Time signal manipulation detection using remotely managed time
AssigneeSchweitzer Engineering Laboratories, Inc.
InventorsMichael B Bryson, Dennis Haes
Life of this patent
Estimating the term…
Abstract
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.
Claims18
A protective system for detecting and mitigating against manipulated time signals in an electric power delivery system, the protective system comprising:
- a first protective device disposed at a local location of the electric power delivery system, wherein the first protective device is configured to:
- provide a first protective operation at the local location;
- receive a local time signal generated based at least in part on a common time source;
- and
- transmit the local time signal via a communication system;
- and
- a second protective device in communication with a remote location of the electric power delivery system, wherein the second protective device is configured to:
- provide a second protective operation at the remote location;
- receive a remote time signal generated based at least in part on the common time source;
- receive the local time signal from the first protective device via the communication system;
- calculate a time difference between the remote time signal and the local time signal, wherein the time difference is at least partly due to latencies in communication between the first protective device and second protective device;
- compare the time difference with a threshold;
- and
- when the time difference exceeds the threshold,
- detect a time signal manipulation that indicates that the local time signal or the remote time signal, or both, are inaccurate;
- and
- upon detection of the time signal manipulation, modify the second protective operation to avoid use of electrical power system information from the first protective device.
A tangible, non-transitory, computer-readable medium comprising instructions that, when executed by a processor, cause the processor to:
- receive a first time signal, wherein the first time signal is derived from a common time source;
- receive a second time signal from a local intelligent electronic device (IED) via a communication system, wherein the second time signal is derived from the common time source;
- calculate a time difference between the first time signal and the second time signal;
- compare the time difference with a threshold amount of time;
- determine the threshold amount of time to be the greater of one of the following:
- a system time delay;
- a first time signal accuracy associated with a protective operation of the local intelligent electronic device;
- and
- a second time signal accuracy associated with a protective operation of a remote intelligent electronic device coupled remotely relative to the local intelligent electronic device;
- and
- when the time difference exceeds the threshold amount of time, detect a time signal manipulation.
A device, comprising:
- a comparator configured to compare a first time signal and a second time signal to a threshold amount of time;
- and
- a first logic gate coupled to the comparator, wherein the comparator outputs a first voltage signal corresponding to a first logic state voltage level to the logic gate in response to a time difference between a transmission of the first time signal and a transmission of the second time signal being greater than the threshold amount of time, and wherein the logic gate generates a control signal to indicate a time signal manipulation in response to the first voltage signal from the comparator.
Dependencies are inferred from the claim text.