A cable wrapping intermediate joint structure

Abstract

This invention relates to the field of cable joint technology, specifically to a cable wrapping intermediate joint structure, comprising two cables and cable cores, the cable cores being wrapped with a cable insulation layer; a pre-insulated arc, sleeved on the cable insulation layer, the pre-insulated arc not in contact with the outer shielding layer of the cable insulation, the side of the pre-insulated arc away from the outer shielding layer of the cable insulation being inclined, the arc surface being coated with semi-conductive paint; and an insulating self-adhesive tape, wrapped between the two pre-insulated arcs, both the pre-insulated arcs and the insulating self-adhesive tape being made of EPDM rubber. By employing a geometric method to improve the distribution of the electric field strength, system failures caused by increased dielectric loss in the stress control zone during cable operation are avoided. By increasing the geometric dimensions of the additional insulation, the surface stray capacitance is increased, and the capacitive current flowing into the semi-conductive end of the terminal insulation is dispersed to each stray capacitor, thereby achieving a uniform electric field distribution at the shielding end.

Description

Technical Field

[0001] This invention relates to the field of cable joint technology, and specifically to a cable wrapping intermediate joint structure. Background Technology

[0002] For a long time, cable joints have been the weakest link in cable systems. Statistical analysis of cable accident data in major cities across the country shows that the four main causes of power cable operation failures are: manufacturing failure of the cable itself, quality of laying and installation, manufacturing quality of accessories, and external damage. If external damage or human factors are not considered, cable failures caused by accessories account for as much as 64% of the total operation failures, and more than 90% of these are failures of intermediate joints.

[0003] Commonly used connectors are classified into wrap-around, cold shrink, heat shrink, and fusion splice connectors. Cold shrink and heat shrink connectors are prefabricated and suitable only for general installation scenarios. Fusion splice connectors are complex to install, require a large installation space, are expensive, and have low market acceptance.

[0004] Wrap-around intermediate joints are often used in scenarios requiring long-term immersion in water, for irregularly shaped joints, or in situations with limited installation space or emergency repairs due to their field-made nature, flexible installation, and good waterproof performance.

[0005] Traditional wrapped joints retain the original reactive force cone and use a stress control strip, a material with a high dielectric constant, to control the electric field distribution at the cable break. This is known as the stress layer control method (also called the parametric method). The stress control strip typically has a high dielectric constant, is a polar material, and is greatly affected by temperature; that is, the dielectric constant decreases as temperature increases. Since the electric field distribution of the wrapped joint depends on the stress control strip, and changes in the dielectric constant of the stress control strip directly affect the electric field distribution of the wrapped joint, distortion is more likely to occur, leading to breakdown in the wrapped portion of the stress control strip. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, this invention provides a cable wrapping intermediate joint structure that effectively solves the problem in existing technologies where the stress control strip can easily distort the field strength distribution of the joint, leading to breakdown of the stress control strip wrapping.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a cable wrapping intermediate joint structure, comprising two cables, and further comprising:

[0009] The cable includes cable cores, and two cable cores are wound together. The cable cores are wrapped with a cable insulation layer, the cable insulation layer is wrapped with a cable insulation outer shielding layer, and the cable insulation outer shielding layer is wrapped with a cable copper shielding layer.

[0010] A pre-insulated arc is fitted onto the cable insulation layer with an interference fit. The pre-insulated arc does not contact the cable insulation outer shielding layer. The side of the pre-insulated arc away from the cable insulation outer shielding layer is a sloping surface, and the side of the pre-insulated arc away from the cable insulation outer shielding layer is an arc surface. The arc surface is coated with semi-conductive paint.

[0011] An insulating self-adhesive tape is wrapped between two pre-made insulating arcs, and neither end of the insulating self-adhesive tape contacts the arc surface. Both the pre-made insulating arcs and the insulating self-adhesive tape are made of EPDM rubber.

[0012] Furthermore, a connecting pipe is provided at the junction of the two cable cores, and both ends of the connecting pipe are not in contact with the cable insulation layer.

[0013] Furthermore, both ends of the connecting pipe are conical.

[0014] Furthermore, a semi-conductive self-adhesive tape is wrapped around the outside of the connecting tube, and both ends of the semi-conductive self-adhesive tape are in contact with the ends of the cable insulation layer.

[0015] Furthermore, the cable insulation layers of both cables are conical at one end.

[0016] Furthermore, a semi-conductive self-adhesive tape is wound between the copper shielding layers of the two cables, and the material of the semi-conductive self-adhesive tape is EPDM rubber.

[0017] Furthermore, a copper wire mesh is wrapped around the semiconductive self-adhesive tape wound around the copper shielding layer of the cable, and constant force springs are provided at both ends of the wrapped copper wire mesh. A PVC tape is wound around the outside of the copper wire mesh, and the PVC tape completely covers the constant force springs.

[0018] The technical solution provided by this invention has the following advantages compared with the known prior art:

[0019] The novel wrapping joint of this invention reduces the installation difficulty for installers. The pre-fabricated insulation arc prevents inconsistencies in the shape of the stress control strip due to different installers. This solves the problem of failure and breakdown caused by heat generation after long-term operation due to material defects in the stress control strip. Furthermore, all materials of the wrapping joint are made of EPDM rubber. During power system operation, when the cable heats up, the components undergo a secondary vulcanization reaction due to similar compatibility, reducing gaps and further improving electrical performance while minimizing safety hazards.

[0020] By using a geometric method to improve the distribution of electric field strength, system failures caused by increased dielectric loss of the stress control strip during cable operation are avoided. By increasing the geometric dimensions of the additional insulation and increasing the surface stray capacitance, the capacitive current flowing into the semiconductive end of the terminal insulation is dispersed to each stray capacitor, thereby achieving a uniform distribution of the electric field at the shield end. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0022] Figure 1 This is a diagram of the cable pretreatment structure.

[0023] Figure 2 This is a structural diagram of the cable after the cable wrapping joint is completed;

[0024] Figure 3 Diagram showing the installation process of a cable wrapping connector;

[0025] Figure 4 This is a cross-sectional view of the cable wrapping joint.

[0026] Figure 5 This is a diagram showing the electric field distribution of a cable wrapping joint.

[0027] Figure 6 This is a schematic diagram of the electric field path at the wrapping joint;

[0028] Figure 7 for Figure 6 Tangential electric field strength between pre-insulated arc and cable insulation layer;

[0029] Figure 8 for Figure 6 Tangential electric field strength at the interface between the self-adhesive insulating tape and the pre-insulated arc;

[0030] Figure 9 for Figure 6 Tangential electric field strength between the self-adhesive insulating tape and the cable insulation layer;

[0031] Figure 10 for Figure 6 Normal field strength at the interface between the pre-insulated arc and the outer semiconducting strip;

[0032] Figure 11 This is a schematic diagram of the pre-insulated arc section;

[0033] Figure 12 A cross-sectional view of the pre-insulated arc section;

[0034] Figure 13 This is a side view of the prefabricated insulating arc section.

[0035] The labels in the diagram represent: 1. Cable; 11. Cable core; 12. Cable insulation layer; 13. Cable insulation outer shielding layer; 14. Cable copper shielding layer; 2. Connecting pipe; 3. Semi-conductive self-adhesive tape; 4. Pre-insulated arc; 41. Bevel; 42. Arc surface; 43. Semi-conductive paint; 5. Insulating self-adhesive tape. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0037] The present invention will be further described below with reference to embodiments.

[0038] Example: Reference Figures 1-4 as well as Figures 11-13 A cable wrapping intermediate joint structure includes two cables 1, and further includes:

[0039] Cable 1 includes cable cores 11, and two cable cores 11 are wound together. A connecting tube 2 is provided at the junction of the two cable cores 11, and both ends of the connecting tube 2 are not in contact with the cable insulation layer 12. Both ends of the connecting tube 2 are conical. The cable cores 11 are wrapped with cable insulation layer 12, and the cable insulation layer 12 is wrapped with cable insulation outer shielding layer 13. The cable insulation layers 12 of the two cables 1 are conical at one end close to each other. The cable insulation outer shielding layer 13 is wrapped with cable copper shielding layer 14. Semi-conductive self-adhesive tape 3 is wrapped around the connecting tube 2, and both ends of the semi-conductive self-adhesive tape 3 are in contact with the ends of the cable insulation layer 12.

[0040] A pre-insulated arc 4 is sleeved on the cable insulation layer 12, and the two are interference fit. The pre-insulated arc 4 does not contact the cable insulation outer shielding layer 13. The side of the pre-insulated arc 4 away from the cable insulation outer shielding layer 13 is a slope 41, and the side of the pre-insulated arc 4 away from the cable insulation outer shielding layer 13 is an arc surface 42. The arc surface 42 is coated with semi-conductive paint 43.

[0041] Insulating self-adhesive tape 5 is wrapped between two pre-insulated arcs 4, and neither end of the insulating self-adhesive tape 5 contacts the arc surface 42. The pre-insulated arcs 4 and the insulating self-adhesive tape 5 are both made of EPDM rubber. A semi-conductive self-adhesive tape 3 is wrapped between the copper shielding layers 14 of the two cables 1. The semi-conductive self-adhesive tape 3 is made of EPDM rubber.

[0042] The semi-conductive self-adhesive tape 3 wrapped around the copper shielding layer 14 of the cable is covered with copper wire mesh, and constant force springs are provided at both ends of the wrapped copper wire mesh. PVC tape is wrapped around the outside of the copper wire mesh, and the PVC tape completely covers the constant force springs.

[0043] like Figure 3 Cable 1 is stripped and pretreated.

[0044] A connecting pipe 2 is crimped onto the outside of the two cable cores 11.

[0045] Then, a semi-conductive self-adhesive tape 3 is wrapped around the outside of the connecting tube 2.

[0046] Pre-insulated arcs 4 are installed on both sides of the cable insulation layer 12 near the outer shielding layer 13 of the cable insulation.

[0047] The self-adhesive insulating tape 5 wraps around the pre-insulated arc 4 on one side to the pre-insulated arc 4 on the other side and covers the cable insulation layer 12.

[0048] The semi-conductive self-adhesive tape 3 wraps around the copper shielding layer 14 of the cable from one side to the copper shielding layer 14 of the cable on the other side, and covers the pre-insulated arc 4 and the insulating self-adhesive tape 5.

[0049] like Figure 4 As shown, the semiconductive self-adhesive tape 3 located at the internal connecting tube 2 is the inner semiconducting tape, while the semiconducting self-adhesive tape 3 wrapped around the copper shielding layer 14 of the cable is the outer semiconducting tape.

[0050] The prefabricated insulating arc 4 is made entirely of EPDM rubber, which has good insulation and corona resistance, and high breakdown voltage. Semi-conductive paint 43 is sprayed onto the outer surface of one side of the prefabricated insulating arc 42.

[0051] The prefabricated insulating arc 4 is formed by one-time injection molding, with a simple structure and a yield rate of over 95%. Traditional cold shrink joints require processing semi-conductive components first, followed by secondary injection molding of insulating components, which easily leads to poor adhesion, excessive glue on the joint surface, and other problems, resulting in a yield rate generally below 80%.

[0052] The pre-insulated arc 4, the semi-conductive self-adhesive tape 3, and the insulating self-adhesive tape 5 are all made of EPDM rubber. During the operation of the power system, the cable 1 generates heat due to the current flowing through it. The EPDM rubber undergoes secondary vulcanization during the heating process, resulting in cross-linking and mutual solubility, which further reduces the gap.

[0053] from Figures 5-9 As can be seen from the electric field curve, under an operating voltage of 8.7kV, the maximum electric field strength between the interfaces is:

[0054] Let the tangential electric field strength between the pre-insulated arc 4 and the cable insulation layer 12 be E1 (e.g. Figure 7 (as shown)

[0055] Let the tangential electric field strength at the interface between the insulating self-adhesive tape 5 and the prefabricated insulating arc 4 be E2 (e.g. Figure 8 (as shown)

[0056] Let the tangential electric field strength between the insulating self-adhesive tape 5 and the cable insulation layer 12 be E3 (e.g. Figure 9 (as shown)

[0057] Let the normal electric field strength at the interface between the pre-insulated arc 4 and the outer semiconducting strip be E4 (e.g., Figure 10 (As shown).

[0058] The tangential electric field strength E1max between the pre-insulated arc 4 and the cable insulation layer 12 is 0.323kV / mm;

[0059] The tangential electric field strength at the interface of the self-adhesive insulating tape 5, the pre-insulated arc 4, and the cable insulation layer 12 is E2max=E3max=0.55kV / mm;

[0060] The normal electric field strength at the interface between the pre-insulated arc 4 and the outer semiconducting strip is E4max = 1.51 kV / mm;

[0061] Considering the on-site withstand voltage of the 8.7 / 15kV cable is 39kV, and the electric field strength coefficient is 39 / 8.7=4.5, the electric field strengths under the 39kV withstand voltage are as follows:

[0062] The tangential electric field strength E1max between the pre-insulated arc 4 and the cable insulation layer 12 is 1.4535kV / mm.

[0063] The tangential electric field strength at the interface of the self-adhesive insulating tape 5, the pre-insulated arc 4, and the cable insulation layer 12 is E2max=E3max=2.475kV / mm;

[0064] The normal electric field strength at the interface between the pre-insulated arc 4 and the outer semiconducting strip is E4max = 6.795 kV / mm;

[0065] in conclusion:

[0066] Based on the field strength data under 39kV withstand voltage, it is easy to see that the tangential field strength between the pre-insulated arc 4 and the cable insulation layer 12 is only 1.4535kV / mm. This indicates that the pre-insulated arc 4 effectively distributes the field strength evenly. Even if an air gap is generated during the installation process (with additional wrapping of the tape), there will be no discharge phenomenon with a field strength of 1.4535kV / mm. There are no potential hidden dangers. The product design has good performance and can ensure long-term normal operation.

[0067] The tangential electric field strength at the interface of the self-adhesive insulating tape 5, the pre-insulated arc 4, and the cable insulation layer 12 is the largest, at 2.475 kV / mm. Since the pre-insulated arc 4 is a rubber prefabricated component with a relatively smooth and flat outer surface, air gaps are less likely to occur during the tape winding process; therefore, it can be considered as a single unit. The withstand voltage of the conventional self-adhesive insulating tape 5 is 20 kV / mm, far exceeding the maximum tangential electric field strength on the outer surface of the pre-insulated arc 4. There are no potential hidden dangers, the product design exhibits good performance, and it can ensure long-term normal operation.

[0068] The maximum normal electric field strength at the interface between the pre-insulated arc 4 and the outer semiconducting strip is 6.795 kV / mm, while the conventional withstand voltage value of the insulating material used in the pre-insulated arc 4 is not less than 23 kV / mm, which is much greater than the maximum normal electric field strength on the outer surface of the pre-insulated arc 4. There are no potential hidden dangers, the product design has good performance, and it can ensure long-term normal operation.

[0069] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cable wrap-around type intermediate joint structure comprising two cables (1), characterized in that, Also includes: The cable (1) includes a cable core (11), and two cable cores (11) are wound together. The cable core (11) is wrapped with a cable insulation layer (12), the cable insulation layer (12) is wrapped with a cable insulation outer shielding layer (13), and the cable insulation outer shielding layer (13) is wrapped with a cable copper shielding layer (14). A pre-insulated arc (4) is fitted on the cable insulation layer (12) with an interference fit. The pre-insulated arc (4) does not contact the cable insulation outer shield layer (13). The side of the pre-insulated arc (4) away from the cable insulation outer shield layer (13) is a slope (41), and the side of the pre-insulated arc (4) away from the cable insulation outer shield layer (13) is an arc surface (42). The arc surface (42) is coated with semi-conductive paint (43). An insulating self-adhesive tape (5) is wrapped between two pre-made insulating arcs (4), and neither end of the insulating self-adhesive tape (5) contacts the arc surface (42). The pre-made insulating arcs (4) and the insulating self-adhesive tape (5) are both made of EPDM rubber. A connecting tube (2) is provided at the junction of the two cable cores (11), and both ends of the connecting tube (2) are not in contact with the cable insulation layer (12); The connecting tube (2) is wrapped with a semi-conductive self-adhesive tape (3), and the two ends of the semi-conductive self-adhesive tape (3) are in contact with the ends of the cable insulation layer (12). The cable insulation layers (12) of the two cables (1) are conical at one end.

2. A cable wrap-around type intermediate joint structure according to claim 1, characterized by Both ends of the connecting pipe (2) are conical.

3. A cable wrap-around type intermediate joint structure according to claim 1, wherein A semi-conductive self-adhesive tape (3) is wound between the copper shielding layers (14) of the two cables (1), and the material of the semi-conductive self-adhesive tape (3) is EPDM rubber.

4. The cable wrapping intermediate joint structure according to claim 1, characterized in that, A copper wire mesh is wrapped around the outside of the semiconductive self-adhesive tape (3) wrapped on the copper shielding layer (14) of the cable, and constant force springs are provided at both ends of the wrapped copper wire mesh. A PVC tape is wrapped around the outside of the copper wire mesh, and the PVC tape completely covers the constant force springs.

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