23 Installation and Operating Instructions V04
5.4.4 Residual current protection
The inverter is equipped with an all-pole sensitive residual current monitoring
unit(RCMU) with an integrated differential current sensor which fulfills the
requirementsof DIN VDE 0100-712 (IEC60364-7-712:2002).Therefore an external
residual current device (RCD) is not required. If an external RCD needs to be installed
because of local regulations, a RCDtype A or type B can be installed as an additional
safety measure.
The all-pole sensitive residual current monitoring unit (RCMU) detects alternating and
direct differential current. The integrated differential current sensor detects the
current difference between the neutral conductor and the line conductor. If the
current difference increases suddenly, the inverter disconnects from the grid. The
function of the all-pole sensitive residual current monitoring unit (RCMU) has been
tested in accordance with IEC 62109-2.
Tip about the
external residual current device (RCD)
Where an external residual current device (RCD) is required in a TT or TN-S
system, install a residual current device which trips at a residual current of
100mA or higher.
For each connected inverter, a rated residual current of 100mA has to be
provided. The rated residual current of the RCD must be equal to at least the
sum of the rated residual currents of the connected inverters.That means that,
if, for example, 2 transformerless inverters are connected, the rated residual
current of the RCD must be at least 200mA.
