An electrode model and method for variable curvature of oil paper insulation electrodes

Abstract

This invention discloses a variable-curvature oil-paper insulation electrode model and method. The test model includes components such as a ground electrode terminal, a ground electrode fastening bolt, a moving rod, a high-voltage electrode terminal, a high-voltage electrode fastening bolt, a ground electrode slider, a ground electrode epoxy board, and a high-voltage electrode epoxy mold. The high-voltage electrode epoxy mold conformally fits the high-voltage electrode. During use, the curvature of the high-voltage electrode can be adjusted by the customized epoxy mold. The invention also provides a corresponding test method. This invention effectively solves the problem of inaccurate breakdown field strength test results in ordinary oil-paper insulation breakdown tests due to the inability to reproduce the curved insulation structure inside the transformer. It provides a high-voltage electrode device for studying the breakdown characteristics of oil-paper insulation materials under strong electric fields, and has significant engineering practical value for in-depth research into the failure mechanism of transformer main insulation systems and improving insulation design levels.

Description

Technical Field

[0001] This invention belongs to the field of high voltage and insulation technology, specifically relating to an oil-paper insulating electrode model and method with variable electrode curvature. Background Technology

[0002] The oil-paper insulation structure is the core of the main insulation of oil-immersed power transformers. During long-term operation, the transformer's insulation system is subjected to the combined effects of multiple stresses, including electrical, thermal, and mechanical stresses. Among these, the uniformity of the electric field intensity is a key factor determining the insulation life and reliability. In actual transformers, the insulation layers between the high-voltage and low-voltage windings, and between the windings and the core, are not ideal parallel flat plates, but rather exhibit a complex concentric cylindrical structure with specific curvature. This curvature effect leads to uneven electric field distribution, with the maximum electric field intensity often concentrated on the electrode surface with the smaller radius of curvature, thus significantly affecting the breakdown behavior and partial discharge characteristics of the oil-paper insulation.

[0003] Currently, when evaluating the performance of oil-paper insulation materials in a laboratory environment, the internationally accepted standard methods (such as IEC 60243) mainly recommend using several typical electrode structures, such as parallel plate electrodes, ball-plate electrodes, or needle-plate electrodes. Although these traditional electrode models are simple in structure and easy to implement, they cannot realistically simulate the geometric characteristics of the internal insulation structure of a transformer, especially the influence of curvature on the electric field distribution.

[0004] In view of the above factors, a model and method for an oil-paper insulated electrode with variable electrode curvature is provided. The high-voltage electrode changes its curvature through a mold. The corresponding curvature is determined according to the test requirements. The test is conducted by customizing multiple sets of molds, which provides a good experimental basis for comparative tests of the breakdown strength of oil-paper composite insulation under different curvatures. Summary of the Invention

[0005] The purpose of this invention is to provide a paper-insulated electrode model and method with variable electrode curvature to solve the problems mentioned in the background art.

[0006] 2. The objective of this invention is achieved through the following technical solution: a paper-insulated electrode model with variable electrode curvature, comprising a ground electrode terminal block, wherein the ground electrode terminal block is assembled to a ground electrode terminal block fixing seat by means of screw connection, and the ground electrode terminal block fixing seat is assembled into a preset threaded hole of the ground electrode epoxy mold by means of hexagonal screws, thereby fixing the ground electrode in a preset installation position of the ground electrode epoxy mold.

[0007] A high-voltage electrode epoxy mold is provided on the opposite side of the ground electrode epoxy plate. A high-voltage electrode terminal is installed on one side of the high-voltage electrode epoxy mold. The high-voltage electrode terminal is assembled to the high-voltage electrode terminal fixing seat by screw connection. The high-voltage electrode terminal fixing seat is assembled to the high-voltage electrode epoxy mold by hexagonal screws, and the high-voltage electrode is screwed and fixed in the preset installation position of the high-voltage electrode epoxy mold.

[0008] The ground electrode epoxy mold and the high voltage electrode epoxy mold are arranged opposite each other in the horizontal direction, and the ground electrode and the high voltage electrode are respectively located on the opposite inner side of the ground electrode epoxy mold and the high voltage electrode epoxy mold, forming the electrode pair required for oil paper insulation test.

[0009] The oil-paper insulated test electrode pair, formed by the ground electrode and the high-voltage electrode respectively located in the epoxy mold of the ground electrode and the epoxy mold of the high-voltage electrode, is set in the oil tank.

[0010] Furthermore, the ground electrode terminal is made of iron and is assembled to the ground electrode terminal fixing base by a screw connection to form an electrical connection with the ground electrode. The high voltage electrode terminal is made of iron and is assembled to the high voltage electrode terminal fixing base by a threaded connection to form an electrical connection with the high voltage electrode.

[0011] Furthermore, the lower part of both the ground electrode epoxy mold and the high voltage electrode epoxy mold protrudes to form a convex structure, which is used to sit on the concave groove at the bottom of the oil tank.

[0012] Furthermore, the bottom surface of the oil tank is provided with a concave structure, a ground electrode epoxy mold and a high-voltage electrode epoxy mold, the protruding part of the mold is embedded in the concave groove, and the mating surfaces of the two are in contact with each other. The groove is provided with a 1cm graduation line, so that the distance between the ground electrode epoxy mold and the high-voltage electrode epoxy mold can be precisely controlled.

[0013] Furthermore, the bottom of the oil tank is equipped with casters, which are screwed and fixed to the four corners of the bottom of the oil tank to support the flexible movement of the oil paper insulated electrode model device;

[0014] Furthermore, the high-voltage electrode is a deformable metal electrode, and the inner side of the high-voltage electrode epoxy mold is provided with an arc-shaped groove with a preset curvature. The high-voltage electrode is attached to the inner surface of the arc-shaped groove. By the tightening force of the high-voltage electrode epoxy mold fastening bolts, the curvature of the outer surface of the high-voltage electrode is made consistent with the curvature of the surface where the arc-shaped groove of the high-voltage electrode epoxy mold is located, so that the two conformally fit together, thereby achieving precise control of the curvature of the high-voltage electrode.

[0015] Furthermore, the fuel tank is made of acrylic sheet, and the joints between the sheets are sealed and bonded with epoxy AB glue to ensure that the fuel tank is leak-free.

[0016] Furthermore, the caster wheel is a polyurethane caster wheel with braking function.

[0017] A method for testing the breakdown field strength of oil-paper insulation using an electrode model with variable electrode curvature includes the following steps;

[0018] Step 1: Use the high-voltage electrode epoxy mold to set the high-voltage electrode to curvature A, evenly attach the oil-impregnated paperboard to the surface of the high-voltage electrode, and use the high-voltage electrode epoxy mold fastening bolts to tightly fit the oil-impregnated paperboard, high-voltage electrode, and high-voltage electrode epoxy mold together.

[0019] Step 2: According to the test requirements, move the epoxy mold for the ground electrode and the epoxy mold for the high-voltage electrode so that the distance between the high-voltage electrode and the ground electrode is d. Connect the high-voltage electrode terminal and the ground electrode terminal to the high voltage and ground respectively;

[0020] Step 3: Fill the oil tank with transformer oil. Let it stand for 15-30 minutes to remove any air bubbles that may have gotten into the oil;

[0021] Step 4: Using the rapid voltage boosting method, refer to IEC 60243-1. Apply the AC test voltage from zero at a uniform rate (e.g., 200V / s);

[0022] Step 5: When the sample breaks down (manifested as a sharp increase in current in the test circuit, triggering overcurrent protection, the appearance of carbon particles in the insulating paper, and the breakdown path visible to the naked eye), record the breakdown voltage value U;

[0023] Step 6: Refer to IEC 60243-1 and perform 5 tests. Take the median of the test results as the breakdown voltage value. If any test result deviates from the median by more than 15%, perform another 5 tests. Then take the median of the 10 tests as the breakdown voltage value.

[0024] Step 7: Due to the introduction of curvature, the electric field distribution is not uniform. The value should be calculated based on the distance dc between the center points of the electrodes: Eb=U / dc.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] In this invention, the high-voltage electrode curvature is changed by a mold. The corresponding curvature is determined according to the test requirements. Multiple sets of molds are customized for testing, which provides a good test basis for the comparative test of the breakdown strength of oil-paper composite insulation under different curvatures.

[0027] This invention solves the problem that ordinary oil-paper insulation tests cannot reproduce the curved insulation structure inside the transformer, leading to distorted breakdown field strength test results. It designs a high-voltage electrode device that can study the breakdown characteristics of oil-paper insulation materials under strong electric fields, which has important engineering practical value for in-depth research on the failure mechanism of transformer main insulation system and improving insulation design level. Attached Figure Description

[0028] Figure 1 This is a block diagram of the overall structure of the present invention;

[0029] Figure 2 This is a side view of the present invention;

[0030] Figure 3 This is a top view of the present invention;

[0031] Figure 4 This is a schematic diagram of the epoxy plate side of the ground electrode of the present invention;

[0032] Figure 5 A flowchart of the test method for performing a breakdown test using the present invention;

[0033] Figure Labels

[0034] In the diagram, 1. Ground electrode terminal; 2. Ground electrode terminal holder; 3. High-voltage electrode terminal; 4. High-voltage electrode terminal holder; 5. Ground electrode epoxy mold; 6. High-voltage electrode epoxy mold; 7. Ground electrode fastening bolt; 8. High-voltage electrode epoxy mold fastening bolt; 9. Oil tank; 10. High-voltage electrode; 11. Caster wheel; 12. Hex bolt; 13. Ground electrode; Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Specific Implementation Example 1:

[0039] like Figure 1-3 As shown, a paper-insulated electrode model with variable electrode curvature includes a ground electrode terminal 1. The ground electrode terminal 1 is assembled to the ground electrode terminal fixing seat 2 by a screw connection. The ground electrode terminal fixing seat 2 is screwed into the preset threaded hole of the ground electrode epoxy mold 5 by a hexagonal screw 12, and the ground electrode 13 is screwed and fixed in the preset installation position of the ground electrode epoxy mold 5.

[0040] A high-voltage electrode epoxy mold 6 is provided on the opposite side of the ground electrode epoxy plate 5. A high-voltage electrode terminal 3 is installed on one side of the high-voltage electrode epoxy mold 6. The high-voltage electrode terminal 3 is assembled to the high-voltage electrode terminal fixing seat 4 by screw connection. The high-voltage electrode terminal fixing seat 4 is assembled to the high-voltage electrode epoxy mold 6 by hexagonal screws 12, and the high-voltage electrode 10 is screwed and fixed in the preset installation position of the high-voltage electrode epoxy mold 6.

[0041] The ground electrode epoxy mold 5 and the high voltage electrode epoxy mold 6 are arranged opposite each other in the horizontal direction, and the ground electrode 13 and the high voltage electrode 10 are respectively located on the opposite inner sides of the ground electrode epoxy mold 5 and the high voltage electrode epoxy mold 6, forming the electrode pair required for oil paper insulation test.

[0042] The oil-paper insulated test electrode pair, formed by the ground electrode 13 and the high-voltage electrode 10 respectively located in the ground electrode epoxy mold 5 and the high-voltage electrode epoxy mold 6, is set in the oil tank 9.

[0043] The ground electrode terminal 1 is made of iron and is assembled to the ground electrode terminal fixing base 2 by a screw connection, forming an electrical connection with the ground electrode 13. The high voltage electrode terminal 3 is made of iron and is assembled to the high voltage electrode terminal fixing base 4 by a threaded connection, forming an electrical connection with the high voltage electrode 10.

[0044] The ground electrode terminal fixing base 2 is a cube with rounded corners. It is fixed to the ground electrode epoxy mold 5 by four hexagonal screws 12. The center is a circular through hole with threads on the hole wall to allow the ground electrode terminal 1 to be rotated and fixed, forming an electrical connection with the ground electrode 13. The ground electrode epoxy mold 5 has a through hole in the center. The through hole is a light hole. The ground electrode 13 is fixedly connected to a metal rod. The other end of the metal rod extends to the end face of the ground electrode epoxy mold 5 and contacts and engages with the ground electrode terminal fixing base.

[0045] The high-voltage electrode terminal fixing base 5 is a cube with rounded corners. It is fixed to the high-voltage electrode epoxy mold 6 by four hexagonal screws 12. The center is a circular through hole with threads on the hole wall to allow the high-voltage electrode terminal 3 to be rotated and fixed, forming an electrical connection with the high-voltage electrode 10. The high-voltage electrode epoxy mold 6 has a through hole at its center, which is a smooth hole. The high-voltage electrode 10 is fixedly connected to a metal rod, and the other end of the metal rod extends to the end face of the high-voltage electrode epoxy mold 6 to contact and engage with the high-voltage electrode terminal fixing base 4.

[0046] like Figure 2 As shown, the ground electrode epoxy mold 5 is a rectangular flat plate structure, and the ground electrode 13 is a rectangular metal electrode; screw holes are opened at the four corner edges of the ground electrode epoxy mold 5 and the ground electrode 13, and the ground electrode fastening bolts 7 are inserted into the screw holes to screw and fix the ground electrode epoxy mold 5 and the ground electrode 13.

[0047] The high-voltage electrode epoxy mold 6 has a surface where the high-voltage electrode terminal fixing seat 4 is located and Figure 4 Similarly, the high-voltage electrode epoxy mold 6 is a rectangular flat plate structure, and the high-voltage electrode 10 is a rectangular metal electrode; mounting holes are provided at the four corners of both the high-voltage electrode epoxy mold 6 and the high-voltage electrode 10, and the high-voltage electrode epoxy mold fastening bolts 8 are inserted into the bolt holes to screw and fix the high-voltage electrode epoxy mold 6 and the high-voltage electrode 10; the inner side of the high-voltage electrode epoxy mold 6 is provided with an arc-shaped groove with a preset curvature, and the high-voltage electrode 10 is a deformable metal electrode; during assembly, the high-voltage electrode 10 fits against the inner surface of the arc-shaped groove, and the locking force of the high-voltage electrode epoxy mold fastening bolts 8 makes the curvature of the outer surface of the high-voltage electrode consistent with the curvature of the surface where the arc-shaped groove of the high-voltage electrode epoxy mold 6 is located, so that the two conformally fit together;

[0048] The oil tank 9 is made of acrylic sheet, and the joints of the sheets of the oil tank 9 are sealed and bonded with epoxy AB glue to ensure that the oil tank 9 is leak-free.

[0049] The universal wheel 11 is a polyurethane universal wheel with braking function. The universal wheel 11 is screwed and fixed to the four corners of the bottom of the oil tank 9 to support the flexible movement of the oil paper insulated electrode model device. Its braking function is realized by the brake pedal of the universal wheel 11. Specific Implementation Example 2:

[0051] Based on the first specific embodiment, this embodiment has been improved. The groove of the oil tank 9 is provided with a scale line with a division of 1cm, so that the distance between the ground electrode epoxy mold and the high voltage electrode epoxy mold can be precisely controlled. Specific Implementation Example 3:

[0053] like Figure 5 As shown, a method for testing the breakdown field strength of oil-paper insulation using an electrode model with variable electrode curvature includes the following steps;

[0054] Step 1: Use the high-voltage electrode epoxy mold 6 to set the high-voltage electrode 10 to curvature A, and evenly attach the oil-impregnated paperboard to the surface of the high-voltage electrode 10. Secure the oil-impregnated paperboard, high-voltage electrode 10, and high-voltage electrode epoxy mold 6 tightly together using the high-voltage electrode epoxy mold fastening bolts 8.

[0055] Step 2: According to the test requirements, move the ground electrode epoxy mold 5 and the high-voltage electrode epoxy mold 6 so that the distance between the high-voltage electrode 10 and the ground electrode 13 is d. Connect the high-voltage electrode terminal 3 and the ground electrode terminal 1 to the high voltage and ground respectively;

[0056] Step 3: Fill oil tank 9 with transformer oil. Let it stand for 15-30 minutes to remove any air bubbles that may have mixed in with the oil;

[0057] Step 4: Using the rapid voltage boosting method, refer to IEC 60243-1. Apply the AC test voltage from zero at a uniform rate (e.g., 200V / s);

[0058] Step 5: When the sample breaks down (manifested as a sharp increase in current in the test circuit, triggering overcurrent protection, the appearance of carbon particles in the insulating paper, and the breakdown path visible to the naked eye), record the breakdown voltage value U;

[0059] Step 6: Refer to IEC 60243-1 and perform 5 tests. Take the median of the test results as the breakdown voltage value. If any test result deviates from the median by more than 15%, perform another 5 tests. Then take the median of the 10 tests as the breakdown voltage value.

[0060] Step 7: Due to the introduction of curvature, the electric field distribution is not uniform. The value should be calculated based on the distance dc between the center points of the electrodes: Eb=U / dc.

[0061] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0062] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A paper-insulated electrode model with variable electrode curvature, characterized in that: Includes a ground electrode terminal (1), which is assembled to a ground electrode terminal fixing seat (2) by a screw connection. The ground electrode terminal fixing seat (2) is screwed into a preset threaded hole of the ground electrode epoxy mold (5) by a hexagonal screw (12), and the ground electrode (13) is screwed and fixed in a preset installation position of the ground electrode epoxy mold (5). A high-voltage electrode epoxy mold (6) is provided on the opposite side of the ground electrode epoxy plate (5). A high-voltage electrode terminal (3) is installed on one side of the high-voltage electrode epoxy mold (6). The high-voltage electrode terminal (3) is assembled to the high-voltage electrode terminal fixing seat (4) by screw connection. The high-voltage electrode terminal fixing seat (4) is screwed onto the high-voltage electrode epoxy mold (6) by hexagonal screws (12). The high-voltage electrode (10) is screwed and fixed to the preset installation position of the high-voltage electrode epoxy mold (6). The ground electrode epoxy mold (5) and the high voltage electrode epoxy mold (6) are arranged opposite each other in the horizontal direction, and the ground electrode (13) and the high voltage electrode (10) are respectively located on the opposite inner side of the ground electrode epoxy mold (5) and the high voltage electrode epoxy mold (6), forming the electrode pair required for the oil paper insulation test. The oil-paper insulation test electrode pair formed by the ground electrode (13) and the high voltage electrode (10) respectively located in the ground electrode epoxy mold (5) and the high voltage electrode epoxy mold (6) is set in the oil tank (9).

2. The oil-paper insulated electrode model with variable electrode curvature according to claim 1, characterized in that: The ground electrode terminal (1) is made of iron and is assembled to the ground electrode terminal fixing seat (2) by screw connection, forming an electrical connection with the ground electrode (13). The high voltage electrode terminal (3) is made of iron and is assembled to the high voltage electrode terminal fixing seat (4) by thread connection, forming an electrical connection with the high voltage electrode (10).

3. The oil-paper insulated electrode model with variable electrode curvature according to claim 2, characterized in that: The lower part of the epoxy mold for the ground electrode (5) and the epoxy mold for the high voltage electrode (6) both protrude to form a convex structure, which is used to sit on the concave groove at the bottom of the oil tank (9).

4. The oil-paper insulated electrode model with variable electrode curvature according to claim 3, characterized in that: The bottom surface of the oil tank (9) is provided with a concave structure (16), a ground electrode epoxy mold (5) and a high voltage electrode epoxy mold (6). The protruding part of the mold is embedded in the concave groove, and the contact surfaces of the two are in contact with each other. The groove is provided with a scale line with a division of 1cm, so that the distance between the ground electrode epoxy mold (5) and the high voltage electrode epoxy mold (6) can be precisely controlled.

5. The oil-paper insulated electrode model with variable electrode curvature according to claim 4, characterized in that: The bottom of the oil tank (13) is provided with casters (11), which are screwed to the four corners of the bottom of the oil tank (9) to support the flexible movement of the oil paper insulating electrode model device.

6. The oil-paper insulated electrode model with variable electrode curvature according to claim 5, characterized in that: The high-voltage electrode (10) is a deformable metal electrode. The inner side of the high-voltage electrode epoxy mold (6) is provided with an arc-shaped groove with a preset curvature. The high-voltage electrode (10) is attached to the inner surface of the arc-shaped groove. The tightening force of the high-voltage electrode epoxy mold fastening bolt (8) makes the curvature of the outer surface of the high-voltage electrode (10) consistent with the curvature of the arc-shaped groove of the high-voltage electrode epoxy mold (6), so that the two conformally fit together, thereby achieving precise control of the curvature of the high-voltage electrode (10).

7. The oil-paper insulated electrode model with variable electrode curvature according to claim 6, characterized in that: The oil tank (9) is made of acrylic sheet. The joints of the sheets of the oil tank (9) are sealed and bonded with epoxy AB glue to ensure that the oil tank (9) is leak-free.

8. The oil-paper insulated electrode model with variable electrode curvature according to claim 7, characterized in that: The caster wheel (11) is a polyurethane caster wheel with braking function.

9. A method for testing the breakdown field strength of oil-paper insulation using an oil-paper insulation electrode model with variable electrode curvature according to claim 8, characterized in that: Includes the following steps; Step 1: Use the high voltage electrode epoxy mold (6) to set the high voltage electrode (10) to curvature A, attach the oil-impregnated paperboard evenly on the surface of the high voltage electrode (10), and use the high voltage electrode epoxy mold fastening bolts (8) to tightly fit the oil-impregnated paperboard, the high voltage electrode (10), and the high voltage electrode epoxy mold (6). Step 2: According to the test requirements, move the ground electrode epoxy mold (5) and the high voltage electrode epoxy mold (6) so that the distance between the high voltage electrode (10) and the ground electrode (13) is d. Connect the high voltage electrode terminal (3) and the ground electrode terminal (1) to the high voltage and ground respectively. Step 3: Fill the oil tank (9) with transformer oil and let it stand for 15-30 minutes to remove any air bubbles that may have entered the oil; Step 4: Using the rapid voltage boosting method, refer to IEC 60243-1 and apply the AC test voltage from zero at a uniform rate (e.g., 200V / s). Step 5: When the sample breaks down (manifested as a sharp increase in current in the test circuit, triggering overcurrent protection, the appearance of carbon particles in the insulating paper, and the breakdown path visible to the naked eye), record the breakdown voltage value U; Step 6: Refer to IEC 60243-1 and perform 5 tests. Take the median of the test results as the breakdown voltage value. If any test result deviates from the median by more than 15%, perform another 5 tests. Then take the median of the 10 tests as the breakdown voltage value. Step 7: Due to the introduction of curvature, the electric field distribution is not uniform. The value should be calculated based on the distance dc between the center points of the electrodes: Eb=U / dc.

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