Electricity supply for the Cuillin

Here's the view at the start of our walk. We climbed Bruach na Frithe which is just visible on the right hand side. But look at the electricity cables. They lead to the Allt Mor Dearg house. 3 cables take the supply left to right from Sligachan, but only 2 cables go to the house. Is one live and one neutral? Or is the central wire the earth connection? I think the very top wire on 42500V lines is earth. Our house is supplied in a similar manner to this but we only get one cable. Will have to investigate.