Crosslinked polyethylene medium high voltage insulated power cable and process for the production thereof

Abstract

The application relates to the technical field of power cables, and provides a cross-linked polyethylene medium-high voltage insulation power cable and a preparation process, which comprises a cable core and a shielding layer, an insulation layer and a cladding layer outside the cable core; the outer side of the insulation layer is provided with an insulation repair layer, the outer side of the insulation repair layer is longitudinally provided with a sealing layer, the outer side of the sealing layer is an axial corrugated structure, the outer side of the sealing layer is filled with a water-blocking layer, the outer side of the water-blocking layer is provided with a buffer layer, the buffer layer is located on the inner side of the cladding layer, the outer side of the cladding layer is detachably provided with a sheath layer, and the sheath layer comprises a plurality of detachably connected armored units. Through the insulation repair layer outside the insulation layer, the water-blocking layer outside the sealing layer and the buffer layer on the inner side of the cladding layer, macroscopic protection is formed by locally filling the gaps of the cladding layer with the buffer layer, microscopic protection is formed by filling the local defects of the insulation layer with the insulation repair layer, and then the longitudinal gaps of the sealing layer are filled with the water-blocking layer.

Description

Technical Field

[0001] This invention relates to the field of power cable technology, and more specifically, to a cross-linked polyethylene medium-high voltage insulated power cable and its manufacturing process. Background Technology

[0002] Cross-linked polyethylene insulated power cables are a type of cable widely used in medium and high voltage power transmission. The cross-linking process makes polyethylene molecules form a three-dimensional network structure, which significantly improves heat resistance, mechanical strength and dielectric properties. They have advantages such as large current carrying capacity, good insulation performance, light weight and convenient laying. They are commonly used in power transmission and distribution lines with voltage levels from 10kV to 220kV and are suitable for urban power grids, industrial parks and long-distance power transmission.

[0003] Currently, in environments such as underwater or in troughs where water accumulates for extended periods or is damp, the moisture in cross-linked polyethylene insulated power cables gradually penetrates into the cable's insulation layer under the combined action of an electric field and water. This forms tiny tree-like channels inside the cable, causing the insulation material to gradually lose its insulating properties, ultimately leading to cable breakdown and power outages.

[0004] To address the aforementioned issues, this application proposes a cross-linked polyethylene medium- and high-voltage insulated power cable and its manufacturing process. Summary of the Invention

[0005] The purpose of this invention is to provide a cross-linked polyethylene medium-voltage insulated power cable and its manufacturing process, which solves the problem of moisture corrosion of cables in humid environments in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] A cross-linked polyethylene medium- and high-voltage insulated power cable includes a cable core and a shielding layer, an insulation layer, and a covering layer on its outer side;

[0008] An insulating repair layer is provided on the outside of the insulating layer. A sealing layer is longitudinally wrapped on the outside of the insulating repair layer. The outer side of the sealing layer has an axial corrugated structure. A water-blocking layer is filled on the outside of the sealing layer. A buffer layer is provided on the outside of the water-blocking layer. The buffer layer is located on the inside of the covering layer. A sheath layer is detachably installed on the outside of the covering layer. The sheath layer includes multiple detachably connected armored units.

[0009] A manufacturing process for a cross-linked polyethylene medium- and high-voltage insulated power cable includes the following steps:

[0010] S1: The shielding layer, insulation layer, and insulation repair layer are extruded sequentially to the outside of the stranded cable core using a co-extrusion device;

[0011] S2: Multiple metal strips are longitudinally wrapped around the outside of the insulation repair layer using a longitudinal wrapping device to form a sealing layer with an axial corrugated structure;

[0012] S3: The gel is filled to the outside of the sealing layer using a coating device or a ring injection device to form a water-resistant layer with a circular outer surface;

[0013] S4: The buffer layer and the covering layer are extruded sequentially to the outside of the water-blocking layer using a co-extrusion device;

[0014] S5: After the cable is laid, multiple armored units are fitted onto the outside of the cable body and fixed by inserting fixing pins into through holes. Then, adjacent armored units are connected into one unit through a transfer mechanism to form an axially extending sheath layer.

[0015] The beneficial effects of this invention are:

[0016] 1. By setting an insulating repair layer inside the sealing layer and wrapping it around the insulation layer, the functional microspheres mixed inside the insulating repair layer can soften and penetrate into the defect gap when a local defect occurs in the insulation layer under the action of local electric field and heat, thereby locally filling the defect and forming micro-protection. This can not only form a self-healing effect of the insulation layer, but also eliminate water tree gaps, effectively ensuring the performance of the cable in humid environments.

[0017] 2. By setting a buffer layer on the inside of the sheath, the buffer layer provides cushioning and disperses external impact forces. The filling material of the buffer layer can promptly wrap the damaged gaps when the sheath is damaged, and locally fill the cable gaps to form macroscopic protection, thereby preventing moisture erosion and protecting the integrity of the cable's internal structure.

[0018] 3. By setting a water-blocking layer inside the cable, connecting the outer buffer layer and the inner sealing layer, and utilizing the microcapsules inside the water-blocking layer, it can not only fill the longitudinal gaps of the sealing layer to inhibit moisture penetration, but also rupture at cracks to release monomers to polymerize and form a seal, thus combining macro-protection and micro-protection to form a multi-layer waterproof effect.

[0019] 4. By installing a set of sheathing layers on the outside of the cable, drainage channels and arc-shaped baffles can be used to guide external water to the bottom of the cable to avoid direct contact. It can also resist external impacts and protect against damage caused by external factors. Furthermore, the armored unit of a certain area can be disassembled individually during inspection and maintenance. The structure is simple and convenient for assembly and operation and maintenance. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the radial cross-sectional structure of the cable according to the present invention;

[0022] Figure 2 This is a schematic diagram of the three-dimensional structure of the cable of the present invention;

[0023] Figure 3 This is a schematic diagram of the axial planar structure of the cable of the present invention;

[0024] Figure 4 This is an exploded structural diagram of the water-blocking layer and sealing layer of the present invention;

[0025] Figure 5 This is a schematic diagram of the internal structure of the insulating repair layer and the water-blocking layer of the present invention;

[0026] Figure 6 This is a schematic diagram of the sheath layer structure of the present invention;

[0027] Figure 7 This is a schematic diagram of the first embodiment of the transfer mechanism of the present invention;

[0028] Figure 8 This is a schematic diagram of the second embodiment of the transfer mechanism of the present invention;

[0029] Figure 9 This is a schematic diagram of the internal structure and a portion thereof of the armored unit of the present invention;

[0030] Figure 10 This is an exploded structural diagram of the opening region of the armored unit of the present invention;

[0031] The attached diagram lists the components represented by each number as follows:

[0032] In the picture:

[0033] 1. Cable core; 2. Shielding layer; 3. Insulation layer; 4. Insulation repair layer; 5. Sealing layer; 6. Water-blocking layer; 7. Buffer layer; 8. Covering layer; 9. Sheath layer;

[0034] 401. Functional microspheres;

[0035] 51. Arc-shaped protrusion; 52. Arc-shaped depression;

[0036] 601. Microcapsules;

[0037] 61. Filling section;

[0038] 91. Armored unit; 92. Side guard; 93. Closing mechanism; 94. Adapter mechanism; 95. Sealing gasket; 96. Arc-shaped guard;

[0039] 901. Drainage channel;

[0040] 921. Positioning hole;

[0041] 931, Clamping plate one; 9311, Extension plate; 93111, Fixing pin;

[0042] 932, Clamping plate two; 9321, Through hole;

[0043] 94a1, Elastic Clip 1; 94a2, Elastic Clip 2; 9401, Locking Pin;

[0044] 9601, Drainage outlet. Detailed Implementation

[0045] 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 embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] A cross-linked polyethylene medium- and high-voltage insulated power cable and its manufacturing process are disclosed. The cable is designed to improve its performance in humid environments. The process involves an insulation repair layer 4 on the outside of the insulation layer 3, a water-blocking layer 6 on the outside of the sealing layer 5, and a buffer layer 7 on the inside of the covering layer 8. The buffer layer 7 partially fills the gaps in the covering layer 8 to form macroscopic protection, the insulation repair layer 4 fills the local defects in the insulation layer 3 to form microscopic protection, and the water-blocking layer 6 fills the longitudinal gaps in the sealing layer 5, connecting the insulation repair layer 4 and the buffer layer 7 to form a multi-layered waterproof effect, which helps to improve the cable's performance in humid environments.

[0047] In some embodiments, the specific structure of the cross-linked polyethylene high-voltage insulated power cable is as follows: Figure 1-3 As shown, the cable body includes a cable core 1 and a shielding layer 2 and an insulation layer 3 on its outer side, and also includes an outermost covering layer 8;

[0048] Specifically, please refer to Figure 2-4 The cable body is internally wrapped with a sealing layer 5, which provides the main waterproof function;

[0049] The outer side of the sealing layer 5 has an undulating structure, including an arc-shaped protrusion 51 and an arc-shaped depression 52, with multiple strips longitudinally wrapped around it. The arc-shaped protrusion 51 and the arc-shaped depression 52 are circumferentially connected to form a ring structure, while also forming an axial wave structure.

[0050] It should be noted that the sealing layer 5 is a metal strip structure made of corrosion-resistant aluminum alloy strip or galvanized steel strip, which is pre-rolled into a continuous annular corrugated shape to form an arc-shaped protrusion 51 and an arc-shaped recess 52.

[0051] Specifically, please refer to Figure 2-5 A water-blocking layer 6 is formed on the outside of the sealing layer 5 by coating or injection.

[0052] Water-blocking layer 6 is a special water-blocking self-healing gel. The body contains densely distributed microcapsules 601. The microcapsules 601 contain monomers and catalysts, which can undergo a polymerization reaction after rupture and then flow to the gap under external pressure, thereby forming a filling and sealing effect.

[0053] The water-blocking layer 6 fills the corrugated structure of the sealing layer 5, and a raised filling part 61 is formed on the inner side of the water-blocking layer 6.

[0054] It is understandable that the filling of the sealing layer 5 by the water-blocking layer 6 can also allow the gel to enter the longitudinal gaps of the sealing layer 5, locally filling any gaps that may exist, reducing the probability of water tree formation, and preventing the longitudinal spread of water.

[0055] It is also understandable that the flow and sealing effect of microcapsules can also form a seal in time when defects occur in the bulk of adjacent layer structures, thereby inhibiting the expansion of defects;

[0056] Specifically, please refer to Figure 2-4 A buffer layer 7 is extruded between the water-blocking layer 6 and the covering layer 8. It is a solid ring structure that fills all the space between the water-blocking layer 6 and the covering layer 8.

[0057] The buffer layer 7 is a highly elastic water-blocking polymer, such as silicone rubber, which is chemically bonded or physically bonded to the water-blocking layer 6 and the covering layer 8, forming a whole.

[0058] Understandably, the buffer layer 7, as the main bearing unit for cable elastic buffering, can absorb and disperse the impact force generated by the outside on the cable, and can also form a wrap in time when the outer covering layer 8 is damaged, preventing moisture from entering from the defect and causing radial spread.

[0059] Specifically, please refer to Figure 2-5 An insulating repair layer 4 is provided between the insulating layer 3 and the sealing layer 5. By co-extruding with the insulating layer 3, the insulating repair layer 4 and the insulating layer 3 form a tightly bonded integrated structure.

[0060] The insulating repair layer 4 is a dynamically responsive semi-conductive shielding composite structure, comprising a substrate and functional units;

[0061] The substrate of the insulation repair layer 4 is a cross-linked semi-conductive shielding material, and the functional unit of the insulation repair layer 4 is a functional microsphere 401, which is densely distributed inside the substrate.

[0062] Functional microsphere 401 is an electric field responsive microsphere structure with a shell made of flexible semi-conductive polymer and internally encapsulated with high dielectric constant, low viscosity liquid silicone oil and nano-scale water-blocking powder.

[0063] It should be noted that the shell material can be a semi-conductive polymer composed of an ethylene-acrylate copolymer matrix and a conductive filler of carbon nanotubes or graphene nanosheets; the liquid silicone oil can be a silicone oil body composed of methylphenyl silicone oil with high phenyl content and a hydrogen-containing silicone oil crosslinking agent; and the water-blocking powder can be modified nano-montmorillonite.

[0064] It is understandable that when the insulation layer 3 is affected by the bending and twisting of the cable and produces local defects, the electric field inside the cable will be abnormally concentrated at the defect, thereby generating electric field stress and Joule heat on the functional microsphere 401, which softens the shell of the functional microsphere 401, thereby enhancing the permeability of the functional microsphere 401, and finally causing the encapsulant to seep out to the defect area, forming a local filling effect, which can homogenize the local electric field at the defect and suppress partial discharge.

[0065] It is also understandable that the nano-water-blocking powder contained in the encapsulation can be injected into the defect area to fill the initial water tree gaps caused by electric field distortion, thereby preventing further water infiltration and spread.

[0066] Specifically, please refer to Figure 2-3 and Figure 6-10 A sheath layer 9 is provided on the outside of the cable body, which is composed of multiple individual armor units 91, and the armor unit 91 is an alloy strip structure.

[0067] The armored unit 91 has an arc-shaped cross-section, an overall ring structure, and an opening on one side. The opening is installed below the cable.

[0068] Among them, the armored unit 91 has side blocks 92 extending radially outward on both sides, and a drainage groove 901 is formed between the side blocks 92 and the outer side of the armored unit 91.

[0069] Among them, the opening of the armor unit 91 is fixedly installed with a closing mechanism 93, including a clamping plate 931 and a clamping plate 932;

[0070] Both sides of the clamping plate 931 extend into the clamping plate 932, and the extension plate 9311 extends radially inward and vertically into a vertical plate structure. The inner side of the vertical plate structure is fixedly installed with a fixing pin 93111.

[0071] Furthermore, through holes 9321 are provided on both sides of the clamping plate 932 for connecting the fixing pin 93111;

[0072] It is understandable that by moving the clamping plate 931, the vertical plate structure of the extension plate 9311 passes over the clamping plate 932 and enters its other side, thereby allowing the fixing pin 93111 to be inserted into the through hole 9321 to form a fixed connection, thereby closing the armor unit 91 into a ring structure.

[0073] Furthermore, the armored units 91 are arranged at equal intervals along the axis, and the outer sides of adjacent side guards 92 are connected and fixed through a connecting mechanism 94;

[0074] The adapter mechanism 94 includes an elastic clip 94a1, which is an open ring structure. Side plates extend radially inward from both sides of the body. A locking pin 9401 is fixedly installed on the inner side of the side plate for inserting into the positioning hole 921 opened on the inner side of the side block 92.

[0075] Optionally, the adapter mechanism 94 includes a second elastic clip 94a2, which differs from the first elastic clip 94a1 in that the first elastic clip 94a1 is an open-type circular structure that gathers multiple locking pins 9401, while the second elastic clip 94a2 is shorter and only has a pair of locking pins 9401 installed, making it an independent fixing structure.

[0076] Furthermore, sealing gaskets 95 are fixedly installed on both the sides and inner surfaces of the armored unit 91;

[0077] The sealing gasket 95 on the inner surface of the armored unit 91 is used to form a seal against the cable;

[0078] The sealing gaskets 95 on the side of the armored unit 91 are used to form a seal when two adjacent sealing gaskets 95 abut against each other when adjacent armored units 91 are connected.

[0079] It should be noted that the sealing gasket 95 is made of [material name missing].

[0080] In addition, arc-shaped baffles 96 are installed on the opposite sides of the clamping plate 931 and clamping plate 932. The arc-shaped baffles 96 are axially symmetrically distributed in pairs. A drain outlet 9601 is formed in the center of each pair of arc-shaped baffles 96, which is connected to the drain trough 901.

[0081] Understandably, the sheath layer 9, placed on the outside of the cable, forms a rigid protection to resist external impacts, and uses the drainage groove 901 and the drainage port 9601 to discharge accumulated water to the bottom of the cable, thereby preventing water from directly contacting the cable.

[0082] It is also understandable that the detachable connection between adjacent armored units 91 allows for the individual removal of a section, facilitating cable inspection and maintenance.

[0083] Based on the above, it can be seen that the cable first resists external impact and reduces the contact rate with water through the sheath layer 9, forming external protection;

[0084] Secondly, the cable forms an outer ring of macroscopic protection by wrapping the defective area of ​​the covering layer 8 with the buffer layer 7 inside, and then the insulation repair layer 4 automatically fills the defective gaps of the insulation layer 3 to form an inner ring of microscopic protection. The transition space between the buffer layer 7 and the insulation repair layer 4 is filled by the water-blocking layer 6, thus forming a multi-level protection effect inside, inside and outside, effectively inhibiting the generation and spread of water trees inside the cable.

[0085] It should be noted that the cable core 1, shielding layer 2, insulation layer 3, and sheathing layer 8 are all standard features of cross-linked polyethylene medium- and high-voltage insulated power cables, for example:

[0086] The cable core 1 is made of copper conductors twisted around a central reinforcing rib;

[0087] The shielding layer 2 is a semi-conductive layer extruded onto the outside of the cable core 1, and is made of cross-linked semi-conductive polyolefin shielding material;

[0088] Insulation layer 3, a cross-linked polyethylene layer extruded outside the shielding layer 2, is the main insulation of the cable;

[0089] Sheathing layer 8 is extruded from a high-strength thermoplastic polyurethane outer sheath and forms the outermost sheath structure of the cable.

[0090] The cable core 1, shielding layer 2, insulation layer 3, and covering layer 8 are conventional technical means in this field and will not be described in detail here.

[0091] In some publications, the manufacturing process of cross-linked polyethylene medium and high voltage insulated power cables is as follows: Specifically, copper conductors are stranded around a central reinforcing rib using a stranding device according to the stranding pitch and direction specified in the industry to form a cable core 1. A shielding layer 2, an insulation layer 3, and an insulation repair layer 4 containing functional microspheres 401 are sequentially extruded on the outside of the cable core 1 using a three-layer co-extrusion device. Multiple tapes are longitudinally wrapped around the outside of the insulation repair layer 4 using a longitudinal wrapping device to form a sealing layer 5 with an axial corrugated structure. A gel containing microcapsules 601 is filled onto the outside of the sealing layer 5 using a coating device or a ring injection device to form a water-blocking layer 6 with a circular outer surface. A buffer layer 7 and a covering layer 8 are sequentially extruded onto the outside of the water-blocking layer 6 using a double-layer co-extrusion device. Finally, after the cable is laid, an armor unit 91 is fitted onto the outside of the cable body and fixed by inserting a fixing pin 93111 into a through hole 9321. Then, adjacent armor units 91 are connected into one unit by a transfer mechanism 94 to form an axially extending sheath layer 9.

[0092] In the description of this specification, references to terms such as "an embodiment," "example," and "specific example" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0093] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A cross-linked polyethylene medium- and high-voltage insulated power cable, characterized in that: It includes the cable core (1) and its outer shielding layer (2), insulation layer (3) and covering layer (8); An insulating repair layer (4) is provided on the outside of the insulating layer (3). A sealing layer (5) is longitudinally wrapped on the outside of the insulating repair layer (4). The sealing layer (5) has an axial corrugated structure on the outside. A water-blocking layer (6) is filled on the outside of the sealing layer (5). A buffer layer (7) is provided on the outside of the water-blocking layer (6). The buffer layer (7) is located on the inside of the covering layer (8). A sheath layer (9) is detachably installed on the outside of the covering layer (8). The sheath layer (9) includes multiple detachably connected armored units (91). The insulating repair layer (4) is a dynamically responsive semi-conductive shielding composite structure, and functional microspheres (401) are uniformly dispersed inside the insulating repair layer (4). The substrate of the insulating repair layer (4) is a cross-linked semi-conductive shielding material, and the functional unit of the insulating repair layer (4) is a functional microsphere (401) which is densely distributed inside the substrate; The functional microsphere (401) is an electric field responsive microsphere structure with a shell made of flexible semi-conductive polymer and encapsulated with high dielectric constant, low viscosity liquid silicone oil and nano-scale water-blocking powder inside.

2. The cross-linked polyethylene medium-voltage insulated power cable according to claim 1, characterized in that: The outer side of the sealing layer (5) includes an arc-shaped protrusion (51) and an arc-shaped recess (52), which are axially connected and are both arc-shaped structures.

3. The cross-linked polyethylene medium-voltage insulated power cable according to claim 2, characterized in that: The water-blocking layer (6) is a self-healing water-blocking gel structure. Microcapsules (601) are uniformly distributed inside the water-blocking layer (6). The inner side of the water-blocking layer (6) fills into the arc-shaped recess (52) to form a filling part (61).

4. The cross-linked polyethylene medium-voltage insulated power cable according to claim 1, characterized in that: The buffer layer (7) is a highly elastic water-blocking polymer structure. The buffer layer (7) is closely attached to the water-blocking layer (6) and the covering layer (8), and is the main buffer structure of the cable.

5. The cross-linked polyethylene medium-voltage insulated power cable according to claim 1, characterized in that: The armored unit (91) has side blocks (92) on both sides, and a drainage groove (901) is formed between the side blocks (92) and the armored unit (91). A sealing gasket (95) is fixed on the inner surface of the side blocks (92) and the side away from the armored unit (91).

6. The cross-linked polyethylene medium-voltage insulated power cable according to claim 5, characterized in that: An adapter mechanism (94) is sleeved on the outer side of the adjacent side guard (92). The adapter mechanism (94) includes an elastic clip one (94a1) or an elastic clip two (94a2). The inner sides of the two side plates of the elastic clip one (94a1) or the elastic clip two (94a2) are fixed with a locking pin (9401). The side guard (92) near the armor unit (91) has a positioning hole (921) for inserting the locking pin (9401).

7. The cross-linked polyethylene medium-voltage insulated power cable according to claim 1, characterized in that: The armor unit (91) has a closing mechanism (93) at its opening, including a clamping plate one (931) and a clamping plate two (932). An extension plate (9311) is fixed on both sides of the clamping plate one (931). A fixing pin (93111) is fixed on the inner side of the vertical plate structure of the extension plate (9311). Through holes (9321) for inserting the fixing pin (93111) are opened on both sides of the clamping plate two (932).

8. The cross-linked polyethylene medium-voltage insulated power cable according to claim 7, characterized in that: The opening of the armor unit (91) is also provided with an arc-shaped baffle (96), and a drain outlet (9601) is formed between adjacent arc-shaped baffles (96). The drain outlet (9601) is connected to the drain trough (901). One end of the arc-shaped baffle (96) is fixedly installed on the side of the first clamp (931) or the second clamp (932).

9. A manufacturing process for a cross-linked polyethylene medium-high voltage insulated power cable, applied to the cross-linked polyethylene medium-high voltage insulated power cable as described in any one of claims 1-8, characterized in that, Includes the following steps: S1: The shielding layer (2), the insulation layer (3), and the insulation repair layer (4) are extruded sequentially to the outside of the stranded cable core (1) using a co-extrusion device; S2: Multiple metal strips are longitudinally wrapped around the outside of the insulation repair layer (4) using a longitudinal wrapping device to form a sealing layer (5) with an axial corrugated structure. S3: The gel is filled into the outside of the sealing layer (5) by coating equipment or ring injection equipment to form a water-resistant layer (6) with a circular outer surface. S4: The buffer layer (7) and the covering layer (8) are sequentially extruded onto the outside of the water-blocking layer (6) using a co-extrusion device; S5: After the cable is laid, multiple armored units (91) are fitted onto the outside of the cable body, and a closed fixing is formed by the insertion of the fixing pin (93111) and the through hole (9321). Then, the adjacent armored units (91) are connected into one unit by the adapter mechanism (94) to form an axially extending sheath layer (9).

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