A surge arrester, usually a stack of metal-oxide varistor blocks in a porcelain or polymer housing, has a sharply nonlinear characteristic: it passes negligible current at system voltage and heavy current once a lightning or switching surge drives it above its protective level. It is mounted close to transformers, cable terminations and line entries with short leads, because protection degrades with distance and lead length. Ratings cover continuous operating voltage, rated voltage and energy absorption.
Surge arrester on B phase at the cable pole blew its disconnector, the earth lead's hanging loose, so that cable is unprotected.
Line crews often say lightning arrester; on low-voltage installations the equivalent device is called an SPD, surge protective device.
Also heard as
- lightning arrester
- arrestor
Related terms
Insulation coordination
Sizing insulation and surge arresters together so any flashover lands at a cheap, self-restoring point, not inside plant.
BIL
Basic lightning impulse insulation level: the peak impulse voltage equipment must withstand without breakdown.
Overvoltage category
Class from I to IV ranking equipment by its position in an installation and the surges it must survive.
Flashover
Disruptive discharge over or around insulation that creates a short circuit through the air.