A method for improving the structure of current transformer expander based on reinforcing ring

Abstract

The present invention discloses a method for improving the structure of a current transformer expander based on a reinforcement ring. The improved expander structure of the current transformer includes: a bellows, a non-contact reinforcement ring, an end tube and a flange. The present invention installs a reinforcement ring at the interface between the bellows and the end tube of the expander, and uses an auxiliary gasket during the installation process to allow an axial gap between the reinforcement ring and the bellows and the end tube. The non-contact reinforcement ring structure can reduce the extrusion stress caused by the deformation difference between the reinforcement ring and the bellows under the action of an external load. The structural improvement method proposed by the present invention can improve the elastic pressure compensation capability and strength performance of the current transformer expander.

Description

Technical Field

[0001] The invention relates to the technical field of improving the reliability of electrical equipment, and more specifically to a method for improving the structure of a current transformer expander based on a reinforcement ring. Background Art

[0002] Typical faults of oil-immersed current transformers include oil leakage, abnormal expansion, abnormal oil chromatography, abnormal secondary circuit, etc. In the daily operation and maintenance of current transformers, the incidence of abnormal expansion is higher than other types of faults. The metal expander is installed on the top of the current transformer. As a fully sealed oil protection device for the current transformer, it can adjust the thermal expansion and contraction of the insulating oil volume inside the current transformer caused by temperature changes, and can also release the accumulated pressure caused by slow faults such as overheating and partial discharge, playing a certain explosion-proof role.

[0003] Existing current transformer expanders all use unreinforced bellows, the expansion joint has a weak bearing capacity, and when the expander is subjected to large forces, irreversible deformation may occur, making the current transformer expander function ineffective. At present, some other large-scale equipment will use reinforced expanders, which are composed of structures such as bellows and reinforcement rings, but the existing reinforcement ring structures are mostly circular rings and hollow circular rings. These reinforcement structures will sharply increase the rigidity of the expansion joint, limit the expansion range of the expansion joint, and have limitations.

[0004] At the same time, due to the complexity of the current transformer structure, the reinforcement ring design of these large equipment is not suitable for current transformers. Therefore, it is necessary to study a new reinforcement ring structure to effectively improve the bearing capacity of the current transformer expansion joint, and to study the assembly gap between the reinforcement ring and the expansion joint, so as to further improve the expander structure of the current transformer and improve the expander pressure performance. Summary of the invention

[0005] The purpose of this method is to propose a method for improving the structure of a current transformer expander based on a reinforcing ring to solve the above technical problems.

[0006] To achieve the above-mentioned purpose, the present invention provides a method for improving the structure of a current transformer expander based on a reinforcement ring, characterized in that the expander structure of the improved current transformer includes: a bellows, a reinforcement ring, an end pipe and a flange; the reinforcement ring is installed on the outside of the interface between the first layer of the bellows and the end pipe, and the lower end of the reinforcement ring and the flange are welded into one body by a mechanical welding method; the improved expander is connected to the upper end outlet of the current transformer oil storage cabinet and fixed by a flange; an outer cover shell is provided on the outside of the expander, and a hole is drilled at the lower end of the outer cover shell, which is fixed to the shell of the current transformer oil storage cabinet by screws.

[0007] Furthermore, the reinforcement ring adopts a non-contact installation method. During the welding process, the thickness of dg A thin gasket is placed between the end pipe and the reinforcement ring along the axial direction. After the reinforcement ring is fixed and welded, the gasket is removed so that there is a gap d between the first layer of bellows, the end pipe and the axial end face of the reinforcement ring. g , gap distance d g Select the formula that satisfies:

[0008]

[0009] C b is the bellows welding correction factor; δ is the material thickness of the bellows, in mm; σ b is the allowable stress of the bellows material at the design temperature, in MPa; p is the design pressure of the current transformer expander, in MPa.

[0010] Furthermore, the reinforcing ring is made of high magnetic permeability material, the upper part of the reinforcing ring cross section is a quarter circle, the lower part is a rectangle, and the radius r of the upper quarter circle of the reinforcing ring cross section is c Satisfy the formula:

[0011] r c =0.25d w -d g

[0012] d w is the wave distance of the bellows, in mm;

[0013] The width of the rectangle at the bottom of the reinforcement ring section and the radius r of the quarter circle at the top of the reinforcement ring section c Likewise, the length of the rectangle is the same as the height of the end tube.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The present invention installs a reinforcement ring on the outside of the interface between the bellows and the end pipe of the expander, and uses auxiliary gaskets to create an axial gap between the reinforcement ring, the bellows and the end pipe during the installation process. The non-contact reinforcement ring structure can reduce the extrusion stress caused by the deformation difference between the reinforcement ring and the bellows under the action of external loads. The structural improvement method proposed in the present invention can improve the elastic pressure compensation capability and strength performance of the current transformer expander. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the schematic diagram of the improved current transformer expander structure

[0017] Figure 2 is a schematic diagram of a cross-section of a reinforcing ring structure; DETAILED DESCRIPTION

[0018] The following is a clear and complete description of the technical solution in the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Embodiment 1

[0020] This embodiment proposes a method for improving the structure of a current transformer expander based on a reinforcement ring, and the method comprises the following steps:

[0021] Step 1: Determine the installation gap between the reinforcement ring and the current transformer expander

[0022] Current transformers of different voltage levels are suitable for expanders with different design parameters. Expanders with different design parameters have different expander deformations under the same pressure. The installation gap between the reinforcing ring (2) and the current transformer expander (7) is determined based on parameters such as the specific material thickness and design pressure of the current transformer expander.

[0023] Gap distance d g Select the formula that satisfies:

[0024]

[0025] C b is the bellows welding correction factor; δ is the material thickness of the bellows, in mm; σ b is the allowable stress of the bellows material at the design temperature, in MPa; p is the design pressure of the current transformer expander, in MPa.

[0026] Step 2: Design the reinforcement ring structure

[0027] The reinforcing ring (2) is made of a high magnetic permeability material. The reinforcing ring is designed to be a non-standard circular ring, whose cross section is composed of a quarter circle and a rectangle. The upper part is a quarter circle (9), and the lower part is a rectangle (10). The radius r of the upper quarter circle (9) of the reinforcing ring cross section is c Satisfy the formula:

[0028] r c =0.25d w -d g

[0029] d w is the wave distance of the bellows, in mm;

[0030] The width of the lower rectangle (10) of the reinforcing ring cross section and the radius r of the upper quarter circle (9) of the reinforcing ring cross section cSimilarly, the length of the rectangle is the same as the height of the end tube (3).

[0031] Step 3: Structural Installation

[0032] The structure of the expander (7) of the improved current transformer includes: a bellows (1), a reinforcing ring (2), an end tube (3) and a flange (5);

[0033] The reinforcing ring (2) is installed on the outside of the interface between the first layer of corrugated pipe (4) and the end pipe (3). The reinforcing ring (2) is installed in a non-contact manner. During the welding process, a thickness of d is firstly g A thin gasket is placed between the end pipe (3) and the reinforcement ring (2) along the axial direction, and the lower end of the reinforcement ring is welded to the flange (5) by a mechanical welding method. After the reinforcement ring (2) is fixed and welded, the gasket is removed, so that a gap d is present between the axial end faces of the first layer of bellows (4), the end pipe (3) and the reinforcement ring (2). g .

[0034] The improved expander (7) is connected to the upper outlet of the current transformer oil storage cabinet (6) and fixed by a flange; an outer cover shell (8) is provided outside the expander, and a hole is drilled at the lower end of the outer cover shell (8) and fixed to the shell of the current transformer oil storage cabinet (6) by screws.

[0035] The above content is merely an illustration of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific structure described. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for improving the structure of a current transformer expander based on a reinforcing ring, characterized in that: The structure of the expander of the improved current transformer includes: a bellows, a reinforcement ring, an end pipe and a flange; the reinforcement ring is installed outside the interface between the first layer of the bellows and the end pipe, and the lower end of the reinforcement ring is welded to the flange as a whole by a mechanical welding method; the improved expander is connected to the upper end outlet of the current transformer oil storage cabinet and fixed by a flange; an outer cover shell is provided outside the expander, and a hole is drilled at the lower end of the outer cover shell, which is fixed to the shell of the current transformer oil storage cabinet by screws; The reinforcing ring adopts a non-contact installation method. During the welding process, the reinforcing ring with a thickness of d is first g A thin gasket is placed between the end pipe and the reinforcement ring along the axial direction. After the reinforcement ring is fixed and welded, the gasket is removed so that there is a gap d between the first layer of bellows, the end pipe and the axial end face of the reinforcement ring. g , gap distance d g Select the formula that satisfies: C b is the bellows welding correction factor; δ is the material thickness of the bellows, in mm; σ b is the allowable stress of the bellows material at the design temperature, in MPa; p is the design pressure of the current transformer expander, in MPa; The reinforcing ring is made of high magnetic permeability material. The upper part of the reinforcing ring cross section is a quarter circle, and the lower part is a rectangle. The radius r of the upper quarter circle of the reinforcing ring cross section is c Satisfy the formula: <h2 style=";text-align:left;direction:ltr">r<h2 style=";text-align:left;direction:ltr"> c <h2 style=";text-align:left;direction:ltr"> <0.25d<h2 style=";text-align:left;direction:ltr"> w <h2 style=";text-align:left;direction:ltr"> -d<h2 style=";text-align:left;direction:ltr"> g d w is the wave distance of the bellows, in mm; The width of the rectangle at the bottom of the reinforcement ring section and the radius r of the quarter circle at the top of the reinforcement ring section c Likewise, the length of the rectangle is the same as the height of the end tube.

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