Power monitoring system and method

• US 6,415,244 B1
• Filed: 03/31/1999
• Issued: 07/02/2002
• Est. Priority Date: 03/31/1998
• Status: Expired due to Term

• Current Assignee: Mehta Tech, Inc.
• Original Assignee: Mehta Tech, Inc.
• Inventors: Dickens, Richard T., Siem, James E., Havens, Robert E.
• Primary Examiner(s): Bui, Bryan
• Application Number:
  US09/282,834
• Time in Patent Office: 1,189 Days
• Field of Search: 702/187-188, 702/57-59, 702/79-80, 702/63-64, 702/70-71, 324/500, 324/512, 324/520-522, 341/126, 341/132, 361/79-80
• US Class Current: 702/187
• CPC Class Codes: G01R 19/2513 Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging

Abstract

A uniquely configured electrical power transmission data recorder system generates a first data stream. The first data stream is a digitized form of an electric power signal being monitored. The data recorder calculates a second data stream from the first data stream. The second data stream is a phasor representation of the electrical power signal being monitored. Vectors of the second data stream are provided at a lower frequency than vectors of the first data stream. The data recorder system associates different fault triggers with each of the data streams. When the data recorder detects a condition that activates one or more of the fault triggers, it generates a power fault record. The power fault record has a prefault portion corresponding to a time period before a fault is detected and a postfault portion corresponding to a time period after the fault ceases. The system may include a number of different processors dedicated to different power monitoring and data recording tasks.

Claims

1. A system, comprising:

a data recorder to monitor an electrical power transmission, said data recorder including;

a plurality of analog input channels;

a converter to digitize an analog signal from at least one of said analog input channels;

a signal analysis subsystem responsive to said converter to provide;

(a) a first data stream at a first rate, said first data stream being a digitized form of said analog signal;

(b) a second data stream calculated from said first data stream, said second data stream including a phasor representation of said analog signal and being provided at a second rate slower rate than said first rate;

(c) a trigger signal responsive to a predetermined condition of said first data stream or said second data stream representative of an electrical power transmission anomaly; and

wherein said subsystem is operable to generate a data record in response to said trigger signal, said data record including a prefault data segment corresponding to a time period before said anomaly starts and a postfault data segment corresponding to a time period after said anomaly ceases, said prefault data segment and said postfault data segment each including at least a portion of said first data stream and said second data stream.

2. The system of claim 1, wherein said data record further includes an in-trigger segment corresponding to a time period during which said anomaly persists.

3. The system of claim 1, wherein said data recorder includes a real time clock coupled to said subsystem.

4. The system of claim 1, wherein said data recorder further includes a number of discrete inputs, a user input interface, and a discrete output control interface each operatively coupled to said subsystem.

5. The system of claim 1, wherein said subsystem includes a first processor to provide said first data stream, a second processor to calculate said second data stream, and a third processor to provide said data record.

6. The system of claim 5, wherein said first processor and said second processor are operatively coupled to a first memory.

7. The system of claim 6, wherein said subsystem includes a third processor operatively coupled to said first memory.

8. The system of claim 7, wherein said third processor is operatively coupled to a second memory and a communication device.

9. The system of claim 8, further comprising a central processing unit operatively coupled to said communication device to communicate with said third processor, said third processor being operable to transmit said data record to said central processing unit, said central processing unit including a mass storage device to store said data record.

10. A method, comprising:

digitally sampling an electrical waveform corresponding to an electrical power transmission to generate a first data stream of waveform samples at a first rate;

calculating a second data stream from the first data stream with a first processor, the second data stream corresponding to a phasor representation of the waveform, the second data stream being provided at a second rate slower than the first rate by a predetermined amount;

buffering the first and second data streams in a first memory;

accessing the first memory with a second processor to periodically derive a first set of values to add to the first data stream and a second set of values to add to the second data stream; and

generating a power disturbance record, the record including at least a prefault portion and a postfault portion of one of the first and second data streams after said accessing.

11. The method of claim 10, further comprising assembling the record in a second memory with a third processor, the third processor being operatively coupled to the first and second memories.

12. The method of claim 11, further comprising detecting a number of trigger conditions separated in time and occurring during said evaluating and storing a record for each of the trigger conditions.

13. The method of claim 10, wherein the first data stream includes discrete event data.

14. The method of claim 10, wherein said evaluating includes calculating at least one of waveform magnitude, power, impedance, or frequency from said first or second data stream.

15. The method of claim 10, wherein the record includes an in-trigger portion corresponding to an active trigger condition determined by the second processor.

16. The method of claim 10, further comprising generating a third data stream at a third rate, the third rate being slower than the second rate by a predetermined amount, and wherein the third data stream includes a phasor representation of the waveform.

17. A method, comprising:

digitally sampling an electrical waveform corresponding to an electrical power transmission to generate a first data stream of waveform samples at a first rate;

calculating a second data stream from the first data stream, the second data stream being representative of the waveform and being provided at a second rate, the second rate being slower than the first rate by a predetermined amount;

evaluating the first data stream to detect a first type of power transmission disturbance and the second data stream to detect a second type of power transmission disturbance; and

generating a power disturbance record in response to said evaluating, the record including at least a prefault portion and a postfault portion of each of the first and second data streams.

18. The method of claim 17, further comprising generating a sequence of events data record stream, the record including at least a portion of the sequence of events data record stream.

19. The method of claim 17, wherein the first data stream includes discrete event data.

20. The method of claim 17, wherein said evaluating includes calculating at least one of waveform magnitude, power, impedance, or frequency from the first or second data stream.

21. The method of claim 17, wherein:

said evaluating includes periodically deriving a first set of values from the first data stream and a second set of values from the second data stream; and

said generating includes providing at least a portion of one of the first or second sets of values in the record.

22. The method of claim 17, further comprising generating a third data stream at a third rate, the third rate being slower than the second rate, and the third data stream including a phasor representation of the electrical waveform.

23. The method of claim 17, further comprising detecting a number of trigger conditions separated in time during said evaluation and storing a record for each of the trigger conditions in a memory.

24. The method of claim 17, wherein said digitally sampling, said calculating, and said evaluating are performed by a data recorder, the data recorder further including a number of analog input channels, a number of discrete inputs, and a number of discrete outputs, the data recorder being operatively coupled to a central processing unit.

25. The method of claim 24, further comprising transmitting the record from the data recorder to the central processing unit.

26. The method of claim 24, wherein the recorder includes a first processor performing said calculating, a second processor performing said evaluating, a third processor assembling the record, and a shared memory operatively coupled to the first, second, and third processors.

27. A data recording system, comprising:

a data recorder to sense at least three analog waveforms corresponding to a three-phase electrical power transmission;

first means for sampling at least one of the waveforms to generate a first data stream of waveform samples at a first rate;

second means for calculating a second data stream from the first data stream, the second data stream corresponding to a phasor representation of the waveform, the second data stream being provided at a second rate slower than the first rate by a predetermined amount;

third means for evaluating the first and second data streams to correspondingly include a first set of derived values in the first data stream and a second set of derived values in the second data stream; and

fourth means for generating a power anomaly record, the record including at least a prefault portion and a postfault portion, the prefault and postfault portions each including at least a portion of one of the first data stream and the second data stream.

28. The system of claim 27, wherein said first means includes an A/D converter for each of said waveforms, said second means includes a first digital signal processor, and said third means includes a second digital signal processor.

29. The system of claim 27, wherein said second means generates a third data stream at a third rate slower than the second rate.

30. The system of claim 27, wherein the first set includes at least one of the magnitude, power, impedance, or frequency determined from the first data stream.