Utility Week

40 | AUGUST 2022 | UTILITY WEEK Analysis London's Power Tunnels National Grid's mammoth £1 billion project to dig tunnels beneath London should help safeguard electricity suppliers in the capital for the next 120 years. W hile an overwhelming majority of Brits were booting up home offices for months of Zoom calls and vir- tual meetings on day one of the UK's Covid- 19 lockdown in March 2020, National Grid mobilised a seven-year, £1 billion project to dig 32.5km of "Power Tunnels" – nearly as long as the total walking distance of the Three Peaks Challenge – 30m beneath south London to keep residents of seven boroughs connected to safe and reliable electricity. "We had foremen and operatives arriv- ing to site with letters on BEIS [Department of Energy, Business and Industrial Strategy] and National Grid headed paper so that if they were stopped by police they wouldn't get turned around," National Grid project director Gareth Burden tells Utility Week Innovate. "You can't quite believe that was where we were." Due to complete and be fully operational in 2027, London Power Tunnels Two, the southern leg of what Burden describes as "rewiring London and connecting with the capital", follows the successful completion of a similar scheme to build 32km of tunnels and two substations in north London in 2018 – claimed to be the first major investment in the capital's electricity transmission system in more than half a century. Three metres in diameter, the tunnels have a lifespan of more than 100 years – though the high-voltage cables they carry will need to be replaced more regularly to meet future demand and facilitate city-wide, whole systems, growth. "We're rewiring London because our con- nections between our substations rely on circuits that were put in in the fi›ies and six- ties, and have reached the end of their asset life," Burden says. He explains that new infrastructure sufficient to power half a mil- lion kettles will also facilitate demand load growth off the back of new developments at Battersea Power Station and Nine Elms alongside broader EV uptake. "We'll be able to re-cable with very mini- mal disruption to London as a city going forward," he adds, "assuming we still need the transmission system in the way it is at the moment, and there's no indication, even in the long term, that that would change drastically." A boring world first Quite apart from starting work under a strin- gent code of pandemic practice – a rigorous "test, test, test" culture, outdoor briefings to ensure social distancing, and mask wearing – Burden says south London's ground itself is "challenging". "I remember going into the bottom of the sha›s at New Cross and feeling like Mother Nature telling you we shouldn't be doing this – it was raining downstairs," he explains. Yet, as of April, National Grid had four tunnel boring machines in the ground, cov- ering 10.5km of tunnel, and a first break- through slated for summer. With around a

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