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A rectangle with an arrow through it, between line and earth.
Also known as: Lightning arrester, Surge protective device, SPD, Box with an arrow to earth
A surge arrester is a deliberately non-linear component: an insulator at working voltage and a conductor above it, so a lightning surge is diverted to earth while normal current is not. It is drawn between the line and the earth symbol because that is the only place it makes sense.
Denotes a surge arrester: a device presenting high impedance at normal voltage and low impedance above a threshold, diverting transients to earth.
Contexts: Electrical equipment
Is connected between the protected conductor and earth, which is why the symbol is always drawn with an earth connection.
Contexts: Electrical equipment
Degrades cumulatively with each surge absorbed, so an arrester that has done its job may no longer protect and requires periodic replacement.
Contexts: Electrical equipment
An upright rectangle with a diagonal arrow drawn through it, a line entering the top and an earth symbol below.