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CN-122000255-A - Fuse tube of drop-out fuse with automatic on-off function and manufacturing method thereof

CN122000255ACN 122000255 ACN122000255 ACN 122000255ACN-122000255-A

Abstract

The invention discloses a fuse tube of a drop-out fuse with an automatic on-off function, which comprises a fuse tube body, a serial automatic on-off branch arranged in the fuse tube body, wherein the serial automatic on-off branch is configured to have the following electrical characteristics that the serial automatic on-off branch is in a conducting state under an alternating current running working condition and in an off state under a direct current test feeding working condition, and a gradient potential transition and shielding integrated structure arranged at the connecting end part of the serial automatic on-off branch and the fuse tube body. By constructing an integrated shielding structure of a curved equipotential ring, a shielding cup and a conductive gradient coating at the end of the melting tube, a continuously controllable potential gradient is formed in a three-dimensional space by utilizing a potential transition layer, so that end electric field distortion generated by introducing a serial automatic on-off branch is effectively eliminated, a local field intensity peak value is obviously reduced, and a local discharge starting voltage is improved, thereby greatly delaying the aging rate of an insulating medium.

Inventors

  • CAI DUJIA
  • CAI MINGHUANG
  • LIN YOUCHAO
  • CHEN XIAOKE
  • Wei Junye
  • ZHOU FANGKUN
  • LIN ZHONG
  • CHEN XIANZHI

Assignees

  • 海南电网有限责任公司乐东供电局

Dates

Publication Date
20260508
Application Date
20251231

Claims (10)

  1. 1. A fuse tube of a drop-out fuse with an automatic on-off function is characterized by comprising a fuse tube body (1), a serial automatic on-off branch circuit (2) arranged in the fuse tube body (1), wherein the serial automatic on-off branch circuit (2) is configured to have the following electrical characteristics that the fuse tube is in a conducting state under an alternating-current running working condition and is in an off state under a direct-current test feeding working condition; The gradient potential transition and shielding integrated structure (3) is arranged at the connecting end part of the serial automatic on-off branch circuit (2) and the fusion tube body (1).
  2. 2. The fuse tube with automatic on-off function of claim 1, wherein the gradient potential transition and shielding integrated structure (3) comprises a curved equipotential ring (31) which is arranged around a connection terminal of the serial automatic on-off branch circuit (2) and used for expanding an end equipotential surface; A shield cup (32) which is coated on the lead wire switching area of the connecting terminal and is electrically connected with the curved equipotential ring (31); and the conductive gradient coating (33) is attached to the inner wall of the end part of the fusion tube body (1) and is distributed along the axial direction, and is used for realizing smooth potential transition from high potential to an insulating medium.
  3. 3. The fuse tube with automatic on-off function of claim 1, wherein the conductive gradient coating (33) is a high-resistance conductive material layer arranged along the axial direction; The surface resistivity of the conductive gradient coating (33) is in gradient change along the axial direction, the resistivity of the conductive gradient coating (33) near the high-potential conductor side is the lowest, and the resistivity near the insulator side is the highest.
  4. 4. The drop-out fuse tube with automatic on-off function as recited in claim 3, wherein said conductive gradient coating (33) is made of a conductive filler containing graphite powder and silicon carbide micropowder, and the gradient distribution of the surface resistivity is controlled by changing the content of said conductive filler.
  5. 5. The fuse tube with automatic on-off function of claim 1, wherein a potential transition layer (34) is arranged between the outer edge of the curved equipotential ring (31) and the conductive gradient coating (33); the potential transition layer (34) comprises a first conductive composite pad (341), a second conductive composite pad (342) and a third conductive composite pad (343), and the volume resistivity of each conductive composite pad is sequentially increased so as to form a series resistance network between the curved equipotential ring (31) and the conductive gradient coating (33), so that voltage drops are distributed according to a preset proportion.
  6. 6. The fuse tube with automatic on-off function of claim 1, wherein said potential transition layer (34) is divided into three sections, and the volume resistivity of each section of said conductive composite pad is stepwise progressive.
  7. 7. The fuse tube with automatic on-off function of claim 1, wherein the shielding cup (32) is a thin-walled metal cup or a metallized composite cup; The rim of the cup opening of the shielding cup (32) is subjected to chamfering or arc transition treatment.
  8. 8. The fuse tube with automatic on-off function of claim 1, wherein the inner edge of the curved equipotential ring (31) is electrically connected with the terminal of the serial automatic on-off branch circuit (2), the outer edge extends towards the inner wall of the fuse tube body (1), and the outer surface of the curved equipotential ring is provided with a smooth curved profile.
  9. 9. The fuse tube with the automatic switching function of the drop-out fuse of claim 1, further comprising an axial lead transition structure (4); the axial lead transition structure (4) comprises a lead (41) arranged along the axial direction and a shielding bush (42) coaxially arranged with the lead (41).
  10. 10. A method of manufacturing a fuse tube for a drop-out fuse with an automatic on-off function as claimed in any one of claims 1 to 9, comprising the steps of: after assembling the lead wires of the serial automatic on-off branch circuits (2) and the connecting pieces, installing the curved equipotential ring (31) and the shielding cup (32), and finally paving the potential transition layer (34) and the conductive gradient layer on the inner wall of the end part; the electric connection treatment, namely fixing the curved equipotential ring (31) and the shielding cup (32) with preset equipotential points in a riveting and conductive adhesive dual connection mode; And vacuum filling, namely placing the assembled assembly in a vacuum environment, carrying out primary vacuumizing and primary curing through an exhaust groove preset at the end part, and then carrying out secondary curing at a temperature higher than that of the primary curing so as to eliminate shrinkage stress.

Description

Fuse tube of drop-out fuse with automatic on-off function and manufacturing method thereof Technical Field The invention relates to the technical field of power distribution, in particular to a fuse tube of a drop-out fuse with an automatic on-off function and a manufacturing method thereof. Background Drop-out fuses are the most commonly used short circuit and overload protection switches in power distribution networks. In daily operation and maintenance and fault finding of a 10kV distribution line, a direct-current high-voltage test method (insulation detection by using a direct-current test instrument) is a common means for judging the fault property of the line. However, since a voltage transformer (PT) is connected in parallel in the power distribution network, the primary side coil thereof has a low impedance characteristic to direct current. When direct current test is carried out, direct current high voltage can directly access ground or enter adjacent phase through PT neutral point, so that detection failure is caused. Therefore, the traditional operation flow requires operation staff to manually climb a pole to disconnect the PT drop switches one by one before trial delivery, and the PT drop switches are restored after detection is completed, so that the labor intensity is high, the time consumption is long, and the safety risk is increased due to frequent operation. In order to solve the above problems, some automatic blocking schemes have been developed in the prior art. For example, patent document CN113517084B discloses a "direct-current high-voltage breaker type cable", in which a main capacitor formed by connecting a plurality of capacitor cores in parallel is integrated in a cable insulation coating layer, thereby realizing a function of blocking direct-current communication. Although such externally-hung or cable-type solutions can avoid manual operation PT to some extent, the original line connection structure often needs to be changed, or additional installation space is occupied, and mechanical strength and ageing resistance of the cable form in long-term outdoor operation are also challenged. In order to further improve the integration level and operation and maintenance convenience of the equipment, an automatic on-off technology (or called serial automatic on-off branch) directly integrated in the melting pipe is developed in the industry. The technology directly packages the functional module with the characteristics of alternating current and direct current in the fusion tube of the drop-out fuse, and realizes the noninductive replacement of plug and play. After the automatic on-off branch is integrated into the melting pipe with a narrow space, a new technical problem is brought to the design of an insulation structure at the end part of the melting pipe, and in order to realize the electric connection between the automatic on-off branch and a fuse main loop in a limited pipe diameter, the end part area inevitably has the structural characteristics of conductor switching, lead sharp bending, space shrinkage and the like. These discontinuous metal edges and narrow electrical gaps are extremely prone to electric field distortion, resulting in significant increases in local field strength, causing corona or partial discharge. The end of the melting tube is usually encapsulated with a material such as epoxy resin. In the three-combination area of the metal-pouring sealant-insulating pipe wall, micro air gaps or micro cracks are easy to generate due to different thermal expansion coefficients of materials and limitation of a pouring technology. Under the action of a high electric field, the defect points become convergence points of electric field lines, accelerate medium aging and even lead to surface flashover breakdown. The built-in automatic on-off branch presents different impedance characteristics under different working conditions such as alternating current operation, direct current test feeding, lightning surge and the like, so that the potential distribution of the end connection point fluctuates severely along with the working conditions. Without the potential gradient control design of the system, transient overvoltage is easily coupled to internal weak current devices, resulting in breakdown damage. Disclosure of Invention Therefore, the invention aims to solve the technical problems that after the automatic on-off branch is integrated in the fuse tube of the drop-out fuse, the electric field distortion is serious, the partial discharge initial voltage is low and the insulating medium is easy to age due to the complicated structure of the end connecting area. The technical problem is solved by the technical scheme that the fuse tube with the automatic on-off function of the drop-out fuse comprises a fuse tube body, and a serial automatic on-off branch arranged in the fuse tube body, wherein the serial automatic on-off branch is configured to have the following electrical