also termed breaking capacity, is the
unaffected (prospective) r.m.s. value of the mains follow current, which can automatically
be extinguished by the SPD when UC is applied. Either the indicated follow
current extinguishing capability of the SPDs corresponds to the maximum prospective
short-circuit current at the SPD’s installation site, or a corresponding backup fuse shall be chosen for the protective device that interrupts the mains follow current
through the protective device