Surge Arrestors - An Introduction

A surge arrestor is an electric equipment used in substations and switch yards.  The surge arrester is used to protect the substation equipment from surges caused by lightning or by sudden switching.

The surge arrestor is an insulator which is a non-linear resistor. This means that the surge arrestor has high resistance at the operating voltage and low resistance as the voltage increases.

Thus when lightning strikes the overhead conductors in a substation, the arrestor acts like a conductor and discharges the surge to the ground.

Surge arrestors are usually constructed of MOV(Metal oxide varistor).  Zinc oxide is a widely used non-linear resistor.  The zinc oxide is the form of blocks which are stacked inside the arrestor.

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