Protection Measures against Wire Breaking due to Lightning on Overhead Power Distribution Lines

A wire breakage accident of overhead power distribution lines (OPDL) has a great impact on the reliability of power supply and public safety. As the wire of an OPDL has been changed from a bare wire to an insulated (covered) wire, the number of wire breakage accidents increases rapidly. Regarding the wire breakage of insulated wires, the authors explain the mechanism of the OPDL wire breakage accident and evaluate the countermeasures used in Japan. Insulated wires are more susceptible to wire breakage accidents than bare wires. Also, when a lightning strike occurs on a support pole of a distribution line, a wire breakage accident is most likely to occur. In rare cases, the wire breaks in the middle between two poles. Its cause is mostly a side flash from a tree. In Japan, various methods such as improved electric wires, special arcing horns, and arcing horns with zinc oxide elements have been applied as measures against wire breaking, and certain effects have been confirmed.