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Shield wire
a cable conductor, also known as an overhead earth wire; the grounded wire in aerial power lines that protects the conductive wires from direct lightning strikes. Shield wires are suspended above the current-carrying cables and are earthed at each pylon. They are usually made from galvanised steel, and measure 50-70 mm in diameter. The protectivity of a shield wire depends on the angle of protection; at less than 20 degrees, a lightning strike becomes unlikely. In the case of lines on metal pylons at 110 kW and above, shield wires are usually deployed along the entire length of the line; on lower-voltage lines they are used only on approaches to substations.
