Abstract: Illustrative GFCI devices and methods maintain safety while reducing the risk of unnecessary interruptions. One illustrative GFCI circuit includes: a first operational amplifier configured to couple to a first current transformer that senses a net current through multiple power conductors, the first operational amplifier configured to convert a signal current from a signal terminal of the first current transformer to a signal voltage, the signal voltage having an inverse dependence on frequency; an analog to digital converter configured to provide samples of the signal voltage; and a controller configured to interrupt at least one of the multiple power conductors when an magnitude measurement derived from the samples exceeds a frequency-independent and/or phase-independent threshold a predetermined number of times or for a predetermined time period.