Selection of a Type 2 SPD

From Electrical Installation Guide

Maximum discharge current Imax

The maximum discharge current Imax is defined according to the estimated exposure level relative to the building's location.

The value of the maximum discharge current (Imax) is determined by a risk analysis (see table in Figure J32).

Fig. J32 – Recommended maximum discharge current Imax according to the exposure level
Exposure level
Low Medium High
Building environment Building located in an urban or suburban area of grouped housing Building located in a plain Building where there is a specific risk: pylon, tree, mountainous region, wet area or pond, etc.
Recommended Imax value (kÂ) 20 40 65