Numerical study on multi-pantograph railway operation at high speed

University dissertation from Stockholm : KTH Royal Institute of Technology

Abstract: Multi-pantograph operation allows several short electric multiple unit (EMU) trainsets to be coupled or decoupled to adapt to daily or seasonal passenger-flow variation. Although this is a convenient and efficient way to operate rolling stock and use railway infrastructure, pantographs significantly influence each other and even significantly change the dynamic behaviour of the system compared to single-pantograph operation in the same condition. The multi-pantograph system is more sensitive and vulnerable than the single-pantograph system, especially at high operational speeds or with pantographs spaced at short distances. Heavy oscillation in the system can result in low quality of current collection, electromagnetic interference, severe wear on the contact surfaces or even structural damage. The mechanical interaction between the pantograph and the catenary is one of the key issues which limits the maximum operational speed and decides the maintenance cost.    Many researchers have paid a lot of attention to the single-pantograph operation and have made great progress on system modelling, optimizing, parameter studies and active control. However, how the pantographs in a train configuration affect each other in multi-pantograph operation and which factors limit the number of pantographs is not fully investigated. Nowadays, to avoid risking operational safety, there are strict regulations to limit the maximum operational speed, the maximum number of pantographs in use, and the minimum spacing distance between pantographs. With the trend of high-speed railways, there are huge demands on increasing operational speed and shortening spacing distance between pantographs. Furthermore, it is desirable to explore more practical and budget-saving methods to achieve higher speed on existing lines without significant technical modification.    In addition to a literature survey of the dynamics of pantograph-catenary systems, this thesis carries out a numerical study on multi-pantograph operation based on a three-dimensional pantograph-catenary finite element (FE) model. In this study, the relationship between dynamic performance and other parameters, i.e. the number of pantographs in use, running speed and the position of the pantographs, are investigated. The results show that the spacing distance between pantographs is the most critical factor and the trailing pantograph does not always suffer from deterioration of the dynamic performance. By discussing the two-pantograph operation at short spacing distances, it is found that a properly excited catenary caused by the leading pantograph and the wave interference between pantographs can contribute to an improvement on the trailing pantograph performance. To avoid the additional wear caused by poor dynamic performance on the leading pantograph and achieve further improvement at high speeds, it is suggested to use the leading pantograph as an auxiliary pantograph, which does not conduct any electric current and optimize the uplift force on the leading pantograph. After a brief discussion on some system parameter deviations, it is shown that a 30% of speed increase should be possible to achieve while still sustaining a good dynamic performance without large modifications on the existing catenary system.