The residual current monitor RCM470DY monitors the residual current (AC, DC pulsating) in unearthed AC or 3NAC systems (IT systems). The residual current is evaluated directionally, i.e. only insulation faults detected on the load side are signalled. That allows selective fault location in extended IT systems.

A precondition for the use of the device are sufficient high leakage capacitances upstream the CT so that a residual current higher than the response value can flow. However, a high leakage current is not desirable in many sectors so that principally the value of the maximum permissible leakage current of the IT system and the application field has to be taken into consideration when using directionally discriminating residual current monitors. Also the nominal voltage has to be considered when selecting the appropriate device since the measuring principle requires the neutral point displacement voltage of the IT system to be monitored.

Version RCM475DY utilises an internal measuring current transformer, ø 18 mm.

• Internal measuring current transformer ø 18 mm
• Response value, adjustable 10 mA…10 A
• Response delay, adjustable 0…10 s
• Alarm relay with two potential-free changeover contacts
• N / O or N / C operation, selectable