A method for detecting an open-phase condition of a transformer having a grounded-wye high voltage side connection including monitoring current flowing in a neutral connection on the high voltage side of the transformer in real time by voltage relaying and current relaying to identify an open phase condition signature in a signal capable of characterizing change of current magnitude. A current signal may be injected onto the neutral terminal and the zero-sequence mode of the transformer monitored to detect an open-phase condition indicated by an increase in network impedance and decrease or elimination of the injection current.

A system for detecting miswiring in an AC power supply for an appliance may comprise a phase sensor sensing the phase difference between the first and a second hot line powering heavy electrical loads therebetween, and a control module coupling to the phase and voltage sensors. The control module may identify a fault condition and may disconnect different electrical loads from the power supply in the fault condition.

A system for current measurement and ground fault detection is disclosed. In embodiments, the system includes a plurality of phase current measurement coils configured to detect phase currents associated with at least one portion of a multi-phase system. The system further includes a plurality of phase current measurement circuits and a ground fault detection circuit connected to the phase current measurement coils. The phase current measurement circuits are configured to measure the phase currents detected by the phase current measurement coils, and the ground fault detection circuit is configured to measure a summation of the phase currents detected by the phase current measurement coils.

A ground fault monitoring system for an electrical service panel is provided. The ground fault monitoring system includes a current transformer coupled to a primary bonding location of the electrical service panel. The ground fault monitoring system also includes a current monitoring device in communication with the current transformer to detect ground fault electrical current returning to the electrical service panel. The ground fault monitoring system also includes a ground fault output interface in communication with the current monitoring device to provide ground fault status of the electrical service panel.

A system for testing a ground fault detection system in an electric circuit establishes a ground connection between a bus and the ground via an inverter and a load by closing an inverter switch of the inverter and a grounding switch disposed between the load and the ground, determines whether the ground connection is detected, and determines a fault in the ground fault detection system responsive to the first ground connection not being detected by the ground fault detection system. Optionally, a ground fault may be identified by determining three phase voltages provided from each of plural inverters, determining symmetrical components of the three phase voltages for each of the inverters, and identifying a ground fault in one or more of the inverters while powered by the power supply based on the symmetrical components.

A method for detecting faults (4) in a three-phase electrical distribution network comprising determining a zero sequence current (21C), a first phase current (21A) and a second phase current (21B) at a location of the three-phase electrical distribution network, determining first filtered currents (22) by removing a frequency component from the determined currents corresponding to a fundamental frequency of the electrical distribution network through filtering out said frequency component, determining directions of the first filtered currents during a first time period (23), and comparing said directions (24) relatively to each other, and, if at least one of the determined directions is opposite with respect to at least one of the other two determined directions, signaling a detection of a fault (25).

A multi-phase VFD system with frequency compensated ground fault protection includes a variable frequency drive (VFD) power supply, a motor coupled to the VFD power supply by a plurality of power wires and a relay, an annular magnetic core provided with a sensor winding, where the plurality of power wires extend through the annular magnetic core, an analog signal conditioner, an analog-to-digital (A/D) converter, and a digital processor performing a Fast Fourier Transform (FFT) process on the received digital output of the A/D converter to provide frequency information which is used to develop a frequency equalized transfer function for calculating ground fault current.

The present application is directed to a three phase power transmission system including a first conductor line, a second conductor line and a third conductor line. One or more sensors are configured to detect traveling waves in each of the first second and third conductors. A controller is configured to receive data transmitted by the one or more sensors and determine which of the traveling modal waves is a first metallic mode wave (MM1), a second metallic mode (MM2) wave and/or a ground mode (GM0) wave. The controller is operable to determine which of the conductor lines are faulted based on detection of one or more of MM1 waves, MM2 waves and/or GM0 waves.

An apparatus for determining a phase associated with a ground fault on a multi-phase power distribution network, the apparatus configured to, based on determination of a spike fault, determine which of a plurality of RMS values of phase-to-phase fault currents is the minimum, said minimum RMS value indicative of a particular phase of the multi-phase power distribution network associated with the ground fault.

A system for current measurement and ground fault detection is disclosed. In embodiments, the system includes a plurality of phase current measurement coils configured to detect phase currents associated with at least one portion of a multi-phase system. The system further includes a plurality of phase current measurement circuits and a ground fault detection circuit connected to the phase current measurement coils. The phase current measurement circuits are configured to measure the phase currents detected by the phase current measurement coils, and the ground fault detection circuit is configured to measure a summation of the phase currents detected by the phase current measurement coils.