VARIMETER RCM residual current monitors for grounded TN and TT systems

A residual current monitor (RCM) watches for leakage current in grounded supply networks, meaning TN and TT systems. Unlike a residual current circuit breaker (RCD), which trips and cuts power the moment a rated residual current is reached, an RCM raises a warning instead, for example through an output contact. That makes it the right choice where a fault should be reported but the plant must keep running, avoiding costly shutdowns or lost data.

Measurement relies on an external residual current transformer. Every conductor of the protected feeder, except PE, passes through it. In a healthy circuit the currents cancel out to zero, so nothing is induced. When an insulation fault lets current leak to earth, the resulting imbalance produces a signal that the monitor evaluates. Catching creeping insulation damage this early also reduces the latent fire risk and lets maintenance be planned outside production hours.

DOLD's VARIMETER RCM series covers type A devices for AC and pulsating DC residual currents (per IEC/TR 60755) and all-current sensitive type B devices that also detect smooth DC. Just send us the part number or a short description of your network and we'll help you choose the right type.

• Type A: AC and pulsating DC residual currents (IEC/TR 60755)
• Type B: all-current sensitive, including smooth DC
• Signals faults early without shutting the system down
• Settings made with latching rotary switches
• Wire break detection in the measuring circuit