High voltage transmission lines are grid lines used to deliver electricity over long distances. The high voltage is required to reduce the amount of energy lost during the distance.

In Europe, those high voltages are considered to range between 110 and 750kV.

Transmission lines generally tend to use high-voltage three-phase alternating current (AC) to ensure reducing the loss of energy during long-distance transmissions.

However, high-voltage direct-current (HVDC) technology proves to be more efficient in transmissions over very long distances of more than 600 km.

An 'overground' power line is a structure used for power transmission and distribution across large distances. It represents uninsulated electrical cables (commonly multiples of three for three-phase power) suspended by towers or poles.

The method uses the surrounding air as insulation method, making it generally the least costly method of power transmission for large quantities of electric energy.