ABB UNO-2.0-I-OUTD Product Manual page 44

712.413.1.1.1.2 When an electric system includes a PV power supply
system without at least a simple separation between the AC side and
the DC side, the differential device installed to provide protection against
indirect contact by automatic disconnection of the power supply must be
of the B type in accordance with IEC 60755/A 2.
When the PV inverter is not in terms of its construction such as to put
continuous ground fault current (cc) into the electrical system, a differen-
tial switch of type B is not required according to IEC 60755/A 2.
Note: The first section of the article, in reference to the "simple separation between the AC
side and the DC side", considers isolation transformers that operate at low frequency (grid
frequency).
ABB inverters with a high frequency transformer are equipped with an iso-
lation transformer for each of the DC/DC converters which operates at
high frequency (switch-over frequency of the converter). This transformer
allows for high frequency galvanic isolation between the DC and AC side of
the system. In addition to this the inverters include protection mechanisms
so that they cannot input ground fault currents.
ABB declares that the ABB high-frequency isolated inverters are in terms
of their construction continuous ground fault currents and therefore, in ac-
cordance with Article 712.413.1.1.1.2 of Section 712 of CEI 64-8/7 Norms
there is no requirement that the differential installed downstream of the
inverter is type B in accordance with IEC 60755 / A 2.
The use of an AC type circuit breaker with differential thermal magnetic protection with trip-
ping current of 30 mA is advisable so as to prevent false tripping, due to the normal capacitive
leakage current of photovoltaic modules.
In the case of systems consisting of multiple inverters connected to a single switch with diffe-
rential protection, it is recommended to install a device that allows the adjustment of the trip
value and timing of intervention.
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5 - Installation