If an inverter has been operating without any issues suddenly loses grid/load readings and stops allowing PV to generate (except for charging batteries) this is a sign that the grid relay has been disconnected. Below is an overview of why this happens and what actions can be taken to troubleshoot and resolve.
Example of power flow screen when grid relay is disconnected
No grid or house load and PV will only be allowed to generate if batteries need more charge.
Typical Generation Graph When Grid Relay is Disconnected
No load, no grid and PV only charging batteries.
Why does a grid relay disconnect?
The inverter will do this to protect from potential damage when voltage and frequency readings from the grid are either too high or too low. The thresholds for these can be found at the bottom of the 'Grid Settings' page. When the system measures anything outside of these parameters from the grid it will instantly disconnect for 60 seconds before attempting to reconnect.
Just above this section in the 'Grid Settings' you will see similar thresholds set for 'Normal Connect' (the initial startup sequence when waiting for the inverter Normal light to illuminate) and 'Reconnect After Trip' (when relay disconnects and the inverter will try to re-establish it's connection to the grid. These value will vary depending on the grid mode selected.
How to Confirm if a Grid Relay Has Disconnected
In Sunsynk Connect you can go the Equipment tab and then select the Grid tab on the right hand side where you will see Relay Status. If Relay Status shows as Closed this means the relay is connected, or will show disconnected if it is not.
N.B. the grid relay status is not tracked on Lifelynk inverters.
Potential Cause - Protection Device Tripped
If the grid voltage readings are very low (typically less than 10V) this means that the grid voltage is not properly reaching the inverter - this is a sign that an external protection device (MCB, RCD etc.) or the internal AC breaker inside the inverter (if the model has one) has tripped and will need to be reset. Until this is reset the inverter will not go back into normal because the grid voltage will never reach the 'Reconnect After Trip' thresholds. Below is a screenshot from the Custom Data in Sunsynk Connect showing the grid voltage on a single phase system which has had a protection device trip (V-grid-L1).
Solution - Reset tripped protection device and the inverter will reconnect the grid relay when it measures normal readings. Further investigation will be needed to identify the cause of the trip
Potential Cause - Grid Overvoltage/Frequency
If the grid voltage measures higher voltage than the parameters set for the Overvoltage thresholds then the relay will disconnect until the readings drop back down to the acceptable range. Grid voltage spikes can be caused by issues with the grid, large power fluctuations and large amounts of export from properties in the local area.
If the grid voltage is still being measured at a normal value of around 230V while the relay is disconnected then this suggests that nothing has tripped but the inverter is waiting for the parameters to be met for it to reconnect after trip.
Solution - If the issue persists and grid overvoltage is being exceeded regularly then the installer or end user must contact their DNO and inform them that the grid voltage is too high and causing issues with their PV system. The DNO can then carry out some works to stabilize the voltage and prevent the values from exceeding the overvoltage limit.
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