An electricity pylon or transmission tower is a tall, usually steel lattice structure used to support overhead electricity conductors for electric power transmission., England]] (the vertical string of insulators) and conductor vibration dampers (the weights attached directly to the conductors) on a 275,000 volt suspension tower near Thornbury, South Gloucestershire, England]]. The first tower is a tension type. The others are suspension type.]]
High voltage AC transmission towers
Three-phase electric power systems are used for high and extra-high voltage AC transmission lines (50 kV and above). The towers must be designed to carry three (or multiples of three) conductors. The towers are usually steel lattices or trusses (wooden structures are used in Germany in exceptional cases) and the insulators are either glass or porcelain discs assembled in strings, whose length is dependent on the line voltage and environmental conditions. One or two earth conductors (alternative term: Groun