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It is well-known that the amorphous modules suffer from a significant initial degradation during the first two or three operating months due to the Staebler-Wronski effect. This is sometimes specified in the data sheets, and the voltage can be about 10% over the stabilized value. But the STC values specified in the datasheets (used for establishing the model) are always the stabilized ones.

Simulation:

The simulation itself doesn't take the initial degradation into account: it always works with the stabilized STC values. The initial over-performance is considered as temporary, and neglected.

System Sizing:

As the electrical data used for the sizing of the PV array are the stabilized ones, dangerous voltages overcoming the absolute admissible voltages may appear just after the commissioning of the system. This over-voltage may be taken into account in the Sizing dialog.

Now when the commissioning takes place in Summer, the reference sizing low temperature may be chosen much higher than the usual yearly worst-case temperature. With a usual temperature coefficient muVco of around -0.3%/°C, and a reference temperature gain of 20°C  (+10°C instead of -10°C usual in middle Europe), this will reduce the Voc value by 6%.

Otherwise, if in the reality your sizing overcomes the voltage limit, you can also suppress one module in each string during the first operating months.