What level of surge protection distribution box

Generally, a level one surge protector (M100B+C/3+N) is required for the main distribution, and a level two or three surge protector (M40B4) is required for the distribution box. According to the principle of graded lightning protection, and based on the likelihood of a building being struck by lightning, it is necessary to deploy surge protector against lightning in stages to. Overvoltage due to lightning strikes or uncontrolled switching operations can reach peaks of up to several 1'000 volts., MUA-100, MUA-50) Type 2 in the sub-distribution board (e. 1 standard: High exposure (Category C) at service entrances Medium exposure (Category B) at distribution panels Low exposure (Category A) at point-of-use equipment Installing appropriately. [pdf]