the disturbance from the strike.
Could this happen again?
Orsted says that the fault was rectified, though it won’t say when. Over the weekend National Grid paid almost £100,000 to “constrain” Hornsea to run below its maximum output. Senior industry sources believe this may have been due to the risk before the fault was fixed; National Grid denies this.
Was Hornsea a risk because it was still being built?
Industry sources suggest the fact that Orsted is still commissioning Hornsea made faults more likely. Should it have been allowed to generate so much power at this stage? One City source questioned whether Orsted could have sought to start generating early for financial benefit. Orsted said it “absolutely refutes” that construction was rushed and emphasised that it had to “fulfil hundreds of compliance tests approved by National Grid” before it could start generating.