High transmission lines are placed vertical or horizontal and why?

Horizontal arrangement

• Uniform electric field distribution: In the horizontal arrangement, the three-phase conductors are on the same horizontal plane. This arrangement helps to make the electric field distribution around the conductors more uniform. A uniform electric field distribution can reduce the occurrence of corona. Corona refers to the discharge phenomenon that occurs when the air around the conductors is ionized under high voltage. It can cause power loss and radio interference.

• Facilitate construction and maintenance: The tower structure of the horizontal arrangement is relatively simple, making it easier to erect and install the conductors during construction. At the same time, during the later maintenance and overhaul process, workers can more conveniently access each conductor for inspection, repair, replacement and other operations.

• Suit the corridor terrain: For some areas with relatively flat terrain and wide line corridors, the horizontal arrangement can make full use of the space and reduce the land occupation of the line.

Vertical arrangement

• Save the line corridor: In the vertical arrangement, the three-phase conductors are arranged vertically along the tower. This arrangement occupies less lateral space and is suitable for use in areas with narrow line corridors, such as the city center and mountainous areas with limited terrain.

• Improve the line stability: When the vertically arranged conductors are subjected to external forces such as wind and earthquake, their stability is relatively better due to the lower center of gravity. Compared with the horizontal arrangement, the vertically arranged conductors are less likely to gallop in windy weather, thus reducing the collision and wear between the conductors and lowering the incidence of line faults.

• Reduce inter-phase interference: The vertical arrangement can make the distance between the three-phase conductors relatively larger, thereby reducing the electromagnetic interference between phases and improving the quality and reliability of power transmission.