The three types of SPD
Type 1 SPD
The Type 1 SPD is recommended in the specific case of service-sector and industrial buildings, protected by a lightning protection system or a meshed cage.
It protects electrical installations against direct lightning strokes. It can discharge the back-current from lightning spreading from the earth conductor to the network conductors.
Type 1 SPD is characterized by a 10/350 µs current wave.
Type 2 SPD
The Type 2 SPD is the main protection system for all low voltage electrical installations. Installed in each electrical switchboard, it prevents the spread of overvoltages in the electrical installations and protects the loads.
Type 2 SPD is characterized by an 8/20 µs current wave.
Type 3 SPD
These SPDs have a low discharge capacity. They must therefore mandatorily be installed as a supplement to Type 2 SPD and in the vicinity of sensitive loads.
Type 3 SPD is characterized by a combination of voltage waves (1.2/50 μs) and current waves (8/20 μs).
Fig. J18 – SPD standard definition
| Direct lightning stroke | Indirect lightning stroke | ||
|---|---|---|---|
| IEC 61643-1 | Class I test | Class II test | Class III test |
| IEC 61643-11/2011 | Type 1 :  |
Type 2 :  |
Type 3 :  |
| EN/IEC 61643-11 | Type 1 | Type 2 | Type 3 |
| Former VDE 0675v | B | C | D |
| Type of test wave | 10/350 | 8/20 | 1.2/50 + 8/20 |
- Note 1: There exist
+ 
SPD (or Type 1 + 2 SPD) combining protection of loads against direct and indirect lightning strokes. - Note 2: some SPD can also be declared as
.