Abstract: A fault detector detects grounded-neutral faults. The fault detector is configured to: receive a first signal from a first induction circuit, the first induction circuit configured to detect a current imbalance between a line conductor and a neutral conductor; determine a first frequency and a first phase of a noise signal component of the first signal; output a noise cancellation signal to a primary side of the first induction circuit, the noise cancellation signal having the first frequency of the noise signal component and an opposite phase than the first phase of the noise signal component; and generate a trip signal based on determining that an impedance of the neutral conductor to ground is at or below a threshold level based upon the first signal received during the injection of the noise cancelation signal.

Abstract: A current transformer includes a housing including generally cylindrical outer and inner walls defining an internal chamber, a front face enclosing one end of the internal chamber, a base, and a central opening defined by the inner wall. A generally toroidal current transformer core is disposed within the internal chamber. A secondary wiring is disposed about the transformer core and is configured to generate a current in response to magnetic flux in the transformer core. A pin housing is disposed on the front face of the housing adjacent the base. The pin housing has electrically conductive pins. A test wire passes through the central opening. The secondary wiring is electrically connected to a first pair of the pins and the test wire is electrically connected to a second pair of the pins.

Abstract: A fault detector detects grounded-neutral faults. The fault detector is configured to: receive a first signal from a first induction circuit, the first induction circuit configured to detect a current imbalance between a line conductor and a neutral conductor; determine a first frequency and a first phase of a noise signal component of the first signal; output a noise cancellation signal to a primary side of the first induction circuit, the noise cancellation signal having the first frequency of the noise signal component and an opposite phase than the first phase of the noise signal component; and generate a trip signal based on determining that an impedance of the neutral conductor to ground is at or below a threshold level based upon the first signal received during the injection of the noise cancelation signal.

Abstract: A current transformer includes a housing including generally cylindrical outer and inner walls defining an internal chamber, a front face enclosing one end of the internal chamber, a base, and a central opening defined by the inner wall. A generally toroidal current transformer core is disposed within the internal chamber. A secondary wiring is disposed about the transformer core and is configured to generate a current in response to magnetic flux in the transformer core. A pin housing is disposed on the front face of the housing adjacent the base. The pin housing has electrically conductive pins. A test wire passes through the central opening. The secondary wiring is electrically connected to a first pair of the pins and the test wire is electrically connected to a second pair of the pins.

Abstract: A detector is provided that generates a leakage signal corresponding to a current imbalance between a line conductor and a neutral conductor for a load, and selectively injects a test signal into the neutral conductor. A frequency of the test signal substantially corresponds to a utility frequency. The detector measures a first value of the leakage signal, determines if the first value is less than first threshold value, and begins injection of the test signal into the neutral conductor in response to determining that the that first value is less than the first threshold value. In response to injecting the test signal, the detector measures a second value of the signal, determines if the second value is greater than a second threshold value, and disconnects the line conductor from the load in response to determining that the second value is greater than the second threshold value.

Abstract: An electronic trip device is described that includes a test current generator and a leakage current detection circuit. The test current generator is coupled to a conductor and configured to provide a test current having a magnitude to the conductor in response to a selection to test the electronic trip device. The conductor is a line conductor or a neutral conductor. The leakage current detection circuit is configured to detect a current difference between the neutral conductor and the line conductor. The leakage current detection circuit is configured to provide, in response to the selection to test the electronic trip device, a tripless error indication if the detected current difference is less than a first threshold value.

Abstract: An electronic trip device is described that includes a test current generator and a leakage current detection circuit. The test current generator is coupled to a conductor and configured to provide a test current having a magnitude to the conductor in response to a selection to test the electronic trip device. The conductor is a line conductor or a neutral conductor. The leakage current detection circuit is configured to detect a current difference between the neutral conductor and the line conductor. The leakage current detection circuit is configured to provide, in response to the selection to test the electronic trip device, a tripless error indication if the detected current difference is less than a first threshold value.