Abstract: 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.

Abstract: Systems and methods to estimate trapped charge for a controlled automatic reclose are described herein. For example, an intelligent electronic device (IED) may calculate an analog amount of trapped charge of each phase of a power line based on voltage measurements of the power line. The IED may close a switching device of each phase at a time corresponding to a point-on-wave associated with the analog amount of trapped charge of the respective phase.

Abstract: 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.

Abstract: Detection and protection against electric power generator rotor turn-to-turn faults, rotor multi-point-to-ground faults, and rotor permanent magnet faults is provided herein. A fractional harmonic signal is used to determine the rotor fault condition. The fractional harmonic signal may be a fractional harmonic magnitude of the circulating current of one phase. The fractional harmonic may be a fractional harmonic magnitude of a neutral voltage. A tripping subsystem may issue a trip command based upon detection of a rotor turn-to-turn fault condition.

Abstract: Detection of electric power generator stator ground fault conditions and protection of the generator due to such conditions is provided herein. In one embodiment, a generator protection element may calculate generator third harmonic voltage quantities using measurements from the generator terminals, and determine a stator ground fault condition using the calculated generator third harmonic voltage quantity. A tripping subsystem may issue a trip command based upon detection of a stator ground fault condition.

Abstract: Electric power generator protection is secured by detecting wiring errors to an intelligent electronic device using terminal third voltages at the terminal (VT3) and third harmonic voltages at the neutral (VN3). When an angle between VT3 and VN3 is outside of an acceptable range, a wiring defect is detected, and certain protective operations are blocked. An alarm may be generated, facilitating personnel to identify and rectify the wiring defect. Wiring defects may further be detected when a torque calculated using VT3 and VN3 exceeds a predetermined error threshold. Security of protection elements is increased by detection of wiring defects that may have resulted in misoperation of the protection elements.

Abstract: Disclosed are systems and methods to determine a direction to a fault of an electrical generator using sensitive current. A ground fault is determined using voltage signals from the generator installation. Incremental residual values of the sensitive current, along with the voltage, are used to determine a direction to the fault. The generator may be high-impedance grounded. The systems and methods further indicate the direction to a fault where multiple generators are connected using a common generation bus.

Abstract: Disclosed are systems and methods to determine an overexcitation condition on electric power delivery system equipment that includes a magnetizing core. Overexcitation conditions are determined even during sub-synchronous resonance, ferro-resonance, and other complex events. Power system voltage is integrated and normalized to determine a flux on the magnetizing core. The flux is compared with a protection model to determine the overexcitation condition on the magnetizing core. Once an overexcitation condition is detected, a protective action may be taken to remove power from the effected power delivery system equipment.

Abstract: Disclosed are systems and methods to determine a direction to a fault of an electrical generator using sensitive current. A ground fault is determined using voltage signals from the generator installation. Incremental residual values of the sensitive current, along with the voltage, are used to determine a direction to the fault. The generator may be high-impedance grounded. The systems and methods further indicate the direction to a fault where multiple generators are connected using a common generation bus.

Abstract: Disclosed are systems and methods to determine an overexcitation condition on electric power delivery system equipment that includes a magnetizing core. Overexcitation conditions are determined even during sub-synchronous resonance, ferro-resonance, and other complex events. Power system voltage is integrated and normalized to determine a flux on the magnetizing core. The flux is compared with a protection model to determine the overexcitation condition on the magnetizing core. Once an overexcitation condition is detected, a protective action may be taken to remove power from the effected power delivery system equipment.

Abstract: Detection and protection against electric power generator stator ground fault conditions in multiple-generator high-impedance grounded installations is provided herein. In one embodiment, a generator protection element may block a determination of a fault using third harmonic voltages when the third harmonic voltage from the generator is less than a factor of the maximum third harmonic voltage from all of the generators on the common bus. A tripping subsystem may issue a trip command based upon detection of a stator ground fault condition.

Abstract: Detection and protection against electric power generator stator ground fault conditions in multiple-generator high-impedance grounded installations is provided herein. In one embodiment, a generator protection element may block a determination of a fault using third harmonic voltages when the third harmonic voltage from the generator is less than a factor of the maximum third harmonic voltage from all of the generators on the common bus. A tripping subsystem may issue a trip command based upon detection of a stator ground fault condition.

Abstract: Detection of electric power generator stator ground fault conditions and protection of the generator due to such conditions is provided herein. In one embodiment, a generator protection element may calculate generator third harmonic voltage quantities using measurements from the generator terminals, and determine a stator ground fault condition using the calculated generator third harmonic voltage quantity. A tripping subsystem may issue a trip command based upon detection of a stator ground fault condition.