The installation of overhead lines generally involves the following steps:
Surveying and Design-The line route should be designed to follow the most direct path possible, avoiding obstacles. Once the general route is determined, a field survey of the terrain along the path must be conducted.
Staking and Positioning-During this phase, the locations of key angle poles, the spacing between poles, and the specific type of pole for each location are determined. Wooden stakes are driven into the ground at each pole-pit site and marked with the corresponding pole number. The configuration for any necessary guy wires (stays) is also specified.
Foundation Excavation-Before digging the pole pits, the accuracy of the staked positions must be verified. The shape of the pit-circular or stepped-is determined by the soil conditions. For firm soil and poles under 10 meters in height, a circular pit is used; for looser soil and poles taller than 10 meters, a three-tiered stepped pit is excavated.
Pole Erection-Typically, components such as crossarms and insulators are attached to the pole while it is still on the ground, after which the entire assembly is raised into position. The erection process must be both rapid and safe. Once the pole is upright, its orientation is adjusted before backfilling begins. The soil should be compacted in 300-millimeter layers. During compaction, tamping must be performed alternately on opposite sides of the pole to prevent it from shifting or tilting.
Guy Wire Installation-Guy wires must be positioned to counteract unbalanced forces. The angle between the guy wire and the pole should generally be 45 degrees, and in no case less than 30 degrees.
Cable Unreeling-To unreel the conductor, a shaft (spindle) is inserted through the center hole of the cable reel. The ends of the shaft are then placed onto the supports of an unreeling stand. The stand must be adjusted so that both ends are level and the cable reel is lifted clear of the ground.
Conductor Stringing-Each conductor is permitted to have only one splice (joint) within any single span. However, in sections crossing roads, rivers, railways, significant structures, power lines, or communication lines, neither the conductors nor the overhead ground wires (lightning protection wires) are permitted to have any splices. Once the conductors are connected, they must be tensioned.
