The power blackout that hit the UK this month was the worst in more than a decade. About 1m homes were left without power, passengers were stranded on crippled trains, an Ipswich hospital and Newcastle airport lost power. Tuesday’s report from the National Grid blaming the outage on two generators suddenly tripping out after a lightning strike leaves many questions unanswered. Ofgem, the energy regulator, is right to investigate whether any companies involved breached operating licences. But the incident raises loud alarms about the resilience of Britain’s energy system.
National Grid says the Hornsea offshore wind farm off Yorkshire and the Little Barford gas-fired plant in Bedfordshire both went offline seconds after lightning struck a high-voltage transmission line near Bedford on August 9. With some other small-scale suppliers also cutting out, some 1.9 gigawatts of generation was lost — far more than the 1GW of reserve power the grid was holding, as required by regulators. When the frequency on the grid, which reflects the stability of the system, dropped below allowable levels, 5 per cent of supplies were automatically cut to low-voltage distribution networks to help restore balance and prevent a worse blackout.
National Grid says two generators tripping off the system at once is exceptional and safeguards worked largely as they should. It remains unclear, however, how a routine lightning strike knocked two providers offline. Also unanswered is why some priority consumers such as an airport that should have been protected were hit by the supply cut. Unforeseen vulnerabilities were also exposed. While electricity to the rail network was not cut, 60 Govia Thameslink trains “reacted unexpectedly” to the frequency disturbance; 30 needed engineers to restart them.
Lessons need to be learnt from the incident in the light of an ever more sophisticated economy and demands to shift to renewable energy sources — and provide more power to charge electric vehicles — to help reduce carbon emissions. As Dieter Helm, an economist who carried out a 2017 review of energy costs, has noted, an increasing reliance on high-tech data and communications systems makes the economy more vulnerable to even short interruptions. Ensuring priority consumers such as critical infrastructure are properly protected is vital.
The shift away from coal and gas as baseload suppliers towards multiple smaller and more intermittent renewable sources also makes the task of managing the power system more complex. National Grid says the fact a wind generator was involved in this month’s incident has no significance. But some analysts say wind farms provide less “inertia”, or resistance to frequency drops on the grid, than traditional generators, making frequency more vulnerable to sudden supply drops.
The regulator should examine whether reserve power requirements — obliging the grid to hold back-up power equivalent to the biggest generator on the system that day — are sufficient. National Grid says increasing this would carry a cost. But that should be weighed against the potential costs to the economy of damage to, and failures of, critical infrastructure.
Bolstering network resilience will require government, regulators and power companies to work together. The collapse of two nuclear power station projects within the past nine months makes adoption of a new energy strategy even more pressing. A white paper has been delayed but should be given high priority by the new government. The country could pay a high price if it is not.