20 Installation and Operating Instructions V01
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 requirement
of 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 RCD
type 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 currents. The integrated differential current sensor detects
the current difference between the neutral conductor and the line conductors. 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 according to IEC 62109-2.
5.4.5 Overvoltage category
The inverter can be deployed in grids of installation category III or lower, as defined
under IEC 60664-1. This means that it can be permanently connected at the
grid-connection point in a building. In installations involving long outdoor cable routing,
additional overvoltage-reducing measures must be taken so that the overvoltage
category is reduced from IV to III.
For installing an 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.
