Schweitzer Engineering Laboratories, Inc.

Dennis Haes

Kamal Garg

Hong Chun

Balasubramanian Sridharan

Normann Fischer

Austin Edward Wade

Michael B Bryson

Bryan J Fazzari

William F Allen

Systems and methods are provided for monitoring or protecting an electric power distribution system using protective devices that may rely on accurate time signals from a common time source. A first protective device may receive a first time signal deriving from the common time source and a second protective device may receive a second time signal deriving from the common time source. The first time signal and the second time signal may be compared; when a difference between them exceeds a defined threshold, time signal manipulation may be detected. The protective devices may modify their operation in response to or to account for the time signal manipulation.

Time signal manipulation detection using remotely managed time

Systems and methods to isolate faults and restore power are described herein. For example, an intelligent electronic device (IED) may receive a blocking signal indicating a fault is detected on a power line. The IED may obtain one or more current measurements of the power line. The IED may determine that a fault is not present on the power line at the IED based on the one or more current measurements. The IED may trip a first current interruption device of the IED The IED may send a close permissive signal to another IED indicating that the other IED is permitted to permitted to close an open current interruption device of the other IED to restore power to one or more loads.

Fault isolation and restoration scheme

A location of a broken electrical conductor of an electric power delivery system may be detected by monitoring a rate of change of phase voltage and/or a rate of change of zero-sequence voltage at various points on the conductor. Intelligent electronic devices (IEDs) such as phasor measurement units may be used to obtain measurements and calculate synchrophasors. The synchrophasors may be used by a central controller to determine which two continuous IEDs measure rates of change of voltages of opposite polarities, where the broken conductor is between the two continuous IEDs. The synchrophasors may be used by a central controller to determine which two continuous IEDs where one exhibits a zero-sequence voltage magnitude that exceeds a predetermined threshold for a predetermined time, wherein the zero-sequence voltage magnitude of the other of the continuous IEDs does not exceed the predetermined threshold.

Voltage derivative and zero-sequence broken conductor detection

Disclosed herein are a variety of systems and methods related to detection of a cross-country fault in an electrical power system. In one embodiment, a system consistent with the present disclosure may be configured to monitor electrical parameters in the electrical power system. The system may determine when a voltage magnitude of one phase exceeds a first voltage threshold. The one phase that exceeds the first voltage threshold may be identified as an un-faulted phase. The system may further be configured to determine that the voltage magnitude of the un-faulted phase exceeds a second threshold based on a zero-sequence voltage. The system may further be configured to determine that a phase angle between the un-faulted phase and the zero-sequence voltage is within a range. A protective action to clear the cross-country fault condition may be implemented upon identification of a cross-country fault.

Detection of cross-country faults

An intelligent electronic device (IED) may provide point on wave switching. The IED may receive a control operation request, and determine when to issue a control command to cause a switch to change positions. The actuation of the switch may occur at a target point on an alternating current. An IED may have a processor that is too slow to implement a switch when a desired point on an alternating current first occurs. Accordingly, some embodiments may compensate for the processing speed of an IED by determining a number of processor cycles needed (in advance) to issue a control command so that the resulting action results in the desired point on wave open or close.

Point on wave switching using slow speed processing

Disclosed are adaptive communication assisted protection and control. Local intelligent electronic devices (IEDs) associated with local switching devices and having unique IDs may transmit switch status and unique IDs to an area IED. The area IED may calculate topology using switch status, and provide control information to local IEDs using the topology. The area IED may communicate the unique ID of the local IED calculated to be immediately upstream of each local IED and, upon detection of a fault, the local IEDs may send blocking signals that include the received unique ID of the IED immediately upstream therefrom. The area IED may communicate control commands that include the unique IDs and control commands for the local IEDs to take the control action. Upon matching of the unique ID in the control command with its own unique ID, the local IEDs may take the control action and transmit remaining actions.

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Colfax, WA, United States of America

Dennis Haes