Passive monitoring the integrity of current sensing devices and associated circuitry in GFCI and AFCI protective devices is provided. A protection circuit interrupter employs a capacitively coupled noise signal obtained by an arrangement of one or both of line side arms relative to a Rogowski coil. The noise signal is monitored while the line and load sides of a protective circuit interrupter are disconnected, and the connection of the line and load sides disabled if the noise signal fails to correlate sufficiently to a reference noise cycle. When the line and load sides are connected, the RMS value of the observed current signal is monitored such that the line and load sides are disconnected if the observed current signal fails to meet an RMS threshold. The observed current signal is compensated by subtracting the reference noise cycle prior to monitoring for the fault condition applicable to the protective device.

A ground fault circuit interrupter (GFCI) can include a current transformer (CT) comprising a single core, a first winding wound around the single core, and a second winding wound around the single core. The GFCI can include a ground fault (GF) detection module operatively connected to the first winding to receive signals from the first winding and configured to determine whether a line-to-ground fault exists. The GFCI can also include a GN stimulus operatively connected to the second winding to provide a GN stimulus signal to the second winding. The GFCI can also include a grounded neutral (GN) detection module operatively connected to second winding and configured to receive signals from the second winding to determine whether a neutral-to-ground fault exists.

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.

Passive monitoring the integrity of current sensing devices and associated circuitry in GFCI and AFCI protective devices is provided. A protection circuit interrupter employs a capacitively coupled noise signal obtained by an arrangement of one or both of line side arms relative to a Rogowski coil. The noise signal is monitored while the line and load sides of a protective circuit interrupter are disconnected, and the connection of the line and load sides disabled if the noise signal fails to correlate sufficiently to a reference noise cycle. When the line and load sides are connected, the RMS value of the observed current signal is monitored such that the line and load sides are disconnected if the observed current signal fails to meet an RMS threshold. The observed current signal is compensated by subtracting the reference noise cycle prior to monitoring for the fault condition applicable to the protective device.

An integrated circuit includes front-end circuitry coupled to a current sensor, which is coupled to alternating current (AC) mains, and to convert a leakage current to a converted voltage. An analog-to-digital converter (ADC), coupled to the front-end circuitry, converts the converted voltage to a digital signal. The ADC includes limit detection circuitry to detect the digital signal indicating the converted voltage is lower than a low threshold limit or higher than a high threshold limit and output a limit interrupt in response to the detection. Control logic is coupled to an output of the ADC and to process, in response to receiving the limit interrupt, the digital signal to determine a root mean square (RMS) value, and output a trip signal to trip logic to cause a disconnect of a current supplied to a load by the AC mains in response to the RMS value satisfying a threshold trip value.