obtaining a time/current through fault protection curve that is defined by a plurality of time/current points for the transformer that identifies when the transformer may experience thermal or mechanical damage in response to a certain current flow over a certain time in the transformer winding;

selecting a time multiplier; and

determining an operating curve for the electronic interrupting device, wherein the operating curve identifies when the electronic interrupting device will open in response to a certain current flow over a certain time, by multiplying the multiplier and a time portion of each of the plurality of time/current points on the through fault protection curve for a first portion of the operating curve, and providing a one fundamental power frequency cycle portion of the operating curve that defines a current that if exceeded will cause the electronic interrupting device to operate after one fundamental power frequency cycle.