Single-wire Earth Return - Networks and Circuits

Networks and Circuits

As demand grows, a well-designed SWER line can be substantially upgraded without new poles. The first step may be to replace the steel wire with more expensive copper-clad or aluminum-clad steel wire.

It may be possible to increase the voltage. Some distant SWER lines now operate at voltages as high as 35 kV. Normally this requires changing the insulators and transformers, but no new poles are needed.

If more capacity is needed, a second SWER line can be run on the same poles to provide two SWER lines 180 degrees out of phase. This requires more insulators and wire, but doubles the power without doubling the poles. Many standard SWER poles have several bolt holes to support this upgrade. This configuration causes most ground currents to cancel, reducing shock hazards and interference with communication lines.

Two phase service is also possible with a two-wire upgrade: Though less reliable, it is more efficient. As more power is needed, the lines can be upgraded to match the load, from single wire SWER to two wire, single phase and finally to three wire, three phase. This ensures a more efficient use of capital and makes the initial installation more affordable.

Customer equipment installed before these upgrades will all be single phase, and can be reused after the upgrade. If small amounts of three-phase power are needed, it can be economically synthesized from two-phase power with on-site equipment.