Method and system for monitoring winding insulation resistance

• US 6,794,883 B2
• Filed: 03/13/2003
• Issued: 09/21/2004
• Est. Priority Date: 03/19/2002
• Status: Expired due to Term

• Current Assignee: Kato Engineering, Inc. (Nidec Corporation)
• Original Assignee: Emerson Electric Company
• Inventors: Klingel, John C.
• Primary Examiner(s): Deb, Anjan K.
• Application Number:
  US10/249,067
• Publication Number:
  US 20030178999A1
• Time in Patent Office: 558 Days
• Field of Search: 324/522, 324/509, 324/510, 324/772, 324/545, 324/546, 324/551, 324/705, 324/713, 324/523-524, 361/20, 361/23, 361/42, 702/57-59, 702/65
• US Class Current: 324/522
• CPC Class Codes: G01R 31/1227 of components, parts or materials G01R31/1209, G01R31/1218, G01R31/18 take precedence; circuits therefor G01R31/14; testing vessels of electrodes G01R31/16
• CPC Class Codes: G01R 31/346 Testing of armature or field windings

Abstract

A method and system for determining the resistance of a winding insulation. The method includes applying a pulsed voltage having a maximum value and a minimum value to the winding insulation. The maximum and minimum values of the pulsed voltage are both negative values in certain exemplary implementations. The values of the maximum and minimum current flowing through the winding insulation are determined, and the winding insulation resistance is calculated based on the difference between the maximum and minimum current. A ground fault may be detected based on the calculated winding insulation resistance. The winding insulation monitoring system includes a sense resistor connected to the winding insulation and a pulsed voltage source is coupled to the sense resistor to apply the pulsed voltage to the winding insulation via the sense resistor. A processing device has input terminals coupled to the sense resistor and is programmed to determine the resistance of the winding insulation, which may include calculating the difference between the minimum and maximum current flowing through the sense resistor.

Claims

1. A method of determining the resistance of a winding insulation, comprising:

applying a pulsed voltage having a maximum value and a minimum value to the winding insulation, wherein the maximum and minimum values are both negative values with respect to the winding negative;

determining the maximum current flowing through the winding insulation corresponding to the maximum value of the pulsed voltage;

determining the minimum current flowing through the winding insulation corresponding to the minimum of the pulsed voltage;

determining the difference between the maximum and minimum current; and

calculating the winding insulation resistance based on the difference between the maximum and minimum current.

2. The method of claim 1, further comprising detecting a ground fault based on the calculated winding insulation resistance.

3. The method of claim 2, wherein the winding is a generator field winding, the method further comprising determining the winding insulation voltage, and comparing the winding insulation voltage to the generator field winding voltage to determine the relative location of a ground fault.

4. The method of claim 1, wherein applying the pulsed voltage includes applying the pulsed voltage to a acme resistor connected in series with the insulation.

5. The method of claim 4, wherein determining the maximum and minimum current flowing through the winding insulation includes calculating the current flowing through the sense resistor corresponding to maximum and minimum voltage values, respectively.

6. A winding insulation monitoring system, comprising:

a sense resistor connected to the winding insulation;

a pulsed voltage source coupled to the sense resistor to apply a pulsed voltage having maximum and minimum values to the winding insulation via the sense resistor, wherein the maximum and minimum values or the pulsed voltage are both negative values; and

a processing device having input terminals coupled to the sense resistor, the processing device programmed to determine the resistance of the winding insulation based on the minimum and maximum values of the pulsed voltage.

7. The monitoring system of claim 6, further comprising a diode connected in series between the winding insulation and the sense resistor.

8. The monitoring system of claim 6, further comprising a diode connected in series between the sense resistor and a circuit common.

9. The monitoring system of claim 6, wherein the processor is programmed to calculate the current flowing through the sense resistor.

10. The monitoring system of claim 6, wherein the winding is a rotor winding, and wherein the monitoring system includes a stationary portion and a rotating portion mounted to rotate with the rotor.

11. The monitoring system of claim 10, wherein the rotating portion includes the processor and sense resistor.

12. The monitoring system of claim 10, further comprising a transmitter and a transmit antenna connected to an output terminal of the processor.

13. The monitoring system of claim 12, wherein the stationary portion includes a receive antenna for receiving data from the transmit antenna.

14. The monitoring system of claim 13, wherein:

the stationary portion includes an inductive loop connected to a power source; and

the rotating portion includes a pick up coil connected to the processor.

15. A generator system, comprising:

a rotor;

a field winding situated in the rotor;

insulation isolating the field winding from the rotor,

an exciter circuit connected to the field winding, and

a winding insulation monitor, including;

a stationary portion including a receive antenna and an inductive loop coupled to a power source; and

a rotating portion mounted to rotate with the rotor, the rotating portion including a sense resistor connected to the winding insulation, a processing device having input terminals coupled to the sense resistor, a transmit antenna connected to an output terminal of the processing device, and a pick up coil for inductive coupling with the inductive loop to power the rotating portion;

wherein a pulsed voltage having maximum and minimum values is applied to the winding insulation via the sense resistor, the maximum and minimum values both being negative values with respect to the winding negative, and wherein the processing device is programmed to determine the resistance of the winding insulation based on the minimum and maximum values of the pulsed voltage.

16. The generator system of claim 15, wherein processor is programmed to calculate the current flowing through the sense resistor.

17. The generator system of claim 15, further comprising a diode connected in series between the winding insulation and the sense resistor.

18. The generator system of claim 15, further comprising a diode connected in series between the sense resistor and a circuit common.