Towers are generally classified by shape into five types: goblet-shaped, cat-head-shaped, (shàng)-shaped, (gān)-shaped, and barrel-shaped. They are also classified by purpose into tension towers, straight-line towers, angle towers, transposition towers (towers for changing conductor phase positions), terminal towers, and crossing towers.
Based on their function in transmission lines, towers can be classified into straight-line towers, tension towers, angle towers, transposition towers, crossing towers, and terminal towers. Straight-line towers and tension towers are erected on straight sections of the line; angle towers are erected at bends in the transmission line; tall crossing towers are erected on both sides of the object being crossed; transposition towers are installed at regular intervals to balance the impedance of the three conductors; and terminal towers are erected where the transmission line connects to the substation structure.
Based on the structural materials used, towers used in transmission lines mainly include reinforced concrete poles and iron towers. From the perspective of maintaining overall structural stability, they are classified into self-supporting towers and guyed towers. There are various structural forms of power transmission towers. Looking at the transmission lines already built in my country, iron towers are commonly used for voltage levels greater than 110kV, while reinforced concrete poles are commonly used for voltage levels less than 66kV. Tower guy wires are used to balance the lateral load and conductor tension of the tower, reducing bending moments at the tower base. Using guy wires reduces the consumption of tower materials and lowers the cost of the line. Guyed towers are commonly used on routes in flat terrain. The selection of tower type and shape should be based on calculations to ensure that electrical requirements are met while also considering the voltage level, number of circuits, terrain conditions, and geological conditions of the transmission line. The appropriate tower type for a specific project should be selected based on practical considerations, and through economic and technical comparisons, the most technologically advanced and economically reasonable tower type should be chosen.