Transposition tower

In electrical power transmission, a transposition tower is a transmission tower that changes the relative physical positions of the conductors of a transmission line in a Polyphase system. A transposition tower allows these sections to be connected together, while maintaining adequate clearance for the conductors. This is important since it distributes electrical impedances between phases of a circuit over time, reducing the problem of one conductor carrying more current than others.

Karlsruhe transposition tower

Three-level Transposition tower

Top of a transposition tower

Transposition tower Of the 150kV line Eerde - Eindhoven Oost

Double-circuit lines are usually set up with conductors of the same phase placed opposite each other. For example, a section of a line may be (top-to-bottom) phases A-B-C on the left, also phases C'-B'-A' on the right. The next section may be B-C-A on the left, also A'-C'-B' on the right. Therefore, the rotation on each side of the tower will be opposite.^[1] Transposition helps to reduce the mutual coupling between conductors and between conductors and ground.^[2] It also useful in mitigating issues like induced voltages in nearby telephone lines.^[3]

Gallery

• 
  Here, on the right the phases are rotated; on the left, two phases are swapped, thus the rotation sense changed.
• 
  Transposition tower. On the right side, the phases are rotated upward, on the left side downward.
• 
  Transposition in the span field of a 420 kV-line in Sweden

• 
  Transposition on a single-phase line
• 
  Transposition by using multiple towers
• 
  Transposition by using elongated traverses

See also

• Suspension tower
• Dead-end tower