Revealed: London's network of power tunnels

The vast Thames Water Ring Main and Jubilee Line Extension projects impressed us with further proof that tunnelling can deliver major urban infrastructure with minimum impact. Less dramatic, but arguably more important, is London's little-known but fast-expanding network of deep power tunnels. Creation of the UK's national grid in the 1960s made London's old power stations redundant but the 66 kV central distribution network was still good for a few more years. However, by the 1980s, this needed upgrading to 132 kV to keep up with the city's voracious appetite for electricity—and trenching was an increasingly less viable option. This paper reports on the key design and construction aspects of London Electricity's 30 km network of high-voltage cable tunnels, their many advantages, the lessons that have been learned and plans for the future.