Find the right NKT contacts for your region here.
Beddington Underground Cables

Beddington/London, United Kingdom

Underground tunnel project for 400 kV cables to optimize enery supply for southern London - 30 km total length

Key Facts


National Grid

Total cable route length

30 km

Location of the project

Croydon, London, UK


2006 – 2011

Quantity of order

A turnkey 400 kV copper XLPE cable system


  • Development of a tunnel concept for cable-laying.
  • Design, engineering and manufacturing of a cable system with fire retardant outer sheath.
  • Supply of 400 kV straight joints and dry terminations.
  • Installation of cables and monitoring system. ▪ Onsite testing.

The project

The expansion of the grid in South London called for power transmission development expertise.

The Beddington power transmission project was a vital component when the circular electricity grid in Croydon, in the south of London, was to be expanded from 275 kV (kilovolt) to 400 kV.
A tunnel, 10 km long and 3 m in diameter, was bored for the cable-laying between the Beddington and Rowdown substations. This solution prevented traffic disturbances during the construction work, avoided problems with the existing underground infrastructure and allowed for efficient installation.
NKT has a splendid track-record when it comes to developing special solutions for safe and stable power transmission and we are happy to have received the contract for this challenging turnkey cable system project. The mission included everything from specific product development in close collaboration with the customer through to manufacturing of cables and accessories. Onsite installation, final testing and subsequent project acceptance by the customer were also integrated in the contract.
Reference Map Beddington

The solution

We produced and laid a total of 30 km of 400 kV 2500 mm² copper XLPE cable in the tunnel.

Before the actual work onsite began, we built a full-scale tunnel model. The installation simulations conducted in the tunnel model guaranteed a subsequent perfect fit of all the components and ensured trouble-free onsite installation. During the preparation work, we also developed a special tunnel vehicle and installed steel support systems for smooth cable routing.
A great result of the intensive cooperation with our customer was a cable design characterised by minimal transmission losses and extremely low electromagnetic emissions.
We produced the cable system in our state-ofthe-art factory in Cologne, Germany. The cables had a length of 1100 m per drum and a total weight of 60 tonnes, and we managed to transport them across Europe from Cologne to London on extra wide drums specifically developed for this purpose.
To maximize the transfer potential, the cable was cross-bonded and implemented. A monitoring system helped ensuring maximum safety and full availability of electrical energy. Thanks to our extensive knowledge, strict preparations and collaborative skills, this project was a complete success.
“The cable system in the tunnel is characterised by minimal losses and extremely low electromagnetic emissions.”
Beddington Underground Cables