This occurs because, to push power into the grid, the inverter must slightly increase the voltage, and if the existing grid voltage is already high, this increase can trigger the inverter’s safety mechanism, causing it to disconnect to prevent damage and maintain grid stability.

How AC Overvoltage Stops Power Export

Inverter Voltage Requirement:

For a solar inverter to send power to the grid, it needs to raise the AC voltage above the grid’s voltage to overcome electrical resistance and push the power into the network.

Grid Instability:

When the grid’s voltage is already high, often due to many solar systems feeding into the local area or high consumption in the neighborhood, your inverter may struggle to find a path to export power.

Safety Shut Down:

To prevent damage to itself and other connected appliances, the inverter will disconnect from the grid if the voltage exceeds a predetermined safe limit, effectively stopping the power export.

Causes of AC Overvoltage

High Grid Voltage:

The most direct cause is that the grid voltage, measured at the point of connection, is already at or near the limit set in your inverter’s settings.

Inverter Voltage Rise:

During full sun, your solar system can generate a lot of power, causing the voltage to increase as it flows along the wiring to your home and the grid. If your home’s power usage is low at this time, more power will be exported, leading to a greater voltage rise.

Inadequate Cabling:

If the wiring or connections from your inverter to the grid have too much resistance, it can cause the voltage to creep up significantly as power is exported.

What Happens to Your Power Export

Disconnection:

Your inverter will shut down temporarily, and you will not be exporting any power to the grid.

Reduced Generation:

The system will remain disconnected until the grid voltage drops back into the acceptable range, causing you to miss out on potential export revenue and reducing your overall solar energy production.

Potential Solutions

Contact Your Installer/Electrician:

A qualified professional can check your system, including the wiring and connections, and investigate whether the issue is with your local grid.

Adjust Inverter Settings:

Your installer may be able to adjust the voltage trip settings on your inverter to a slightly higher limit, though this should be done cautiously and in consultation with your grid operator.

Grid Provider Intervention:

For widespread issues, your local District Network Operator (DNO) may need to adjust a tap at the substation transformer to lower the overall grid voltage in your area.