With the introduction of inverter energy systems (IESs) to electricity distribution networks, it is important for electricity distributors to know the nature of new challenges to basic protection systems in the low-voltage (LV) network as the penetration of IESs in distribution networks increases. For any feeder on a low voltage network hosting IESs, fault currents will have a contribution from both the upstream source and from the IESs connected on that same feeder. The clearing times of upstream fuses can be affected by the additional current contribution from IESs. It is shown how fuse coordination can be preserved in LV networks with high penetrations of IES, so that cables are still protected. An IES will shut off under fault conditions either because the voltage dips below a threshold, or the upstream fuse clears the fault. Guidelines are presented to help combat sympathetic tripping and blinding of fuse protection systems.