This is a very interesting comment because you give me the opportunity to clarify the end of life mode of SPD (including MOVs and gas tube):
Let me explain two cases.
A surge arrester can happen at the end of life in the following cases:
a) by thermal runaway due to an accumulation of excessive constraints of not exceeding its lightning
attributes, leading to a slow destruction of its internal components.
The disconnection of the SPD is provided by a thermal fuse associated with the electronic components (MOVs) inside the SPD
b) by short-circuit due to exceeding the maximum flow capacity or due to a fault under 50hz from the electrical distribution network (neutral rupture ,…). The disconnection of the SPD is provided by an external or integrated short circuit protection device like fuse or circuit breaker.
Considering the short circuit protection device(b), why choose circuit breaker instead of fuse?
● Choose the rating must consider both surge withstand and low short circuit breaking capability
● Compare to fuses, CBs have good compromise between surge withstand and low short circuit breaking capability
*The same rating CB has better surge withstand capability than fuse
*The lower rating CB has better short circuit breaking capability
For instance, SPD with following characteristics : In=5kA, Up=1,3kV is coordinated with its short circuit protection device:
* circuit breaker C curve 20A
* or fuse 22×58 63A