Surge Arresters
The main task of an arrester is to protect equipment from the effects of overvoltages. During normal operation, it should have no negative effect on the power system. Moreover, the arrester must be able to withstand typical surges without incurring any damage. Nonlinear resistors with the following properties fulfill these requirements:
_ Low resistance during surges so that overvoltages are limited
_ High resistance during normal operation, so as to avoid negative effects on the power system and
_ Sufficient energy absorption capability for stable operation with this kind of nonlinear resistor, there is only a small flow of current when continuous operating voltage is being applied.
When there are surges, however, excess energy can be quickly removed from the power system by a high discharge current.
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