HomeElectrificationSicat's 10-year service milestone and an increasing demand for Static Frequency Converters

Sicat’s 10-year service milestone and an increasing demand for Static Frequency Converters

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In 2005 the overhead line equipment (OLE) engineering team from Siemens Rail Electrification designed a replacement for the life-expired OLE equipment on the six and a half mile Glasgow Shields Junction to Paisley Gilmour Street line. Ten years on and the equipment has delivered outstanding service, achieving exceptional reliability, availability and maintainability (RAM) scores on this suburban route.

Siemens’ lightweight Sicat SA system was accepted as a replacement for the route’s existing Mark 2 galvanised system from the 1960s, with new aluminium cantilever supports being retro-fitted into the existing infrastructure. This was the first such system to be installed in the UK.

Network Rail’s strict brief for the system upgrade specified that no new structures were to be introduced as direct replacements for the existing support assemblies. Siemens successfully met this requirement by introducing a cantilever that was far lighter than the existing steel arrangement and, using readily available solutions, the system designers were also able to interface the Sicat SA system with other Mark 1 and Mark 3 OLE systems.

Catering for a high number of multiple- pantographs, (capable of supporting operations up to 160 kilometres per hour), the route called for high availability and robust, long-life performance, which Sicat SA has delivered. The system has proved to be exceptionally reliable, its performance vindicating the decision to replace the original equipment, both from an asset management and a maintenance perspective.

Effectively providing a modern, like-for-like replacement, the system can be installed with minimum disruption and impact on the network. The Sicat SA lightweight arrangements allow for single mobile elevated work platform (MEWP) handling, a reduction in on-line plant, and safer manhandling at height, compared to that of heavier cantilevers. The system may also be constructed both on- and off-site, offering the potential for significant cost savings over the entire programme.

Commenting on the work, James Goulding from Siemens Rail Electrification said: “The durability of the Sicat system in such a demanding application has been outstanding, perfectly demonstrating its exceptional performance capability.”

Danish electrification programme

The 14-year programme by Danish rail operator Banedanmark to electrify large parts of Denmark’s rail network is now well into its fourth year. Developed to create a sustainable and flexible framework within which both passenger and freight rail networks can operate, the network will deliver more stable and more cost-effective operation. It will also achieve significant environmental benefits, with the introduction of an expanded fleet of electric trains providing cleaner, quieter and more efficient operation.

In May 2015 Siemens Rail Electrification was awarded the contract to electrify nine rail routes, with the company appointed to equip about 1,300 kilometres of the country’s rail network with electrical overhead lines.

Working as part of a consortium with construction partner Per Aarsleff AS, by project completion in 2026, the company will have fitted overhead contact lines in a 2x25kV configuration to nine tracks on the network. The electricity supply will also be installed with substations, autotransformer stations and remote control equipment.

The scheme, which incorporates a Siemens Sicat SX solution for the overhead contact line, is now being rolled-out, with work underway on the electrification of the 57-kilometre double track stretch between Esbjerg and Lunderskov in the west of the country.

One of the key benefits of the Sicat SX system is that its lightweight design allows greater distances between poles. As a result, the steelwork requirement is much less than for traditional systems and far fewer foundations need to be dug.

Installation of the system is also fast and straightforward – with the layout being planned and designed by a software tool. The cantilevers are therefore able to be pre-assembled with a quick-fixing device, enabling a more flexible, efficient and cost-effective build programme to be followed. This all leads to a safer working environment for the installation team, with reduced risk of accidents due to fewer possessions being required in the build phase.

From a UK perspective, James Goulding added: “Building on the work that we are undertaking in Denmark, we would be able to build a model to address some of the challenges that will face the UK’s National Electrification Programme – with the aim of producing a safer, more cost- efficient and less risky approach to delivery.

“Sicat SX’s design means that it needs fewer posts and therefore fewer foundations per kilometre than conventional systems. These longer span lengths make installation faster, less disruptive and significantly more cost- effective, all of which are major advantages given the UK’s tight midweek possession regimes.

“This would particularly benefit routes that are affected by the Government’s electrification review.”

SFCs – now with MMC!

As a global leader in the development and supply of traction power supply systems, Siemens has installed static frequency convertors (SFCs) for infrastructure operators across Europe and the United States, the systems delivering single-phase traction power solutions from three-phase networks.

With the first installation over 20 years ago, and over 30 installations successfully commissioned in the last six years alone, the company’s portfolio of SFC projects includes the world’s largest converter, the 180-megawatt (MW) system in the Richmond area of Philadelphia.

In essence, SFC systems consist of only one converter that directly couples two networks, with the three-phase AC voltage being directly converted into a single-phase AC voltage with different frequency.

Supplied as part of the company’s Sitras® range, the newest generation of Siemens’ SFC Plus traction converters feature innovative modular multilevel converter (MMC) technology, which means that no traction transformer is needed to feed the overhead contact line. The company’s multilevel traction converters are quiet, space-efficient and require minimal maintenance.

The system’s flexibility extends to its housing, with both conventional building and containerised solutions available. This smaller physical footprint reduces the turnkey costs and makes this an ideal option where trackside space is limited and/or costly. A simple, single-circuit cooling system is provided for cooling the converter.

Because it uses a relatively low number of proven and robust standard components, MMC technology provides a high degree of flexibility in converter design and station layout, simplifying the design, planning, installation and commissioning processes, as well as any subsequent engineering tasks.

For rail infrastructure owners and operators, this means it is fast and efficient to install – with reduced grid/distribution network operator high-voltage connection costs, as well as simpler and more cost-effective maintenance, and reduced service requirements. The system also provides traction power network resilience.

Covering both central and decentralised traction power supply systems, Sitras SFC Plus systems provide a high degree of efficiency over the entire operating range, optimising the use of the primary energy and delivering high availability. The SFC can control harmonics, voltage flicker, power factor and voltage unbalance at the point of common coupling (PCC).

These modular converters provide the flexibility for each system to be adapted to meet the rail operator’s specific requirements, with block capacities of 12 to 120 MW and the ability to connect multiple blocks in parallel. As a result, a total power rating of up to 600 MW is attainable.

Where multiple converters are specified, a higher-level station control system can also be used. This specifies the operating mode and output power of the individual converter blocks that are operated so that the highest degree of efficiency is achieved with an optimised number of start/ stop operations. This means that in normal operation, the entire system can be operated unmanned, with monitoring and control being carried out remotely at the control centre.

The system can also operate in a number of different modes according to the network requirements – variable or fixed frequency operation (for central networks and decentralised networks respectively) and phase-shift operation in the event of failure of the three-phase network.

Importantly, these systems do not require neutral sections for phase separation within the SFC-fed section or area. This is significant, as neutral sections typically require quarterly to half-yearly maintenance to remain reliable, with design flaws in existing neutral sections proving to place considerable demand on maintenance resource and renewals funding.

James Goulding added: “Already used in rail applications across Europe and North America, Siemens Sitras SFC Plus systems are increasingly being considered for both mainline and metro applications – in the UK and elsewhere. Given their flexibility, cost effectiveness and the range of installation, operational and environmental benefits they deliver, these systems look set to become a preferred solution for infrastructure operators.”


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