For ‘protection against indirect shock hazard’ in TN systems, overcurrent and residual
current devices have been approved. For the use of SPDs this means that these protective
devices may only be arranged downstream of the devices for ‘protection against indirect
shock hazard’ in order to ensure that the measure to protect against life hazards also
operates in the event of a failure of an SPD. If an SPDclass I or II is installed downstream
of a switching device [e.g. RCD (residual current operate of protective device), fuses], it
has to be expected that the discharged impulse current interrupts the circuit due to false
tripping of the switching devices or that the distribution board will be overloaded.