A transformer system including a transformer including a set of wye windings, a three-phase current transformer, a neutral-current transformer, and a controller. The three-phase current transformer outputs a first signal indicative of a three-phase current conducting through the set of wye windings and the three-phase current transformer. The neutral-current transformer couples the current flowing from the ground to the neutral node of the transformer, and outputs a second signal indicative of a neutral current conducting from the ground node to the neutral node of the transformer. The controller receives the first signal and the second signal, determines whether an external ground fault condition or an internal ground fault condition is present based on the three-phase current and the neutral current, and determines whether a wiring error is present for the three-phase current transformer or the neutral-current transformer based on the three-phase current and the neutral current.

A ground fault current interrupter circuit includes a plurality of comparators, threshold generation circuitry, and a plurality of timer circuits. Each of the comparators is configured to compare a threshold voltage to a signal representative of a difference of current flow to a load and current flow from the load. The threshold generation circuitry is configured to generate a plurality of different threshold voltages. Each of the different threshold voltages is provided as the threshold voltage for one of the comparators. Each of the comparators is coupled to one of the timer circuits, and the one of the timer circuits is configured to activate a fault signal responsive to activation of an output of the comparator for a time that is related to the threshold voltage provided to the comparator. The time increases with lower values of the threshold voltage.

A grounded neutral fault detector that includes induction circuits and a controller is provided. The controller is configured to determine a frequency of a test signal by measuring load noise based on a first leakage signal corresponding to a first current imbalance between the line conductor and the neutral conductor for the load without the test signal being injected, analyzing a frequency spectrum of the load noise, and selecting the frequency of the test signal. The controller is further configured to inject the test signal at the selected frequency to the neutral conductor, measure impedance of a current loop formed by a potential grounded neutral fault based on a second leakage signal corresponding to a second current imbalance with the test signal being injected, and determine a grounded neutral fault.

A cool running ground fault circuit interrupter (GFCI) with radio frequency (RF) noise suppression and a Capacitive Power Supply tbr interrupting the flow of current through a pair of load and neutral lines extending between an input power source and a load is provided. The GFCI includes a pair of switches disposed between the input power source and the load. The switches are actuated by a relay circuit initially powered by a booster circuit and a constant on power supply. A capacitive power supply for cool operation of the GFCI is connected to the load line via a current limiting resistor and provides power to the constant on power supply circuit.

Apparatuses and methods for passively monitoring the integrity of current sensing devices and associated circuitry in protective devices such as Ground Fault Circuit Interrupters and Arc Fault Circuit Interrupters are provided. A protection circuit interrupter employs a capacitively coupled noise signal obtained by an arrangement of one or both of the 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 otherwise compensated by subtracting the reference noise cycle prior to monitoring for the fault condition applicable to the protective device.

A circuit interrupter including a line conductor, a neutral conductor, a power supply, a ground fault current transformer structured to sense a ground fault current from current flowing through the line and neutral conductors, a grounded neutral detection circuit including a filtering stage structured to high-pass filter the ground fault current, and a processor structured to receive an output of the grounded neutral detection circuit and to determine whether a grounded neutral is present based on the output of the grounded neutral detection circuit.

A circuit interrupter including a first electrical conductor, a second electrical conductor, separable contacts, an operating mechanism configured to open and close said separable contacts, a trip circuit configured to trip open said separable contacts, a ground fault detection circuit configured to sense a difference between a current through the first electrical conductor and a current through the second electrical conductor and to output an output signal based on said sensed difference, a power supply, a confirmation circuit structured to input a confirmation signal to the power supply, and a processor configured to receive said direct current power and said output signal. The processor is configured to determine whether a characteristic of said confirmation signal is present in said output signal and to control the trip circuit based on said determination.

The line power and neutral conductors for an arc fault sensing circuit interrupter such as in a miniature circuit breaker are arranged as a rigid conductor surrounding and holding an insulated flexible conductor when passing through the Ground Fault Interrupter current transformer. Voltage metering takes place across the rigid conductor to enable arc fault detection and ground fault detection in the miniature circuit breaker within the space of a single current transformer.

Apparatuses and methods for passively monitoring the integrity of current sensing devices and associated circuitry in protective devices such as Ground Fault Circuit Interrupters and Arc Fault Circuit Interrupters are provided. A protection circuit interrupter employs a capacitively coupled noise signal obtained by an arrangement of one or both of the 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 otherwise compensated by subtracting the reference noise cycle prior to monitoring for the fault condition applicable to the protective device.

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.