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 . 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 . 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. . Relating the contact force between the catenary and pantograph with the line irregularities, Collina et al.  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.
Ambrosio, J., Pombo, J., Pereira, M., Antunes, P., & Mosca, A. (2012). Recent Developments in Pantograph-Catenary Interaction Modelling and Analysis. International Journal of Railway Technology, 1(1), 249-278. https://doi.org/10.4203/ijrt.1.1.12