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Appendix: TN Systems
Symmetra MW 800 kW 3 × 400/230 V Installation - 990-1510D 35
Additional requirements for generating sets (IEC 60364-5-55 551.4.2)
To be used when the generating set provides a switched alternative to the public supply.
Protection by automatic disconnection of supply must not rely on the connection to the earthed points
of the public supply system when the generator is operating as a switched alternative to a TN system.
A suitable earth electrode must be provided.
Protective devices in TN systems
The following protective devices are recognized in TN systems:
• Overcurrent protective devices
• Residual current protective devices (not to be used in TN-C systems)
When a residual current protective device is used in a TN-C-S system, a PEN conductor must not be
used on the load side. The connection of the protective conductor to the PEN conductor must be made
on the source side of the residual current protective device (see below illustration):
L1 L1
L1 L1
L1 L1
PEN N
SOURCE LOAD
PE
Residual Current Sense