Good day, we have a 90kW 3 phase system using 6 X 15KVA Quattro's. Last week we had a ESKOM supply issue as one of the fuses blew on the L2. The system immediately showed that the grid was lost but we noticed that the output frequency was up and down. (50-53Hz) This of course stopped the Fronius inverters as they gave an error - Input Frequency to High.
We solved this by switching the ESKOM breaker off until they replaced the fuse.
Question is how come the inverters did not regulate the frequency to 50Hz. Below the output frequency until we switched the breaker off just before 7AM.