An example method of operating a power distribution system including a plurality of source and tie circuit protection devices coupled between at least one source and a protection zone is disclosed. The protection zone includes a distribution bus and a plurality of feeder circuit protection devices coupled between the distribution bus and a plurality of loads. The method includes determining an electric current flowing through each source and tie circuit protection device, determining whether any of the feeder circuit protection devices is outputting a ZSI blocking signal, and controlling operation of the plurality of source and tie circuit protection devices according to an enhanced partial differential protection scheme based on a combination of the determined currents through the source and tie circuit protection devices and the determination of whether any of the feeder circuit protection devices is outputting a ZSI blocking signal.