The public may have to consider paying for more back up power in order to prevent a repeat of the 9 August blackout, energy experts have warned following the publication of the National Grid Electricity System Operator (ESO) report into the incident.

The interim report on the power cut, which left nearly a million people without power and severely disrupted many commuters’ homeward journeys, confirmed that it was triggered by a lightning strike on the Eaton Socon, Wymondley Main transmission circuit.

Immediately following the strike, it said the Hornsea offshore windfarm and Little Barford gas power station almost simultaneously reduced their energy supply to the grid, removing approximately 1.4Gw of generation from the grid.

Professor Tim Green, co-director of Imperial College London’s Energy Future Lab, told Utility Week that the incident raised questions about resilience and the public’s appetite for funding it.

He said: “To have two large generators falling off the system pretty much simultaneously is an exceptionally rare event. While the power cuts were obviously very frustrating for those hit by them, the reaction was pretty impressive and a lot of the knock-on problems were not actually anything to do with low-frequency demand disconnection (LFDD).

“In terms of whether National Grid is holding the right level of reserve – when the power cut happened they were holding just over 1Gw and it looks like at least 90 per cent of that came good.

“If the decision is taken that we need to double that you’re looking at close to £300 million a year. If you spread that over 25 million customers, that’s £12 a year. Longterm, do people want to invest in the system to that level, to prepare for the worst case scenario? Perhaps we need a national conversation about it.”

But he said that the blackout was a “rare occurrence” and it is “Ill-informed to think you can entirely guard against something similar ever happening in the future.”

Thomas Edwards, senior modeller at Cornwall Insight, agreed that more reserve capacity, like batteries and gas plants that can rapidly be fired up, may need to be procured if it is judged that similar power cuts must be avoided.

While National Grid was holding 1Gw of response capacity, the overall loss of transmission connected generation was over 1.3Gw.

“There is a balance here between the likelihood and scale of potential distribution and the amount consumers might be prepared to pay to avoid this in our increased digitalised aged”, Edwards said.

“The investigations will need to evaluate the way the National Grid assesses response and reserve given the changing mix of generation on the system and how services are provided and contracted for, including the liabilities on providers unable to fulfil their obligations.”

The conclusion that variable renewable generation was not to blame for the major recent blackout was seized by green energy group.

Some critics had cited the failure of the Hornsea windfarm as evidence of the grid’s growing vulnerability to disruption due to its increasing reliance on more intermittent renewable generation.

RenewableUK’s deputy chief executive Emma Pinchbeck said: “National Grid has stated that the outage had nothing to do with the variability of renewables. To ensure our power system is as robust as possible going forward, we need to upgrade our old infrastructure so that we have a grid fully fit for the energy transition and which makes the most of cheap flexible, renewable technologies.”

Her comments were echoed by Richard Black, director of the Energy and Climate Intelligence Unit (ECIU)

He said: “It (the report) makes clear however that the power cut cannot be blamed on the increase in renewables, as some people have claimed; multiple factors were involved, so highlighting just one is misleading.”

Black also highlighted the report’s finding that the outage itself was not responsible for the widespread disruption seen on the railways, given that the electricity supply to rails and overhead lines stayed on and signalling failures were small.

He said: “It raises the question of whether some modern trains are overly sensitive to voltage fluctuations and hard to restart.”

He added: “Ofgem’s own inquiry will now focus on whether any of the companies involved were at fault – for example, in not providing enough security against generation faults.

“What is less clear is who will inquire into Ofgem itself; as the regulator, it has a duty to ensure not only that the current system is robust, but also that companies are investing in clean technologies such as battery storage quickly enough to decarbonise in line with government policy and keep the lights on while doing so.”

The GMB used the report’s publication to call for the National Grid ESO to be brought into public ownership.

Justin Bowden, national secretary of the UK’s second biggest union, said National Grid must ensure it had enough spare capacity to cope with unexpected outages, which it said would only become more frequent as the UK switches over to renewables.

He said: “Whatever the final outcome of the blackout inquiry some lessons should already have been learned to make sure lightning doesn’t strike twice.

“A private monopoly like National Grid is not the best way of ensuring that the lights are kept on. It is time that this part of the National Grid was brought into the public sector.”

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