Quote:
Originally Posted by Dave Rowland
Except for when a third (and fourth in the case of tube trains) rail is present, I don't know of any system anywhere whereby the power is in the two rails....  |
Sorry to be the bearer of bad news, but...In most railway traction systems where there is 3rd rail or catenary supply the current flows through the train and
exits through the running rails back to the source via earth. Where else could it go ? There has to be a complete circuit.
Which is why they say do not step on any rail !
Because the running rail is bonded to earth at regular intervals there should be negligible resistance, and since Voltage drop=Current x Resistance (Ohms law) there should be negligible voltage between the running rail and earth.
However if the bonding comes loose or undone the resistance to earth at that point will increase, possibly leading to a significant voltage becoming present there. This is why the UK rulebook states that on OHLE systems you must report a loose or damaged "Red Bond" immediately.
If these people are getting a 'buzz' out of the running rail there may already be a faulty earth. !
