# US 2013/0157593 A1 · Systems and Methods for Time Synchronization of IEDs via Radio Link

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2013/0157593 A1
- Document ID: US20130157593A1
- Status: Published application
- Kind: A1
- Application number: 13/327,531
- Filed: 2011-12-15
- Published: 2013-06-20
- Earliest claimed: 2011-12-15
- Assignees: Schweitzer Engineering Laboratories, Inc.
- Inventors: Shankar V. Achanta
- Web page: https://patentgrep.com/patent/US20130157593A1

## CPC

- 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)}
- 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)}
- 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)}
- H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H)
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)

## 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

### Claim 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 via the radio transmitter requesting a response; and
receive the response 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 generate an adjusted time signal based upon the master time signal and the propagation delay, and
wherein the adjusted time signal is transmitted via the radio transmitter.

### Claim 2 (depends on 1)

The IED of claim 1, 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.

### Claim 3 (depends on 1)

The IED of claim 1, 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.

### Claim 4 (depends on 3)

The IED of claim 3, wherein the independent time source signal receiver module is configured to receive an independent time signal from a global positioning system.

### Claim 5 (depends on 1)

The IED of claim 1, wherein the time signal module comprises a time source configured to generate the master time signal.

### Claim 6 (depends on 1)

The IED of claim 1, 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.

### Claim 7 (depends on 1)

The IED of claim 1, 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.

### Claim 8 (depends on 1)

The IED of claim 1, 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.

### Claim 9

An intelligent electronic device (IED) configured to adjust a time signal received via a radio signal from a second IED by a calculated propagation delay, 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 local time signal;
a time signal synchronization module configured to:
transmit a request via the radio transmitter for a master time signal; and
receive the master time signal via the radio receiver after a first time delay; and
a propagation delay calculation module configured to determine a propagation delay associated with the received master time signal; and
a time signal adjustment module configured to adjust the received master time signal by the propagation delay and use the adjusted time signal to synchronize the local time signal with the master time signal.

### Claim 10 (depends on 9)

The IED of claim 9, 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.

### Claim 11 (depends on 9)

The IED of claim 9, 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;
wherein the time signal module is configured to synchronize the local time signal with the independent time signal; and
wherein the time signal adjustment module is configured to use the adjusted time signal to synchronize the local time signal with the master time signal only when the independent time source signal receiver module loses reception of the independent time signal.

### Claim 12 (depends on 11)

The IED of claim 11, wherein the independent time source signal receiver module is configured to receive an independent time source signal from a global positioning system.

### Claim 13 (depends on 9)

The IED of claim 9, wherein the time signal module comprises a time source configured to generate the local time signal.

### Claim 14 (depends on 9)

The IED of claim 9, wherein the time signal synchronization module is further configured to receive a processing delay, the processing delay corresponding to the difference between when a second IED received the request for the master time signal and when the second IED transmitted the master time signal; and
wherein determining a propagation delay associated with the received master time signal comprises subtracting the processing delay from the first time delay and dividing the difference in half.

### Claim 15 (depends on 9)

The IED of claim 9, 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.

### Claim 16 (depends on 9)

The IED of claim 9, wherein the time signal adjustment module is configured to synchronize the local time signal with the master time signal to within at least 1 millisecond.

### Claim 17

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; and
transmitting a time signal of the first IED adjusted by the propagation delay 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 time signal of the first IED.

### Claim 18 (depends on 17)

The method of claim 17, 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.

### Claim 19 (depends on 17)

The method of claim 17, further comprising detecting the loss of communication between the first IED and a primary independent time source; and
wherein transmitting the time signal of the first IED adjusted by the propagation delay to the second IED occurs subsequent to the detection of the loss of communication between the first IED and the primary independent time source.

### Claim 20 (depends on 19)

The method of claim 19, wherein the primary independent time source comprises a global positioning system.

### Claim 21 (depends on 17)

The method of claim 17, 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.

### Claim 22 (depends on 17)

The method of claim 17, 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.

### Claim 23

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 time signal of the second IED;
receiving a radio signal response from the second IED after a first time delay, the response including the time signal of the second IED;
determining a propagation delay between the first IED and the second IED by dividing the first time delay in half; and
synchronizing a time signal of the first IED with the time signal of the second IED using the determined propagation delay.

### Claim 24 (depends on 23)

The method of claim 23, 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 actually 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.

### Claim 25 (depends on 23)

The method of claim 23, further comprising detecting the loss of communication between the first IED and a primary independent time source; and
wherein synchronizing the time signal of the first IED with the received time signal of the second IED adjusted by the propagation delay occurs subsequent to the detection of the loss of communication between the first IED and the primary independent time source.

### Claim 26 (depends on 25)

The method of claim 25, wherein the primary independent time source comprises a global positioning system.

### Claim 27 (depends on 23)

The method of claim 23, 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.

### Claim 28 (depends on 23)

The method of claim 23, wherein synchronizing a time signal of the first IED with the received time signal of the second IED using the determined propagation delay is accurate to within at least 1 millisecond.

### Claim 29

An intelligent electronic device (IED) configured to adjust a time signal received via a radio signal from a second IED by a calculated propagation delay, 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 local time signal;
a time signal synchronization module configured to receive a master time signal from the second IED transmitted at a known interval via the radio receiver after a propagation time delay; and
a time signal adjustment module configured to adjust the received master time signal by the propagation delay and use the adjusted time signal to synchronize the local time signal with the master time signal.

### Claim 30

The IED of FIG. 29, wherein the known interval comprises a pulse-per-second (PPS)