Determining Electric Grid Endpoint Phase Connectivity

• US 20100060259A1
• Filed: 05/27/2009
• Published: 03/11/2010
• Est. Priority Date: 09/05/2008
• Status: Active Grant

• Current Assignee: Itron Networked Solutions, Inc. (Itron, Inc.)
• Original Assignee: Silver Spring Networks, Inc. (Itron, Inc.)
• Inventors: Gostrer, Alexander, van Greunen, Jana, Vaswani, Raj
• Granted Patent: US 8,207,726 B2
• Time in Patent Office: Days
• US Class Current: 324/86
• CPC Class Codes: G01R 29/18 Indicating phase sequence; Indicating synchronism
• CPC Class Codes: H02J 13/00009 using pulsed signals
• CPC Class Codes: H02J 13/0001 using modification of a parameter of the network power signal
• CPC Class Codes: H02J 13/00034 the elements or equipment being or involving an electric power substation
• CPC Class Codes: H02J 3/00 Circuit arrangements for ac mains or ac distribution networks
• CPC Class Codes: H02J 3/002 Flicker reduction, e.g. compensation of flicker introduced by non-linear load
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 10/52 Outage or fault management, e.g. fault detection or location
• CPC Class Codes: Y04S 40/121 using the power network as support for the transmission

Abstract

The service phase of the electrical connection to a customer endpoint device located within a power distribution system is determined by various techniques. At the feeder level, the system may be programmed to induce momentary power interruptions, thereby causing missed zero crossings at the customer endpoint devices. The pattern of these interruptions is a controlled one, designed specifically to avoid causing noticeable disruption even to sensitive devices, but to be unusual enough that it is statistically unlikely to be naturally occurring. The monitoring of the zero crossing information is used to determine the phase of the service line to the customer endpoint devices.

Claims

1. A method of determining a service phase of an endpoint device in a power distribution system, the method comprising:

sending a message to a point in the power distribution system requesting a temporary power interruption on one of a plurality of phases of a feeder line to customer sites;

receiving a report from at least one of a plurality of endpoint devices at respective customer sites indicating whether the power interruption was detected by the endpoint device; and

mapping an endpoint device that reported the detection of the power interruption to the respective phase on which the power interruption was created.

2. The method of claim 1, wherein the point in the power distribution system to which the message is sent is a substation.

3. The method of claim 1, wherein the plurality of endpoint devices are programmed to detect, log, and report power interruptions.

4. The method of claim 1, wherein the plurality of endpoint devices detect the power interruption by monitoring missed zero crossings in alternating current power within a predetermined time period.

5. The method of claim 1, wherein the power interruption is induced serially on each phase of the feeder line at a given time for a predetermined period of time.

6. The method of claim 5, wherein the mapping of the endpoint device is performed at a back office server having information pertaining to the power interruption being induced on a particular phase, and based on the reports received from the end-point devices, the back office server links the end-point device reporting the power interruption at the given time to the particular phase.

7. The method of claim 1, wherein a single power interruption is detected when the endpoint device measures a zero-crossing for a period of time that is less than a predetermined maximum time period and longer than a predetermined minimum time period.

8. The method of claim 7, wherein the maximum time period is determined so that a device, to which the power is supplied, avoids reacting to the interruption as a loss of power.

9. The method of claim 7, wherein duration of a power interruption for the predetermined minimum time period causes the endpoint devices to measure zero-crossing data, and send a report containing the measured data.

10. A method of determining a service phase of an endpoint device in a power distribution system, the method comprising:

identifying a plurality of endpoint devices that communicate with a host device;

synchronizing the plurality of endpoint devices temporarily with the host device;

detecting last zero-crossings in alternating current power within a predetermined time period at each endpoint device;

measuring the relative phase difference of the plurality of endpoint devices based on timestamps of the detected last zero-crossings; and

determining the service phase of each endpoint device based on the measured relative phase difference.

11. The method of claim 10, wherein measuring the relative phase difference of the plurality of endpoint devices includes calculating the difference between a timestamp of the last zero-crossing detected at a first endpoint device and a timestamp of the last zero-crossing detected at a second endpoint device.

12. The method of claim 11, wherein, if the calculated difference between the timestamps is within a predetermined range of zero, then both of the endpoint devices are determined to be on the same service phase.

13. The method of claim 11, wherein, if the calculated difference between the timestamps is approximately 5.5 ms for 60 Hz power service or 6.6 ms for 50 Hz power service, then the relative phase difference between the endpoint devices is determined to be 120°

.

14. The method of claim 11, wherein, if the calculated difference between the timestamps is approximately 11 ms for 60 Hz power service or 13.2 ms for 50 Hz power service, then the relative phase difference between the endpoint devices is 240°

.

15. A method of determining a service phase of an endpoint device in a power distribution system, the method comprising:

sending, from a host, a request to the endpoint device requesting zero-crossing delta data detected at the endpoint device;

receiving, at the host, a response message from the endpoint device including zero-crossing delta data detected at the endpoint device indicating the difference between the time when a last zero-crossing was detected at the endpoint device and when the response message was created by the endpoint device;

calculating zero-crossing delta data detected at the host, the zero-crossing delta detected at the host indicating the difference between the time when a last zero-crossing was detected at the host and the time when the response message was received by the host;

calculating a phase shift from the endpoint device based on the zero-crossing delta data detected at the endpoint device, the calculated zero-crossing delta data detected at the host, a message latency time, and a frequency period of a feeder line electrically connected to the endpoint device; and

determining the service phase of the endpoint device based on the calculated phase shift.

16. The method of claim 15, wherein the host is a neighboring node of the endpoint device.

17. The method of claim 15, wherein the host is an access point with which the endpoint device communicates.

18. The method of claim 15, wherein the message latency time is the time period from when the response message was created at the endpoint device to when the response message was received at the host.

19. The method of claim 18, wherein the message latency time is an aggregated message latency time in which each endpoint device along a path including a plurality of endpoint devices adjusts the message latency time by adding its own latency time to the message latency time.

20. The method of claim 15, wherein determining the service phase of the endpoint device includes determining a service phase of the host and then determining the service phase of the endpoint device based on the calculated phase shift and the service phase of the host.

21. The method of claim 20, wherein the host has knowledge of its service phase.

22. The method of claim 20, wherein the host does not have knowledge of its service phase and requests its service phase from a back office which has knowledge of the host'"'"'s service phase.

23. A method of determining a service phase of an endpoint device in a power distribution system, the method comprising:

sending a request from a first endpoint device to a neighboring endpoint device requesting zero-crossing delta data detected at the neighboring device;

receiving, at the first endpoint device, a response message from the neighboring device including the zero-crossing delta data detected at the neighboring device, the zero-crossing delta data detected at the neighboring device indicating the difference between the time when a last zero-crossing was detected at the neighboring device and when the response message was created by the neighboring device;

calculating, at the first endpoint device, zero-crossing delta data detected at the first endpoint device, the zero-crossing delta data detected at the first endpoint device indicating the difference between the time when a last zero-crossing was detected at the first endpoint device and the time when the response message was received by the first endpoint device;

calculating a phase shift from the neighboring device based on the zero-crossing delta data detected at the neighboring device, the calculated zero-crossing delta data detected at the first endpoint device, a message latency time, and a frequency period of a feeder line electrically connected to the neighboring device; and

determining the service phase of the neighboring device based on the calculated phase shift.

24. The method of claim 23, wherein the calculated phase shift is reported to an upstream node, and wherein the determining step is performed at the upstream node.

25. The method of claim 24, wherein determining the service phase of the neighboring device includes determining a service phase of the first endpoint device and then determining the service phase of the neighboring device based on the calculated phase shift and the service phase of the neighboring device.

26. The method of claim 23, wherein each endpoint device stores phase shift information for all of its neighboring endpoint devices.