Using Bogie-Mounted Sensors to Understand the Dynamics of Third Rail Current Collection Systems

Abstract

Electric railways collect power from the infrastructure via various current collection systems. For high-voltage AC- and DC-powered railways, this is usually achieved using overhead electrification equipment and a train-borne pantograph. The dynamics of such systems are well understood, and the systems are able to be operated under a range of conditions and speeds. Lower-voltage DC-powered railways (<1500 V) use a current collecting shoe as part of a shoegear system and track side electrification infrastructure in the form of a conductor rail. The dynamics of such systems are equally as complex as those of overhead systems. This is due to the interaction between the conductor rail and the track system, coupled with the dynamics of the conductor shoe assembly, which are mechanically linked with the bogie and axle systems. The systems also collect high currents (<2000 A), and therefore maintaining an effective electrical contact is essential. The interface between the conductor shoe and conductor rail is regulated through standards and guidelines. However, there are numerous engineering challenges in the effective management of the whole system that have yet to be addressed. The mechanical design of the system must balance the requirements of good fatigue life with appropriate impact strength. Other issues such as removal of contaminants from the conductor rail surface and shoe wear also have an impact on the design. This article presents some experimental results from a bogie-mounted instrumentation system designed to monitor a typical example of a shoegear assembly operated on the UK railway system. The results indicate that the shoegear broadly performs in accordance with the design guidelines. Several points of loss of contact were observed, and it is shown that the contact force between the conductor shoe and rail can be estimated. The mean force was found to vary with third rail height, but a wide distribution of forces is found at any one height because of hysteresis in the shoegear. Large, but short-term, forces and torques occur because of third rail irregularities and ramps.