Overhead distribution lines are made of aluminium not wood.

20 feet.

Overhead electrical lines are usually made of aluminum, and some have a steel strand added which is used to give the conductor more strength (not to carry current).

Contour lines enable us to see changes in elevation using an overhead map

Overhead power lines are insulated from ground, typically using strings of glass or ceramic insulators. The wire itself is bare, though - it does not have insulation on it. There are many different types of overhead power line, but I'm not aware of any that actually have insulation.