ABSTRACT
The comprehensive assessment of energy consumption of electric traction systems is only possible if all effects in the supply chain are considered. The contribution explains the energy interrelations for a typical Metro system with a length of 20 km. It evaluates the system wide energy saving methodologies measured at substation level, where energy billing is located.
The energy characteristics are investigated using the simulating the traction power supply during scheduled train operation with the software Sitras© Sidytrac for case studies. The results allow the comparison and assessment of the individual effect related to the same baseline. The energy saving variants comprise regenerative braking trains, influence of speed, weight, heating and cooling in trains, influence of the traction supply voltage, the reduction of losses and the installation of inverters and energy storage units in substations.
The results are extrapolated to annual energy consumption for cost assessment and also to annual CO2 emissions for environmental considerations.
In particular regenerative braking results in high annual energy savings of more than 15 GWh. The CO2 emissions are reduced in this case by more than 15 000 tons. Adopted operation combined with less transport performance allows considerable savings with without major effort.
The traction power supply can contribute with reduced losses and improved distribution of regenerative braking energy and increased nominal voltage.
In the substations along the line the installation of inverters in parallel to the rectifiers allows the exchange of waste recuperative energy with the three-phase feeding network. This energy can be used for other substations or other three-phase consumers.
Energy storage units in the substation save excessive energy which cannot be used by other trains and provides it when required later on.
The results of the investigations are explained in detail and are shown in a comprehensive graphical overview.
Keywords: Energy efficiency, Metro systems, Traction power supply.
