One for us

The fourth wire
If you notice the electric transmission wires while travelling in train or by road you will notice a set of four transmission wires going along with you on the way parallel to the road or rail which are basically high voltage wires to decrease the power losses in carriage of electricity from one place to another. Once I asked a village electrician who was repairing the switch of a street light on the pole that what are these four wires meant for ? Why there is not a single wire instead of four?
He told me that if we look up the lowermost wire nearest to us is meant for carrying a positive current, the one next to it above is for carriage of negative current ,the third one from the bottom is a neutral wire which helps in absorbing the leakage current if there is any short circuiting in the system for the safety.
“And the fourth one at the top”, I asked him curiously
“That is meant for the birds to sit and rest” he replied confidently.