Surge Arrester (Lightning Arrester)

A protective device connected between a phase conductor and ground that limits the magnitude of lightning-induced and switching-induced overvoltages to safe levels, protecting transformers and other insulation from damage. Modern surge arresters use Metal Oxide Varistor (MOV) elements that are highly nonlinear: they present high impedance at normal operating voltage but become conductive almost instantaneously when voltage exceeds the protective level, diverting the energy surge harmlessly to ground. Arresters are installed at substation line entrances, at transformer terminals — the most critically protected equipment — and at strategic points along the line.

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