A method for manufacturing a high voltage cable for simulating defects and a cable manufactured by the method

Abstract

The present invention discloses a method for manufacturing a high-voltage cable for simulating defects and a cable manufactured therefrom, which relates to the field of high-voltage transmission lines, and comprises the following steps: after co-extruding the three layers of conductor shielding, insulation layer and insulation shielding layer, a buffer layer, corrugated insulation paper and a corrugated aluminum sheath are sequentially coated on the outside of the insulation shielding layer. The buffer layer is wrapped around the outside of the insulation shielding layer by an overlapping wrapping method; the corrugated insulation paper is wrapped around the outside of the buffer layer by an intermittent wrapping method; the corrugated aluminum sheath is welded to the outside of the corrugated insulation paper by argon arc welding, and the corrugation direction is opposite to the winding direction of the corrugated insulation paper. The present invention simulates the poor electrical contact caused by white spot material between the buffer layer and the aluminum sheath in a defective cable by intermittent wrapping of the corrugated insulation paper, and can be applied to relevant verification experiments of various defective cable detection and repair methods.

Description

Technical Field

[0001] The invention relates to the field of high voltage transmission lines, to the manufacturing technology of high voltage XLPE cables, and in particular to a manufacturing method of high voltage cables for simulating defects and a cable manufactured using the same. Background Art

[0002] With the continuous increase in the cableization rate in urban areas, high-voltage XLPE cables are widely used in high-voltage cable systems. The buffer layer structure inside the cable plays an important role in the reliability of cable power transmission. When the high-voltage cable is laid underground, it is easily damaged by external forces and causes moisture intrusion. Under the combined effects of electrical, thermal and chemical factors, non-conductive white spots will appear in the buffer layer, which will deteriorate the electrical connection between the buffer layer and the aluminum sheath, and then cause the buffer layer to burn out.

[0003] Some scholars have explored effective detection and repair methods for the current fault problems in the buffer layer of high-voltage XLPE cables. The research of these methods requires a large number of white spot defective cables as test samples. However, most defective cables are laid underground, and the location of white spot defects is difficult to determine, so it is difficult to directly obtain defective cable samples. The acquisition of defective cables has become a bottleneck in the research of buffer layer detection and repair.

[0004] The existing method for manufacturing defective cables is to accelerate the natural growth of white spots by injecting water and heating and drying the cables. The existing method has a complex manufacturing process and relatively high cost, and it is impossible to obtain a large number of cable samples with controllable buffer layer defects in a short time. Therefore, it is necessary to propose a low-cost and high-efficiency defective cable manufacturing method to provide material support for research related to buffer layer defect detection and repair. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to serve the research field of high-voltage cable buffer layers and provide a method for manufacturing a defective cable structure with poor electrical connection between the buffer layer and the aluminum sheath. This method proposes a defective cable manufacturing scheme that can form partial discharge inside the cable, has low production cost and short production cycle, meets the need for obtaining a large number of cable defect samples required for high-voltage cable buffer layer defect fault detection and repair, and helps solve the problem of buffer layer defect faults.

[0006] In view of the deficiencies in the prior art, the present invention provides a method for efficiently obtaining a large number of simulated defective cables and the cables manufactured therefrom, so as to overcome the problem that it is difficult to obtain samples of high-voltage XLPE defective cables.

[0007] To achieve the above object, the present invention provides a method for manufacturing a high-voltage cable for simulating defects, which comprises the following steps:

[0008] Drawing the conductor material into monofilaments and annealing, twisting and plying to form a conductor;

[0009] Sequentially extruding a conductor shielding layer, an insulating layer and an insulating shielding layer around the outer periphery of the conductor;

[0010] Winding outside the insulating shielding layer to form a buffer layer;

[0011] Winding the buffer layer to form corrugated insulation paper;

[0012] A spiral corrugated aluminum sheath is armored outside the corrugated insulating paper.

[0013] The method for manufacturing a high-voltage cable for simulating defects as described above, further comprises: the conductor material is a soft round copper wire that complies with the provisions of GB / T 3953-2009.

[0014] The high-voltage cable manufacturing method for simulating defects as described above further comprises: the conductor shielding layer, the insulating layer and the insulating shielding layer are extruded to the outer periphery of the conductor by a three-layer co-extrusion method, wherein the conductor shielding layer and the insulating shielding layer are firmly bonded to the insulating layer respectively.

[0015] The high-voltage cable manufacturing method for simulating defects as described above, further: the conductor shielding layer and the insulating outer shielding layer are made of cross-linked semi-conductive shielding plastic, and the temperature resistance grade of the semi-conductive shielding plastic is compatible with the cross-linked polyethylene insulation, and the connection surface between the conductor shielding layer and the insulating layer is smooth and continuous; the physical properties of the semi-conductive shielding plastic are required to have a volume resistivity of less than 1.0Ω·m and a tensile strength of not less than 12.0MPa at 23°C.

[0016] The manufacturing method of the high-voltage cable for simulating defects as described above, further comprises: the insulating layer adopts cross-linked polyethylene without filler, and the physical properties of the cross-linked polyethylene are required to be less than 2.35 and the volume resistivity is greater than 1.0×10 13 Ω·m, tensile strength 17MPa.

[0017] The method for manufacturing a high-voltage cable for simulating defects as described above, further comprises: the buffer layer comprises a semi-conductive non-woven fabric layer and a semi-conductive fluffy cotton layer, wherein polyacrylate expanded powder is adhered between the semi-conductive non-woven fabric and the semi-conductive fluffy cotton, and the volume resistivity of the buffer layer is greater than 1000Ω·m.

[0018] The method for manufacturing a high-voltage cable for simulating defects as described above is further characterized in that: the buffer layer has a thickness of 2 mm, a width of 80 mm, and an overlap rate of 50%.

[0019] The high-voltage cable manufacturing method for simulating defects as described above is further characterized in that: the corrugated insulation paper is wrapped in a gap-type winding manner, the wrapping direction is oblique to the thread direction of the spiral corrugated aluminum sheath, and the gap width is 10% of the width of the insulating tape; the corrugated insulation paper has a thickness of 0.74 mm, a width of 38 mm, a power frequency breakdown strength of less than 3 kV / mm, and a voltage rise rate of 200 V / s.

[0020] The high-voltage cable manufacturing method for simulating defects as described above is further characterized in that: the spiral corrugated aluminum sheath is made of aluminum or aluminum alloy with a purity of not less than 99.5%, the thread pitch is 25 mm, the aluminum strip used for the spiral corrugated aluminum sheath should comply with the requirements of GB / T 3880.1-2012, the elongation of the aluminum strip should not be less than 16%, and after welding is completed, the air gap thickness between the buffer layer and the spiral corrugated aluminum sheath is 6.6 mm, wherein the air gap thickness is the maximum thickness of the air gap between the buffer layer at the top of the cable body and the inner side of the crest when the buffer layer is in close contact with the bottom of the trough of the spiral corrugated aluminum sheath under the action of gravity.

[0021] A cable manufactured using the high-voltage cable manufacturing method for simulating defects as described above, the cable comprising a conductor, a conductor shielding layer, an insulating layer, an insulating shielding layer, a buffer layer, corrugated insulating paper and a corrugated aluminum sheath arranged in sequence from the inside to the outside.

[0022] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The defective cable of the present invention effectively isolates the electrical connection between the buffer layer and the aluminum sheath by wrapping the corrugated insulating paper structure between the buffer layer and the aluminum sheath. At the same time, the use of a thinner buffer layer with a higher resistivity can increase the potential difference between the buffer layer and the aluminum sheath, increase the unevenness of the air gap layer structure, and more easily form a stable discharge signal than a normal cable or a white spot defective cable under the same conductor voltage.

[0024] (2) In addition, the insulating paper has a wrinkled structure rather than a smooth structure, which easily forms a local electric field concentration, further reducing the discharge threshold between the buffer layer and the aluminum sheath.

[0025] (3) In addition, the air gap layer structure with a relatively large gap can provide a longitudinal flow channel for the cable repair fluid, making it easier for the repair fluid to flow inside the cable.

[0026] (4) In addition, the intermittently wrapped corrugated insulation paper structure can provide a good conductive channel for the repair liquid to connect the buffer layer and the aluminum sheath, thereby improving the repair effect.

[0027] (5) In addition, by setting the thread pitch of the corrugated aluminum sheath to 25 mm, it is possible to ensure that the corrugated insulation paper with a width of 38 mm can effectively insulate the contact interface between the buffer layer and the aluminum sheath at a gap width of 10%.

[0028] (6) Defective cables wrapped with corrugated insulation paper provide a more convenient and effective source of defective cable samples for buffer layer fault detection and repair research. The fixed defective cable structure makes the discharge signal relatively more stable and easier to capture, and saves the manufacturing cost and time of defective cables. It can be applied to relevant verification experiments of buffer layer defective cable detection and repair methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 A flowchart of a high voltage cable manufacturing method for simulating defects according to an embodiment of the present invention;

[0031] Figure 2 is a schematic diagram of the outer structure of a conductor according to an embodiment of the present invention;

[0032] Figure 3 This is a schematic structural diagram of a cable manufactured by a high-voltage cable manufacturing method for simulating defects according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0034] Example:

[0035] It should be noted that the terms "including" and "having" and any variations of the embodiments of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0036] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0037] In the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] The following is combined with Figure 1-Figure 3 The manufacturing method of the high-voltage cable with simulated defects is specifically introduced.

[0039] like Figure 1 As shown in the manufacturing flow chart, a method for manufacturing a high-voltage cable for simulating defects includes the following steps:

[0040] S1. The conductor is drawn into single filaments by a wire drawing device, the single filaments are annealed by wire drawing, and are twisted by a frame twisting machine to form a conductor. In this embodiment, the single filaments need to meet the requirements of GB / T 3953-2009.

[0041] S2, the conductor shielding layer, the insulating layer and the insulating shielding layer are extruded outside the conductor. In this embodiment, the conductor shielding layer, the insulating layer and the insulating shielding layer are extruded to the outer periphery of the twisted conductor by a three-layer co-extrusion process, and are firmly bonded to the insulating layer. Furthermore, the conductor shielding layer and the insulating outer shielding layer should adopt a cross-linked semi-conductive shielding plastic, and its temperature resistance grade should be compatible with the cross-linked polyethylene insulation. The interface between the semi-conductive layer and the insulating layer should be smooth and continuous. Furthermore, the insulating material used for the insulating layer is cross-linked polyethylene without filler. Furthermore, the dielectric constant of the insulating material at 23°C should be less than 2.35, the volume resistivity should be greater than 1.0×1013Ω·m, and the tensile strength should be greater than 17MPa. Furthermore, the volume resistivity of the semiconductor shielding material at 23°C is less than 1.0Ω·m, and the tensile strength is not less than 12.0MPa.

[0042] S3. Wrap the buffer layer outside the insulating shielding layer by a wrapping machine, wherein the cable is pulled to the No. 1 wrapping machine by a guide wheel, the wrapping machine overlap rate is set to 50%, and the buffer layer is wrapped outside the insulating shielding layer. In this embodiment, the buffer layer structure is composed of a layer of semi-conductive non-woven fabric and a layer of semi-conductive fluffy cotton, with a layer of polyacrylate expansion powder glued in the middle. The volume resistivity of the buffer layer should be greater than 1000Ω·m.

[0043] S4. Wrap the corrugated insulation paper outside the buffer layer through a wrapping machine, wherein the cable is pulled to the No. 2 wrapping machine through a guide wheel, the wrapping machine gap rate is set to 10%, the corrugated insulation paper is wrapped to the outside of the buffer layer, and the traction machine is used to reel in the wire. In this embodiment, the thickness of the corrugated insulation paper is 0.74mm, the width is 38mm, and the power frequency breakdown strength is less than 3kV / mm (boost rate 200V / s). Furthermore, the thickness of the corrugated insulation paper is 0.74mm, the width is 38mm, and the power frequency breakdown strength is less than 3kV / mm (boost rate 200V / s).

[0044] S5. Wrap the corrugated aluminum sheath around the corrugated insulation paper, such as Figure 3 As shown, the direction of the insulating paper wrapping is oblique to the direction of the aluminum sheath wrapping; after determining that the air gap thickness is 6.6mm, the corresponding aluminum strip width is calculated and trimmed, and then welded by argon arc welding, followed by corrugation. In this embodiment, the spiral corrugated aluminum sheath should be made of aluminum or aluminum alloy with a purity of not less than 99.5%, and the thread pitch is 25mm.

[0045] As an optional implementation, in step S3, the overlap rate is measured in real time when wrapping begins, and the next wrapping step can be performed only when the overlap rate of the buffer layer is stabilized at 50%.

[0046] As an optional implementation, in step S4, the overlap rate is measured in real time when the wrapping starts, and the next wrapping step can be performed only when the overlap rate of the corrugated insulation paper is stabilized at 10%.

[0047] As an optional implementation, in step S5, the thickness of the air gap between the buffer layer and the spiral corrugated aluminum sheath is 6.6 mm. The air thickness refers to the maximum thickness of the air gap between the buffer layer at the top of the cable body and the inner side of the crest when the buffer layer is in close contact with the bottom of the trough of the spiral corrugated aluminum sheath under the action of gravity.

[0048] The present invention also provides a cable manufactured by the manufacturing method. The cable comprises, from inside to outside, a conductor, a conductor shielding layer, an insulating layer, an insulating shielding layer, a buffer layer, corrugated insulating paper, and a corrugated aluminum sheath.

[0049] The present invention effectively isolates the electrical connection between the buffer layer and the aluminum sheath by gap-wrapping crepe paper with certain insulation performance between the buffer layer and the aluminum sheath of the high-voltage cable, simulates the poor electrical contact caused by white spots between the buffer layer and the aluminum sheath in the defective cable, and can be applied to relevant verification experiments of various defective cable detection and repair methods.

[0050] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0051] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable ordinary technicians in the field to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made based on the essence of the content of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for manufacturing a high voltage cable for simulating defects, characterized in that: The following steps are involved: Drawing the conductor material into monofilaments and annealing, twisting and plying to form a conductor; Sequentially extruding a conductor shielding layer, an insulating layer and an insulating shielding layer around the outer periphery of the conductor; Winding outside the insulating shielding layer to form a buffer layer; Wrapping the corrugated insulation paper outside the buffer layer; the corrugated insulation paper is wound in a gap-type manner, the winding direction is oblique to the thread direction of the spiral corrugated aluminum sheath, and the gap width is 10% of the insulation tape width; the corrugated insulation paper has a thickness of 0.74 mm, a width of 38 mm, a power frequency breakdown strength of less than 3 kV / mm, and a voltage rise rate of 200 V / s; A spiral corrugated aluminum sheath is armored outside the corrugated insulating paper; the spiral corrugated aluminum sheath is made of aluminum or aluminum alloy with a purity of not less than 99.5%, and the thread pitch is 25mm. The spiral corrugated aluminum sheath adopts aluminum strip, and the elongation of the aluminum strip should not be less than 16%. After welding, the thickness of the air gap between the buffer layer and the spiral corrugated aluminum sheath is 6.6mm, wherein the thickness of the air gap is the maximum thickness of the air gap between the buffer layer at the top of the cable body and the inner side of the crest when the buffer layer is in close contact with the bottom of the trough of the spiral corrugated aluminum sheath under the action of gravity.

2. The method for manufacturing a high voltage cable for simulating defects according to claim 1, characterized in that: The conductor material is a soft round copper wire.

3. The method for manufacturing a high voltage cable for simulating defects according to claim 1, characterized in that: The conductor shielding layer, the insulating layer and the insulating shielding layer are extruded onto the outer periphery of the conductor by a three-layer co-extrusion method, wherein the conductor shielding layer and the insulating shielding layer are firmly bonded to the insulating layer respectively.

4. The method for manufacturing a high voltage cable for simulating defects according to claim 1, characterized in that: The conductor shielding layer and the insulating shielding layer are made of cross-linked semi-conductive shielding plastic, and the temperature resistance grade of the semi-conductive shielding plastic is compatible with the cross-linked polyethylene insulation. The connecting surface between the conductor shielding layer and the insulating layer is smooth and continuous. The physical property requirements of the semi-conductive shielding plastic are that at 23°C, its volume resistivity is less than 1.0Ω·m and its tensile strength is not less than 12.0MPa.

5. The method for manufacturing a high voltage cable for simulating defects according to claim 1, characterized in that: The insulating layer is made of filler-free cross-linked polyethylene, and the physical properties of the cross-linked polyethylene are required to be less than 2.35 and greater than 1.0×10 13 Ω·m, tensile strength 17MPa.

6. The method for manufacturing a high voltage cable for simulating defects according to claim 1, characterized in that: The buffer layer comprises a semi-conductive non-woven fabric layer and a semi-conductive fluffy cotton layer, wherein polyacrylate expansion powder is applied between the semi-conductive non-woven fabric and the semi-conductive fluffy cotton, and the volume resistivity of the buffer layer is greater than 1000Ω·m.

7. The method for manufacturing a high voltage cable for simulating defects according to claim 1, characterized in that: The buffer layer has a thickness of 2 mm, a width of 80 mm, and an overlap rate of 50%.

8. A cable manufactured by the method for manufacturing a high-voltage cable for simulating defects according to any one of claims 1 to 7, characterized in that: The cable comprises a conductor, a conductor shielding layer, an insulating layer, an insulating shielding layer, a buffer layer, corrugated insulating paper and a corrugated aluminum sheath which are arranged in sequence from the inside to the outside.

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