Sanding bar
A contact strip is part of a pantograph on rail vehicles . The contact strip establishes the contact between the live contact line and the vehicle. Depending on the design of the pantograph and the upper current to be transmitted, it can have one or more, usually two, contact strips. They are placed on the frame of the pantograph and are pressed against the contact wire during operation, so that a conductive connection exists. Contact strips are usually made of graphite , as this is electrically conductive, but the contact wire is less mechanically stressed than steel or other materials. The material pairing is selected in such a way that wear occurs primarily on the easily replaceable contact strips and, if possible, not on the contact wire.
conditions
Particularly with pantographs on vehicles for high speeds and high outputs, very high demands are placed on the contact strip. At speeds of 300 km / h in planned operation (and even more in test purposes), it has to withstand the forces that act between it and the catenary, as well as withstand air resistance and the dynamic lift and downforce that it creates. This is difficult in the high speed range because the contact line is never horizontal and the pantograph has to compensate for the constantly changing height difference between the vehicle and the contact wire. In particular at support points where the chain system is less elastic, the pallet can jump and an arc occurs. Extreme temperatures occur that leave notches in the contact strip. If the thermal or dynamic load (e.g. due to the impact of an icicle frozen on the line ) is too high, the contact strip can break.
Contact strip breakage monitoring
If the contact strip breaks, there is an operational risk because the pantograph no longer runs cleanly along the catenary, the fragments can get caught in the chain system and damage it or tear it down and destroy it. To avoid this, the bars in newer vehicles are equipped with a contact bar breakage monitoring system. The contact strips are hollow and filled with compressed air , which is connected to the pneumatic lifting device of the pantograph. If the contact strip breaks, the air escapes at the break point and the pressure in the system drops, which has the direct consequence that the current collector with the defective contact strip is lowered.