While RCD devices (residual current circuit breakers) switch off the power supply when a certain residual current is exceeded, RCM measurement devices display the current value, record the long-term trend, and report when a critical value is exceeded. This message can also be used to switch off the power supply via external switching devices (contactors, relays). Residual current monitoring (RCM) devices are used to detect and report residual currents at an early stage. Countermeasures can be initiated in good time so that the system does not have to be shut down. This allows measures to be taken in the event of slowly deteriorating insulation values or gradually increasing residual currents, for example due to aging insulation, even before the system is switched off, e.g.:
Residual current measurement in connection with energy measurement in combined energy/RCM measurement devices in electrical systems is a preventive measure for fire protection and maintenance. Downtimes and the associated costs are reduced. Timely and preventive maintenance also significantly improves the efficiency and availability of a system thanks to the additional information gained from an RCM measurement device.
In particular, permanent RCM monitoring is essential in order to avoid any unwanted surprises during operation and to be constantly informed about the current status of the system.
The standard applies to residual current monitoring devices for domestic installations and similar applications.
Modern, highly integrated measurement devices allow the combined measurement of
The functionality of RCM measurement devices is based on the residual current principle. All conductors at the measurement point (outgoing circuit to be protected), with the exception of the protective conductor, are routed through a residual current transformer. In the absence of any faults, the sum of all currents is zero. If, on the other hand, a residual current flows via ground, the current difference in the residual current transformer causes a current that is evaluated by the electronics of the RCM measurement device.
The measuring method is described in IEC/TR 60755. A distinction is made here between type A and type B.
Residual currents caused by insulation faults can pose a considerable safety risk in electrical installations. An appropriate protection concept can detect residual currents, eliminate insulation faults in good time and thus ensure system availability. RCM stands for Residual Current Monitoring and means monitoring the residual current in electrical systems. This current is calculated from the sum of the currents of all conductors except the protective conductor (PE) that lead into the system. Residual currents are typically the result of insulation faults, leakage currents or e.g. EMC filter leakage currents.
