Overvoltage Protection - Siemens RXB Series Basic Documentation

Overvoltage protection,

secondary protection
AC 230/400 V mains
network
KNX network
Effect of surge
protectors
Note
Surge arresters in bus
terminal technology
For internal use only
Siemens
Building Technologies
9.7.2 Overvoltage protection
Overvoltage protection acts as secondary protection. Surge protectors are installed
in the AC 230/400 V mains network and in the KNX network.
Surge arrester (Class B) for the AC 230/400 V mains network:
Nominal discharge capacity of at least 5 kA (8/20 µs)
Protection level < 2 kV
If varistors are used, they must be thermally monitored, and provided with
insulating equipment.
Surge arresters for the KNX network
Nominal discharge capacity of at least 5 kA (8/20 µs)
Protection level < 2 kV
The surge arrester must be matched to the KNX (TP1) levels.
The surge protector protects the bus devices from overvoltages (transient surge
voltages) which can be picked up by the bus cables. If the protective effect is
damaged (e.g. by exceeding the permitted number of surge arresters), this results
in a bus fault (bus low resistance). Note that no message is generated by this bus
fault. Faulty surge arresters must be replaced immediately.
Using surge arresters can improve the interference immunity of a KNX (TP1) network
regardless of any overvoltage protection measures in conjunction with lightning
protection.
Surge arresters normally have the same dimensions as bus connection terminals.
However, the surge arresters can be distinguished by their color (blue) and the
additional earth conductor. Where surge arresters are used instead of bus terminals,
they must be connected to the nearest grounding point (e.g. protective conductor).
Surge arresters (manufacturer: Dehn) are available from Siemens as off-the-shelf
components in bus terminal format.
Overvoltage protection
During engineering, make sure surge arresters can be installed, and that there is a
connection point for them.
KNX bus communications
Appendix
Order no. 5WG1 190-8AD01
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CE1P3127en
2013-04-08