An electric propulsion system is described that includes at least one branch for distributing electrical power, provided by a power source, to one or more loads. The at least one branch is partitioned into one or more zones and comprises a plurality of branch isolation devices that are configured to isolate the at least one branch from the power source in response to a fault current at the at least one branch. In addition, the at least one branch comprises a respective pair of zone isolation devices for each respective zone from the one or more zones. The respective pair of zone isolation devices for each respective zone is configured to isolate the respective zone from the at least one branch, during a test of the at least one branch for identifying which of the one or more zones is a source of the fault current.