Methods and apparatus for monitoring power flow in a conductor

• US 20060241880A1
• Filed: 01/17/2006
• Published: 10/26/2006
• Est. Priority Date: 07/18/2003
• Status: Abandoned Application

• Current Assignee: Power Measurement Ltd. (Schneider Electric SE)
• Original Assignee: Power Measurement Ltd. (Schneider Electric SE)
• Inventors: Cumming, Daniel A., Forth, J. Bradford, Lightbody, Simon H.
• Application Number:
  US11/333,822
• Publication Number:
  US 20060241880A1
• Time in Patent Office: Days
• US Class Current: 702/60
• CPC Class Codes: G01R 21/133 by using digital technique
• CPC Class Codes: G01R 22/063 related to remote communication
• CPC Class Codes: G01R 22/10 using digital techniques

Abstract

An energy monitoring device includes means for sensing current in a power line and generating an analog signal representative thereof. The energy monitoring device includes means for generating a digital representation of the current. The energy monitoring device includes means for assuming a voltage value and calculating at least one measure of power consumption using the sensed current and the assumed voltage. A method executable by said energy monitoring device is also disclosed.

Claims

1. A method of monitoring electrical energy consumed by an electrical load, the method comprising:

sensing actual current flow in at least one power line which is supplying electrical energy to said load, said at least one power line being further characterized by an actual voltage value associated with said actual current flow;

generating an analog signal indicative of the amount of actual current flow sensed in said at least one power line;

converting said analog signal to a digital representation of said amount of said actual current flow;

providing an assumed voltage value of said at least one power line, wherein said assumed voltage value may be different than said actual voltage value, said assumed voltage comprising an approximation of said actual voltage value; and

calculating at least one measure of power consumption by said electrical load based on said digital representation, said calculating being further based on said assumed voltage value instead of said actual voltage value.

2. The method of claim 1, wherein said providing further comprises providing said assumed voltage value from a memory, said assumed voltage value comprising a digital representation of said approximation of said actual voltage value.

3. The method of claim 1, wherein said providing further comprises providing said assumed voltage value as an analog signal indicative thereof, the method further comprising converting said analog signal indicative of said assumed voltage value to a digital representation of said assumed voltage value, said calculating being based thereon.

4. The method of claim 1 wherein said providing further comprises:

providing an assumed magnitude value of said actual voltage value and a phase relationship between said actual current flow and said actual voltage value.

5. The method of claim 4, wherein said providing further comprises:

determining a magnitude of said actual current flow; and

adjusting said phase relationship based on said magnitude of said actual current flow.

6. The method of claim 4, wherein said providing further comprises determining said phase relationship by interpolation based on at least one known phase relationship, each of said at least one known phase relationship being associated with a particular possible magnitude value of said actual current flow.

7. The method of claim 1, wherein said digital representation further comprises a waveform representative of said actual current flow, said providing further comprising:

providing at least one characteristic current waveform representative of an approximation of said actual current flow, each of said at least one characteristic current waveform being associated with at least one assumed voltage waveform representative of an approximation of said actual voltage value, each of said at least one characteristic current waveform being associated with said at least one assumed voltage waveform.

8. The method of claim 7, wherein each of said at least one characteristic current waveform is associated with said at least one assumed voltage waveform by a time relationship associated with each of said at least one assumed voltage waveform.

9. The method of claim 7, wherein said providing further comprises:

comparing said waveform of said actual current flow with a subset of said at least one assumed current waveform; and

selecting an associated one of said at least one assumed voltage waveform associated with said at least one assumed current waveform which most closely approximates said waveform of said actual current flow.

10. The method of claim 7, wherein said sensing further comprises sensing said actual current flow during a transient event.

11. The method of claim 10, wherein said transient event comprises at least one of startup of said electrical load, shutdown of said electrical load, a surge, a sag or combinations thereof.

12. The method of claim 1, further comprising:

sensing said actual voltage value from said at least one power line;

generating an analog signal indicative of said actual voltage value sensed from said at least one power line;

converting said analog signal indicative of said actual voltage value to a digital representation of said actual voltage value; and

wherein said calculating further comprises calculating said at least one measure of power consumption based on said digital representation of said actual voltage value instead of said assumed voltage value.

13. The method of claim 12, wherein said calculating further comprises comparing said at least one measure of power consumption based on said assumed voltage value with said at least one measure of power consumption based on said actual voltage value.

14. The method of claim 15, further comprising:

providing an indication of historical accuracy of said at least one measure of power consumption based on said assumed voltage value.

15. The method of claim 12, wherein said sensing said actual voltage value further comprises sensing said actual voltage value without interrupting said at least one power line.

16. The method of claim 15, wherein said sensing said actual voltage value without interrupting said at least one power line further comprises piercing an insulative layer covering said at least one power line and contacting a conductor underneath said insulative layer.

17. The method of claim 1, further comprising:

communicating said at least one measure of power consumption to a data collection device by communicating said at least one measure of power consumption to a first monitoring device, said first monitoring device being coupled with a second monitoring device and operative to communicate said at least one measure of power consumption to said second monitoring device, said second monitoring device coupled with said data collection device and operative to communicate said at least one measure of power consumption to said data collection device.

18. A monitoring device for monitoring electrical energy consumed by an electrical load, the monitoring device comprising:

a current sensor operative to sense actual current flow in at least one power line which is supplying electrical energy to said load, said at least one power line being further characterized by an actual voltage value associated with said actual current flow, said current sensor being further operative to generate an analog signal indicative of the amount of actual current flow sensed in said at least one power line;

an analog to digital converter coupled with said current sensor and operative to convert said analog signal to a digital representation of said amount of said actual current flow;

a input operative to receive an assumed voltage value of said at least one power line, wherein said assumed voltage value may be different than said actual voltage value, said assumed voltage value comprising an approximation of said actual voltage value; and

a processor coupled with said analog to digital converter and said memory and operative to calculate at least one measure of power consumption by said electrical load based on said digital representation, said calculation being further based on said assumed voltage value instead of said actual voltage value.

19. The monitoring device of claim 18, wherein said input comprises a memory coupled with said processor, said memory storing said assumed voltage value, said assumed voltage value comprising a digital representation of said approximation of said actual voltage value.

20. The monitoring device of claim 18, wherein said input comprises an analog voltage input coupled with said analog to digital converter, said assumed voltage value being coupled with said analog voltage input, wherein said analog to digital converter is further operative to convert said assumed voltage value to a digital representation and transmit said digital representation of said assumed voltage value to said processor to be used in said calculation.

21. The monitoring device of claim 19, wherein said memory is operative to store an assumed magnitude value of said actual voltage value and a phase relationship between said actual current flow and said actual voltage value.

22. The monitoring device of claim 21, wherein said processor is further operative to determine a magnitude of said actual current flow and adjust said phase relationship based on said magnitude of said actual current flow.

23. The monitoring device of claim 21, wherein said processor is further operative to determine said phase relationship by interpolation based on at least one known phase relationship, each of said at least one known phase relationship being associated with a particular possible magnitude value of said actual current flow.

24. The monitoring device of claim 18, wherein said digital representation further comprises a waveform representative of said actual current flow, said monitoring device further comprising at least one characteristic current waveform representative of an approximation of said actual current flow and coupled with said processor, each of said at least one characteristic current waveform being associated with at least one assumed voltage waveform representative of an approximation of said actual voltage value, each of said at least one characteristic current waveform being associated with said at least one assumed voltage waveform.

25. The monitoring device of claim 24, wherein said processor is further operative to compare said waveform of said actual current flow with a subset of said at least one assumed current waveform and select an associated one of said at least one assumed voltage waveform associated with said at least one assumed current waveform which most closely approximates said waveform of said actual current flow.

26. The monitoring device of claim 25, wherein said selection by said processor is based on at least one of:

fuzzy logic;

artificial intelligence;

point by point comparison;

or

combinations thereof.

27. The monitoring device of claim 24, wherein said current sensor is further operative to sense said actual current flow during a transient event.

28. The monitoring device of claim 27, wherein said transient event comprises at least one of startup of said electrical load, shutdown of said electrical load, a surge, a sag or combinations thereof.

29. The monitoring device of claim 18, further comprising:

a voltage sensor operative to sense said actual voltage value from said at least one power line and generate an analog signal indicative of said actual voltage value sensed from said at least one power line;

wherein said analog to digital converter is further coupled with said voltage sensor and further operative to convert said analog signal indicative of said actual voltage value to a digital representation of said actual voltage value; and

wherein said processor is further operative to calculate said at least one measure of power consumption based on said digital representation of said actual voltage value instead of said assumed voltage value.

30. The monitoring device of claim 29, wherein said processor is further operative to compare said at least one measure of power consumption based on said assumed voltage value with said at least one measure of power consumption based on said actual voltage value.

31. The monitoring device of claim 29, wherein said processor is further operative to provide an indication of historical accuracy of said at least one measure of power consumption based on said assumed voltage value.

32. The monitoring device of claim 29, wherein said voltage sensor is further operative to sense said actual voltage value further without interrupting said at least one power line.

33. The monitoring device of claim 32, wherein said voltage sensor is further operative to pierce an insulative layer covering said at least one power line and contact a conductor underneath said insulative layer.

34. The monitoring device of claim 18, further comprising:

a communications interface operative to communicate said at least one measure of power consumption to a data collection device by communicating said at least one measure of power consumption to a first remote monitoring device, said first remote monitoring device being coupled with a second remote monitoring device and operative to communicate said at least one measure of power consumption to said second monitoring device, said second remote monitoring device coupled with said data collection device and operative to communicate said at least one measure of power consumption to said data collection device.

35. A monitoring device for monitoring electrical energy consumed by an electrical load, the monitoring device comprising:

means for sensing actual current flow in at least one power line which is supplying electrical energy to said load, said at least one power line being further characterized by an actual voltage value associated with said actual current flow;

means for generating an analog signal indicative of the amount of actual current flow sensed in said at least one power line;

means for converting said analog signal to a digital representation of said amount of said actual current flow;

means for providing an assumed voltage value of said at least one power line, wherein said assumed voltage value may be different than said actual voltage value, said assumed voltage comprising an approximation of said actual voltage value; and

means for calculating at least one measure of power consumption by said electrical load based on said digital representation, said calculating being further based on said assumed voltage value instead of said actual voltage value.

36. The monitoring device of claim 35, wherein said means for providing an assumed voltage comprises a communications port.

37. The monitoring device of claim 35, wherein said input comprises a communications port.