Distributed Solar Integration Experiences - Utility Variable ...

Fault Current Contributions of InvertersiPre-faultInverter Fault CurrenttI ratedBest Case: May last only a fewmilliseconds (less than ½ cycle) for manytypical PV, MT and fuel cell invertersWorst Case: may last for up to the IEEE 1547limits and be up to 200% of rated current (butusually it is 100-150% for most brands)Note: Note: The The nature nature of of the the fault fault contribution from from an an inverter is is a function of ofthe the inverter controller design/settings, the the thermal protection functions for forthe the IGBT IGBT and and the the depth depth of of voltage voltage sag sag at at the the inverter terminals. For Forscreening it it is is safe safe to to assume that that fault fault currents never never exceed exceed 2 times timesthe the inverter steady steady state state current current rating rating for for any any duration exceeding ½cycle. cycle. In In fact, fact, test test results results show show that that nearly nearly all all products have have only only 1.0 1.0 to to1.5 1.5 per per unit unit current fault fault current.Prepared by Nova Energy Specialists, LLC 22