Power quality is increasingly important in the consideration of railway systems. Poor power quality affects the performance of trains and introduces problems for local distribution networks.This paper looks at improving modelling techniques to assess the power quality of a railway system. Modelling techniques used to simulate electrified railways are adapted to simulate power quality aspects with improved computational efficiency. The model developed is used to assess the voltage regulation and harmonic distortion of a rail system, and harmonic distortion on the local distribution network.
Reducing energy consumption in electrified transit systems is becoming increasingly important as energy prices rise and environmental concerns become more prominent. In electrified transit systems, significant savings can be accomplished by utilizing braking energy. Energy from regenerative braking can be used to power vehicles via the traction supply system, or stored on board vehicles using energy storage devices. The effectiveness and energy savings of regenerative braking or on board energy storage is dependent on the nature of the system, particularly the vehicle drive cycles and service frequency. The paper describes an analysis methodology developed to consider energy flows in an electrified transit system, hence enabling the potential benefits of regenerative braking and energy storage devices to be assessed.
The London Underground Sub Surface Railway (SSR) is due for a major upgrade by 2018. The upgrade will include the procurement of new rolling stock, a new signalling control system, a significant increase in service frequencies, and a significant power supply infrastructure upgrade. Investigation of energy efficiency measures, such as optimal rolling stock power with use of coasting in the run profiles, higher supply voltage, and conductor rail of lower resistance, allowed the system wide whole life costs to be significantly reduced with no reduction in customer benefits. The optimisation study undertaken achieved cost savings of £25m in capital expenditure and £70m in whole life costs, as well as a 20% energy and CO2 reduction, for the same improvement in customer journey time performance post upgrade. The paper describes in detail how the optimisation study was performed.
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