UK Business Secretary Andrea Leadsom has set out the scope of the government's investigation into the power cut that affected a million homes and caused travel disruption across England and Wales on 9 August as generators cut off unexpectedly around 5.00pm. The National Grid said disconnections at the Bedfordshire-based Little Barford gas-fired power station and Hornsea offshore wind farm in Yorkshire had caused the blackout.

Business Secretary Andrea Leadsom (Image: UK Government)

The inquiry is being led by the Energy Emergencies Executive Committee (E3C) - a partnership between government, regulator Ofgem and industry - which will produce a full report within 12 weeks.

In a statement issued today by the Department for Business, Energy and Industrial Strategy (BEIS), Leadsom said: "Friday's power outages caused significant chaos and disruption to hundreds of thousands of people. National Grid is urgently reviewing what happened and will shortly report to Ofgem to consider what action may need to be taken.

"National Grid has already confirmed that the incident was not linked to the variability of wind power, a clean, renewable energy source that the government is investing in as we work towards becoming a net-zero emissions economy by 2050. Friday’s incident does however demonstrate the need to have a diverse energy mix."

E3C will establish what happened to cause the outage and if correct procedures were followed. It will also consider whether improvements are needed to prevent future power cuts and better respond if they do occur, including minimising impacts on people and essential services. Its review will complement the investigation being undertaken by energy regulator Ofgem into how the electricity operator responded in line with its licence conditions and system security standards.

The power disruption resulted from the operation of Low Frequency Demand Disconnection relays on the GB Power System at about 4:54pm, impacting hundreds of thousands of customers, and causing significant secondary impacts in particular to the transport network, BEIS said. Though demand was fully restored within 90 minutes, secondary impacts continued to be felt for much of the day, it added.

In particular E3C will: assess direct and secondary impacts of the event across GB electricity networks; identify areas of good practice and where improvements are required for system resilience; consider load shedding in regard to essential service customers and prioritisation; consider timeliness and content of public communications during the incident; and make recommendations for essential service resilience to power disruptions.

Low-carbon energy was used to generate more than half of the electricity used in the UK for the first time last year, according to national statistics released in July. Renewables and nuclear power made up almost 53% of generation in 2018, while the UK’s use of coal fell by a quarter to a record low of just 5%.

Although the government's policy to phase out coal in the UK is clear, gas was the biggest single source of electricity generation last year, at 39%. Zero-carbon nuclear power supplied nearly one-fifth of Britain's electricity, but the current fleet of reactor units will be retired by 2030 and Hinkley Point C in Somerset is the only new nuclear power plant under construction.

On 21 June, the UK became the first advanced economy to legislate for net-zero emissions, aiming to end its contribution to climate change by 2050. Two days later, it set out proposals to explore the use of the Regulated Asset Base approach to attract significant private investment for future nuclear power in the UK.