A transposition tower is a specialized type of transmission tower that is used to periodically change the physical positions of the three-phase conductors. This strategic re-arrangement, known as transposition, is essential for long-distance overhead transmission lines to address inherent imbalances in the electrical system.

On an overhead line, the geometric spacing of conductors is often asymmetrical (e.g., in a horizontal or vertical configuration), which leads to different values of inductance and capacitance for each phase. This asymmetry causes an unbalanced voltage drop, even when the load currents are perfectly balanced. To correct this, a line is divided into three equal sections, and the conductors are transposed at specific towers so that each phase occupies each of the three physical positions for one-third of the total line length. This ensures that the average inductance and capacitance for each phase are equal over the entire line, leading to a balanced system.