Civils and stations

13.11.07

Making the right connections

The first train will enter service in only a matter of weeks time and probably the last thing on the mind of passengers speeding to Europe on High Speed 1 is “will the power supply to the train fail and interrupt my journey?” Fine wines and cheese or preparations for a meeting maybe, but not “will the build up of aluminium hydroxide on the cable joints cause the power to fail?” It is natural to assume that the experts are looking after such issues and they are. One is Davor Vujatovic, EDF energy engineering manager, High Speed 1.


Currently based at a site near Singlewell, Kent, Davor is overseeing the completion of the installation of the final section of the power network, which will enable the trains to run from London to Europe at up to 300kph. Working closely with main contractor Birse Power Networks (a Balfour Beatty Company) and suppliers including 3M – which has provided many of the joints and terminations used in the project – Davor and his colleagues have created a highly advanced power system that will see the High Speed 1 through to its completion, on time and within budget. This is despite it being one of the most challenging rail projects of recent times.

“The second section of the rail link – from Fawkham to St Pancras – brought new challenges for us,” says Davor. “In many places, it goes deep under London and therefore travels in tunnels. This meant several demanding requirements and limitations on the specifications of the 25 kV power cable joints and terminations that provide the traction power for the train derived from the 400kV National Grid network and distributed through London Tunnels. Similar specification had to be applied to the 11kV supplies to auxiliary services, such as lighting, signalling, tunnel ventilation, pumping stations and so on, derived from 11kV EDF energy networks distribution network and further distributed through private 11kV network through London Tunnels, Thames Tunnel and railway open route.

The first requirement was safety. No heat source or open flames could be used to seal the connections. The second was space. Confined areas and trunking demanded that equipment had to be of limited dimensions. The third was reliability and consistency of cable connection which meant the installation of the joint or termination had to be easy and straightforward.

“We then asked Birse, our main contractor, to select both joints and terminations that met these basic requirements,” Davor continues. “In addition, we asked them to set the technical specifications of products.” Given the technical limitations of the project, Birse knew it had quite a challenge on its hands.

John Hughes, electrical engineer, Birse Process Engineering Ltd, recalls how the final decision to recommend 3M Cold Shrink joints and terminations came about.
“The High Speed 1 railway is the first new railway to be built in the UK for over a century. This meant we were breaking new ground,” says John. “Taking 25kV and 11kV supplies through tunnels to meet strict 21st century safety regulations meant specifying joints and terminations which no supplier stocked as standard product. Fortunately, 3M met the challenge with modifications to its Cold Shrink joints and terminations and by incorporating other products from the 3M arsenal of innovative technology. To meet the specialised earthing requirements, the earth connections were taken outside the joint and cross-bonded. To comply with the LS0H standard (low smoke, zero halogen) – mandatory in tunnel sections – 3M incorporated its specialised 69 fire tape into the product spec.”

Approved by Network Rail
The 3M Cold Shrink design is approved by Network Rail and used by six of the major UK power utilities, so Birse knew it was a serious product. Inherent in its design is the control of stress in the connections, protection of the joint and consistency of installation quality.

3M Cold Shrink is ideal for situations such as this because it does not require any heat to be used, meaning that there is no need for gas bottles or flames on site, plus it is rapid to install, important in projects where time is of the essence. There is no need for additional specialist tools either and, as it is supplied in preformed kits, is easy to transport to the site. Its design reduces the chance of manual error and it is highly durable, meaning that there is less risk of faults in the future and the benefit of a long product life.

This is how the 3M Cold Shrink method works: rubber joint bodies and terminations are pre-stretched in the factory and assembled on a removable supporting plastic core. Out in the field, the tube is placed over the joint or termination point and when the inner plastic core is unwound and removed, the accessory sleeve shrinks to provide a watertight seal.

Naturally, a project of this scale has to take place in phases. “We are installing the 11kV network first, followed by the 25kV. We energised parts of the High Speed 1 Section 2 auxiliary supplies early in 2006. Terminations are still being installed in other parts of the network” adds Davor.

So when speeding to that important meeting in Brussels, or lunch in Paris, remember what keeps the train moving.

Tell us what you think – have your say below, or email us directly at opinion@railtechnologymagazine.com

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