Method and system for providing power factor correction in a power distribution system

• US 7,804,280 B2
• Filed: 05/11/2007
• Issued: 09/28/2010
• Est. Priority Date: 11/02/2006
• Status: Active Grant

• Current Assignee: S&C Electric Company
• Original Assignee: Current Technologies LLC (Pattern Inc.)
• Inventors: Berkman, William H., Radtke, William O., Deaver, Brian J. Sr.
• Primary Examiner(s): Laxton; Gary L
• Application Number:
  US11/747,454
• Publication Number:
  US 20080106241A1
• Time in Patent Office: 1,236 Days
• Field of Search: 323/207, 323/208, 323/209, 323/212, 323/218, 323/210, 307/11, 307/14, 307/31, 307/105, 340/310.11, 340/310.14, 340/658, 340/663, 700/286, 700/297, 700/298
• US Class Current: 323/210
• CPC Class Codes: H02J 3/1828 with stepwise control, the possibility of switching in or out the entire compensating arrangement not being considered as stepwise control
• CPC Class Codes: Y02E 40/30 Reactive power compensation

Abstract

A device for providing power factor correction of a low voltage subnet that includes a low voltage feeder line that is connected to one or more low voltage power supply lines that supply power to one or more customer premises is provided. In one embodiment, the device includes a power factor measurement module configured to measure power parameters for determining a power factor of the power traversing the low voltage subnet; a power factor correction assembly configured to vary a capacitance connected to the low voltage feeder of the low voltage subnet; a controller in communication with the power factor measurement assembly and the power factor correction assembly. The controller may be configured to cause the power factor correction assembly to change the capacitance based on the determined power factor. The controller may form part of a power line communication device configured to provide communications to the one or more customer premises.

Claims

1. A device for providing power factor correction of a power line carrying power having a voltage and a current, comprising:

a power factor measurement module configured to measure the current and the voltage of the power line;

a power factor correction assembly including a capacitance configured to be connected to the power line;

wherein said power factor correction assembly is configured to vary the capacitance;

a controller in communication with said power factor measurement assembly and said power factor correction assembly;

a communication module in communication with said controller;

wherein said controller is configured to cause said communication module to transmit data of the measured current and voltage to a remote computer system;

wherein said controller is responsive to a command originating from the remote computer system to cause said power factor correction assembly to change the capacitance, substantially at a zero crossing of the voltage of the power carried by power line; and

wherein said controller is configured to cause said power factor correction assembly to increase the capacitance upon determining that the voltage of the power line is below a predetermined voltage.

2. The device of claim 1,

wherein said controller is configured to cause said communication module to transmit an alert to the remote computer system upon determining that the voltage of the power line is below the predetermined voltage.

3. The device of claim 1, wherein said controller is configured to cause said power factor correction assembly to change the capacitance based on information stored in a memory communicatively coupled to said controller.

4. The device of claim 1, further comprising a memory storing data that includes a power factor and an associated capacitance value.

5. The device of claim 4, wherein said controller is configured to cause said power factor correction assembly to change the capacitance to a capacitance value associated with a power factor stored in said memory.

6. The device of claim 1, wherein

said controller is configured to receive interval data from the remote computer system,

wherein the interval data comprises data of an interval for repeatedly obtaining data of the current and the voltage of the power line;

and

wherein said controller is configured to store the received interval data in a memory.

7. The device of claim 1, further comprising a filter in series with said capacitance and configured to attenuate power signal harmonics.

8. The device of claim 1, further comprising a filter in series with said capacitance and configured to attenuate power line communication signals.

9. The device of claim 1, wherein said controller is configured to determine a power factor from data of the measured current and voltage received from said power factor measurement module.

10. The device of claim 1, wherein said controller forms part of a communication device configured to provide communications to one or more user devices.

11. The device of claim 1, wherein said power factor correction assembly comprises a capacitor bank having a first terminal and a second terminal and wherein said first terminal is connected to a low voltage feeder line and said second terminal is connected to a non-energized power line conductor.

12. The device of claim 1, wherein said controller is configured to receive data from said power factor measurement module comprising measurement data obtained subsequent to a change in the capacitance by said power factor correction assembly and, based on the received data, to detect a failure of said power factor correction assembly.

13. The device of claim 1, wherein said remote computer system is configured to determine a power factor from data of the measured current and voltage received from said controller.

14. The device of claim 1, wherein said power factor correction assembly is configured to vary a first capacitance connected to a first energized conductor of a low voltage feeder and to vary a second capacitance connected to a second energized conductor of the low voltage feeder.

15. The device of claim 1, further comprising:

a memory storing data that includes operational data comprising a plurality of power factors and a plurality of associated capacitance values;

said memory in communication with said controller; and

wherein said controller is configured to receive updated operational data via a transmission from the remote computer system and to store the updated operational data in said memory.

16. A system for providing power factor correction to a power distribution system that includes a plurality of power lines, the system comprising:

a remote computer system;

a plurality of correction assemblies, each comprising;

a first capacitance configured to be connected to one of the plurality of power lines;

a first switch configured to connect said first capacitance to the one power line and disconnect said first capacitance from the one power line;

a first voltage sensor device configured to measure the voltage of the one power line;

a first current sensor device configured to measure the current carried by the one power line;

a communication module; and

a first controller in communication with said first switch and said communication module and configured to receive current data from said first current sensor device and receive voltage data from said first voltage sensor device;

wherein said first controller is configured to determine a power factor based on said current data and said voltage data;

wherein said first controller is configured to cause said communication module to transmit the power factor to the remote computer system;

wherein said remote computer system is configured to process received power factor data from a plurality of the correction assemblies;

wherein said remote computer system is configured to transmit one or more control messages to one or more correction assemblies in response to processing data from one or more correction assemblies;

wherein said first controller of each correction assembly is configured to respond to one or more control messages received from said remote computer system to operate said first switch to connect or disconnect said first capacitance, substantially at a zero crossing of the voltage of the one power line.

17. The system of claim 16, wherein each of the plurality of correction assemblies further comprises a first modem configured to communicate with a user device disposed in a customer premises supplied power by the low voltage subnet and wherein said first modem is in communication with said first controller.

18. The system of claim 16, wherein each of the plurality of correction assemblies further comprises a first modem configured to communicate over the medium voltage power line and in communication with said first controller.

19. The system of claim 16, wherein said first controller is configured to cause said communication module to transmit a notification to said remote computer system upon determining that the voltage of the one power line is below a threshold voltage.

20. The system of claim 16, wherein each of the plurality of correction assemblies further comprises a filter in series with said first capacitance and configured to attenuate power signal harmonics.

21. The system of claim 16, wherein each of the plurality of correction assemblies further comprises a filter in series with said first capacitance and configured to attenuate power line communication signals.

22. The system of claim 16, wherein said first controller is configured to

operate said first switch to connect said first capacitance to the power line upon determining that the voltage of the one power line is below a threshold voltage.

23. The system of claim 16, wherein the one power line includes a low voltage feeder line that is connected to one or more low voltage power supply lines that supply power to one or more customer premises and wherein said first capacitance is configured to be connected to the low voltage feeder line.

24. The system of claim 16, wherein the one power line comprises a low voltage subnet that includes a low voltage feeder line that is connected to one or more low voltage power supply lines supplying power to one or more customer premises, the system further comprising:

a second capacitance and wherein said first and second capacitance are each configured to be connected to a different low voltage power supply lines of the low voltage subnet.

25. The system of claim 24, wherein the current sensor device is configured to measure the current traversing the low voltage feeder line.

26. The system of claim 16,

wherein said first controller is configured to receive data at least from said first voltage sensor both before and after a connection of said first capacitance to the power line and, based on the received data, to detect a failure of said correction assembly.

27. The system of claim 16,

wherein each of the plurality of correction assemblies comprises a fuse in series with said first capacitance.

28. The system of claim 16, wherein each of the plurality of correction assemblies comprises:

a memory storing data that includes operational data comprising a plurality of power factors and a plurality of associated capacitance values;

said memory in communication with said first controller; and

wherein said first controller is configured to receive updated operational data via a transmission from the remote computer system and to store the updated operational data in said memory.