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Metros & Urban Rail

Traction Power Case Study: Integration of Static Frequency Converters into a metropolitan network

Traction Power Case Study

Queensland’s Moreton Bay Rail (MBR) project is the first metropolitan rail network system to adopt Static Frequency Converter (SFC) technology in Australia. 


Aurecon, as part of the AECOM Aurecon Joint Venture (AAJV), is the principal electrical designer of the feeder stations for this landmark project.

Alan Buttery, a senior electrical engineer based in Aurecon's Brisbane office, shares insightas to why an SFC solution was selected, how it is being delivered and what benefits it will produce for the transport network.

Single phase supply

Until recently railway feeder stations consisted of transformers which derived a single phase supply from two phases of a utility’s three phase network. Unfortunately, the supply of a significant single phase load from a three phase grid results in voltage imbalance.

This typically restricts the connection voltage to transmission levels (≥110 kV) and can require additional equipment to counter such imbalance effects.

The SFC is a power electronic based alternative to the traditional transformer based feeder station, having a number of distinct advantages including:

  • The ability to connect at lower distribution voltages (i.e. 33 kV), which are more abundant and less expensive to work with than transmission infrastructure.
  • The ability to draw from the grid as a three phase balanced load at a nominated power factor (i.e. the ‘perfect’ HV customer)
  • An increase in traction supply reliability with the potential to operate in synchronism with adjacent feeder stations, turning the railway into a meshed network
  • Better regulation of traction wiring voltages and capture of train regenerative braking

While SFCs have been utilised in European railways for some time, they are only just beginning to find their way to Australia. The MBR project is the first such implementation of SFCs in an Australian metropolitan rail network, with Aurecon engaged, as part of the AECOM Aurecon Joint Venture (AAJV), the principal electrical designer of the feeder stations for the project.

MBR is adding 12.6 km of dual track from Petrie, located on Queensland Rail’s existing North Coast Line (NCL) to Kippa-Ring, servicing six new passenger stations and a 10 x 6 car stabling facility at Kippa-Ring. 

MBR will provide a dedicated public transport corridor for the Moreton Bay region, which is experiencing significant population growth. Queensland Rail’s initial power analysis selected 2 x 33 kV connected SFC feeder stations as the most suitable option to supply MBR, due to a lack of readily-available 110 kV infrastructure and project time/cost constraints. 

An additional benefit was the ability for the SFCs to provide support to the adjacent NCL, if synchronised.

Moreton Bay Rail graph

Above: A high-level electrical arrangement of MBR and the adjacent NCL, showing MBR synchronised with a transformer at Bald Hills Feeder Station (synchronised track denoted in green).


First-principles engineering

The SFC’s unique abilities required a significant amount of first-principles engineering to be undertaken prior to their integration into Queensland Rail’s existing rail network. In addition to the ‘business as usual’ substation design, we contributed to:

  • Modifying the typical railway interlocking schemes to accommodate the SFC’s synchronising abilities and energisation/earthing sequences.
  • Developing a new protection philosophy for both the three and single phase Gas Insulated Switchgear (GIS), given the SFC’s fault current limiting behaviour and synchronising abilities. New relays and schemes were introduced, with utility protection concepts introduced to the rail environment.
  • Assisting Queensland Rail with the utility connection assessments at both SFC sites and adjacent 110/25 kV feeder stations.
  • Modelling the MBR corridor and adjacent North Coast line to examine traction return current splits, metalwork voltages during faults and harmonic interaction between feeder stations, traction wiring and rolling stock.

The above tasks involved working closely with Queensland Rail, the SFC and prefabricated switchroom vendor and Energex.

Moreton Bay Rail graph

Above: A conceptual model of Rothwell Feeder Station. From the right hand side clockwise – prefabricated switchroom with cable trench, single phase filter, 2 x 11/0.433 kV padmounts, SFC single phase transformer and signalling filter, containerised SFC, three phase transformer and heat exchanger.

MBR is currently well into construction, with factory testing of the major substation components underway. Following factory testing, the SFC and prefabricated switchrooms will be delivered to site where commissioning will commence.

The rail line is anticipated to be delivered by late 2016.

The AAJV is well placed to assist rail entities in SFC integration and SFC-related engineering studies, having experience with both GE and ABB 50 hertz SFC technologies.

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