Bonding of temporary metal fences at a Railway station platform

Yes it is something of a curious system.

The feeder design actually allow a greater voltage drop in the catenary to allow economy of design and allows feeder stations to be located further apart, with consequent lower number of national grip supply points.  I have seen models with a worst case far-end catenary voltage of less than 20kV (some of the trains decide that enough is enough if the supply voltage drops to 19kV and pull their own plug).

Fortunately the system has a much lower impedance in the return paths, so we are able and obliged to design the system so as to keep rail (traction return) voltages below 25V at stations otherwise there would be intolerable touch potentials at the rails, or at any bonded metalwork, much of which is accessible to rail staff and the general public alike.

One can see that the network is far from simple, with multiple effective earth connections in the return path.  There are other subtleties which I won't bore anyone else with here.

On a final point, the booster transformer system is being phased out because certain unscrupulous people would steal the copper conductors (a hazardous occupation, with at least one culprit 'paying the price' instead of 'getting the price' later).  Longer term plans will replace this with high level aluminium conductors as part of improved system designs (AT).

Yes it is something of a curious system.

The feeder design actually allow a greater voltage drop in the catenary to allow economy of design and allows feeder stations to be located further apart, with consequent lower number of national grip supply points.  I have seen models with a worst case far-end catenary voltage of less than 20kV (some of the trains decide that enough is enough if the supply voltage drops to 19kV and pull their own plug).

Fortunately the system has a much lower impedance in the return paths, so we are able and obliged to design the system so as to keep rail (traction return) voltages below 25V at stations otherwise there would be intolerable touch potentials at the rails, or at any bonded metalwork, much of which is accessible to rail staff and the general public alike.

One can see that the network is far from simple, with multiple effective earth connections in the return path.  There are other subtleties which I won't bore anyone else with here.

On a final point, the booster transformer system is being phased out because certain unscrupulous people would steal the copper conductors (a hazardous occupation, with at least one culprit 'paying the price' instead of 'getting the price' later).  Longer term plans will replace this with high level aluminium conductors as part of improved system designs (AT).