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
55
Residual-current monitors (RCM)
Used in conjunction with appropriate circuit breakers, residual-current monitors (RCMs)
provide fire and system protection even at high levels of grounding resistance (in TT
systems, for example). When operating on TT systems for infeed powers exceeding 55 kW,
and with systems that extend across a large area, residual current monitors must be installed
in addition to the appropriate circuit breakers.
Fire hazard and danger of a plant standstill when residual currents occur
Residual currents in the power supply that are not detected can cause fires and failures in
the entire system.
• Always install residual-current monitors in conjunction with suitable circuit breakers.
Conditions when using differential current monitoring devices:
● Only use AC/DC-sensitive RCM type B devices with delayed tripping that guarantee
reliable tripping even for smoothed DC residual currents.
● Connect parts of the drive system (power drive system) and the machine that can be
touched to the system's protective conductor.
● Do
route the protective conductor through the measuring current transformer, as this
would cancel its protection function.
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