One of the reasons that electricity is so useful is that it is relatively easy to move it around. One of the most noticeable ways that electricity is distributed around the country is by overhead line.
Overhead lines are easily noticeable. The chances are that you can see some right now from where you are sitting.
The design of an overhead line depends on whether it will carry high or low voltages.
Low voltage overhead lines tend to be similar to the wires in your house, except a bit thicker. They will be made up from a number of strands of conductor, usually copper or aluminium, wrapped in a plastic insulator.
Because these lines are carried on wooden poles and are generally quite close to the ground, the insulator stops accidental short circuits to earth, if for example the wire is touched by a tree branch or a passing lorry.
High voltage overhead lines are carried by steel pylons and are much higher above the ground. This puts them out of the way of tree branches and accidental collisions with lorries and buses.
Because of the high voltages being carried, these cables are much thicker than low voltage cables and as they are so high up, they do not need to be covered by an insulating layer. They are usually made from aluminium reinforced with steel (ACSR).
Overhead lines need to be securely fixed to their pole or pylon. For high voltage, un-insulated lines, this can be tricky as trying to join them directly to a steel pylon will interrupt the current.
To prevent this, the line is connected to the pylon by an insulator. These are the dark coloured disc-like objects that hang down from the pylon arms, to which the lines are connected. The discs may be made from porcelain, glass or glass-reinforced polymer (GRP).