The general difference between MRCD and RCM is that the Residual Current Monitor (RCM) is for monitoring purposes and the MRCD for protection purposes. Due to this, MRCDs are characterised by the
Many types of loads that are temporarily or mainly disconnected (standby mode) must function reliably when needed. This applies, for example, to fire pumps, slide-valve drives, lift motors or
Other installations rely on HRG to allow continued operation with one ground fault. Refineries, saw mills, petrochemical facilities, factories, pipelines, food processors, and pulp mills are
By the use of residual current monitoring systems, a message is given to the user before the shutdown threshold of an RCD is reached.
RCMs (Residual Current Monitors) monitor residual currents in
Increased protection of persons Due to the low fault currents there is no risk of suffering an electric shock.
Increased fire protection The mandatory continuous insulation monitoring reduces
In a low-voltage (typically 600 V or less) high-resistance-grounded (HRG) electrical power system, ground-fault current is limited to a low-enough level that the system need not be immediately
To avoid the situation in which a ground fault is not detectable, leaving the system in an unsafe condition, continuously monitor the NGR with an appropriate device. The NGR must be monitored for
I∆ Residual current/Fault current
I∆n Response residual current
RF Fault resistance
RL Load resistance
IF insulation fault
I1, I2 Operating current
US Supply voltage
PE
RCMs differ in terms of type, frequency and waveform of the currents that they are capable of detecting:
RCM series: Type A residual current monitors in accordance with IEC 60755 for monitoring
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