0.6 / 1kV crosslinked polyethylene cable and preparation method thereof

Abstract

The invention discloses a 0.6 / 1kV cross-linked polyethylene cable and a preparation method thereof, and relates to the technical field of cross-linked polyethylene cables, the 0.6 / 1kV cross-linked polyethylene cable comprises a wire core, a cross-linked polyethylene bottom layer, a protective outer layer and a composite protective layer, and the composite protective layer is prepared by mixing expanded graphite and a thermal response hard generator; when the thermal response hard generating agent is heated and is at the heating reaction temperature, a solid hard object used for improving the hardness of the composite protection layer is generated, and after the expanded graphite is heated to expand and the thermal response hard generating agent is heated to generate the solid hard object, it can be guaranteed that the composite protection layer has the good hardness, and the service life of the composite protection layer is prolonged. When the composite protective layer is impacted in the heating process, the composite protective layer can still resist impact by using a solid hard object generated by heating, so that the situation that the impact resistance of the composite protective layer is seriously reduced after the expanded graphite is heated and expanded is avoided; therefore, the cross-linked polyethylene bottom layer and the wire cores in the cross-linked polyethylene bottom layer can still be well protected after the composite protection layer is impacted in the heating process.

Description

Technical Field

[0001] The invention relates to the technical field of cross-linked polyethylene cables, and in particular to a 0.6 / 1 kV cross-linked polyethylene cable and a preparation method thereof. Background Art

[0002] 0.6 / 1kV cross-linked polyethylene cable is commonly used in medium and low voltage distribution networks. "0.6 / 1kV" refers to the rated voltage of the cable. Among them, 0.6kV is the phase voltage and 1kV is the line voltage. In a three-phase AC system, the line voltage is about 3 times the square root of the phase voltage. For this type of cable, it is mainly used in a three-phase four-wire system, and its phase voltage is 0.6kV and the line voltage is about 1kV. This represents the voltage range in which the cable can work stably for a long time, and is a key parameter for the design and use of cables. The main insulation material of the cable is cross-linked polyethylene. Cross-linked polyethylene is a material that forms a cross-linked structure between polyethylene molecular chains by chemical or physical methods. This structure gives the cable excellent electrical properties, such as high insulation resistance and low dielectric loss, and can also improve the cable's heat resistance, mechanical properties and environmental stress cracking resistance, so that the cable can work normally under a certain temperature and mechanical stress, ensuring the safety and stability of power transmission.

[0003] The structure of 0.6 / 1kV cross-linked polyethylene cable is as follows: China Utility Model "0.6 / 1kV and below cross-linked polyethylene nylon composite insulation PVC sheath control cable" with announcement number CN2446638Y, which is a cross-linked polyethylene insulation extruded on the conductor, and then nylon insulation is set on the cross-linked polyethylene insulation, and a PVC sheath is set outside the cable core composed of conductor cross-linked polyethylene insulation and nylon insulation. In order to improve its flame retardant performance, some 0.6 / 1kV cross-linked polyethylene cables will also fill expanded graphite between the cross-linked polyethylene insulation layer as the bottom layer and the PVC sheath as the outer layer.

[0004] When the cable encounters high temperature or fire, the expanded graphite will expand rapidly to form a "worm-like" graphite expanded material, which covers the internal cross-linked polyethylene substrate, thereby isolating the contact between oxygen and the substrate, preventing the continuous combustion reaction, and also effectively blocking the transfer of heat, reducing the heat radiation of the flame to the unburned part, and preventing the spread of fire; the expanded graphite will absorb a large amount of heat during the process of thermal expansion, thereby reducing the temperature of the surrounding environment and the cross-linked polyethylene cable substrate, slowing down the thermal decomposition rate of the cross-linked polyethylene, making it difficult to reach the temperature conditions required for combustion, thereby inhibiting the occurrence and development of combustion; However, the expanded graphite forms a loose and porous worm-like structure with relatively poor mechanical stability. When the cable is hit or squeezed by external force, it is easy to deform and break, which can easily lead to direct destruction of the expanded graphite layer and expose the cross-linked polyethylene substrate structure of the bottom layer of the cable. Once its structure is destroyed, it cannot effectively perform its flame retardant and heat insulating functions. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings, the present invention aims to provide a technical solution that can solve the above-mentioned problems.

[0006] To achieve the above object, the present invention provides the following technical solution: a 0.6 / 1kV cross-linked polyethylene cable, comprising Wire core; A cross-linked polyethylene bottom layer, which is arranged on the outside of the wire core; A protective outer layer, which is arranged on the outside of the cross-linked polyethylene bottom layer; A composite protective layer, which is disposed between the protective outer layer and the cross-linked polyethylene bottom layer; The composite protective layer is made by mixing at least expanded graphite and a thermally responsive hard generating agent, and the composite protective layer forms a coating on the cross-linked polyethylene bottom layer; when the thermally responsive hard generating agent is heated and at a thermal reaction temperature, it generates a solid hard material for increasing the hardness of the composite protective layer.

[0007] As a further solution of the present invention: the thermally responsive hardness generating agent is composed of: The thermal response temperature T1 of the thermal response hard material generating agent to generate the solid hard material is greater than the lowest temperature T of the expanded graphite when it is thermally expanded.

[0008] As a further embodiment of the present invention, the thermally responsive hardness generating agent is composed of: The total volume V1 of the solid hard material generated after heating is smaller than the total volume V of the thermally responsive hard generating agent before heating.

[0009] As a further solution of the present invention: the thermally responsive hard generating agent is a powdered thermally responsive hard generating agent with a particle size less than 50 μm.

[0010] As a further solution of the present invention: a support layer is arranged between the composite protective layer and the protective outer layer, and the support layer is structured so that a redundant expansion space is formed between the composite protective layer and the protective outer layer.

[0011] As a further solution of the present invention: the support layer is a shock-absorbing support layer made of shock-absorbing material.

[0012] As a further solution of the present invention: the support layer is arranged in a spiral shape and is wound on the outer side of the composite protective layer along the length direction of the wire core; The support layer is constructed so that the expansion redundant space forms a spiral directional expansion redundant space which is arranged between the composite protective layer and the protective outer layer along the spiral direction of the support layer and along the length direction of the wire core.

[0013] Compared with the existing technology, the beneficial effects of this technical solution are: When the thermally responsive hard generating agent is heated and at a thermal reaction temperature, a solid hard material with relatively high hardness is generated accordingly; when the expanded graphite is heated to expand and the thermally responsive hard generating agent is heated to generate a solid hard material, it can ensure that the composite protective layer has a better hardness, so that when the composite protective layer is impacted during the heating process, the solid hard material generated by the heating can still be used to resist the impact, thereby avoiding a serious decrease in the impact resistance of the composite protective layer due to the thermal expansion of the expanded graphite, thereby effectively ensuring that the composite protective layer can still better protect the cross-linked polyethylene bottom layer and the wire core inside it after being impacted during the heating process.

[0014] The present invention provides the following technical solution: A method for preparing a 0.6 / 1kV cross-linked polyethylene cable comprises the following steps: S1, mixing expanded graphite and a thermally responsive hard generating agent to prepare a composite protective material; S2, coating the composite protective material obtained in step S1 on the outer side of the cross-linked polyethylene bottom layer having the wire core to form a composite protective layer; S3. Cover the outer side of the composite protective layer with a protective outer layer.

[0015] As a further solution of the present invention: in step S1, a binder is added for mixing to make the composite protective material in a paste state; in step S2, the paste-like composite protective material is coated on the outside of the cross-linked polyethylene bottom layer by coating.

[0016] As a further solution of the present invention: in step S1, the mixing ratio of expanded graphite and thermally responsive hardness generating agent is any ratio between 1:2-1:5.

[0017] Compared with the prior art, the beneficial effects of this technical solution are: The cable prepared by the method has a thermally responsive hard generating agent that generates a solid hard material with relatively high hardness when heated and at a thermal reaction temperature; after the expanded graphite is heated to expand and the thermally responsive hard generating agent is heated to generate a solid hard material, the composite protective layer can be guaranteed to have a better hardness, so that when the composite protective layer is impacted during the heating process, the solid hard material generated by the heating can still be used to resist the impact, thereby avoiding a serious decrease in the impact resistance of the composite protective layer due to the thermal expansion of the expanded graphite, thereby effectively ensuring that the composite protective layer can still better protect the cross-linked polyethylene bottom layer and the wire core inside it after being impacted during the heating process.

[0018] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0020] Figure 1 is a cross-sectional view of the cable structure of the present invention; Figure 2 It is a flow chart of cable preparation of the present invention. DETAILED DESCRIPTION

[0021] 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 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.

[0022] See also Figure 1-2 In this embodiment, a 0.6 / 1kV cross-linked polyethylene cable includes a core 1, a cross-linked polyethylene bottom layer 2, a protective outer layer 3 and a composite protective layer 4. The cross-linked polyethylene bottom layer 2 is arranged on the outside of the core 1, the protective outer layer 3 is arranged on the outside of the cross-linked polyethylene bottom layer 2, and the composite protective layer 4 is arranged between the protective outer layer 3 and the cross-linked polyethylene bottom layer 2.

[0023] In some embodiments, the cross-linked polyethylene bottom layer 2 may be a layer adjacent to the core 1 .

[0024] In some embodiments, the cross-linked polyethylene bottom layer may be a layer not adjacent to the wire core, and the cross-linked polyethylene bottom layer is configured to protect the wire core. For example, there is at least one first functional layer between the cross-linked polyethylene bottom layer and the wire core, and part of the first functional layer is, for example, an insulating layer.

[0025] If the wire core is a copper core and has multiple bundles of wire cores, each bundle of wire cores is covered by a corresponding PE insulation layer, the cross-linked polyethylene bottom layer simultaneously covers the multiple bundles of wire cores covered with PE insulation layers, and the gap between the cross-linked polyethylene bottom layer and the PE insulation layer is filled with filling rope.

[0026] In some embodiments, the composite protective layer may be an adjacent layer to the cross-linked polyethylene base layer.

[0027] In some embodiments, the composite protective layer 4 may be a layer not adjacent to the cross-linked polyethylene bottom layer 2, and the composite protective layer 4 is configured to protect the cross-linked polyethylene bottom layer 2. For example, there is at least one second functional layer between the cross-linked polyethylene bottom layer 2 and the composite protective layer 4, and part of the second functional layer is, for example, a PVC inner sheath layer 7.

[0028] For example, there are multiple bundles of wire cores 1, each bundle of wire cores 1 is coated with a corresponding cross-linked polyethylene bottom layer 2, and the PVC inner sheath layer 7 simultaneously coats the multiple bundles of wire cores 1 coated with the cross-linked polyethylene bottom layer 2, and the gap between the PVC inner sheath layer 7 and the cross-linked polyethylene bottom layer 2 is filled with a filler 8, such as a filling rope, and the composite protective layer 4 is coated on the outside of the PVC inner sheath layer 7.

[0029] In some embodiments, the protective outer layer 3 is, for example, a PVC sheath layer.

[0030] In this embodiment, the composite protective layer 4 is made of at least expanded graphite mixed with a thermally responsive hard generating agent, and the cross-linked polyethylene bottom layer is coated by the composite protective layer 4. When the thermally responsive hard generating agent is heated and at a thermal reaction temperature, a solid hard material with a relatively high hardness is generated.

[0031] When the expanded graphite expands when heated and the thermally responsive hard generating agent generates solid hard material when heated, the composite protective layer 4 can have a better hardness, so that when the composite protective layer 4 is impacted during the heating process, the solid hard material generated by the heating can still be used to resist the impact, thereby avoiding a serious decrease in the impact resistance of the composite protective layer 4 due to the expansion of the expanded graphite when heated, thereby effectively ensuring that the composite protective layer 4 can still better protect the cross-linked polyethylene bottom layer 2 and the wire core 1 inside it after being impacted during the heating process.

[0032] In this embodiment, the heat-responsive hard generating agent is configured as follows: the heat-responsive temperature T1 of the heat-responsive hard generating agent to generate a solid hard object is greater than the lowest temperature T of the thermal expansion of the expanded graphite. In the process of gradually increasing the heating temperature, the expanded graphite with a lower thermal expansion temperature is first thermally expanded to increase the flame retardant and heat insulation capabilities of the cable, and then the heat-responsive hard generating agent with a higher thermal response temperature generates a solid hard object to avoid excessive restriction of the expansion of the expanded graphite due to the early generation of the solid hard object.

[0033] In this embodiment, the thermally responsive hard generator is configured such that the total volume V1 of the solid hard material generated after being heated is less than the total volume V of the thermally responsive hard generator before being heated. When the thermally responsive hard generator is heated and generates solid hard materials, the space occupied by the solid hard materials is reduced compared to the space occupied by the thermally responsive hard generator before being heated. After the volume is reduced, the gap between the adjacent expanded graphites can be better filled, and heat and oxygen can be better prevented from passing through the gap.

[0034] Preferably, the thermally responsive hard generating agent is a powdered thermally responsive hard generating agent with a particle size of less than 50 μm, so as to achieve a better filling effect.

[0035] In this embodiment, a support layer 5 is provided between the composite protective layer 4 and the protective outer layer 3 , and the support layer 5 is configured to form an expansion redundant space 6 between the composite protective layer 4 and the protective outer layer 3 .

[0036] In this embodiment, the support layer 5 is a shock-absorbing support layer made of shock-absorbing material.

[0037] In some embodiments, the support layer 5 is a shock-absorbing support layer made of TPE elastic material, for example.

[0038] In this embodiment, the supporting layer 5 is arranged in a spiral shape and is wound on the outer side of the composite protective layer 4 along the length direction of the wire core 1; the supporting layer 5 is configured to form a spiral directional expansion redundant space 6 along the spiral direction of the supporting layer 5 and wound along the length direction of the wire core 1 between the composite protective layer 4 and the protective outer layer 3.

[0039] Under normal use, the combination of the expansion redundant space 6 and the shock-absorbing support layer can form support shock absorption and airbag shock absorption, so that the cable has good shock resistance.

[0040] When heated, the redundant expansion space 6 can provide a better expansion space for the expanded graphite, thereby preventing the expanded graphite from excessively squeezing the cross-linked polyethylene bottom layer 2 and the inner wire core during expansion.

[0041] When heated at a continuous high temperature, the spiral directional expansion redundant space formed by the support layer 5 allows the expanded graphite to be guided to expand in a directional manner. On the one hand, the expanded graphite can expand in a directional manner along the guiding direction to avoid concentrated expansion, thereby avoiding concentrated squeezing of the cross-linked polyethylene bottom layer 2 and the internal wire core 1. On the other hand, the expanded graphite is expanded in a wrapped manner around the cross-linked polyethylene bottom layer 2 through the guiding direction, that is, after directional expansion along the spiral directional expansion redundant space, the expanded graphite can form a spiral wrapping around the cross-linked polyethylene bottom layer 2 as much as possible, making the flame retardancy of the cross-linked polyethylene bottom layer 2 more uniform.

[0042] In this embodiment, the temperature at which the expanded graphite begins to expand is between 200 and 300°C, and the thermally responsive hard generating agent is selected, for example, from a material having a thermal decomposition temperature between 340°C and 490°C. It can react thermally according to the following process The solid hard material generated accordingly has high hardness and good flame retardancy. The above-mentioned heat-responsive hardening agent, when reacting with heat to generate a solid hard material, also generates a gaseous substance that can dilute the concentration of combustible gas and oxygen. Preferably, when there is also an expansion redundant space 6, the expansion redundant space 6 is also configured to provide space for the above-mentioned gaseous products to avoid causing excessive pressure.

[0043] In this embodiment, a method for preparing a 0.6 / 1 kV cross-linked polyethylene cable is also provided. The method comprises the following steps: S1, mixing expanded graphite and a thermally responsive hard generating agent to prepare a composite protective material; S2, coating the composite protective material obtained in step S1 on the outer side of the cross-linked polyethylene bottom layer having the wire core to form a composite protective layer; S3. Cover the outer side of the composite protective layer with a protective outer layer.

[0044] In some embodiments, in step S3, a support layer is firstly sleeved on the outer side of the composite protective layer, and then the protective outer layer is coated on the support layer on the outer side of the composite protective layer. After the protective outer layer is coated, the support layer is structured so that a redundant expansion space is formed between the composite protective layer and the protective outer layer.

[0045] In some embodiments, in step S3, the protective outer layer is made of, for example, PVC material and is coated on the support layer outside the composite protective layer by extrusion.

[0046] In some embodiments, the support layer installed in step S3 is made of shock-absorbing material.

[0047] In some embodiments, the support layer sleeved in step S3 is arranged in a spiral shape and is wound on the outside of the composite protective layer along the length direction of the wire core; after being coated with the protective outer layer, the support layer is constructed so that the expansion redundant space forms a spiral directional expansion redundant space along the spiral direction of the support layer and wound between the composite protective layer and the protective outer layer along the length direction of the wire core.

[0048] In some embodiments, in step S1, the mixing ratio of expanded graphite to thermally responsive hardness generating agent is any ratio between 1:2-1:5.

[0049] In some embodiments, in step S1, a volatile binder is added for mixing to make the composite protective material in a paste state; in step S2, the paste-like composite protective material can be coated on the outside of the cross-linked polyethylene bottom layer by a common coating device.

[0050] In some embodiments, the binder is, for example, a terpene resin having a volatilization temperature of 150° C.-180° C. After the paste-like composite protective material is coated on the outside of the cross-linked polyethylene bottom layer, if the content of the binder needs to be reduced, the binder can be volatilized by heating to 150° C.-180° C. (lower than the temperature at which expanded graphite begins to expand).

[0051] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A 0.6 / 1kV cross-linked polyethylene cable, characterized in that: include Wire core; A cross-linked polyethylene bottom layer, which is arranged on the outside of the wire core; A protective outer layer, which is arranged on the outside of the cross-linked polyethylene bottom layer; A composite protective layer, which is disposed between the protective outer layer and the cross-linked polyethylene bottom layer; The composite protective layer is made by mixing at least expanded graphite and a thermally responsive hard generating agent, and the composite protective layer forms a coating on the cross-linked polyethylene bottom layer; when the thermally responsive hard generating agent is heated and at a thermal reaction temperature, it generates a solid hard material for increasing the hardness of the composite protective layer.

2. The 0.6 / 1 kV cross-linked polyethylene cable according to claim 1, characterized in that: The composition of the thermally responsive hardness generating agent is: The thermal response temperature T1 of the thermal response hard material generating agent to generate the solid hard material is greater than the lowest temperature T of the expanded graphite when it is thermally expanded.

3. The 0.6 / 1 kV cross-linked polyethylene cable according to claim 1 or 2, characterized in that: The composition of the thermally responsive hardness generating agent is: The total volume V1 of the solid hard material generated after heating is smaller than the total volume V of the thermally responsive hard generating agent before heating.

4. The 0.6 / 1 kV cross-linked polyethylene cable according to claim 3, characterized in that: The thermally responsive hard generating agent is a powdered thermally responsive hard generating agent with a particle size of less than 50 μm.

5. The 0.6 / 1 kV cross-linked polyethylene cable according to claim 1, 2 or 4, characterized in that: A support layer is arranged between the composite protective layer and the protective outer layer, and the support layer is structured so that a redundant expansion space is formed between the composite protective layer and the protective outer layer.

6. The 0.6 / 1 kV cross-linked polyethylene cable according to claim 5, characterized in that: The support layer is a shock-absorbing support layer made of shock-absorbing material.

7. The 0.6 / 1 kV cross-linked polyethylene cable according to claim 5, characterized in that: The support layer is arranged in a spiral shape and is wound on the outer side of the composite protective layer along the length direction of the wire core; The support layer is constructed so that the expansion redundant space forms a spiral directional expansion redundant space which is arranged between the composite protective layer and the protective outer layer along the spiral direction of the support layer and along the length direction of the wire core.

8. A method for preparing a 0.6 / 1 kV cross-linked polyethylene cable, used for preparing the 0.6 / 1 kV cross-linked polyethylene cable according to any one of claims 1 to 7, characterized in that: The following steps are included S1, mixing expanded graphite and a thermally responsive hard generating agent to prepare a composite protective material; S2, coating the composite protective material obtained in step S1 on the outer side of the cross-linked polyethylene bottom layer having the wire core to form a composite protective layer; S3. Cover the outer side of the composite protective layer with a protective outer layer.

9. The preparation method according to claim 8, characterized in that: In step S1, a binder is added and mixed to make the composite protective material in a paste state; in step S2, the paste-like composite protective material is coated on the outside of the cross-linked polyethylene bottom layer by coating.

10. The preparation method according to claim 8, characterized in that: In step S1, the mixing ratio of expanded graphite and thermally responsive hardness generating agent is any ratio in the range of 1:2-1:5.

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