"Be careful what you wish for as you might get it all". In the case of the DITA, it answers all the questions, solves many of the challenges and delivers a whole range of benefits that align to providing interface, management and resilience in signalling power supplies. 

Technology

Using the proven Class II Switchgear, developed to deliver Network Rail's new signalling projects and provide upgrades to existing legacy systems, the DITA builds on the success gained in safety, system reliability and user interface. In recent years Network Rail's Class II product and system standard have helped to deliver a new generation of signalling power supply products. Alongside this has been a revolution in transformer technology, the use of Aluminium windings, low inrush, high efficiency, reliability and ease of user interface has resulted in a significant range of Class II and hybrid transformers. This range is an unprecedented, new generation of full Class II power transformers that exceed the minimum requirements of Network Rail specifications, with ground breaking benefits. Utilising on board eco-rail technology, which is fast becoming the preferred solution on the railways, the DITA range of transformers are a pioneering technology that delivers the lightest, most compact and environmentally friendly solution available. This range has been developed with Network Rail and deployed to support their DITA and other key improvement schemes such as copper elimination, inrush reduction and sustainability charter targets to reduce carbon emissions throughout the network. 

Waiting in the wings, the supporting act is a range of insulation monitoring and fault location technology that will support the DITA intelligence and allow it to become a strategic management tool, in the network of LV signalling power feeders. Boost capability within the TX tapings allows for multiple benefits when looking to support long feeder distances as well as offering cable reduction possibilities. All this technology needs some careful packaging and the newly approved GFRP Apparatus Case does just that. The twin skin material allows for significant thermal movement whilst managing solar gain and temperature spikes. The case construction has been tested to over 50kVA insulation resistance and therefore provides a very safe environment for the 650V, mitigating against earth bonding this allows for only a moderate earth value to support the IMD device in Class II applications. 

Standards NR/L2/SIGELP 27419

Network Rail have issued this DITA standard with a view to providing an easy step by step guide to identifying, prescribing and implementing DITA in a wide range of feeder scenarios. The standard has allowed designers to understand and then support the specification of DITA on projects as well as giving a benchmark to the supply chain.

Other supporting NR documents including "System Architecture Mix and Match Rules" and "Class II Retrofit Design Philosophy" help to understand the DITA USPs. A recent standard NR/LR/SIGELP 27416 modification of legacy power supplies help to complete the supporting NR documents, providing an outline and some examples of where DITA can be used to great effect. Finally, TECM (Target Earth Calculation Model), this allows designers to establish target values and feeder sub-division lengths, this helps to establish the key locations where DITA will support the network.

Supply Chain Engagement

Riding on the massive success of Class II over recent years, the DITA is a further opportunity to expand the product range and integration possibilities. It is an ideal project for collaboration as no single supplier can offer the entire product range. This collaboration is the key to the success of taking DITA to the market place. As a product that may be considered new and novel, the DITA requires some robust support from the supply chain, to aid design and specification, to demonstrate a wide range of features and benefits, to understand fully and align with the examples set out by Network Rail and finally, to offer the optimum product for application. The opportunity that DITA offers to Network Rail's current infrastructure is substantial; the key to unlocking that potential is early engagement and a real in-depth understanding of the whole system benefits. The wide range of suppliers and collaborators will ensure the success of this innovation, as projects take up the DITA and realise its true potential to deliver the solutions to many unanswered questions. 

Legacy Challenges

The current Network Rail LV network is dominated with Class I IT systems. Many of these have long feeders with significant numbers of FSPs on each feeder and all the usual infrastructure challenges exist, including challenging earthing conditions, cable theft and damage, rodent attack and demanding maintenance conditions. One goal here would be to have a more manageable network, smaller feeders, better fault location, advanced programmable protection systems and controllable interfaces between system architecture. If all the above sounds like a challenge you may be facing then look at DITA.

DITA Payback

As with all new assets there has to be a cost driver, with regards to the DITA this can come in many guises. Providing a definitive and controlled demarcation between Class I and Class II can be a costly business, if it requires the removal and replacement of large amounts of existing infrastructure, the DITA will allow this interface to happen when you want it. The twin output options allow for feeder optimisation, leaving you in control of cable sizes according to load. Dividing up the network into smaller portions will have a significant benefit in fault location, maintenance and re-establishing the operational railway. The DITA offers a significant opportunity to new signalling projects by allowing a legacy interface. Without costly replacement of existing assets, the legacy interface can be selected based on the optimum start and finish, rather than a widespread or complete feeder renewal.

The DITA switchgear assembly allows for the integration of new Class II 2 Core and 4 Core FGT cable as well as offering a Class I interface for 3 Core and armoured legacy systems. The large termination enclosures have been designed in line with BS BS5372:1997 and to facilitate the use of aluminium cable and the PADS approved bi-metallic pins or lugs. This supports Network Rail's Copper Elimination Challenge thereby further reducing material costs. Cable sizes up to 150mm 2 core and 4 core aluminium and copper cable can be accommodated.

Conclusion

There is a unique set of circumstances opening up on the existing rail network, necessity is driving change, challenges are outlined in Network Rail Innovation targets and supported by a range of new SIGELP Standards, products like DITA are an outcome of one of these challenges.

In delivering solutions to this challenge, the supply chain has a significant part to play in delivering the technology improvements, cost savings and collaboration that is critical to meeting CP6 targets.

Riding on the success of Class II, products such as DITA make up a basket of products to deliver with a more resilient Signalling power backbone, for the growing demand on the infrastructure.