SYSTEMS AND METHODS FOR POWER SWING AND OUT-OF-STEP DETECTION USING TIME STAMPED DATA

• US 20090089608A1
• Filed: 09/26/2008
• Published: 04/02/2009
• Est. Priority Date: 09/28/2007
• Status: Active Grant

• Current Assignee: Schweitzer Engineering Laboratories, Incorporated
• Original Assignee: Schweitzer Engineering Laboratories, Incorporated
• Inventors: Guzman-Casillas, Armando
• Granted Patent: US 7,930,117 B2
• Time in Patent Office: Days
• US Class Current: 713/340
• CPC Class Codes: G01R 29/18 Indicating phase sequence; Indicating synchronism
• CPC Class Codes: G06F 1/28 Supervision thereof, e.g. detecting power-supply failure by out of limits supervision
• CPC Class Codes: 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
• CPC Class Codes: H02H 3/28 involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus for transformers H02H7/045
• CPC Class Codes: H02H 3/30 using pilot wires or other signalling channel
• CPC Class Codes: H02H 7/263 involving transmissions of measured values comparison of currents or voltages using pilot wires H02H3/30
• CPC Class Codes: Y02E 40/70 Smart grids as climate change mitigation technology in the energy generation sector
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 10/00 Systems supporting electrical power generation, transmission or distribution
• CPC Class Codes: Y04S 10/22 Flexible AC transmission systems [FACTS] or power factor or reactive power compensating or correcting units

Abstract

A first intelligent electric device (IED) may be placed at a first location in an electrical power system and a second IED may be placed at a second location in the electrical power system. Voltage measurements may be received from the first and second IEDs. The measurements may be time aligned and used to calculate an angle difference between the first location and the second location in the electrical power system. A slip frequency and acceleration may be derived from the angle difference. The angle difference, slip frequency, and acceleration may be used to detect an out-of-step (OOS) condition in the electrical power system and/or a power swing between the first location and the second location in the electrical power system. The angle difference, slip frequency, and acceleration may also be used to predicatively detect OOS conditions.

Claims

1. A method for monitoring an electrical power system, comprising:

receiving a first voltage measurement obtained at a first location in the electrical power system;

receiving a second voltage measurement obtained at a second location in the electrical power system;

time aligning the first voltage measurement and the second voltage measurement;

calculating an angle difference between the first time aligned voltage measurement and the second time aligned voltage measurement; and

using the angle difference to monitor the electrical power system.

2. The method of claim 1, wherein the first voltage measurement and the second voltage measurement each comprise a respective time stamp.

3. The method of claim 2, wherein the first phase voltage measurement and the second phase voltage measurement are time aligned using their respective time stamps.

4. The method of claim 3, wherein the first voltage measurement is obtained by a first intelligent electronic device (IED) communicatively coupled to the first location in the electrical power system, wherein the second voltage measurement is obtained by a second IED communicatively coupled to the second location in the electrical power system, and wherein the first IED and the second IED are communicatively coupled to a common time reference.

5. The method of claim 1, wherein the first voltage measurement and the second voltage measurement each comprise a synchrophasor.

6. The method of claim 5, wherein the first IED comprises an IEEE C37.118 device and the second IED comprises an IEEE C37.118 device, and wherein the first voltage measurement and the second voltage measurement are received by an IEEE C37.118 device.

7. The method of claim 1, further comprising:

receiving a first measurement obtained at the first location in the electrical power system;

comparing the first measurement to a current sensitivity threshold; and

enabling monitoring of the electrical power system using the angle difference if the first measurement satisfies the current sensitivity threshold.

8. The method of claim 1, wherein the first voltage measurement comprises a measurement of a three-phase voltage signal, and wherein the second voltage measurement comprises a measurement of a second three-phase voltage signal, the method further comprising:

calculating a first alpha-Clarke component using the first voltage measurement; and

calculating a second alpha-Clarke component using the second voltage measurement.

9. The method of claim 8, wherein the angle difference is calculated using the first alpha-Clarke component and the second alpha-Clarke component.

10. The method of claim 1, wherein the first voltage measurement comprises a measurement of a first three-phase voltage signal, and wherein the second voltage measurement comprises a measurement of a second three-phase voltage signal, the method further comprising:

calculating a first positive sequence voltage using the first voltage measurement; and

calculating a second positive sequence voltage using the second voltage measurement,

11. The method of claim 10, wherein the angle difference is calculated using the first positive sequence voltage and the second positive sequence voltage.

12. The method of claim 1, wherein using the angle difference to monitor the electrical power system comprises detecting an out-of-step (OOS) condition between the first location in the electrical power system and the second location in the electrical power system using the angle difference.

13. The method of claim 12, wherein detecting an OOS condition in the electrical power system comprises:

detecting a first angle difference that is greater than an out-of-step threshold (OOSTH); and

detecting a second angle difference that is less than a negative OOSTH;

14. The method of claim 13, wherein detecting an OOS condition in the electrical power system comprises:

detecting a first angle difference that is less than a negative out-of-step-threshold (OSSTH); and

detecting a second angle difference that is greater than a OSSTH.

15. The method of claim 13, further comprising clearing an OOS condition detected in the electrical power system upon detecting an angle difference having an absolute value less than or equal to the OSSTH.

16. The method of claim 13, wherein the OOSTH and the negative OOSTH are determined using one of the characteristics of the electrical power system, modeling of the electrical power system, and testing of the electrical power system.

17. The method of claim 1, further comprising calculating a slip frequency using the angle difference.

18. The method of claim 17, wherein the slip frequency comprises one of a derivative with respect to time and a discrete derivative with respect to time of the angle difference.

19. The method of claim 17, further comprising calculating an acceleration using the slip frequency.

20. The method of claim 19, wherein the acceleration comprises one of a derivative with respect to time and a discrete derivative with respect to time of the slip frequency.

21. The method of claim 19, wherein using the angle difference to monitor the electrical power system comprises detecting a power swing in the electrical power system using the angle difference, the slip frequency, and the acceleration.

22. The method of claim 21, wherein detecting a power swing in the electrical power system comprises:

comparing an absolute value of the slip frequency to a first slip frequency threshold;

comparing an absolute value of the acceleration to a first acceleration threshold; and

detecting a power swing if the absolute value of the slip frequency is greater than the first slip frequency threshold, and the absolute value of the acceleration is greater the first acceleration threshold.

23. The method of claim 22, wherein detecting a power swing in the electrical power system further comprises:

comparing the absolute value of the slip frequency to a second slip frequency threshold;

comparing the absolute value of the acceleration to a second acceleration threshold; and

detecting a power swing if the absolute value of the slip frequency is greater than the first slip frequency threshold and less than the second slip frequency threshold, and the absolute value of the acceleration is greater than the first acceleration threshold and less than the second acceleration threshold.

24. The method of claim 23, wherein the first slip frequency threshold is 0.2 Hz, the second slip frequency threshold is approximately 10 Hz, the first acceleration threshold is approximately 0.1 Hz/second, and the second acceleration threshold is approximately 50 Hz/second.

25. The method of claim 23, wherein the first slip frequency threshold, the second slip frequency threshold, the first acceleration threshold, and the second acceleration threshold are determined using one selected from the group consisting of the characteristics of the electrical power system, modeling of the electrical power system, and testing of the electrical power system.

26. The method of claim 23, wherein detecting a power swing further comprises maintaining the slip frequency greater than the first slip frequency threshold and less than the second slip frequency threshold, and maintaining the acceleration greater than first acceleration threshold and less than the second acceleration threshold for one of a predetermined time period, predetermined number of voltage measurements, and predetermined number of clock cycles.

27. The method of claim 19, wherein using the angle difference to monitor the electrical power system comprises predicatively detecting an out-of-step (OOS) condition in the electrical power system using the angle difference, the slip frequency, and the acceleration.

28. The method of claim 27, wherein predicatively detecting an OOS condition in the electrical power system using the angle difference, the slip frequency, and the acceleration comprises;

comparing an operating point determined by the slip frequency and acceleration against a predictive OOS characteristic, and

predicatively detecting an OOS condition if the operating point is outside of the predictive OOS characteristic.

29. The method of claim 28, wherein the predictive OOS characteristic comprises the sum of an acceleration offset value and a product of the slip frequency and an OOS slope constant.

30. The method of claim 29, wherein the acceleration offset value and the OOS slope constant are determined using one selected from the group consisting of characteristics of the electrical power system, modeling of the electrical power system, and testing of the electrical power system.

31. The method of claim 28, wherein predicatively detecting an OOS condition in the electrical power system further comprises maintaining the operating point outside of the predictive OOS characteristic for one of a predetermined time period, predetermined number of voltage measurements, and predetermined number of clock cycles.

32. The method of claim 1, wherein the first location in the electrical power system is approximate to a sending-end generator equivalent of the electrical power system.

33. The method of claim 32, wherein the second location in the electrical power system is approximate to a receiving-end generator equivalent of the electrical power system.

43. The system of claim 33, wherein the characterization module is to detect an out-of-step (OOS) condition between the first location in the electrical power system and the second location in the electrical power system using the angle difference.

44. The system of claim 43, wherein the characterization module is to detect an OOS condition in the electrical power system upon detecting a first angle difference that is greater than an out-of-step threshold (OOSTH) and a second angle difference that is less than a negative OOSTH.

45. The system of claim 44, wherein the characterization module is to detect an OOS condition in the electrical power system upon detecting a first angle difference that is less than a negative out-of-step threshold (OOSTH) and a second angle difference that is greater than a OOSTH.

46. The system of claim 44, wherein the characterization module is to clear an OOS condition detected in the electrical power system upon detecting an angle difference having an absolute value less than or equal to the OSSTH.

47. The system of claim 44, wherein the OOSTH and the negative OOSTH are determined by one of the characteristics of the electrical power system, modeling of the electrical power system, and testing of the electrical power system.

48. The system of claim 33, wherein the characterization function is to calculate a slip frequency using the angle difference.

49. The system of claim 48, wherein the slip frequency comprises one of a derivative with respect to time and a discrete derivative with respect to time of the angle difference.

50. The system of claim 48, wherein the characterization function is to calculate a acceleration using the slip frequency.

51. The system of claim 50, wherein the acceleration comprises one of a derivative with respect to time and a discrete derivative with respect to time of the slip frequency.

52. The system of claim 50, wherein the characterization module is to detect a power swing in the electrical power system between the first location in the electrical power system and the second location in the electrical power system using the angle difference, the slip frequency, and the acceleration.

53. The system of claim 52, wherein the characterization module is to compare an absolute value of the slip frequency to a first slip frequency threshold, to compare an absolute value of the acceleration to a first acceleration threshold, and to detect a power swing if the absolute value of the slip frequency is greater than the first slip frequency threshold and the absolute value of the acceleration is greater than the first acceleration threshold.

54. The system of claim 53, wherein the characterization module is to compare the absolute value of the slip frequency to a second slip frequency threshold and to compare the absolute value of the acceleration to a second acceleration threshold, and is to detect a power swing if the absolute value of the slip frequency is greater than the first slip frequency threshold and less than the second slip frequency threshold, and the absolute value of the acceleration is greater than the first acceleration threshold and less than the second acceleration threshold.

55. The system of claim 54, wherein the first slip frequency threshold is 0.2 Hz, the second slip frequency threshold is 10 Hz, the first acceleration threshold is 0.1 Hz/second, and the second acceleration threshold is 50 Hz/second.

56. The system of claim 54, wherein the first slip frequency threshold, the second slip frequency threshold, the first acceleration threshold, and the second acceleration threshold are determined using one selected from the group consisting of characteristics of the electrical power system, modeling of the electrical power system, and testing of the electrical power system.

57. The system of claim 54, wherein the characterization module is to detect a power swing only if the absolute value of the slip frequency is maintained greater than the first slip frequency threshold and less than the second slip frequency threshold, and the absolute value of the acceleration is maintained greater than the first acceleration threshold and less than the second acceleration threshold for one of a predetermined time period, predetermined number of voltage measurements, and predetermined number of clock cycles.

58. The system of claim 50, wherein the characterization module is to predicatively detect an out-of-step (OOS) condition in the power system using the angle difference, the slip frequency, and the acceleration.

59. The system of claim 58, wherein the characterization module is to predicatively detect the OOS condition by comparing an operating point determined by the slip frequency and the acceleration against a predictive OOS characteristic, and to detect an OOS condition if the operating point is outside of the predictive OOS characteristic.

60. The system of claim 59, wherein the predictive OOS characteristic comprises a sum of an acceleration offset value and a product of the slip frequency and an OOS slope constant.

61. The system of claim 60, wherein the acceleration offset value and the OOS slope constant are determined using one selected from the group consisting of characteristics of the electrical power system, modeling of the electrical power system, and testing of the electrical power system.

62. The system of claim 60, wherein the characterization module is to predicatively detect an OOS condition in the electrical power system if the operating point is maintained outside of the predictive OOS characteristic for one of a predetermined time period, predetermined number of phase voltage measurements, and predetermined number of clock cycles.

63. The system of claim 33, wherein the first IED is communicatively coupled approximate to a sending-end generator equivalent of the electrical power system.

64. The system of claim 63, wherein the second IED is communicatively coupled approximate to a receiving-end generator equivalent of the electrical power system.

34. A system for monitoring an electrical power system comprising a first intelligent electronic device (IED) communicatively coupled to a first location in the electrical power system to obtain voltage measurements therefrom, and a second IED communicatively coupled to a second location in the electrical power system to obtain voltage measurements therefrom, the system comprising:

a communication module communicatively coupled to the first IED and the second IED to receive voltage measurements therefrom, wherein the communication module is configured to time align the voltage measurements received from the first IED with the voltage measurements received from the second IED; and

a characterization module communicatively coupled to the communication module to calculate an angle difference between the time aligned voltage measurements received from the first IED and the second IED and to monitor the electrical power system using the angle difference.

35. The system of claim 34, wherein the voltage measurements received from the first IED and the voltage measurements received from the second IED each comprise a respective time stamp.

36. The system of claim 35, wherein the voltage measurements received from the first IED and the voltage measurements received from the second IED are time aligned using their respective time stamps.

37. The system of claim 36, wherein the first IED and the second IED are communicatively coupled to a common time reference.

38. The system of claim 34, wherein the voltage measurements received from the first IED and the voltage measurements received from the second IED comprise synchronized phasors.

39. The system of claim 38, wherein the first IED comprises a IEEE C37.118 device and the second IED comprises a IEEE C37.118 device, and wherein the communication module comprises an IEEE C37.118 device.

40. The system of claim 34, wherein the voltage measurements received from the first IED and the second IED comprise measurements of a three-phase voltage signal, and wherein the characterization module is to calculate a first set of positive sequence voltages using the voltage measurements received from the first IED, and to calculate a second set of positive sequence voltages using the voltage measurements received from the second IED.

41. The system of claim 40, wherein the characterization module is to calculate the angle difference using the first set of positive sequence voltages and the second set of positive sequence voltages.

42. The system of claim 34, wherein the voltage measurements received from the first IED comprise one selected from the group consisting of first positive sequence voltages and first alpha-Clarke components, and wherein the voltage measurements received from the second IED comprise one selected from the group consisting of second positive sequence voltages and second alpha-Clarke components.

65. A computer-readable storage medium comprising instructions to cause a computing device to perform a method for monitoring an electrical power system, the method comprising:

receiving a plurality of first voltage measurements from a first intelligent electronic device (IED) communicatively coupled to a first location in the electrical power system to obtain voltage measurements therefrom, wherein the first location is approximate to a sending-end generator equivalent of the electrical power system;

receiving a plurality of second voltage measurements from a second IED communicatively coupled to a location in the electrical power system to obtain voltage measurements therefrom, wherein the second location is approximate to a receiving-end generator equivalent of the electrical power system;

time aligning the first plurality of voltage measurements and the second plurality of voltage measurements;

calculating an angle difference between the first time aligned voltage measurements and the second time aligned voltage measurements;

calculating a slip frequency using the angle difference;

calculating an acceleration using the slip frequency;

detecting an out-of-step (OOS) condition in the electrical power system using the angle difference;

detecting a power swing in the electrical power system using the angle difference, the slip frequency, and the acceleration; and

predicatively detecting an OOS condition in the electrical power system using the slip frequency and the acceleration.

66. The computer-readable storage medium of claim 65, wherein detecting an OOS condition comprises:

comparing the angle difference to an out-of-step threshold (OOSTH);

comparing the angle difference to a negative OOSTH; and

detecting an OOS condition if the angle difference is greater than the OOSTH or less than the negative OOSTH.

67. The computer-readable storage medium of claim 65, wherein detecting a power swing using the angle difference, the slip frequency, and the acceleration comprises:

comparing an absolute value of the slip frequency to a first slip frequency threshold and a second slip frequency threshold;

comparing an absolute value of the acceleration to a first acceleration threshold and a second acceleration threshold; and

detecting a power swing if the absolute value of the slip frequency is greater than the first slip frequency threshold and less than the second slip frequency threshold and the absolute value of the acceleration is greater than the first acceleration threshold and less than the second acceleration threshold.

68. The computer-readable storage medium of claim 65, wherein predicatively detecting an OOS condition using the slip frequency and acceleration comprises:

comparing an operating point determined by the slip frequency and the acceleration against a predictive OOS characteristic;

wherein the OOS characteristic comprises a sum of a acceleration offset and a product of the slip frequency and an OOS slope constant; and

predicatively detecting an OOS condition if the operating point is outside of the predictive OOS characteristic.