Overhead railway equipment power lines With overhead railway equipment power lines, wires are used to transmit electrical power from supply points to the railway vehicle and other components along the rail channel. While the rail is on constant movement, it must be ensured that the power is always supplied to the railway vehicles without even the slightest disruptions. Here, an overhead line also known as overhead wire is used as the power transmission medium. There are various terms used in referring to this medium which include; overhead line equipment, overhead contact system, overhead equipment, overhead wiring and catenary. The remaining part of this article will use the term overhead line. Structure of overhead railway equipment: overhead line. The structure of overhead railway equipment lines entails a series of wires suspending above the rail path at great heights that are only accessible by feeder channels from the traveling trains. These transmission media carries along with it very high voltages of power. Over head power lines are fed at certain regular distances due to resistance in transmission cables. From basic science of power transmission, electricity will always develop resistance as it travels along wires and as a result, voltage will be reduced. To avoid this occurrence which might cause under supply of power voltage, electricity in the wires is boosted at certain intervals. Contrary to basic principle of power supply, the overhead line uses only one power channel to transmit power. This is usually the live wire only that gets suspended above the train channel. The other side, which should be neutral, is obtained from the steel bars on which the train wheels rolls. This also saves a great deal in the amount of wire that could rather have been used for supply of neutral channel if there weren’t the steel bars. It is only the trolley bus that uses both channels in supply as there aren’t steel rods plus the fact that they use rubber tires. Tensioning in the overhead railway equipment Tensioning is applied to the overhead line for a number of factors. For one, if there wasn’t tension in the transmitting system, standing waves would have developed and caused regular breakage of the power cables. For this reason, hydraulic tensioning is applied so the wires become tight enough to absorb shockwaves as a result of contact with the moving body (the train). This is also known as auto-tensioning. Tensioning also serves changes brought about to the transmitting channels by changes in temperature, which might increase rate of sagging in the wires. Tensioning is applied in two ways – auto-tensioning and constant tensioning. Here, tensioning is not dependent on temperature in whatever way. It varies somewhere between 9 and 20 newtons per wire. There is a lot that goes into sustaining a healthy overhead line given vital aspects such as temperature and tension. Both of these factors have to be factored in the functioning of
the entire system even though they are rarely related. These two factors also determine the overall length of the overhead line of the overhead railway equipment.
Published on Feb 1, 2013
The structure of overhead railway equipment lines entails a series of wires suspending above the rail path at great heights that are only ac...