Systems and methods for time synchronization of IEDs via radio link

• US 9,590,411 B2
• Filed: 12/15/2011
• Issued: 03/07/2017
• Est. Priority Date: 12/15/2011
• Status: Active Grant

• Current Assignee: Schweitzer Engineering Laboratories, Incorporated
• Original Assignee: Schweitzer Engineering Laboratories, Incorporated
• Inventors: Achanta, Shankar V.
• Primary Examiner(s): Tran, Tuan A
• Application Number:
  US13/327,531
• Publication Number:
  US 20130157593A1
• Time in Patent Office: 1,909 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: H02H 1/0061 concerning transmission of signals transmission of measured quantities or switching orders; sectionalised protection involving signal transmission between at least two stations H02H7/261; comparison of the voltage or current values at two spaced portions of a single system H02H3/28; transferring the output of a sensing member to another variable G01D5/00; electrical measuring arrangements using modulation of electromagnetic waves, e.g. light beams G01R15/24, G01R15/26
• CPC Class Codes: H04J 3/0638 Clock or time synchronisation among nodes; Internode synchronisation synchronization for ring networks H04L12/422; data switching networks with synchronous transmission H04L12/43
• CPC Class Codes: H04J 3/0667 Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays arrangements for monitoring round trip delays in packet switching networks H04L43/0864

Abstract

The present disclosure provides systems and methods for synchronizing the time signals of master and remote IEDs using a radio link. According to one embodiment, a master IED may transmit an adjusted time signal to a remote IED via a radio signal. The master IED may determine a propagation delay between the master IED and a remote IED. The master IED may then adjust a master time signal by the propagation delay and transmit the adjusted time signal to the remote IED. Alternatively, a remote IED may request and receive a master time signal from a master IED via a radio signal. The remote IED may then determine the propagation delay and adjust the received master time signal accordingly. According to various embodiments, the time signal of a master and remote IED may be synchronized to within at least one millisecond.

Claims

1. An intelligent electronic device (IED) configured to transmit a time signal adjusted by a calculated propagation delay via a radio link, the IED comprising:

a radio transmitter configured to transmit radio signals;

a radio receiver configured to receive radio signals;

a time signal module configured to maintain a master time signal;

a time signal synchronization module in communication with the radio transmitter and the radio receiver, the time signal synchronization module configured to;

transmit a radio signal to a receiving IED via the radio transmitter requesting a response; and

receive the response from the receiving IED via the radio receiver after a first time delay;

a propagation delay calculation module configured to determine a propagation delay associated with the response; and

a time signal adjustment module configured to calculate a new time signal for the receiving IED, the new time signal representative of a time from the master time signal and adjusted by the propagation delay, and

wherein the radio transmitter transmits the new time signal via the radio link to the receiving IED subsequent to a detection of loss of communication with a primary independent time source.

2. A method for synchronizing a first intelligent electronic device (IED) and a second IED, comprising the first IED:

transmitting a radio signal to the second IED requesting a response from the second IED;

receiving a response via a radio signal from the second IED after a first time delay;

determining a propagation delay between the first IED and the second IED by dividing the first time delay in half;

calculating a new time signal for the second IED, the new time signal representative of a time from a master time signal and adjusted by the propagation delay; and

transmitting the new time signal for the second IED to the second IED via a radio signal in order for the second IED to synchronize a time signal of the second IED with the new time signal, subsequent to a detection of loss of communication with a primary independent time source.

3. The method of claim 2, wherein receiving a response from the second IED after a first time delay further comprises:

receiving a response including a processing delay corresponding to the difference between when the second IED received the request from the first IED and when the second IED transmitted the response to the first IED; and

wherein determining a propagation delay between the first IED and the second IED by dividing the first time delay in half further comprises;

subtracting the processing delay from the first time delay prior to dividing the first time delay in half.

4. The method of claim 2, wherein the primary independent time source comprises a global positioning system.

5. The method of claim 2, further comprising the first IED transmitting data to the second IED via a radio signal, the data relating to the monitoring of at least one component in an electric power delivery system.

6. The method of claim 2, wherein the time signal of the first IED adjusted by the propagation delay transmitted to the second IED is configured to allow the second IED to synchronize the time signal of the second IED to the time signal of the first IED to within at least 1 millisecond.

7. An intelligent electronic device (IED) configured to transmit a time signal adjusted by a calculated propagation delay via a radio link, the IED comprising:

a radio transmitter configured to transmit radio signals;

a radio receiver configured to receive radio signals;

a time signal module configured to maintain a master time signal;

a time signal synchronization module in communication with the radio transmitter and the radio receiver, the time signal synchronization module configured to;

transmit a radio signal to a receiving IED via the radio transmitter requesting a response; and

receive the response from the receiving IED via the radio receiver after a first time delay;

a propagation delay calculation module configured to determine a propagation delay associated with the response; and

a time signal adjustment module configured calculate a new time signal for the receiving IED based upon the master time signal and the propagation delay, and

wherein the radio transmitter transmits the new time signal via the radio link to the receiving IED subsequent to a detection of the loss of communication with a primary independent time source.

8. The IED of claim 7, further comprising a processor and a computer-readable storage medium in communication with the processor;

and

wherein the propagation delay calculation module and the time signal adjustment module comprise software modules within the computer-readable storage medium.

9. The IED of claim 7, further comprising an independent time source signal receiver module configured to receive an independent time signal and provide the independent time signal to the time signal module;

and

wherein the time signal module is configured to synchronize the master time signal with the independent time signal.

10. The IED of claim 9, wherein the independent time source signal receiver module is configured to receive an independent time signal from a global positioning system.

11. The IED of claim 7, wherein the time signal module comprises a time source configured to generate the master time signal.

12. The IED of claim 7, wherein the response received by the time signal synchronization module comprises a processing delay corresponding to the difference between when a second IED received the request for a response and when the second IED transmitted the response;

and

wherein determining a propagation delay associated with the response comprises subtracting the processing delay from the first time delay and dividing the difference in half.

13. The IED of claim 7, further comprising a data communications module configured to transmit data via the radio transmitter, the data relating to the monitoring of at least one component in an electric power delivery system.

14. The IED of claim 7, wherein the time signal adjustment module is configured to generate the adjusted time signal with sufficient accuracy to allow for time signal synchronization to within at least 1 millisecond.