Life-time of SPD

IEC 61643-12: 2002 6.2.3.1 Prospective life

Depending on the types of surges and their frequency of occurrence, the life of an SPD may be long or short. For example, if a few seconds after the installation of an SPD, having a maximum discharge current Imax of 20 kA 8/20, a lightning current of 30 kA 8/20 occurs, the SPD is likely to fail. Its real lifetime will only be a few seconds in this case! This extreme case shows that any prospective lifetime given by a manufacturer can only be based on standardized testing and cannot be a guarantee.

It is only possible to consider prospective lifetimes. For example, SPDs having a maximum discharge current of 10 kA and 20 kA 8/20 can both be destroyed in a few seconds after installation, if a 30 kA lightning current occurs. In general conditions, the lifetime of the 20 kA rated SPD is expected to be longer than that of the 10 kA rated SPD.