Sometimes customers complain that in a PV Plant some SUN2000 inverters restart by themselves every 10-20 minutes. They appear with “no irradiation detected” 
and after a few seconds they reach “irradiation detected” 
and then restart normally. 
For this situation we have checked the log files from those inverters and the problem is that the grid voltage is too high. The inverters very often generated Grid Overvoltage alarm:
In this case we recommend decreasing the transformer voltage or if this is not possible to increase the overvoltage parameters with 5-10 Vac on the inverters (from Neteco, Smart Logger Interface or SUN2000 APP). We preferably recommend the decrease with 5-10 Vac from the transformer.
Here comes the question - But in this case why don’t we have problems with all the inverters from that Trafo Station? Why do we have problems only with 2 inverters? Do they have different settings on them?
Fore sure all the inverters have the same settings but when the inverters will start to produce, the grid voltage range will be increased form the standard 220/230 Vac to 235/245 Vac (as an example). In that case when the voltage range starts with 245Vac, then the inverter will also start to produce the voltage that will become higher than 255 Vac.
This is the moment when some inverters will stop producing to decrease under the overvoltage limit. The inverters that will stop producing should be any of this PV Plant, but not always the same inverters.
It is better to decrease the grid voltage from the transformer Plot Tap. If this is not possible then increase the over voltage limit on inverters with 10 Vac through one of above methods.
