Protection against overvoltages and impulse currents (such as switching and
lighting surges). Limit overvoltage to a level acceptable by the equipment to
be protected and divert surge currents
Type 1 + 2: Surge arrester designed to run off energy caused by an
overvoltage comparable to that of a direct lightning (10/350 wave)
Class 1 and indirect lightning (8/20 wave), Class II
: Surge arresters installed at the main switchboard