UK Power Networks has completed a major phase of a £7 million electricity infrastructure upgrade in South London, using horizontal directional drilling (HDD) to install high-voltage cables beneath an operational railway and tram network.
The project involves replacing existing cable circuits between Sydenham Park and Churchfields with nine kilometres of new 33kV cabling. A key engineering challenge was the route beneath the railway and tram lines at Avenue Road Station, where a 50cm tunnel was created to accommodate ducts and cables while rail services continued above.
HDD enabled the installation to be completed underground without major excavation of the surrounding roads or disruption to railway operations. The technique involved drilling a pilot bore before progressively increasing its diameter to accommodate the cable ducts.
Portfolio manager Claire Sheridan said: “The HDD is a complex engineering operation that keeps the trains running and the streets open while the works take place. First we drill a small pilot hole, then we progressively widen it four times in order to achieve the correct diameter to pull the ducts through. We pulled the ducts through beneath the railway, keeping a safe distance from homes and track.”
The new cables use cross-linked polyethylene (XLPE) insulation and are intended to improve network resilience and reliability for thousands of electricity customers. The project also incorporates spare ducts to provide capacity for future network upgrades.
The work is being delivered in coordination with a separate £20 million project involving 132kV cables between Beddington and Sydenham. Together, the projects represent approximately £30 million of investment in the local electricity network.
“We’re installing modern cross-linked polyethylene cables, futureproofing the network and delivering a more resilient supply for our customers.” said Jason Callaghan, project manager at UK Power Networks. “The main driver for the project is to upgrade the cable circuits between Sydenham Park and Churchfields, it’s a major step forward for local network reliability. There has been close liaison with Transport for London, Network Rail and the council, to carry out the HDD effectively.”
The constrained urban environment presented additional engineering challenges, with existing utility infrastructure underground and residential streets, tramlines and an active railway above ground.
Fintan McCusker of McCormack Drilling added: “This was a challenging project given the tight suburban location, railway infrastructure, and utilities to be negotiated by HDD. Our team worked closely with UK Power Networks and Clancy to develop a workable solution to the many engineering challenges at this location. It required meticulous attention to detail right through from feasibility, design, planning through to installation.”
The project has also required coordination between engineering, consenting and stakeholder teams to manage the complex urban environment.
“Working alongside UK Power Networks Major Projects Consents and Stakeholder Engagement teams in a complex urban environment, Savills Land Assembly and Building & Project Consultancy teams provided a suite of services to support the successful delivery of this project,” said Richard Fisher, client delivery lead within Savills Utilities and Infrastructure team. “Close coordination between teams across UK Power Networks, Savills, and delivery contractors was essential in securing the necessary consents and maintaining relationships with stakeholders throughout the project.”
The project supports continued modernisation of South London’s electricity infrastructure while demonstrating how trenchless installation techniques can reduce disruption when high-voltage assets must cross operational transport infrastructure.
