Keywords: railway overhead systems, high-speed railway pantographs, high-speed railway catenaries, contact mechanics, multibody systems.

Today, railway vehicles with electrical traction are the most economical, ecological, and safe means of transportation, making the energy collection of the railway vehicle pantograph on the electrical catenary a crucial element for their reliable running. A limitation on the top velocity of high-speed trains involves the ability to supply the proper amount of energy required to run the engines, through the catenary-pantograph interface [1]. Arising from the loss of contact, not only is the energy supply interrupted, but arching between the collector bow of the pantograph and the contact wire of the catenary also occurs. An increase of the average contact force would improve the energy collecting capabilities but would also lead to a rapid wear of the registration strip of the pantograph, and of the contact wire. The costs associated with the wear of the catenary wire: with a life span of 1-2 decades, and the pantograph collector strips: with a life span below half a year, increase as a result of the poor interaction [2]. The critical wear sections of the catenaries have been related to installation defects and with tensile stress on the contact wire in studies by Gonzalez et al. [3]. Relating the contact force between the catenary and pantograph with the line irregularities, Collina et al. [4] concluded that: the contact wire tension; the geometrical variation of the contact line caused by thermal expansion; and the existence of hard spots, all lead to perturbations on the contact force, contributing to shorten the useful life of the overhead equipment. All the studies referred to demonstrate that the deviations of the contact forces from the nominal specifications lead, at least, to shorter life cycles of the equipment and, eventually, to its catastrophic failure.

The study of the design and operational alternatives for the mechanics of the overhead electrical system require that the dynamics of the pantograph-catenary interaction is properly modelled, and that software used for analysis, design, or maintenance support is not only accurate and efficient, but also allows for the representation of all relevant details to the train overhead energy collector system. The catenary overhead system is mostly a structural system made of beams and cable elements being subjected to external loading caused by winds and pantograph contact forces. Its dynamic response is characterized by small displacements and small elastic strains: being that the axial loading of the wires, and the droppers lack of axial compressive resistance are the only sources of nonlinear structural behaviour. The analysis tools used by designers and analysts are based on the linear finite element method: being that the nonlinear effects are either linearized in turn of their average steady state, in the case of the beams axial loading, or corrected via the force vector of the finite element equations of motion, in the case of the unilateral axial resistance of the droppers [5]. The pantograph system is modelled either using lumped mass or multi-body approaches. Pantograph lumped mass models have to be identified experimentally based on laboratory testing, being basically linear models. Their dynamics can be appraised in a standard linear finite element code together with the catenary systems. Multi-body pantograph models use a multi-body dynamics method for their study and can account for any type of nonlinearity of their mechanical components. However, to be representative, they need to include realistic models of the kinematic joints between the mechanical components and, eventually, the description of the flexibility of the bow. Because of the difference in nature between the finite element and the multi-body methods, the analysis tools need to be able to interchange information during the dynamic analysis. This communication is achieved either by the co-simulation of the codes used for the catenary and the pantograph dynamic analysis, or by the use of a single numerical integrator with both methodologies in a single code [6]. This work overviews the features required for the computational methods used in the analysis of the catenary-pantograph interaction; discusses minimal requirements for model construction; and presents some recent applications to existing high-speed overhead systems.

[1]

A. Collina, S. Bruni, "Numerical simulation of pantograph-overhead equipment interaction", Vehicle System Dynamics, 38(4), 261-291, 2002. doi:10.1076/vesd.38.4.261.8286

[2]

A.W.C. Shing, P.P.L. Wong, "Wear of Pantograph collector strips", J. of Rail and Mass Transit, 222, 169-176, 2008. doi:10.1243/09544097JRRT156

[3]

F. Gonzalez, J. Chover, M. Vasquez, "Dynamic analysis using finite elements to calculate the critical wear section of the contact wire in suburban railway overhead conductor rails", J. of Rail and Mass Transit, 222, 145-157, 2008. doi:10.1243/09544097JRRT144

[4]

A. Collina, F. Fossati, M. Papi, F. Resta, "Impact of overhead line irregularity on current collection and diagnostics on the measurement of pantograph dynamics", J. of Rail and Mass Transit, 221, 547-559, 2007. doi:10.1243/09544097F02105

[5]

F. Rauter, J. Pombo, J. Ambr\'osio, M. Pereira, A. Bobillot, J. Chalansonnet, "Contact model for the pantograph-catenary interaction", JSME International Journal of System Design and Dynamics, 1(3), 447-457, 2007. doi:10.1299/jsdd.1.447

[6]

J. Ambr\'osio, J. Pombo, J. Rauter, M. Pereira, "A memory based communication in the co-simulation of multibody and finite element codes for pantograph-catenary interaction simulation", In C.L. Bottasso, (Editor), "Multibody Dynamics", Springer, Dordrecht, the Netherlands, 231-252, 2008. doi:10.1007/978-1-4020-8829-2_12

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