Wednesday 10 Oct 2012


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Tonnes of copper saved through new approach to signalling power

Network Rail has developed a revolutionary approach to signalling projects that will save 33 % of the copper it would previously have used to distribute power.

For all new projects, power for signals has been sent down three-core armoured cables, known as class 1 distribution. This includes an earth wire, along with the two live wires.

Now after three years of planning and development, a class 2 based signalling power distribution system – using two-core cable – will be deployed, with a reduction in weight, transport costs, laying costs and the cost of the cable itself. The class 2 system is now being used in the Reading resignalling scheme.

Mark Southwell, Network Rail’s IP Signalling programme director, said: “Simply put – the whole system of power transmission had to be redesigned, from the transformers to the switchgear. Normal 3-core cable has steel strands wound through it to protect it from rodent damage and other hazards – which also means that any fault will find its way to all the equipment it connects. A new form of armour had to be developed, along with double or reinforced insulation for signal housing and switchgear.

“Our engineers were also able to integrate identification features within the cable to allow it to be uniquely identified to Network Rail, helping to deter cable theft.”

Network Rail’s technical director Steve Yianni said: “Some signal projects use up to 200 tonnes of copper just in the cables, so we knew that if we could find a way of reducing that, then we could cut costs significantly, and reduce our environmental footprint. Using a class 2 signalling power system had always been thought of as impossible, or at least very difficult, but we proved it could be done. Network Rail has shown that if an engineer has a good idea, they will stand by it and deliver it too.”

To achieve this, the distribution equipment and other parts of the power system, such as switchgear and transformers, are protected with double or reinforced insulation.

For instance, a project to renew 650volt signalling feeder cables in Scotland power will need 89 km of power cable, with 267km of copper cores if it was to use traditional class 1 distribution equipment. That is a saving of 72 tonnes of copper – at £5,000 per tonne.

Notes to editors

Inspired by the need to reduce the cost of a resignalling project in the Midlands, senior design engineer Tahir Ayub was given the time by Network Rail to formulate a plan, followed by a year of developing the safety case and two years of working to develop and implement new Network Rail standards and technology.

He was supported by project engineer Ernest Brigden, as part of the signalling national innovation group within IP Signalling.

The work done to drive the project encouraged Network Rail’s suppliers - 12 different companies in this instance - to innovate and develop new technologies. In fact, those technologies could find outlets in other fields, such as double-insulated streetlamps and even switchgear for electric car chargers.

After trials using the prototype equipment at the Leicester signalling test site, the use of class 2 equipment has now been approved and is ready for rollout across the network. Crossrail, Reading, Watford, Stafford and Wolverhampton resignalling projects are early adaptors to the class 2 based distribution system.

Class 2 cable is a generic term for enhanced unarmoured cable. This new cable provides enhanced mechanical protection, rodent protection (through the use of fibre weave) and security protection, utilising Network Rail identifiers.

A polycarbonate and coating solution was developed to insulate associated equipment, such as switchgear, transformers and signal housings.

Savings from the use of class 2 cable – new standard NR/L2/ELP/27408:

* Weight and cost of copper

* Transport;

* Cost of laying cables

* Time and complexity of design (class 2 does not require earth fault analysis or touch voltage control)

* Less cable contingency ( cable contingency is a cost placed on the cost of cable in case of theft or damage)

* Fewer power supply points required on large schemes

* No need to place the equipment outside the overhead line equipment fall zone

Sample figure: typical cost of 3-core 95mm cable: £20.68 per metre

Typical cost enhanced unarmoured cable 95mm cable: £14.13per metre. A saving of 32 per cent.

The Newport resignalling scheme was used as a test case in building the business case for this project. It was calculated that a saving of £1m would have been achieved in the delivery of the project’s power renewals.


Following the endorsement of the safety case Network Rail issued four new standards detailing the design, construction, installation and test of Class II based signalling power distribution systems. The supply chain was engaged to deliver the new range of products with much of the development costs borne by them. The following suppliers have been actively engaged with Network Rail through the Class II Technology Introduction process:

Transformers: Signalling Solution Limited; Invensys and Trans-Tronic

Rectifiers: Signalling Solution Limited, Invensys, Trans-Tronic

Power Cable: Cleveland Cable, Anixter cable, Eland Cable, Apex Cable

Low Voltage Switchgear: Schneider Electric, CSE Ltd, Henry Williams, Ilecsys, MGB, and Traix.

Auto reconfiguration Systems


Schneider Electric

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