System and method for compensating for potential and current transformers in energy meters

• US 7,305,310 B2
• Filed: 04/18/2005
• Issued: 12/04/2007
• Est. Priority Date: 10/18/2004
• Status: Active Grant

• Current Assignee: EI Electronics LLC (Hubbell, Inc.)
• Original Assignee: Electro Industries/Gaugetech
• Inventors: Werner, Andrew J., Slota, Frederick Blair
• Primary Examiner(s): WACHSMAN, HAL D
• Application Number:
  US11/109,351
• Publication Number:
  US 20060085144A1
• Time in Patent Office: 960 Days
• Field of Search: 702 57- 62, 702/64, 702/65, 702/72, 702/85, 702/106, 702/107, 702/104, 702/108, 702116-118, 702/120, 702/122, 702/124, 702/126, 702/189, 702/198, 702/86
• US Class Current: 702/57
• CPC Class Codes: G01R 22/06 by electronic methods
• CPC Class Codes: G01R 35/04 of instruments for measuring time integral of power or current

Abstract

A meter device for measuring electrical energy is provided. The meter device includes circuitry for measuring at least one parameter of electrical energy provided to the meter device. A storage device is provided for storing at least one calibration factor for compensating for errors associated with at least one of at least one current transformer (CT) and at least one potential transformer (PT) that operates on the electrical energy provided to the meter device. At least one processor is provided for processing the at least one calibration factor for adjusting the measuring for compensating for the errors when measuring the electrical energy.

Claims

1. A meter device for measuring electrical energy comprising:

circuitry for measuring at least one parameter of electrical energy provided to the meter device;

a storage device for storing at least one calibration factor for compensating for errors associated with at least one of at least one current transformer (CT) and at least one potential transformer (PT) that operates on the electrical energy provided to the meter device; and

at least one processor for processing the at least one calibration factor for adjusting the measuring for compensating for the errors when measuring the electrical energy;

wherein calibration factors of the at least one calibration factor correct for errors measured during testing of respective test points of a series of test points, each test point corresponding to a different current magnitude for modeling non-linearity of errors associated with a range of current magnitudes for current signals of the electrical energy operated on by the at least one CT, and at least one calibration point corresponds to each test point; and

wherein the greater the non-linearity of the errors, the greater the concentration of test points.

2. A processing device in communication with a meter device for measuring electrical energy, the processing device comprising:

an input device for receiving input information relating to at least one error, an error of the at least one error related to a difference between an input value corresponding to at least one of voltage, current, and phase shift therebetween associated with electrical energy operated on by at least one of at least one current transformer (CT) and at least one potential transformer (PT) which is provided to the meter device, and a value measured by the meter device which corresponds to the input value;

at least one processor for generating at least one calibration factor, each calibration factor corresponding to an error of the at least one error for adjusting measurement by the meter device in accordance with the error; and

at least one communication device for uploading generated calibration factors to the meter device, wherein the processing device generates control signals for controlling equipment providing the electrical energy operated on by the at least one of the at least one current transformer (CT) and the at least one potential transformer (PT) for providing a selected input value for performing a test, wherein the test comprises at least one of a first test including testing at least one test point in which the processing device controls the equipment for the input value to have a predetermined voltage;

a second test including a first series of test points in which the processing device controls the equipment for the input value to have a different predetermined current for respective test points of the first series of test points with the phase shift being zero degrees; and

a third test including a second series of test points in which the processing device controls the equipment for the input value to have a different predetermined current for respective test points of the second series of test points with the phase shift being sixty degrees.

3. The processing device according to claim 2, wherein after testing a single test point of one of the first series of test points and the second series of test points, the calibration factor corresponding to the at least one error related to the input value used for the single test point is determined and uploaded.

4. The processing device according to claim 2, wherein after testing each of at least two test points of the one of the first series of test points and the second series of test points, the calibration factor corresponding to the at least one error related to the input values used for the respective test point of the at least two test points is determined and uploaded.

5. A processing device in communication with a meter device for measuring electrical energy, the processing device comprising:

an input device for receiving input information relating to at least one error, an error of the at least one error related to a difference between an input value corresponding to at least one of voltage, current, and phase shift therebetween associated with electrical energy operated on by at least one of at least one current transformer (CT) and at least one potential transformer (PT) which is provided to the meter device, and a value measured by the meter device which corresponds to the input value;

at least one processor for generating at least one calibration factor, each calibration factor corresponding to an error of the at least one error for adjusting measurement by the meter device in accordance with the error; and

at least one communication device for uploading generated calibration factors to the meter device, wherein the at least one error is determined by performing a test, including measuring energy associated with a series of at least two test points;

each test point of the series corresponds to a different input current value over a range of input current values of the electrical energy operated on by the at least one CT;

for each test point of the series there is at least one corresponding calibration factor;

respective calibration factors provide for adjusting measurement by the meter device, including correcting for errors of the at least one error related to the input current values to which the respective test points correspond; and

the calibration factors corresponding to the respective test points compensate for non-linearity of the at least one error associated with the range of input current values.

6. The processing device according to claim 5, wherein the greater the non-linearity of the at least one error associated with the range of input current values, the greater the concentration of the test points of the series over the range of input current values.