What keeps the voltage from backfeeding to the grid during a power outage?
We are an electrical coop located in South West Texas and a member has installed a model 5000US solar inverter fed by 21 panels, what keeps the solar panel from sending voltage (reverse power flow) on to the grid during an outage?
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Grid tie inverters are islanding inverters. Before they can produce power they read the voltage of the grid. After a short period of time they then begin duplicating what they see from the grid. If the grid goes down they disconnect automatically. When the grid comes back up they go through this process of restarting all over again.
UL 1741, which all US grid tied inverters are listed to, requires that the inverter disconnect from the grid when the grid voltage or frequency goes outside of a specified range which prevents islanding. So if the grid is not within specifications the inverter will shutdown. When the grid comes back up the inverter will sense this and start up again.
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