National Grid had experienced three blackout “near-misses” in the last few months before Friday's outage left almost a million homes in the dark and forced trains to a standstill around the UK, it has emerged.
The system operator, which is already under investigation by the energy watchdog, has been accused of not doing enough to protect against the risk of blackouts.
Industry sources have now claimed that National Grid has been aware of the growing risk of a wide-scale blackout 'for years', and has suffered a spate of near-misses in recent times, according to The Guardian.
The grid's frequency - a measure of energy intensity- normally sits around 50Hz. However, the paper said that in recent months the grid’s frequency has fallen below 49.6Hz on three different occasions, the deepest falls seen on the UK grid since 2015. On Friday the blackout was triggered when the frequency slumped to 48.88Hz.
In June, the frequency of the grid plummeted to within a whisker of National Grid’s legal limit of 49.5Hz after all three units of EDF Energy’s West Burton gas-fired power plant in Nottinghamshire tripped offline without warning.
Prices delayed by at least 15 minutes.
In addition, the grid’s frequency fell to 49.55Hz on 9 May, and 49.58Hz of 11 July.
A spokesman for National Grid said these events were “independent”. He added that there was “no trend or prediction of more frequency excursions”.
“Over the past four years frequency has regularly fluctuated between the agreed limits, as part of the normal day-to-day operation of the electricity system,” he added.
They will now face an investigation into its handling of the energy system after the first blackout in more than a decade following the shutdown of a gas-fired power plant in Bedfordshire and the Hornsea windfarm in the North Sea at about 5pm of Friday.
Steve Shine, chairman of Anesco, a battery company, said: “It would be easy for National Grid to write this incident off as a fluke event, but they have actually been aware of this potential issue for many years.”
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