News Information

Selection of a Type 1 SPD

2023-03-14

Impulse current Iimp

1.         Where there are no national regulations or specific regulations for the type of building to be protected:

the impulse current Iimp shall be at least 12.5 kA (10/350 µs wave) per branch in accordance with IEC 60364-5-534.

2.         Where regulations exist:

standard IEC 62305-2 defines 4 levels: I, II, III and IV


The table in Figure 2 shows the different levels of Iimp in the regulatory case.



Fig. 1 – Basic example of balanced Iimp current distribution in 3 phase system


Fig. 2 – Table of Iimp values according to the building's voltage protection level (based on IEC/EN 62305-2)

Protection level as per EN 62305-2

External lightning protection system designed to handle direct flash of:

Minimum required Iimp for Type 1 SPD for line-neutral network

I

200 kA

25 kA/pole

II

150 kA

18.75 kA/pole

III / IV

100 kA

12.5 kA/pole


                  

Autoextinguish follow current Ifi

This characteristic is applicable only for SPDs with spark gap technology. The autoextinguish follow current Ifi must always be greater than the prospective short-circuit current Isc at the point of installation.


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