Residual current monitoring from the main distribution board to the final circuit

In modern electrical installations, extensive monitoring by different sensors is required. This is the only way to guarantee both safety and high availability.

Wherever an uninterrupted power supply has to be ensured, whether in industrial plants, data centres or building technology, but at the same time the use of an unearthed power supply (IT system) is not possible for various reasons, monitoring using residual current technology has become established. This technology makes it possible to detect fault currents* in electrical installations long before critical system states or even a shutdown by residual current devices occurs.

• Fault currents do not usually occur spontaneously, for example due to component burning out. Fault currents usually arise over a longer period of time. Various environmental factors are primarily responsible for it. Heat, cold, moisture, mechanical stress and ageing can lead to insulation deterioration in cables and components and thus cause fault currents. The fault currents often do not suddenly increase, but become higher and higher over a longer period of time.

Conventional devices are usually not suitable for monitoring in sub-distribution boards and final circuits. Their measuring ranges are too large to detect smaller fault currents. Bender has therefore developed special sensors and evaluators that are suitable for monitoring electrical installations from the main distribution board to individual final circuits*.

• The consistent use of residual current sensors from the main distribution board to the final circuit allows faults to be detected in good time. The further the equipment is installed towards the final circuits, the more accurately actual fault currents can be distinguished from leakage currents and the better faults can be located.

The Bender portfolio of residual current monitoring devices is designed for installation-wide use and offers flexible solutions for every location. On the one hand, there are powerful products with a high current-carrying capacity for use in the main distribution board and, on the other, compact and cost-effective sensors for monitoring final circuits. The various devices and sensors are equipped with communication interfaces. They can be connected to form a system that is monitored from a central location.

If a larger number of outgoing final circuits are to be equipped with residual current monitoring systems, a six-channel solution can be used with the RCMS150. Like the devices in the RCMB13x series,they combine a measuring current transformer and evaluation electronics in one housing. The technical features are also essentially identical to this device series, meaning that the performance of the RCMS150 is also specially designed for final circuits up to 32 A.

Retrofitting residual current monitoring in existing installations poses particular challenges. On the one hand, there is often very little space available for sensors and evaluators, and on the other hand, installing the sensors is anything but easy. In order to disconnect the cables, the installation must be switched off.

The split-core devices of the RCMB330 series provide a smart single-channel solution that can be easily installed in existing systems: Open the current transformer, place it around the conductors, close it again and wire the interface - done. The installation does not have to be switched off. The RCMB330 combines evaluator and measuring current transformer in a compact housing so that this series can also be used for monitoring final circuits.