Operation and installation manual
Page 79 of 82
(PVI-10.0/12.5-OUTD-xx Rev:1.2)
8.6
Note about the differential protection built in the Power-One Aurora
inverters
Power One Aurora inverters are equipped with a protection device against ground
faults, as per the safety standard required in Germany by VDE V 0126-1-1:2006-02
standard (refer to par. 4.7 of the Standard). All Aurora inverters marketed in Europe
are equipped with this protection, including the versions coded as “IT”, available for
the Italian market.
In particular, Power One Aurora inverters are fitted with a redundancy for leakage
current reading, sensitive to all current components, be it direct or alternating. Ground
leakage current measurement is taken at the same time and separately by 2 different
processors: if only one of them detects a failure, protection is triggered, grid is hence
disconnected and conversion process is stopped.
There is an absolute threshold of 300mA for the total AC+DC leakage current with
protection trigger time of max. 300msec. There are also three more trigger levels with
threshold set at 30mA/sec, 60mA/sec and 150mA/sec respectively, to manage "quick"
variations of the fault current caused by accidental contacts with active leaking parts.
Limit trigger times progressively decrease when fault current variation speed increases
and, from 300msec/max for a variation speed of 30mA/sec, value decreases to
150msec and 40msec for variation speed values of 60mA and 150mA, respectively.
It shall be noticed at any rate that the built-in device only protects the system against
ground faults occurring upstream of the inverter AC terminals (i.e. toward
photovoltaic system DC side and hence toward the photovoltaic modules). The
leakage current that could occur in the AC section, in-between the pickup/input point
and the inverter, are not detected and require an external protection device.
It is recommended to use a switch with C-class thermal cut-out and nominal current of
40A, differential protection in class A or class AC with trigger current of 300mA so as
to avoid any false trigger events of the protection due to the normal capacitive leakage
current of the photovoltaic modules.
