Phototube sensor for active pantograph

In this paper a new measurement system able to detect the losses of contact between the pantograph and the contact line has been studied and set up. The measurement system uses photomultiplier tubes, consisting of a photocathode and a series of electrodes in an evacuated glass enclosure. The aim is to measure the duration of the ultraviolet emission due to electrical arcing during the losses of contact: an advantage of the proposed system is to be not invasive with respect to the pantograph equipment. Measurements carried out during high speed test runs and a statistical analysis of the data have revealed the effectiveness of the proposed sensor for detecting the losses of contact, in order to evaluate and test the performance of running pantographs and of the contact wires. An index defining the quality of the current collection can be extrapolated from the observation of the occurrence of arcing: such piece of information is extremely useful not only for maintenance activities, but also for predicting a control action in the case of servo-actuated pantographs.