Test Body, Test Arrangement, Method For Manufacturing Of A Test Body, And Method For Determining A Moisture Content Of The Insulation Of A Power Transformer During Drying Thereof

• US 20110115506A1
• Filed: 12/01/2010
• Published: 05/19/2011
• Est. Priority Date: 06/26/2008
• Status: Active Grant

• Current Assignee: ABB Technology Limited (ABB Ltd.)
• Original Assignee: ABB Technology Limited (ABB Ltd.)
• Inventors: Gafvert, Uno, Eriksson, Thomas
• Granted Patent: US 8,525,535 B2
• Time in Patent Office: Days
• US Class Current: 324/694
• CPC Class Codes: G01N 27/223 for determining moisture content, e.g. humidity rain detectors on vehicle windows B60S1/0825
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

A test body for use in determining moisture content in a laminated insulation of a power transformer by measuring a dielectric frequency response of the test body. The test body has a laminated structure of the same material as the laminated insulation, and has a shape and a size to obtain moisture content characteristics that resembles the moisture content characteristics of the laminated power transformer insulation. The test body further includes electrodes, which are embedded in the laminated structure.

Claims

1. A test body for use in determining a moisture content in a laminated insulation of a power transformer by means of measuring a dielectric frequency response of said test body, said test body having a laminated structure of the same material as said laminated insulation, and having a shape and a size to obtain moisture content characteristics that resembles the moisture content characteristics of said laminated insulation, characterized in that said test body further comprises electrodes which are embedded in said laminated structure.

2. The test body of claim 1 wherein said laminated structure comprises a plurality of plates adhered to one another.

3. The test body of claim 2 wherein said plates are cellulose pressboards.

4. The test body of claim 2 wherein said electrodes are layers formed on one or more surfaces of the plates.

5. The test body of claim 4 wherein said electrodes are formed on different surfaces of one of the plate.

6. The test body of claims 5 wherein said plurality of plates adhered to one another is at least three and said one of the plates, on whose different surfaces said electrodes are formed, is arranged in the middle of the laminated structure.

7. The test body of claim 5 wherein the plate, on whose surfaces said electrodes are formed, is longer than the other ones of the plates;

and has an end portion, which is protruding from said other ones of the plates and is provided with electrode connectors for said electrodes.

8. The test body of claim 4 wherein said electrodes are formed on different surfaces of different ones of the plates.

9. The test body of claim 4 wherein said electrodes are formed on a single surface of one of the plates.

10. The test body of claim 4 wherein a guard electrode layer is formed on one or more surfaces of the plates.

11. A test arrangement including the test body of claim 1 and means provided for measuring a dielectric frequency response of the test body.

12. A method for manufacturing a test body for use in determining a moisture content in a laminated insulation of a power transformer by means of measuring a dielectric frequency response of said test body, said method comprising the steps of:

laminating together a plurality of plates of the same material as said laminated insulation and of a shape and a size to obtain moisture content characteristics of the plurality of plates laminated together that resembles the moisture content characteristics of said laminated insulation, characterized by the step of;

forming electrodes on one or more surfaces of one or more of the plates prior to the step of laminating, wherein the step of laminating comprises the step of embedding said electrodes in said plurality of plates laminated together.

13. The method of claim 12 wherein said electrodes are formed on said one or more surfaces of said one or more of the plates by means of printing or painting one or more conductive patterns thereon.

14. A method for determining a moisture content in a laminated insulation of a power transformer during or after drying thereof, comprising the steps of:

providing a laminated test body with electrodes embedded therein, wherein the moisture content characteristics of said test body corresponds to the moisture content characteristics of said laminated insulation;

connecting a test device for measuring the dielectric frequency response to said electrodes;

subjecting said test body to an atmosphere corresponding to an atmosphere that said laminated insulation is subjected to;

determining the moisture content of said test body by means of measuring the dielectric frequency response thereof, and

determining the moisture content of said laminated insulation based on the determined moisture content of said test body.

15. The method of claim 14 wherein said test body is subjected to the same atmosphere as said laminated insulation during the entire drying of the laminated insulation of the power transformer.

16. The method of claim 14 wherein said test body is subjected to the same atmosphere as said laminated insulation during the step of mounting the laminated insulation of the power transformer.