Have a look here I have drawings some where and books the actual part that went into the ground looked like an upturned horseshoe with the current collector at the bottom .It was dc current and failsafe all the metal was at zero potential, live at the single pole or plough..Did you know that most tramways found it difficult to compete with other transport forms as most tram companies had to pay for the upkeep of the roadway for about 1yd(mtr) each side of the trackway..then there was lack of investment ie maximise profit,...fiddle with this link as found a couple of dead Links Regards Alan
http://dewi.ca/trains/conduit/ploughs.html