Grid voltage measurement means checking the actual AC voltage at the inverter test points with a meter to confirm a grid voltage alarm. First measure with the DC switch off, line-to-line and line-to-ground, to see whether grid voltage is present and whether it is too high or too low. If the measured voltage really is out of range, contact the utility or power company. Only change the protection limits with the utility's permission. If the AC voltage measures high with the DC switch on and the inverter at full power, the cables between the inverter and the interconnect may be too small. Check the cable size and the voltage drop calculations. Compare the meter reading with the voltage shown on the LCD. If they disagree, the inverter's measurement circuit may be faulty and the inverter may need to be replaced. On three-phase systems, measure each phase. If the phase voltages differ greatly, the cause is grid imbalance and the power company should be contacted. For grid instability alarms, measure the AC voltage and test the AC line for harmonic distortion (THD), both with the DC switch off and with it on.
<!-- review notes
producesc1 verified · fact Grid voltage outside limits
A low reading at the test points confirms an under-voltage alarm. A high reading confirms an over-voltage alarm. If the reading is high only at full power, the AC cables to the interconnect may be undersized.
tbl=13.r4 h=cab3a7061bcdtbl=13.r3 h=52c3fd63f040tbl=49.r3 h=8ede75869601verified by: review-workflowverified on: 2026-10-23
c2 drafted · lead Zero AC grid voltage
For a NO-GRID alarm, AC is checked line-to-line and line-to-ground at the inverter test points.
tbl=14.r2 h=3fc18463c15areview note: support check: partial - NO-GRID says inverter doesn't detect grid and to check AC L-L and L-GND, but doesn't explicitly say measurement shows zero voltage.; review: partial - The NO-GRID row supports checking AC line-to-line and line-to-ground at the test points, but nothing in the passage says the measurement shows zero AC voltage.
c3 verified · fact Unequal phase voltages
Used to confirm a grid voltage unbalance fault. If the spread is within the utility's limits, the imbalance parameter can be adjusted instead.
tbl=50.r1 h=e9dc9b740d24verified by: review-workflowverified on: 2026-10-23
detected_by c5detected_by c5detected_by c4detected_by c4detected_by c5detected_by c5detected_by c5detected_by c4detected_by c4detected_by c5detected_by c5detected_by c5detected_by c5detected_by c6detected_by c6detected_by c5detected_by c5detected_by c5detected_by c6detected_by c6detected_by c5detected_by c5detected_by c4detected_by c3detected_by c3detected_by c3detected_by c4detected_by c3detected_by c3detected_by c3detected_by c3detected_by c5detected_by c4detected_by c3detected_by c3detected_by c3detected_by c4detected_by c3detected_by c3detected_by c3detected_by c4detected_by c3detected_by c3detected_by c3detected_by c4detected_by c3detected_by c3detected_by c3detected_by c4detected_by c3detected_by c3detected_by c3detected_by c4detected_by c3detected_by c4detected_by c4detected_by c3detected_by c4detected_by c3detected_by c3detected_by c4detected_by c4detected_by c5detected_by c4detected_by c4detected_by c4detected_by c4detected_by c4detected_by c4detected_by c4detected_by c4detected_by c4detected_by c5detected_by c5detected_by c4detected_by c4detected_by c4detected_by c4detected_by c5detected_by c6detected_by c5detected_by c8detected_by c6detected_by c5detected_by c4detected_by c6detected_by c7detected_by c6detected_by c5detected_by c8detected_by c5detected_by c5detected_by c8detected_by c5detected_by c6detected_by c5detected_by c4detected_by c6detected_by c7detected_by c6detected_by c5detected_by c8detected_by c5detected_by c8detected_by c5detected_by c4detected_by c6detected_by c3detected_by c5detected_by c7detected_by c5detected_by c6detected_by c4detected_by c8detected_by c4detected_by c7detected_by c8detected_by c5detected_by c6detected_by c6detected_by c5detected_by c7detected_by c5detected_by c7detected_by c5detected_by c4detected_by c6detected_by c7detected_by c6detected_by c5detected_by c5detected_by c4detected_by c6detected_by c8detected_by c3detected_by c5detected_by c7detected_by c7detected_by c4detected_by c5detected_by c5detected_by c4detected_by c4detected_by c3detected_by c5detected_by c4detected_by c4detected_by c4detected_by c3detected_by c3detected_by c4detected_by c3detected_by c3detected_by c3detected_by c3detected_by c4detected_by c3detected_by c4detected_by c4detected_by c4detected_by c4detected_by c4detected_by c4detected_by c5detected_by c4detected_by c5detected_by c5detected_by c5detected_by c5detected_by c5detected_by c5detected_by c4detected_by c3detected_by c4detected_by c4detected_by c4detected_by c4detected_by c4detected_by c4detected_by c5detected_by c4detected_by c4detected_by c4detected_by c4detected_by c3detected_by c3detected_by c3detected_by c7detected_by c5detected_by c7detected_by c7detected_by c7detected_by c6detected_by c4detected_by c6detected_by c6detected_by c6detected_by c6detected_by c6detected_by c6detected_by c6detected_by c6detected_by c6detected_by c6detected_by c6detected_by c4detected_by c6detected_by c6detected_by c6detected_by c4detected_by c3detected_by c4detected_by c3detected_by c3detected_by c3detected_by c3detected_by c3detected_by c6detected_by c6detected_by c6detected_by c4detected_by c6detected_by c6detected_by c6detected_by c6detected_by c6detected_by c6detected_by c4detected_by c6detected_by c6detected_by c6detected_by c8detected_by c8detected_by c8detected_by c6detected_by c8detected_by c8detected_by c8detected_by c7detected_by c11