RCD (Residual-current device)

RCD circuit breakers (Residual Current protective Device) monitor the currents flowing back and forth across it. The sum of these currents is called residual current and is zero in the fault-free state.

If the residual current exceeds approx. 80% of the rated residual current, the switch switches off all poles after 300ms at the latest.

There are different types of RCD switches. FluidSIM supports types A and B. Type A detects sinusoidal AC residual currents and pulsating DC residual currents. Type B additionally detects smooth DC residual currents.

The test button can be used to simulate a fault that trips the switch.

A failure model can be selected for the symbol.

Adjustable parameters

Designation Range Default value
Type A, B B
Rated residual current 1 ... 100000 mA 30
Power grid frequency 30 ... 100 Hz 50

Failure models

Failure model Description
Does not trip The RCD does not trip.
Always trips The RCD always trips.