The contact between pantograph and catenary is the most critical part in the transmission of the electrical power for high-speed trains. Changing the oscillations of the overhead line, combined with the force between the pantograph, catenary and overhead line, can be minimized. Consequently, special pantographs and catenaries have been developed, while constructive modifications continue to be developed. The design criterion includes the permanent contact between the pantograph and the overhead line at high speeds and reducing the airoacustic noise and wear. Because of the difficult dynamic behaviour and very expensive costs for prototypes, all changes and new design concepts for the pantograph-catenary system are based on the dynamic simulation. Currently, it is permitted to carry on analyses for different pantograph concepts (e.g. elasticity) and active control components for innovating concepts.
For reaching superior speeds, researchers are carrying on studies to optimise the design of the Pantograph and catenary system with double pantographs. It was elaborated for the high-speed line Wuhan-Guangzhou (China) to permit trains to reach speeds of 350 km/h. A new scheme has been proposed for the pantograph and catenary system by optimising and rehabilitating the structure and the parameters of the system, including through the type of suspension of the catenary, the stress of the overhead line and the distance between the two pantographs, shows the study “Pantograph and catenary system with double pantographs for high-speed trains at 350 km/h or higher”, published by the Journal of Modern Transportation.
When two high-speed trains are linked together in operation, double pantographs have to be employed due to the restriction of current capacity. However, when the trains are running, pantographs slide along the catenary and cause it to vibrate. The vibration is propagated in the form of a wave along the contact wire.
The contact force between pantograph and catenary may vary considerably. If the space between the two pantographs is not appropriate, the influence of the vibration becomes more evident and may result in zero contact force, arcing and wear of the rear pantograph. Therefore, it is essential to highlight the influence of the space between pantographs on the dyanamic performance of the pantograph and catenary system for trains to reach speeds of 300 – 350 km/h.
When two pantographs run along the contact wire in a coupled form, a vibration waveform of the pantograph moving in the same frequency and parallel direction will result, due to the coupled action between the pantograph and the catenary. The interaction and overlap between the waves would decrease the vibration at contact points, reduce the difference in the static stiffness of the catenary and improve the quality of the current collection of the rear pantograph, the study shows.
Thus, “vibrations caused by the pantographs are in the opposite direction compared those caused by the contact wire when the space between the two pantographs are optimal for speeds of 270, 300, 330 and 350 km/h. When the running speed is around 330-350 km/h, the optimal space is approx. equal to 200 m”, the study shows. For the new scheme of the catenary system, when the space between the two pantographs is 200 m, the contact forces of the rear pantograph fluctuate slightly and are basically consistent with those of the front pantograph. Sustainable operation at 350 km/h can thus be fulfilled.
by Pamela Luică
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