Power oscillation protection

• US 6,476,521 B1
• Filed: 08/31/2000
• Issued: 11/05/2002
• Est. Priority Date: 05/31/2000
• Status: Expired due to Term

• Current Assignee: ABB Power Grids Switzerland AG (ABB Limited)
• Original Assignee: ABB AB (ABB Limited)
• Inventors: Karlsson, Daniel, Löf, Per-Anders
• Primary Examiner(s): Sircus, Brian
• Assistant Examiner(s): POLK, SHARON A
• Application Number:
  US09/653,265
• Time in Patent Office: 796 Days
• Field of Search: 307/102, 307/105, 323/205, 323/207, 323/208
• US Class Current: 307/105
• 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: H02J 3/241 The oscillation concerning frequency

Abstract

The present invention discloses a system protection scheme comprising of at least two system protection terminals (18), introduced at suitable locations in an electric power system (1). The system protection terminals (18) are interconnected by a communication system (22), preferably using a substantially dedicated communication resource. At least-two of the system protection terminals (18) are equipped to collect measurement signals (72) associated with time stamped voltage or current values of the power system at that particular location or quantities derivable therefrom. The measurements are evaluated and related data is spread to other system protection terminals (18). At least one of the system protection terminals (18) is equipped to evaluate the existence of poorly damped power oscillations in the power network and if necessary provide control signals (74) to power system actuating units. The evaluation is preferably based on changes in the node angle differences between the measurement locations.

Claims

1. System protection scheme (SPS) for protection of the integrity of an overall electric power system against poorly damped power oscillations, comprising:

a set of at least two system protection terminals, and

a communication system interconnecting said at least two system protection terminals,

said at least two system protection terminals in turn comprising;

a processor unit, and

a communication unit connected to said processor unit for communication on said communication system,

wherein system protection terminals in a first subset of said set of system protection terminals comprise measurement signal obtaining means connected to said processor unit for collecting measurement signals of measured characteristics of said electric power system, said first subset comprising at least two system protection terminals, said measured characteristics comprising at least one of, time stamped voltage values, time stamped current values, and quantities derivable therefrom,

wherein said processor unit in system protection terminals in a second subset of said set of at least two system protection terminals in turn comprises evaluation means for detecting poorly damped power oscillations based on said measured characteristics from at least two of said system protection terminals in said first subset,

wherein said evaluation means being arranged for obtaining node angle differences between different locations associated with said system protection terminals of said first subset and for determining at least one of amplitude, frequency and damping of said detected power oscillations from said node angle differences, and

wherein said system protection terminals in said second subset further comprising control signal providing means connected to said processor unit for providing control signals to power system actuating units counteracting said poorly damped power oscillations in response to an output of said evaluation means.

2. Scheme according to claim 1, wherein said evaluation means is arranged for obtaining data concerning rotor angle differences between said different locations in said electric power system.

3. Scheme according to claim 1, wherein said evaluation means is arranged for determining a mode of oscillation of said detected power oscillation.

4. Scheme according to claim 1, wherein said control signal providing means is adaptive in response to output data from said evaluation means.

5. Scheme according to claim 1, wherein said evaluation means is arranged for detecting poorly damped power oscillations of a frequency between 0.05 and 4 Hz.

6. Scheme according to claim 1, wherein said communication unit is arranged for communication of data associated with said measurement signals over a substantially dedicated communication resource in said communication system.

7. Scheme according to claim 1, wherein said system protection terminals of said second subset also comprise storage means for storing/retrieving data.

8. Scheme according to claim 1, wherein said communication system is dimensioned to transmit data between any two system protection terminals in said set within a predetermined time.

9. Scheme according to claim 8, wherein said predetermined time is less than 1 s.

10. Scheme according to claim 1, wherein one or more of said system protection terminals may be active in more than one parallel decision process.

11. Electric power system, comprising:

a number of nodes,

power lines interconnecting said nodes,

at least one power generator connected to one of said nodes,

at least one power load connected to one of said nodes, and

an SPS (System Protection Scheme) for protection of the integrity of said electric power system against poorly damped power oscillations,

said SPS in turn comprising;

a set of at least two system protection terminals, and

a communication system interconnecting said at least two system protection terminals,

said at least two system protection terminals in turn comprising;

a processor unit, and

a communication unit connected to said processor unit for communication on said communication system,

wherein system protection terminals in a first subset of said set of system protection terminals comprise measurement signal obtaining means connected to said processor unit for collecting measurement signals of measured characteristics of said electric power system, said first subset comprising at least two system protection terminals, said measured characteristics comprising at least one of, time stamped voltage values, time stamped current values, and quantities derivable therefrom,

wherein said processor unit in system protection terminals in a second subset of said set of at least two system protection terminals in turn comprises evaluation means for detecting poorly damped power oscillations based on said measured characteristics from at least two of said system protection terminals in said first subset,

wherein said evaluation means being arranged for obtaining node angle differences between different locations associated with said system protection terminals of said first subset and for determining at least one of amplitude, frequency and damping of said detected power oscillations from said node angle differences, and

wherein said system protection terminals in said second subset further comprising control signal providing means connected to said processor unit for providing control signals to power system actuating units counteracting said poorly damped power oscillations in response to an output of said evaluation means.

12. System according to claim 11, wherein said evaluation means is arranged for obtaining data concerning rotor angle differences between said different locations in said electric power system.

13. System according to claim 11, wherein said evaluation means is arranged for determining a mode of oscillation of said detected power oscillation.

14. System according to claim 11, wherein said control signal providing means is adaptive in response to output data from said evaluation means.

15. System according to claim 11, wherein said evaluation means is arranged for detecting poorly damped power oscillations of a frequency between 0.05 and 4 Hz.

16. System according to claim 11, wherein said communication unit is arranged for communication of data associated with said measurement signals over a substantially dedicated communication resource in said communication system.

17. System according to claim 11, wherein said system protection terminals of said second subset also comprise storage means for storing/retrieving data.

18. System according to claim 11, wherein said communication system is dimensioned to transmit data between any two system protection terminals in said set within a predetermined time.

19. System according to claim 18, wherein said predetermined time is less than 1 s.

20. System according to claim 11, wherein one or more of said system protection terminals may be active in more than one parallel decision process.

21. System protection method for the protection of the integrity of an overall electric power system against poorly damped power oscillations, comprising the steps of:

collecting measurement signals associated with measured characteristics of said electric power system in at least two locations of said electric power system, said measured characteristics comprising at least one of, time stamped voltage values, time stamped current values, and quantities derivable therefrom,

evaluating said measurement signals, for detecting poorly damped power oscillations based on said measured characteristics,

said evaluating step in turn comprising the steps of obtaining node angle differences between said at least two locations and determining at least one of amplitude, frequency and damping of said poorly damped power oscillations from said node angle differences, and

providing control signals to actuating units in said electric power system, if system protection measures are necessary according to said evaluating step.

22. System protection method according to claims 21, wherein said evaluating step also comprises the step of obtaining data concerning rotor angle differences between said at least two locations in said electric power system.

23. System protection method according to claim 21, wherein said evaluating step further comprises the step of determining a mode of oscillation of said detected power oscillation.

24. System protection method according to claim 21, wherein said step of providing control signals is adaptive in response to the result from said evaluating step.

25. System protection method according to claim 21, wherein said evaluating step in turn comprises the step of detecting poorly damped power oscillations of a frequency between 0.05 and 4 Hz.

26. System protection method according to claim 21, comprising the further step of communicating data over a substantially dedicated communication resource.

27. System protection method according to claim 21, comprising the further step of storing said data comprising measurement data or data derived therefrom.

28. System protection method according to claim 21, wherein said processing step in turn comprises the step of retrieving said stored data.

29. System protection method according to claim 21, wherein said communication step is performed within a predetermined time.

30. System protection method according to claim 29, wherein said predetermined time is less than 1 s.

31. System protection terminal for protection of the integrity of an overall electric power system against poorly damped power oscillations, comprising:

a processor unit,

a communication unit connected to said processor unit,

measurement signal obtaining means connected to said processor unit for collecting measurement signals of measured characteristics of said electric power system, said measured characteristics comprising at least one of, time stamped voltage values, time stamped current values, and quantities derivable therefrom,

said processor unit in turn comprising evaluation means for detecting poorly damped power oscillations based on said measured characteristics and corresponding characteristics for different nodes in said electric power system received by said communication unit,

said evaluation means being arranged for obtaining node angle differences between said different nodes and for determining at least one of amplitude, frequency and damping of said detected power oscillations from said node angle differences, and

control signal providing means connected to said processor unit for providing control signals to power system actuating units.

32. System protection terminal according to claim 31, wherein said evaluation means is arranged for obtaining data concerning rotor angle differences between said different nodes in said electric power system.

33. System protection terminal according to claim 31, wherein said evaluation means is arranged for determining a mode of oscillation of said detected power oscillation.

34. System protection terminal according to claim 31, wherein said control signal providing means is adaptive in response to output data from said evaluation means.

35. System protection terminal according to claim 31, wherein said evaluation means is arranged for detecting poorly damped power oscillations of a frequency between 0.05 and 4 Hz.

36. System protection- terminal according to claim 31, wherein said processing unit further comprises decision processing means for power system control.

37. System protection terminal according to claim 31, wherein said communication unit is arranged for communication of data associated with said measurement signals over a substantially dedicated communication resource.

38. System protection terminal according to claim 31, further comprising storage means for storing data.

39. A computer program product comprising at least one of computer code means and software code portions for making a processor perform the steps of:

collecting measurement signals associated with measured characteristics of said electric power system in at least two locations of said electric power system, said measured characteristics comprising at least one of, time stamped voltage values, time stamped current values, and quantities derivable therefrom,

evaluating said measurement signals, for detecting poorly damped power oscillations based on said measured characteristics,

said evaluating step in turn comprising the steps of obtaining node angle differences between said at least two locations and determining at least one of amplitude, frequency and damping of said poorly damped power oscillations from said node angle differences, and

providing control signals to actuating units in said electric power system, if system protection measures are necessary according to said evaluating step.

40. A computer program product according to claim 39, supplied via a network.

41. A computer readable medium containing program product comprising at least one of computer code means and software code portions for making a processor perform the steps of:

collecting measurement signals associated with measured characteristics of said electric power system in at least two locations of said electric power system, said measured characteristics comprising at least one of, time stamped voltage values, time stamped current values, and quantities derivable therefrom,

evaluating said measurement signals, for detecting poorly damped power oscillations based on said measured characteristics,

said evaluating step in turn comprising the steps of obtaining node angle differences between said at least two locations and determining at least one of amplitude, frequency and damping of said poorly damped power oscillations from said node angle differences, and

providing control signals to actuating units in said electric power system, if system protection measures are necessary according to said evaluating step.