Waveform disturbance detection apparatus and method

• US 4,694,402 A
• Filed: 05/28/1985
• Issued: 09/15/1987
• Est. Priority Date: 05/28/1985
• Status: Expired due to Term

• Current Assignee: Basic Measuring Instruments Co.
• Original Assignee: Basic Measuring Instruments, Inc.
• Inventors: McEachern, Alexander, Nitz, Frederic
• Primary Examiner(s): Krass, Errol A.
• Assistant Examiner(s): Juffernbruch, Daniel W.
• Application Number:
  US06/738,566
• Time in Patent Office: 840 Days
• Field of Search: 364/481, 364/483, 364/487, 361/86, 361/87, 361/96, 361/93, 361/91, 324/77 R, 324/102
• US Class Current: 702/71
• CPC Class Codes: G01R 19/25 using digital measurement techniques
• CPC Class Codes: G01R 29/04 Measuring form factor, i.e. quotient of root-mean-square value and arithmetic mean of instantaneous value; Measuring peak factor, i.e. quotient of maximum value and root-mean-square value
• CPC Class Codes: H02H 3/50 responsive to the appearance of abnormal wave forms, e.g. ac in dc installations

Abstract

A waveform disturbance detection apparatus for detecting disturbances in alternating current electromagnetic energy waveform, the alternating current electromagnetic energy waveform having a plurality of periodic, substantially similar cycles. The detection apparatus comprises converter means for sampling the electromagnetic energy waveform, generating a plurality of samples, and converting the samples into digital signals. The detection apparatus also comprises processing means for evaluating the digital signals so as to detect disturbances in the electromagnetic energy waveform, wherein the processing means detects the disturbances by comparing a particular one of the digital signals that represents a particular one of the samples in a particular one of the cycles with a corresponding one of the digital signals that represents a corresponding one of the samples from the remaining cycles.

Claims

1. A waveform disturbance detection apparatus for detecting disturbances in an alternating current electromagnetic energy waveform, said alternating current electromagnetic energy waveform having a plurality of periodic, normally similar cycles, comprising

converter means for obtaining a plurality of samples from consecutive cycles of said electromagnetic energy waveform;

and

processing means for comparing samples from a selected cycle of the consecutive cycles with corresponding samples from a reference cycle to detect disturbances in said electromagnetic energy waveform, wherein the reference cycle is the cycle which immediately preceded the selected cycle, so that the reference cycle used changes as a different one of the consecutive cycles is selected for processing.

2. The waveform disturbance detection apparatus as claimed in claim 1, wherein the converter means further includes means for converting the plurality of samples into digital signals, and further wherein said processing means performs the comparison of samples by comparing the digital signals corresponding to the samples being compared, the processing means further including

buffer means for storing a plurality of said corresponding digital signals from the reference cycle.

3. The waveform disturbance detection apparatus as claimed in claim 2, wherein in said processing means a disturbance is deemed to have occurred when the difference between a sample from the selected cycle and a corresponding sample from the reference cycle exceeds a predetermined tolerance range, the processing means further comprising

disturbance counter means for counting the number of said disturbances.

4. The waveform disturbance detection apparatus as claimed in claim 3, wherein said disturbance counter means is re-initialized when the sample from the selected cycle is within said predetermined tolerance range.

5. The waveform disturbance detection apparatus as claimed in claim 2, 3 or 4, wherein said processing means replaces said corresponding digital signals contained in said buffer means with the digital signals corresponding to the samples of the selected cycle, so that the selected cycle becomes the reference cycle for the next cycle to be evaluated.

6. The waveform disturbance detection apparatus as claimed in claim 5, wherein said processing means further comprises

post-disturbance buffer means for storing samples from at least one of said consecutive cycles that follows a selected cycle in which the number of disturbances exceed a predetermined limit of said disturbances.

7. The waveform disturbance detection apparatus as claimed in claim 6, further comprises

recorder/display means for recording and displaying said disturbances.

8. The waveform disturbance detection apparatus as claimed in claim 2, 3 or 4, wherein said processing means replaces said corresponding digital signal contained in said buffer means with the digital signals corresponding to the samples of the selected cycle when said digital samples corresponding to the samples of the selected cycle are within said predetermined tolerance range.

9. The waveform disturbance detection apparatus as claimed in claim 8, wherein said processing means further comprises

post-disturbance buffer means for storing samples from at least one of said consecutive cycles that follows a selected cycle in which the number of disturbances exceed a predetermined limit of said disturbances.

10. The waveform disturbance detection apparatus as claimed in claim 9, further comprises

recorder/display means for recording and displaying said disturbances.

11. A waveform disturbance detection apparatus for detecting disturbances in alternating current electromagnetic energy waveform, said alternating current electromagnetic energy waveform having a plurality of periodic, substantially similar cycles, comprising

attenuator means for attenuating said electromagnetic energy waveform, thereby generating an attenuated electromagnetic energy waveform;

amplifier means for amplifying said attenuated electromagnetic energy waveform, thereby generating a modified electromagnetic energy waveform;

analog to digital converter means for sampling said modified electromagnetic energy waveform, generating a plurality of samples, and converting said samples into digital signals; and

processing means for evaluating said digital signals so as to detect disturbances in said electromagnetic energy waveform, wherein said processing means detects said disturbances by comparing a particular one of said digital signals that represents a particular one of said samples in a particular current one of said cycles with a corresponding one of said digital signals that represents a corresponding one of said samples from an immediately preceding one of said cycles, said processing means comprises

buffer means for storing a plurality of said corresponding digital signals, wherein each of said corresponding digital signals is from said immediately preceding cycle, whereby said particular current digital signal is compared with said corresponding digital signal from said immediately preceding cycle; and

disturbance counter means for counting the number of said disturbances, wherein said counter means is incremented when said particular digital signal representing said particular sample exceeds a predetermined tolerance range.

12. The waveform disturbance detection apparatus as claimed in claim 11, wherein said disturbance counter means is re-initialized when said particular digital signal is within said predetermined tolerance range.

13. The waveform disturbance detection apparatus as claimed in claim 11 or 12, wherein said processing means replaces said corresponding digital signal from said immediately preceding cycle contained in said buffer means with said particular current digital signal.

14. The waveform disturbance detection apparatus as claimed in claim 13, wherein said processing means further comprises

post-disturbance buffer means for storing said digital signals of at least one of said cycles that follows said particular current cycle in which the number of disturbances exceed a predetermined limit of said disturbances.

15. The waveform disturbance detection apparatus as claimed in claim 14, further comprises

recorder/display means for recording and displaying said disturbances.

16. The waveform disturbance detection apparatus as claimed in claim 11 or 12, wherein said processing means replaces said corresponding digital signal from said immediately preceding cycle contained in said buffer means with said particular current digital signal when said particular current digital signal is within said predetermined tolerance range.

17. The waveform disturbance detection apparatus as claimed in claim 16, wherein said processing means further comprises

post-disturbance buffer means for storing said digital signals of at least one of said consecutive cycles that follows said particular current cycle in which the number of disturbances exceed a predetermined limit of said disturbances.

18. The waveform disturbance detection apparatus as claimed in claim 17, further comprises

recorder/display means for recording and displaying said disturbances.

19. A method of detecting waveform disturbances in an alternating current electromagnetic energy waveform, said alternating current electromagnetic energy waveform having a plurality of periodic, substantially similar cycles, comprising

sampling said electromagnetic energy waveform to generate a plurality of samples;

converting said samples into digital signals;

storing said digital signals of at least a selected one of said cycles;

storing said digital signals of a particular one of said cycles which immediately precedes said selected one of said cycles;

comparing a particular one of said digital signals that represents a particular one of said samples in said selected cycle with a corresponding one of said digital signals that represents a corresponding one of said samples of the cycle which immediately preceded the selected cycle to detect a disturbance in said particular digital signal; and

counting said disturbance when said particular digital signal exceeds a predetermined tolerance range.

20. The method of detecting waveform disturbances as claimed in claim 19, further comprises

replacing said stored, corresponding digital signal with said particular digital signal.

21. The method of detecting waveform disturbances as claimed in claim 19 or 20, further comprising

restarting the counting of said disturbances from zero when said disturbances for said particular cycle is within a predetermined limit to permit recounting of future said disturbances in a future said particular cycle.

22. The method of detecting waveform disturbances as claimed in claim 21, further comprises

storing said digital signals of at least one of said cycles that follows said particular cycle in which the number of disturbances exceed a predetermined limit of said disturbances.

23. The method of detecting waveform disturbances as claimed in claim 22, further comprises

recording and displaying said disturbances.

24. The method of detecting waveform disturbances as claimed in claim 19, further comprises

replacing said stored, corresponding digital signal with said particular digital signal when said particular digital signal is within said predetermined tolerance range.

25. The method of detecting waveform disturbances as claimed in claim 24, further comprises

restarting the counting of said disturbances from zero when said disturbances for said particular cycle is within a predetermined limit to permit recounting of future said disturbances in a future said particular cycle.

26. The method of detecting waveform disturbances as claimed in claim 25, further comprises

storing said digital signals of at least one of said cycles that follows said particular cycle in which the number of disturbances exceed a predetermined limit of said disturbances.

27. The method of detecting waveform disturbances as claimed in claim 26, further comprises

recording and displaying said disturbances.

28. A method of detecting waveform disturbances in alternating current electromagnetic energy waveform, said alternating current electromagnetic energy waveform having a plurality of periodic, substantially similar cycles, comprising

attenuating said electromagnetic energy waveform to generate an attenuated electromagnetic energy waveform;

amplifying said attenuated electromagnetic energy waveform to generate a modified electromagnetic energy waveform;

sampling said modified electromagnetic energy waveform to generate a plurality of samples;

converting said samples into digital signals;

processing said digital signals to detect disturbances in said electromagnetic energy waveform, said processing step comprising the steps of

storing said digital signals of a particular, current one of said cycles;

storing said digital signals of a cycle which immediately precedes the current one of said cycles;

comparing a particular one of said digital signals that represents a particular one of said samples in said particular current cycle with a corresponding one of said digital signals that represents a corresponding one of said samples of said immediately preceding cycles to detect a disturbance on said alternating current electromagnetic energy waveform; and

counting said disturbance when it exceeds apredetermined tolerance range to obtain a count of the number of the disturbances in the particular current cycle.

29. The method of detecting waveform disturbances as claimed in claim 28, wherein said processing step further comprises

replacing said stored, corresponding digital signal from said immediately preceding cycle with said particular digital signal from said particular current cycle.

30. The method of detecting waveform disturbances as claimed in claim 28 or 29, wherein said processing step further comprises

restarting the counting of said disturbances when said count of said disturbances for said particular cycle is within a predetermined limit to permit recounting of future said disturbances in a future said particular cycle.

31. The method of detecting waveform disturbances as claimed in claim 30, wherein said processing step further comprises

storing said digital signals of at least one of said cycles that follows a particular current cycle in which the count exceeds said predetermined limit of said disturbances.

32. The method of detecting waveform disturbances as claimed in claim 31, further comprises

recording and displaying said disturbances.

33. The method of detecting waveform disturbances as claimed in claim 28, wherein said processing step further comprises

replacing said stored preceding, corresponding digital signal from said immediately preceding cycle with said particular digital signal from said current cycle when said particular digital signal is within said predetermined tolerance range.

34. The method of detecting waveform disturbances as claimed in claim 33, wherein said processing step further comprises

restarting the counting of said disturbances when said count of disturbances for said particular cycle is within a predetermined limit to permit recounting of future said disturbances in a future said particular cycle.

35. The method of detecting waveform disturbances as claimed in claim 34, wherein said processing step further comprises

storing said digital signals of at least one of said cycles that follows said particular current cycle in which the count exceeded a predetermined limit of said disturbances.

36. The method of detecting waveform disturbances as claimed in claim 35, further comprises

recording and displaying said disturbances.

37. A waveshape variance detection apparatus for detecting variances in the shape of a waveform, said waveform having a plurality of periodic, substantially similar cycles, comprising

converter means for sampling said waveform, generating a plurality of samples, and converting said samples into digital signals;

and

processing means for evaluating said digital signals so as to detect said variances, wherein said processing means detects said variances by comparing a particular one of said digital signals that represents a particular one of said samples in a particular one of said cycles with a corresponding one of said digital signals that represents a corresponding one of said samples from an immediately preceding one of said cycles.

38. The waveshape variance detection apparatus as claimed in claim 37, wherein said processing means comprises

buffer means for storing a plurality of said corresponding digital signals, wherein each of said corresponding digital signals is from said immediately preceding cycle, whereby said particular digital signal is compared with said corresponding digital signal.

39. The waveshape variance detection apparatus as claimed in claim 38, wherein said processing means further comprises

variance counter means for counting the number of said variances, wherein said counter means is incremented when said particular digital signal representing said particular sample exceeds a predetermined tolerance range.

40. The waveshape variance detection apparatus as claimed in claim 39, wherein said variance counter means is re-initialized when said particular digital signal is within said predetermined tolerance range.

41. The waveshape variance detection apparatus as claimed in claim 38, 39 or 40, wherein said processing means replaces said corresponding digital signal contained in said buffer means with said particular digital signal.

42. The waveshape variance detection apparatus as claimed in claim 41, wherein said processing means further comprises

post-variance buffer means for storing said digital signals of at least one of said cycles that follows said particular cycle in which the number of variances exceeds a predetermined limit of said variances.

43. The waveshape variance detection apparatus as claimed in claim 42, further comprises

recorder/display means for recording and displaying said variances.

44. A method of detecting variances in the waveshape of a waveform, said waveform having a plurality of periodic, substantially similar cycles, comprising

sampling said waveform to generate a plurality of samples;

converting said samples into digital signals;

storing said digital signals of a particular one of said cycles;

storing said digital signals of the cycle which immediately precedes the particular one of said cycles;

comparing a particular one of said digital signals that represents a particular one of said samples in said particular cycle with a corresponding one of said digital signals that represents a corresponding one of said samples of said immediately preceding cycle to detect a variance in said particular digital signal; and

counting said variance when it exceeds a predetermfined tolerance range.

45. The method of detecting waveshape variances as claimed in claim 44, further comprises

replacing said stored, corresponding digital signal from said immediately preceding cycle with said particular digital signal from said particular one of said cycles.

46. The method of detecting waveshape variances as claimed in claim 44 or 45, further comprises

restarting the counting of said variances when the number of said variances for said particular cycle is within a predetermined limit to permit recounting of future said variances in a future said particular cycle.

47. The method of detecting waveshape variances as claimed in claim 46, further comprises

storing said digital signals of at least one of said cycles that follows said particular cycle in which the number of variances exceeded a predetermined limit of said variances.

48. The method of detecting waveshape variances as claimed in claim 47, further comprises

recording and displaying said variances.

49. A waveform disturbance detection apparatus for detecting disturbances in an alternating waveform having periodic, normally similar cycles, comprising

means for obtaining consecutive samples from a current cycle of the waveform;

means for storing consecutive reference samples from a reference cycle, wherein the reference cycle is the cycle which immediately preceded the current cycle of the waveform;

means for comparing each of the consecutive samples from the current cycle, as each consecutive sample is obtained, to a corresponding one of the reference samples stored in the storing means to detect whether a disturbance is present in the waveform; and

means for replacing each of the reference samples stored in the storing means with the corresponding sample from the current cycle against which it was compared, so that the reference samples in the storing means are updated each time a sample from the current cycle is evaluated.