At the beginning of this year, our colleagues from Dynamic testing laboratory Radka Musilová and Jaroslav Václavík carried out measurements of the pantographs head, which is mounted on ETR700 high-speed trains, on the Italian railway lines. With the heads there is damage of suspension slats on the certain lines. The goal of the measurements was to find out stress of the slats in operation and, if necessary, to reveal in which section and for what reason the damage will occur.
Preparation works began in Pilsen. Based on the calculations MKP and the selection of critical points, the loading of the pantographs was carried out by means of a load cell in three mutually perpendicular directions and the measurements of the response to this force at the strain gauge points. This procedure was chosen not just for verification on the MKP calculations, but also for the possibility of estimating the forces acting on the pantographs during operational measurements. Instead of standard strain gauges were used special Kyowa strain gauges with double grid, resistant to elmg. interferrence, for the test. Thanks to using three independent measuring systems we managed to get valid operating data, as not all measuring systems were able to withstand the hard test till the end. Two telemetric systems were used from two independent manufacturers and one measuring swithcboard, usually used for online measuring. All measuring systems were placed over the pantographs roof insulator and battery charged. Besides resistence strain gauges several acceleration sensors were installed on the head.
What we could, we installed on the new pantograph on its own head already in Pilsen. Remaining installation were done in railway depo in Venice. First, old head of the pantograph was replaced with the new one. Then the measuring switchboard including the battery was placed on the feet above the pantograph insulators and strain gauges on the head were connected to the switchboard with approx. 6 m cables. The measuring was made on the route Venice – Milano and back, so roughly 500 km with the maximum speed 230 km/h. Right after arriving back into the depo the measuing technique and new head were uninstalled. No loosing of the measuring technique was recorded. However, the pantograph was slightly worn out by the ride. After evaluation of the straining of the pantograph head were found no tensions, which could cause not only plastic but also fatigue damage of the slats material. It was also found that the old head of the pantograph was more worn out and if it remained on the pantograph, measured tensions could be higher. Unfortunately it wasn´t possible to carried out the test on the route were the slats damage occurs.