METHODS FOR LOCATING PARTIAL DISCHARGES IN ELECTRICAL APPARATUS

• US 3,775,676 A
• Filed: 07/21/1972
• Issued: 11/27/1973
• Est. Priority Date: 07/21/1972
• Status: Expired due to Term

• Current Assignee: ABB Power T&D Limited (ABB Limited)
• Original Assignee: Charles A. Long, Ronald T. Harrold
• Inventors: Harrold, Ronald T., Long, Charles A.
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US05/273,920
• Time in Patent Office: 494 Days
• Field of Search: 324/51,52,54,55
• US Class Current: 324/523
• 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 31/62 Testing of transformers

Abstract

A three-phase voltage is induced into a first three-phase winding, and by virtue of connections made thereto, a plurality of potential distribution patterns are developed across the first winding with respect to ground, between individual phase windings, and between the first winding and a second winding. Second and third single-phase voltages are induced into the first winding and additional potential distribution patterns are developed. The potential distribution patterns developed by the first, second and third voltages and connections are compared at the corona inception or extinction level to determine the potential common to all three potential distribution patterns produced by the three voltages. The corona source is located at the site within the windings corresponding to this common potential. Observing the relationship of the corona signal to the voltage waveforms provides additional information regarding the corona location, and also about the nature of the corona source.

Claims

1. A method of locating the source of corona discharges in a transformer having first and second windings, said method comprising the steps of:

energizing said first and second windings with a first voltage to provide a first potential distribution pattern between said first winding and ground and a second potential distribution pattern between said first and second windings, detecting corona discharges and noting the magnitude of the first voltage which produces a change in the condition of the corona discharges, energizing said first and second windings with a second voltage to provide a third potential distribution pattern between said first winding and ground and a fourth potential distribution pattern between said first and second windings, detecting corona discharges anD noting the magnitude of the second voltage which produces a change in the condition of the corona discharges, energizing said first and second windings with a third voltage to provide a fifth potential distribution pattern between said first winding and ground and a sixth potential distribution pattern between said first and second windings, detecting corona discharges and noting the magnitude of the third voltage which produces a change in the condition of the corona discharges, comparing the first, third and fifth potential distribution patterns at the first, third and fifth noted magnitudes, respectively, comparing the second, fourth and sixth potential distribution patterns at the second, fourth and sixth noted magnitudes, respectively, determining which potential distribution pattern comparison has a winding potential common to the three potential distribution patterns of that comparison to indicate the radial region in which the corona discharges are located, and determining from the location of the common winding potential the axial location of the corona discharges.

2. The method of locating the source of corona discharges of claim 1 wherein the changes in the condition of the corona discharges produced by the first, second and third voltages are the extinction of the corona discharges as the voltages are decreased.

3. The method of locating the source of corona discharges of claim 1 wherein the changes in the condition of the corona discharges produced by the first, second and third voltages are the inception of the corona discharges as the voltages are increased.

4. The method of locating the source of corona discharges of claim 1 wherein the first and second windings are multiple-phase windings having a plurality of phase windings, the first voltage being a multiple-phase voltage applied to the second winding, the second and third voltages being single-phase voltages applied to a phase winding of the second winding.

5. A method of locating the source of corona discharges in a transformer having first and second three-phase windings, said first winding comprising delta-connected phase windings connected between first, second and third phase terminals, said second winding comprising wye-connected phase windings, said method comprising the steps of:

inducing voltages into the phase windings of said first winding by applying a first three-phase voltage to the second winding, grounding one of said phase terminals to provide a first potential distribution pattern between a phase winding of said first winding and ground, a second potential distribution between the phase windings of said first winding and said second winding, and a third potential distribution pattern between adjacent phase windings of said first winding, detecting corona discharges and noting the magnitude of the first voltage which produces a change in the condition of the corona discharges, inducing voltages into the phase windings of said first winding by applying a second single-phase voltage to the second winding, grounding one of said phase terminals to provide a fourth potential distribution pattern between a phase winding of said first winding and ground, a fifth potential distribution pattern between the phases of said first winding and said second winding, and a sixth potential distribution pattern between adjacent phase windings of said first winding, detecting corona discharges and noting the magnitude of the second voltage which produces a change in the condition of the corona discharges, inducing voltages into the phase windings of said first winding by applying a third single-phase voltage to the second winding, grounding one of said phase terminals to provide a seventh potential distribution pattern between a phase winding of said first winding and ground, an eighth potential distribution pattern between the phases of said first winding and said second winding, and a ninth potential distribution pattern beTween adjacent phase windings of said first winding, detecting corona discharges and noting the magnitude of the third voltage which produces a change in the condition of the corona discharges, comparing the first, fourth and seventh potential distribution patterns at the first, second and third noted magnitudes, respectively, comparing the second, fifth and eighth potential distribution patterns at the first, second and third noted magnitudes, respectively, comparing the third, sixth and ninth potential distribution patterns at the first, second and third noted magnitudes, respectively, determining which potential distribution pattern comparison has a winding potential common to the three potential distribution patterns of that comparison to indicate the radial region in which the corona discharges are located, and determining from the location of the common winding potential the axial location of the corona discharges.

6. The method of locating the source of corona discharges of claim 5 including the steps of:

grounding the first phase terminal when the first voltage is applied, grounding the second phase terminal when the second voltage is applied, and grounding the third phase terminal when the third voltage is applied.

7. The method of locating the source of corona discharges of claim 5 wherein the second three-phase winding includes fourth, fifth, sixth and seventh phase terminals, and wherein the method includes the steps of:

connecting the second voltage between the fourth and sixth phase terminals, and shorting together the fifth and seventh phase terminals.

8. The method of locating the source of corona discharges of claim 7 including the steps of:

connecting the third voltage between the fourth and seventh phase terminals, and shorting together the fifth and sixth phase terminals.

9. A method of locating the source of corona discharges in a multiple-phase delta-connected transformer winding, said method comprising the steps of:

energizing the winding phases with a multiple-phase voltage, detecting corona pulses in said phase winding, determining a first phase relationship between the detected corona pulses and the phase winding voltage at a first phase winding terminal with respect to ground, grounding one terminal of said phase winding and determining a second phase relationship between the detected corona pulses and the phase winding voltage at said first phase winding terminal with respect to ground, determining the electrical distance the corona pulses of the first phase relationship must be shifted to provide the second phase relationship, and converting the determined electrical distance to physical dimensions corresponding to the axial dimension of the phase winding.

10. The method of locating the source of corona discharges of claim 9 including the step of comparing the second phase relationship with typical corona discharge phase relationships to determine the nature of the corona source.