This is probably a 'return conductor'.
Basically, every electrical circuit needs to be a closed loop (Like how a battery has two terminals and every thing has to be connected to both terminals of the battery with two wires, to work).
To...
more... explain in simple terms (though this explanation is technically NOT very accurate), think of the generator at the power station as a having a positive and a negative terminal like a battery. To make the motor in an electric loco work, the positive and negative terminals of the motor have to be connected to the positive and negative terminals of the generator. (There is no positive or negative terminal per se, for an AC alternator, this is only for the sake of explanation)
But we see that our OHE normally has only 1 wire which is in contact with the pantograph (Think of this as the wire connecting the positive terminals). So a second connection is required between the negative terminals to complete the circuit.
Normally, the rails themselves are used for this. Current coming from the OHE passes through the traction motors, and then through the wheels of the loco into the rails below. At regular intervals, the the rails are grounded. Similarly one end of the generator is also grounded. So the earth itself acts as the other wire.
However, the rails are also used for track circuits to control signalling, and there will be railway/telecom communcation cables also near the railway tracks. In some cases, these cables will be close enough to the tracks that the return current in the steel rails can affect the signals in these cables. In these cases, a separate 'return conductor' is provided (which is basically just a wire which is connected to the rails at regular intervals) high above the ground, to minimize the interference.
please wait...Show AI ResponseYes, you are right. The return conductor is an essential part of the electrical circuit in the railway system. It ensures that there is a complete loop for the current to flow, just like how a battery needs both positive and negative terminals to work. In the case of an electric locomotive, the positive and negative terminals of the motor need to be connected to the corresponding terminals of the generator. While the OHE wire serves as one connection, the rails act as the return conductor, completing the circuit. However, sometimes the use of the rails for signaling and communication cables can cause interference. To minimize this interference, a separate return conductor, usually a wire connected to the rails at regular intervals, is provided at a higher level. This helps to maintain the integrity of the signaling and communication systems.