Methods and apparatus for voltage measurement

• US 6,388,435 B1
• Filed: 12/22/1999
• Issued: 05/14/2002
• Est. Priority Date: 12/31/1998
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Ouellette, Maurice J.
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): SUNDARAM, T R
• Application Number:
  US09/471,052
• Time in Patent Office: 874 Days
• Field of Search: 324/142, 324/107, 324/141, 324/111, 324/120, 324/140.R
• US Class Current: 324/142
• CPC Class Codes: G01R 15/04 Voltage dividers
• CPC Class Codes: G01R 21/06 by measuring current and voltage G01R21/08 - G01R21/133 take precedence

Abstract

A method is described for measuring a plurality of line voltages using a measurement circuit, the method including the steps of reducing each line voltage over a first impedance; providing a second impedance between each of the reduced voltages and a measurement circuit common reference point; coupling the common reference point to a voltage line N using a third impedance; and determining line voltage values using measurements of the reduced voltages. The above-described method provides impedance between voltage line N and measurement electronics and thus prevents transient voltages from entering the measurement circuit.

Claims

1. A method for measuring a plurality of line voltages using a measurement circuit, said method comprising the steps of:

reducing each line voltage over a corresponding first impedance;

providing a second impedance between each of the reduced voltages and a measurement circuit common reference point;

providing a third impedance configured to facilitate preventing transient currents within a voltage line;

coupling the common reference point to the voltage line using the third impedance; and

determining line voltage values using measurements of the reduced voltages.

2. A method in accordance with claim 1 wherein said step of determining line voltage values using measurements of the reduced voltages further comprises the step of using a value for the third impedance.

3. A method in accordance with claim 1 wherein the impedances are resistors.

4. A method in claim 1 wherein the voltage line is a neutral line.

5. A method in accordance with claim 1 wherein said step of determining line voltage values using measurements of the reduced voltages comprises the step of measuring the reduced voltages between the corresponding first and second impedances.

6. A method in accordance with claim 5 wherein said step of determining line voltage values using measurements of the reduced voltages comprises the step of determining a current IN connecting to the voltage line in accordance with:

7. A method in accordance with claim 6 further comprising the step of determining line voltage values VAN, VBN and VCN in accordance with:

8. A method in accordance with claim 7 further comprising the step of relating the line voltage values VAN, VBN and VCN to the reduced voltage measurements VaaG, VbbG and VccG in accordance with:

9. A method in accordance with claim 8 further comprising the step of determining the line voltage values in accordance with:

10. A method in accordance with claim 1 wherein the third impedance is ten thousand ohms.

11. A method in accordance with claim 1 wherein at least one of the first impedances is one million ohms and at least one of the second impedances is 348 ohms.

12. A voltage measurement circuit for measuring a plurality of line voltages, said measurement circuit comprising:

a measurement circuit common reference point;

a first impedance for each line voltage and a reduced voltage measurement point for each line voltage, said first impedance coupling the corresponding line voltage to said corresponding reduced voltage measurement point;

a second impedance for each line voltage, said second impedance coupling said corresponding reduced voltage measurement point to said measurement circuit common reference point; and

a third impedance coupling said measurement circuit common reference point to a voltage line, said third impedance configured to facilitate preventing transient currents within said voltage line.

13. A voltage measurement circuit in accordance with claim 12 further comprising a processor configured to determine line voltage values using reduced voltage measurements from said reduced voltage measurement points.

14. A voltage measurement circuit in accordance with claim 13 wherein said processor is further configured to determine line voltage values using a value for said third impedance.

15. A voltage measurement circuit in accordance with claim 12 wherein said impedances are resistors.

16. A voltage measurement circuit in accordance with claim 12 wherein said third impedance couples said measurement circuit common reference point to a neutral line.

17. A voltage measurement circuit in accordance with claim 13 wherein said processor configured to determine line voltage values VAN, VBN and VCN, using reduced voltage measurements from said reduced voltage measurement points, in accordance with:

18. A voltage measurement circuit in accordance with claim 13 wherein said processor being configured to determine line voltage values using reduced voltage measurements from said reduced voltage measurement points comprises said processor being configured to determine line voltage values VAN, VBN and VCN in accordance with:

19. A voltage measurement circuit in accordance with claim 18 wherein said processor being configured to determine line voltage values VAN, VBN and VCN comprises said processor being configured to relate the line voltage values VAN, VBN and VCN to the reduced voltage measurements VaaG, VbbG and VccG in accordance with:

20. A voltage measurement circuit in accordance with claim 19 wherein said processor being configured to relate the line voltage values VAN, VBN and VCN to the reduced voltage measurements VaaG, VbbG and VccG comprises said processor being configured to determine a current IN connecting to the voltage line in accordance with: