Single-wire earth return

Single-wire earth return (SWER) or single-wire ground return is a single-wire transmission line which supplies single-phase electric power from an electrical grid to remote areas at low cost. Its distinguishing feature is that the earth (or sometimes a body of water) is used as the return path for the current, to avoid the need for a second wire (or neutral wire) to act as a return path.

Single-wire earth return is principally used for rural electrification, but also finds use for larger isolated loads such as water pumps. It is also used for high-voltage direct current over submarine power cables. Electric single-phase railway traction, such as light rail, uses a very similar system. It uses resistors to earth to reduce hazards from rail voltages, but the primary return currents are through the rails.

Lloyd Mandeno, OBE (1888–1973) fully developed SWER in New Zealand around 1925 for rural electrification. Although he termed it "Earth Working Single Wire Line", it was often called "Mandeno’s Clothesline". More than 200,000 kilometres have now been installed in Australia and New Zealand. It is considered safe, reliable and low cost, provided that safety features and earthing are correctly installed. The Australian standards are widely used and cited. It has been applied around the world, such as in the Canadian province of Saskatchewan; Brazil; Africa; and portions of the United States' Upper Midwest and Alaska (Bethel).

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