Method and apparatus for synchronizing data in utility system

• US 20080279321A1
• Filed: 05/10/2007
• Published: 11/13/2008
• Est. Priority Date: 05/10/2007
• Status: Active Grant

• Current Assignee: Schneider Electric USA, Inc. (Schneider Electric SE)
• Original Assignee: Square D Company (Schneider Electric SE)
• Inventors: Bickel, Jon A., Ashby, E. Avery
• Granted Patent: US 8,081,726 B2
• Time in Patent Office: Days
• US Class Current: 375/356
• CPC Class Codes: G01D 2204/22 Arrangements for detecting or reporting faults, outages or leaks
• CPC Class Codes: G01D 2204/47 Methods for determining the topology or arrangement of meters in a network
• CPC Class Codes: G01D 4/002 Remote reading of utility meters
• CPC Class Codes: H04B 2203/5433 Remote metering
• CPC Class Codes: H04B 2203/5458 Monitor sensor; Alarm systems
• CPC Class Codes: H04B 2203/5466 using three phases conductors
• CPC Class Codes: H04B 2203/5483 using coupling circuits
• CPC Class Codes: H04B 3/542 the information being in digital form
• CPC Class Codes: Y02B 90/20 Smart grids as enabling technology in buildings sector smart grids supporting the management or operation of end-user stationary applications in general, or like technologies with no associated climate change mitigation effect Y04S20/00
• CPC Class Codes: Y04S 20/30 Smart metering, e.g. specially adapted for remote reading

Abstract

A time synchronization device (TSD) that produces a synchronization signal and couples it onto energized power conductors in a power monitoring system. Monitoring devices coupled to the TSD include frequency detection algorithms, such as a Goertzel filter, for detecting the synchronization signal and interpreting the information encoded in the signal. The frequency of the synchronization signal may correspond to the fourth or tenth harmonic component of the fundamental frequency of the voltage on the power conductors. The magnitude of the signal is selected to be above the expected or established noise floor of the power monitoring system plus a predetermined threshold. The duration of the signal can be varied, such as lasting a full cycle of the fundamental frequency. Multiple TSD signals received in a predetermined sequence may be converted into digital words that convey time, configuration, reset, control, or other information to the monitoring device.

Claims

1. A system for synchronizing a plurality of monitoring devices in a utility monitoring system to a common time reference, comprising:

a time synchronization device that includes a reference clock, a signal generator, and a controller programmed to cause the signal generator to generate a synchronization signal at periodic time intervals that are synchronized with the reference clock, the signal generator coupling the synchronization signal over an energized power conductor; and

a monitoring device coupled to the power conductor and including a controller coupled to a memory, the controller of the monitoring device being programmed to detect at least one characteristic of the synchronization signal and, in response thereto, to store data in the memory indicative of the detection of the synchronization signal.

2. The system of claim 1, wherein the monitoring device is a power meter and further includes a cycle counter that counts the number of cycles on the energized power conductor, the cycle counter incrementing a value in the memory, the data being set to a predetermined value in response to the detection of the synchronization signal.

3. The system of claim 1, wherein the at least one characteristic is at least one of a fundamental frequency, a magnitude, a phase, or a duration, the signal generator operable to generate the synchronization signal and a second synchronization signal having a set of characteristics in which at least one characteristic of the set of characteristics differs from the at least one characteristic of the synchronization signal.

4. The system of claim 3, wherein the fundamental frequency of the synchronization signal corresponds to a harmonic component of the fundamental frequency of the electrical voltage or current.

5. The system of claim 1, the monitoring device further including a communications interface communicatively coupled to a remote system, the monitoring device storing in the memory characteristic data indicative of an electrical characteristic, the monitoring device synchronizing the characteristic data with the synchronization signal and transmitting the characteristic data to the remote system via the communications interface.

6. The system of claim 1, wherein the reference clock is generated from a calendar clock onboard the time synchronization device.

7. The system of claim 1, wherein the reference clock is generated from an external global positioning system.

8. The system of claim 1, wherein the monitoring device is a power meter and further includes a cycle counter that counts the number of cycles on the energized power conductor, and wherein the data indicative of the detection of the synchronization signal includes a time associated with the detection of the synchronization signal and the cycle count associated with the detection of the synchronization signal.

9. The system of claim 1, wherein the synchronization signal includes a plurality of pulses, the monitoring device converting the plurality of pulses to a corresponding digital word indicative of at least a control function, a reset function, a configuration function, or a utility demand interval function.

10. The system of claim 9, wherein the control function includes at least one of an instruction that causes a load coupled to the monitoring device to be turned on or off, or an instruction that causes an actuating device coupled to the monitoring device to change states.

11. The system of claim 9, wherein the reset function includes at least one of an instruction to adjust a counter or value related to an electrical characteristic or an instruction to reset the monitoring device.

12. The system of claim 9, wherein the configuration function includes an instruction to configure a parameter of the monitoring device, the parameter including a value indicative of the at least one characteristic of the synchronization signal.

13. The system of claim 9, wherein the utility demand interval function includes an instruction to increment or reset a utility demand interval counter.

14. A method of communicating a synchronization signal that is interpreted simultaneously by a plurality of monitoring devices in a power monitoring system, comprising:

generating a synchronization signal having at least a magnitude and a duration;

coupling the synchronization signal via power line communication onto one or more power conductors to which the plurality of monitoring devices are coupled at periodic time intervals that are determined by a reference clock external to the plurality of monitoring devices;

receiving, simultaneously at each of the plurality of monitoring devices, the synchronization signal;

detecting at least one of the magnitude or the duration of the synchronization signal; and

responsive to the detecting, storing data in memory indicative of the detection of the synchronization signal.

15. The method of claim 14, wherein the detecting includes filtering the synchronization signal at a harmonic component of the fundamental frequency of the voltage or current in the one or more power conductors.

16. The method of claim 14, further comprising encoding in the synchronization signal at least one of control information, reset information, configuration information, or utility demand interval information, the synchronization signal comprising a plurality of pulses transmitted in a sequence that is decoded and converted into a corresponding digital word by each of the plurality of monitoring devices.

17. The method of claim 14, wherein the storing includes adjusting an on-board clock in at least one of the plurality of monitoring devices to be synchronized with the reference clock.

18. The method of claim 14, further comprising counting, in at least one of the plurality of monitoring devices, the number of zero crossings in the voltage or current in the one or more power conductors and storing the number of zero crossings in a cycle count counter on the at least one of the plurality of monitoring devices, wherein the storing includes resetting the cycle count counter.

19. The method of claim 18, further comprising determining, in at least one of the plurality of monitoring devices, an outage time based on the number of peaks actually counted by the at least one of the plurality of monitoring devices during a time interval between two consecutive synchronization signals and on the number of expected peaks that should have been counted during the time interval.