1. A method for characterizing a device that operated to clear a fault in a power distribution system feeder, the method comprising: receiving measured data corresponding to a current measured along the feeder proximate a substation bus; determining from the measured data that a fault has occurred in at least one phase and has been cleared; subtracting reference data from the measured data to estimate residual fault data; and estimating from the residual fault data a characteristic of the device that operated to clear the fault.