Electric power system waveform search

• US 8,880,368 B2
• Filed: 03/12/2013
• Issued: 11/04/2014
• Est. Priority Date: 06/21/2012
• Status: Active Grant

• Current Assignee: Schweitzer Engineering Laboratories, Incorporated
• Original Assignee: Schweitzer Engineering Laboratories, Incorporated
• Inventors: Zweigle, Gregory C., Hewitt, Eric J, Gotshall, Stanley P
• Primary Examiner(s): Raymond, Edward
• Application Number:
  US13/795,586
• Publication Number:
  US 20130346419A1
• Time in Patent Office: 602 Days
• Field of Search: 702/66, 702/64, 702182-185
• US Class Current: 702/66
• CPC Class Codes: G06F 16/2458 Special types of queries, e.g. statistical queries, fuzzy queries or distributed queries
• CPC Class Codes: G06F 16/31 Indexing; Data structures therefor; Storage structures
• CPC Class Codes: H02J 13/00002 characterised by monitoring
• CPC Class Codes: H02J 13/00034 the elements or equipment being or involving an electric power substation
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 10/30 State monitoring, e.g. fault, temperature monitoring, insulator monitoring, corona discharge

Abstract

The present disclosure relates to searching electric power system waveforms. Disclosed herein are various systems and methods for improving search performance through indexing electric power system waveforms using waveform attributes such as frequency, amplitude, angle, rate of change, and the like. According to some embodiments, multiple indexes may be used together to find information of interest. A reference signal may be utilized according to some embodiments. Normalizing a plurality of waveforms using a reference signal may facilitate the use of an index for comparing two arbitrary waveforms. This disclosure also relates to detecting and indexing islanding conditions in an electric power system. Various embodiments may utilize information relating to islanding conditions in connection with search operations.

Claims

1. A system configured to index data based on at least one characteristic of a plurality of waveforms associated with an electric power distribution system, comprising:

a processor in communication with a bus;

a non-transitory computer-readable storage medium in communication with the bus, the non-transitory computer readable storage medium comprising;

an index module configured to generate a first index based on at least one characteristic of a plurality of waveforms, the index module configured to;

divide each of the plurality of waveforms into a first plurality of temporal segments;

determine at least one index value representative of the characteristic for each of the first plurality of temporal segments in each of the plurality of waveforms;

associate the determined index value of each of the first plurality of temporal segments in each of the plurality of waveforms with a time stamp configured to identify at least one time in the plurality of waveforms based on the determined index value; and

store the time stamp and the determined index value for each of the first plurality of temporal segments in the first index.

2. The system of claim 1, wherein the plurality of waveforms comprise synchrophasor data.

3. The system of claim 1, wherein the at least one index value comprises one of a maximum value and a minimum value within each of the plurality of temporal segments.

4. The system of claim 1, wherein the at least one characteristic comprises one of a frequency, an amplitude, and a rate of change.

5. The system of claim 1, wherein the index module is further configured to generate a second index having a plurality of overlapping temporal segments, the index module being further configured to:

divide each of the plurality of waveforms into a second plurality of temporal segments, the second plurality of temporal segments overlapping the first plurality of temporal segments at least in part, and the first plurality of temporal segments each being longer than the second plurality of temporal segments;

determine at least one index value associated with each of the second plurality of temporal segments for each of the plurality of waveforms;

associate the determined index value associated with each of the second plurality of temporal segments for each of the plurality of waveforms with a time stamp; and

store the time stamp and the determined index value for each of the second plurality of temporal segments in the second index.

6. The system of claim 5, wherein the non-transitory computer-readable storage medium further comprises a search module configured to:

receive at least one search parameter;

search the first index to identify search results that satisfy the at least one search parameter;

identify a portion of the second index based on the search of the first index;

selectively search the identified portion of the second index to identify search results that satisfy the at least one search parameter; and

deliver search results found in the second index.

7. The system of claim 1, wherein the at least one characteristic comprises a phase angle determined with respect to a reference signal.

8. The system of claim 7, wherein the non-transitory computer readable storage medium further comprises a reference signal identification module configured to select a reference signal from among the plurality waveforms.

9. The system of claim 8, wherein the reference signal identification module is configured to complete an iterative analysis for each waveform on the list of waveforms to select the reference signal, the iterative analysis configured to:

calculate a plurality of values corresponding to the plurality of waveforms, each of the plurality of values comprising a plurality of values representing a variance between a waveform under analysis and the reference waveform at a plurality of points in time;

determine a maximum value of the variance in each of the plurality of values;

determine a minimum value of the variance in each of the plurality of values;

calculate a difference between the maximum value of the variance and the minimum value of the variance in each of the plurality of values;

calculate a summation of the difference between the maximum value of the variance and the minimum value of the variance for each of the plurality of values;

select the waveform with the lowest summation;

compare the summation of the selected waveform to an established minimum value; and

if the lowest summation is less than the established minimum value, repeat the iterative process and

set the waveform with the lowest summation as the reference waveform in the next iteration of the iterative process, and

set the lowest summation as the established minimum value;

if the summation is greater than the previously established minimum value,

select the waveform with the lowest summation as the reference signal, and

end the iterative process.

10. The system of claim 7, wherein the non-transitory-readable storage medium further comprises an angle adjustment module configured to:

calculate a plurality of values corresponding to the plurality of waveforms, each of the plurality of values comprising a plurality of values representing a variance between a waveform under analysis and the reference waveform at a plurality of points in time;

determine at least one of the plurality of values is located outside of the range of 45°

±

135°

or −

45°

±

135°

; and

selectively adjust each of the plurality of values by adding 360°

to each value less than 0°

.

11. The system of claim 1, wherein the plurality of temporal segments each have an equal length.

12. The system of claim 1, wherein the plurality of temporal segments have a variable length based on changes in the at least one characteristic.

13. The system of claim 1, wherein the index comprises a plurality of overlapping temporal segments.

14. The system of claim 1, wherein the non-transitory computer-readable storage medium further comprises a search module configured to:

receive at least one search parameter; and

search the index to identify search results that satisfy the at least one search parameter.

15. The system of claim 14, wherein the at least one search parameter corresponds to a phase angle between two of any of the plurality of waveforms.

16. The system of claim 14, wherein the non-transitory computer-readable storage medium further comprises an island detection module configured to determine that at least two of the plurality of waveforms are associated electrically isolated islands.

17. The system of claim 16, wherein the at least one search parameter crosses different electrically isolated islands.

18. The system of claim 16, wherein the island detection module is configured to return an invalid result in response to search parameters involving the electric power distribution system and the electrically isolated island.

19. The system of claim 1, further comprising a communications interface configured to communicate with a network, and wherein the plurality of waveforms are accessible via the network.

20. The system of claim 1, wherein the plurality of temporal segments comprise a corresponding plurality of durations based upon a quantification of an amount of variation in the characteristic during each of the temporal segments.

21. The system of claim 20, wherein the temporal segment having the greatest amount of variation in the characteristic corresponds to the temporal segment having the shortest duration.

22. The system of claim 20, wherein the temporal segment having the least amount of variation in the characteristic corresponds to the temporal segment having the longest duration.

23. A method of indexing data based on at least one characteristic of a plurality of waveforms associated with an electric power distribution system, comprising:

dividing each of the plurality of waveforms into a first plurality of temporal segments;

determining at least one index value representative of the characteristic for each of the first plurality of temporal segments in each of the plurality of waveforms;

associating the determined index value of each of the first plurality of temporal segments in each of the plurality of waveforms with a time stamp configured to identify at least one time in the plurality of waveforms based on the determined index value; and

storing the time stamp and the determined index value for each of the first plurality of temporal segments in a first index.

24. The method of claim 23, further comprising:

dividing each of the plurality of waveforms into a second plurality of temporal segments, the second plurality of temporal segments overlapping the first plurality of temporal segments at least in part, and the first plurality of temporal segments each being longer than the second plurality of temporal segments;

determining at least one index value associated with each of the second plurality of temporal segments for each of the plurality of waveforms;

associating the determined index value associated with each of the second plurality of temporal segments for each of the plurality of waveforms with a time stamp; and

storing the time stamp and the determined index value for each of the second plurality of temporal segments in a second index.

25. The method of claim 23, further comprising:

receiving at least one search parameter; and

searching the first index to identify search results that satisfy the at least one search parameter;

identifying a portion of the second index based on the search of the first index;

selectively search the identified portion of the second index to identify search results that satisfy the at least one search parameter; and

deliver search results found in the second index.

26. The method of claim 23, further comprising selecting a reference signal by:

calculating a plurality of values corresponding to the plurality of waveforms, each of the plurality of vectors comprising a plurality of values representing a variance between a waveform under analysis and the reference waveform at a plurality of points in time;

determining a maximum value of the variance in each of the plurality of values;

determining a minimum value of the variance in each of the plurality of values;

calculating a difference between the maximum value of the variance and the minimum value of the variance in each of the plurality of values;

calculating a summation of the difference between the maximum value of the variance and the minimum value of the variance for each of the plurality of values;

selecting the waveform with the lowest summation;

comparing the selected waveform with the lowest summation to an established minimum value; and

if the lowest summation is less than the established minimum value, repeating the iterative process and

setting the waveform with the lowest summation as the reference waveform in the next iteration of the iterative process, and

setting the lowest summation as the established minimum value;

or

if the summation is greater than the previously established minimum value, selecting the waveform with the lowest summation as the reference signal, and ending the iterative process.

27. The method of claim 23, further comprising:

calculating a plurality of values corresponding to the plurality of waveforms, each of the plurality of values comprising a plurality of values representing a variance between a waveform under analysis and the reference waveform at a plurality of points in time;

determining at least one of the plurality of values is located outside of the range of 45°

±

135°

or −

45°

±

135°

; and

selectively adjusting each of the plurality of values by adding 360°

to each value less than 0°

.

28. The method of claim 23, further comprising:

receiving at least one search parameter; and

searching the index to identify search results that satisfy the at least one search parameter.

29. The method of claim 28, wherein the at least one search parameter corresponds to a phase angle between two of any of the plurality of waveforms.

30. The method of claim 28, further comprising:

determining that two of the plurality of waveforms are associated with electrically isolated islands.

31. The method of claim 30, wherein the at least one search parameter crosses different electrically isolated islands.

32. The method of claim 30, further comprising:

returning an invalid result in response to receiving search parameters involving the electric power distribution system and the electrically isolated island.

33. A system configured to index data based on at least one characteristic of a plurality of waveforms associated with an electric power distribution system, comprising:

a processor in communication with a bus;

a non-transitory computer-readable storage medium in communication with the bus, the non-transitory computer readable storage medium comprising;

an index module configured to generate a first index based on at least one characteristic of a plurality of waveforms, the index module configured to;

divide each of the plurality of waveforms into a first plurality of temporal segments;

determine at least one index value associated with each of the first plurality of temporal segments for each of the plurality of waveforms;

associate the determined index value associated with each of the first plurality of temporal segments for each of the plurality of waveforms with a time stamp;

store the time stamp and the determined index value for each of the first plurality of temporal segments in the first index;

divide each of the plurality of waveforms into a second plurality of temporal segments, the second plurality of temporal segments overlapping the first plurality of temporal segments at least in part, and the first plurality of temporal segments each being longer than the second plurality of temporal segments;

determine at least one index value associated with each of the second plurality of temporal segments for each of the plurality of waveforms;

associate the determined index value associated with each of the second plurality of temporal segments for each of the plurality of waveforms with a time stamp; and

store the time stamp and the determined index value for each of the second plurality of temporal segments in the second index.