Optimal Reduction of Energy Losses in Catenary Wires for DC Railway Systems

Electric railways form a large energy user, covering approximately 50 TWh/year, over 2 % of the total annual electricity consumption in the European Union. The associated costs are a significant part of railway exploitation. Especially in low-voltage DC systems, as used in many parts of Europe, energy losses take a large share of the total energy costs. The losses in the overhead catenary wire take a significant share of these losses. A straightforward way for decreasing the energy losses is to increase the conductor section of the catenary.

The European Copper Institute has initiated a study to investigate the feasibility of increasing the catenary cross-section and to identify advantages and drawbacks. The initial study has focused on the 1500 V DC railway network in The Netherlands, while trying to estimate the scope for energy savings in Europe for 750-3000V DC systems.

If the conductor cross-section is optimised with respect to energy losses, the optimum conductor cross-section has been found to be significantly larger than the current standard. The energy saving will not be sufficient to justify a dedicated project replacing just the feeder wires (and in some cases the support gantries, too). Selective and gradual phasing-in of thicker copper conductors in the feeder wire yields following benefits for stakeholders in the Dutch railway sector:

• an estimated energy saving at 30 GWh/year, or 2% of the total Dutch traction power consumption
• an avoided annual emission of 21,000 tons of CO2 per annum
• improved traction performance and hence better punctuality of trains (to be quantified)
• enhanced energy saving and CO2 emission reduction by regeneration of braking energy (to be quantified).