Siemens SINAMICS S120 - Line Supply Connection Via Residual-Current Devices; Residual-Current Operated Circuit Breakers (RCD)

Line connection and line-side power components
3.4 Line supply connection via residual-current devices
Booksize Power Units
Manual, (GH2), 07/2016, 6SL3097-4AC00-0BP8
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3.4
Line supply connection via residual-current devices
Selectively tripping, AC/DC-sensitive residual-current devices (type B) can be used in
addition to the overcurrent protection devices.
Residual-current devices have to be installed if the power supply conditions in terms of short-
circuit power and loop impedance at the infeed point are not such that the installed
overcurrent protection devices will trip within the prescribed period if a fault occurs.
WARNING
Danger to life due to electric shock of fire when using unsuitable residual current devices
The inverter can cause a current to flow in the protective conductor.
This current can cause the residual current device (RCD) or residual current monitoring
(RCM) to incorrectly trip (nuisance trip). In the case of a fault (ground fault), the fault current
can contain a DC component, which prevents the RCD/RCM from tripping, with the risk of
subsequent electric shock or fire.
• Use the protection and monitoring devices recommended in the documentation.
3.4.1
Residual-current operated circuit breakers (RCD)
Residual-current operated circuit breakers (RCD) can be used in addition to the overcurrent
protection devices provided. They are the preferred solution for operation on TT systems.
Note
Operation on residual
-current operated circuit breakers is currently only possible with Line
Modules up to and including 36
kW.
Conditions when using residual current protective devices:
● Only use a delayed tripping, selective AC/DC-sensitive residual-current operated circuit
breaker, type B.
● Ensure that the loop impedance is maintained corresponding to local installation
regulations.
● Check the total length of the shielded power cables (motor cables incl. line supply
conductors from line filters to the connecting terminals of the Line Module) in the drive
line-up. The total length must be less than 350 m.
● Only operate the system with the recommended line filters.