A fire-resistant medium-voltage power cable

Abstract

The present invention relates to the technical field of power cables, and provides a fireproof medium-voltage power cable, which sequentially includes a conductor, a conductor shielding layer, a cross-linked polyethylene insulation layer, an insulation shielding layer, a metal shielding layer, a fireproof wrapping layer, an oxygen barrier layer, a steel tape armor layer, and a sheath layer from inside to outside. A fireproof filler is arranged between the metal shielding layer and the fireproof wrapping layer. Through the above technical solution, the problem of poor fireproof performance of medium-voltage power cables in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power cables, and specifically, to a fireproof medium-voltage power cable. Background Art

[0002] With the development needs of society, the application fields of medium-voltage power cables are becoming more and more extensive, including urban power distribution, rural power grids, mine power systems, rail transit systems, etc. A medium-voltage power cable is composed of a conductor, an insulating layer, a sheath layer and other accessories. The conductor usually uses copper or aluminum, the insulating layer usually uses materials such as polyethylene, cross-linked polyethylene, and rubber, and the sheath layer usually uses polyolefin materials. Since the fireproof performance of power cables seriously affects life and property safety, the fireproof performance of power cables has attracted much attention from the public. How to provide a fireproof medium-voltage power cable is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0003] The present invention provides a fireproof medium-voltage power cable, which solves the problem of poor fireproof performance of medium-voltage power cables in the related art.

[0004] The technical solution of the present invention is as follows:

[0005] A fireproof medium-voltage power cable, which sequentially includes a conductor, a conductor shielding layer, a cross-linked polyethylene insulating layer, an insulating shielding layer, a metal shielding layer, a fireproof wrapping layer, an oxygen isolation layer, a steel tape armor layer and a sheath layer from inside to outside. A fireproof filler is arranged between the metal shielding layer and the fireproof wrapping layer.

[0006] As a further technical solution, the conductor is a copper conductor.

[0007] As a further technical solution, the metal shielding layer is a copper tape shielding layer.

[0008] As a further technical solution, the sheath layer is made of a low-smoke and halogen-free flame-retardant polyolefin material. The low-smoke and halogen-free flame-retardant polyolefin material includes the following components in parts by mass: 30-50 parts of ethylene-vinyl acetate copolymer, 20-40 parts of ethylene-butene copolymer, 10-30 parts of bimodal terpolymer, 70-90 parts of filler, 30-50 parts of modified metal hydroxide, 3-5 parts of lubricant, and 1-3 parts of antioxidant. The modified metal hydroxide is obtained by modifying metal hydroxide with maleic anhydride grafted polyethylene, aromatic aldehyde and potassium carbonate.

[0009] In order to further improve the fireproof performance of power cables, the present invention uses metal hydroxides modified by maleic anhydride grafted polyethylene, aromatic aldehydes, and potassium carbonate to improve the flame retardancy of the sheath material, thereby achieving the effect of further improving the fireproof performance of power cables. After being modified by maleic anhydride grafted polyethylene, aromatic aldehydes, and potassium carbonate, the metal hydroxides can improve the inorganic nature of the surface of the metal hydroxides. At the same time, during the processing and molding of power cables, maleic anhydride grafted polyethylene and aromatic aldehydes can react under the catalytic action of potassium carbonate to generate unsaturated double bonds and carboxyl groups, which act on the polyolefin serving as the matrix material of the sheath layer, improving the compatibility between the metal hydroxides and the polyolefin, thereby improving the tensile strength and elongation at break of the sheath material, and solving the problem in the prior art that the compatibility between the metal hydroxide flame retardant and the polyolefin material is poor, resulting in poor mechanical properties of the prepared sheath material, achieving the technical effect of improving the mechanical properties of medium-voltage power cables.

[0010] As a further technical solution, the raw materials of the modified metal hydroxides include metal hydroxides, maleic anhydride grafted polyethylene, aromatic aldehydes, and potassium carbonate with a mass ratio of 30-50:5:1-2:0.025-0.075.

[0011] The present invention limits the raw materials of the modified metal hydroxides to metal hydroxides, maleic anhydride grafted polyethylene, aromatic aldehydes, and potassium carbonate with a mass ratio of 30-50:5:1-2:0.025-0.075, further improving the tensile strength and elongation at break of the sheath material.

[0012] As a further technical solution, the metal hydroxides include one or both of magnesium hydroxide and aluminum hydroxide; the aromatic aldehydes include one or both of o-phthalaldehyde and p-phthalaldehyde.

[0013] As a further technical solution, the preparation method of the modified metal hydroxides includes the following steps: After mixing maleic anhydride grafted polyethylene, aromatic aldehydes, and potassium carbonate with a solvent, add metal hydroxides and continue to mix, filter, and dry to obtain the modified metal hydroxides.

[0014] As a further technical solution, the grafting rate of the maleic anhydride grafted polyethylene is 8%.

[0015] The present invention uses maleic anhydride grafted polyethylene with a grafting rate of 8%, further improving the tensile strength and elongation at break of the sheath material.

[0016] As a further technical solution, the filler includes one or both of carbon black and white carbon black.

[0017] As a further technical solution, the lubricant includes one or both of polyethylene wax and stearic acid.

[0018] The working principle and beneficial effects of the present invention are as follows:

[0019] The present invention provides a fire-resistant medium-voltage power cable, which sequentially includes a conductor, a conductor shielding layer, a cross-linked polyethylene insulating layer, an insulation shielding layer, a metal shielding layer, a fire-resistant wrapping layer, an oxygen barrier layer, a steel tape armor layer, and a sheath layer from inside to outside. A fire-resistant filler is arranged between the metal shielding layer and the fire-resistant wrapping layer. The obtained power cable has good fire-resistant performance, and its combustion performance meets the B1 (d2, t0, a1) level in GB 31247-2014 "Classification of the Combustion Performance of Cables and Optical Fibers". Specific embodiments

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work fall within the scope of protection of the present invention.

[0021] The parameters of the raw materials in the following examples and comparative examples are as follows:

[0022] The ethylene-vinyl acetate copolymer is EVA Yangzi BASF V5110J;

[0023] The ethylene-butene copolymer is POE 8180;

[0024] The bimodal terpolymer is bimodal terpolymer FK1820;

[0025] The carbon black is carbon black N550;

[0026] The white carbon black is 800-mesh precipitated white carbon black.

[0027] A fire-resistant medium-voltage power cable, which sequentially includes a copper conductor, a conductor shielding layer, a cross-linked polyethylene insulating layer, an insulation shielding layer, a copper tape shielding layer, a fire-resistant wrapping layer, an oxygen barrier layer, a steel tape armor layer, and a sheath layer from inside to outside. A fire-resistant filler is arranged between the copper tape shielding layer and the fire-resistant wrapping layer; the preparation method of the sheath layer is as follows:

[0028] Example 1

[0029] S1. Dissolve 5 g of maleic anhydride-grafted polyethylene with a grafting rate of 8%, 0.5 g of phthalaldehyde, and 0.05 g of potassium carbonate in 500 mL of water. Add 40 g of aluminum hydroxide and stir and mix at 500 rpm for 30 min. Filter and dry to obtain a modified metal hydroxide;

[0030] S2. Mix 40 parts of ethylene-vinyl acetate copolymer, 30 parts of ethylene-butene copolymer, 20 parts of bimodal terpolymer, 50 parts of carbon black, 30 parts of silica, 40 parts of modified metal hydroxide, 4 parts of stearic acid, and 2 parts of antioxidant 1010 evenly, then transfer them to an internal mixer for mixing. After the temperature reaches 160 °C, transfer them to a single-screw extruder and extrude at 170 °C outside the steel tape armor layer to obtain the sheath layer.

[0031] Example 2

[0032] S1. Dissolve 5 g of maleic anhydride-grafted polyethylene with a grafting rate of 8%, 0.5 g of terephthalaldehyde, and 0.025 g of potassium carbonate in 500 mL of water. Add 30 g of aluminum hydroxide and stir and mix at 500 rpm for 20 min, then filter and dry to obtain the modified metal hydroxide.

[0033] S2. Mix 30 parts of ethylene-vinyl acetate copolymer, 20 parts of ethylene-butene copolymer, 10 parts of bimodal terpolymer, 70 parts of carbon black, 30 parts of modified metal hydroxide, 3 parts of polyethylene wax, and 1 part of antioxidant 1010 evenly, then transfer them to an internal mixer for mixing. After the temperature reaches 160 °C, transfer them to a single-screw extruder and extrude at 170 °C outside the steel tape armor layer to obtain the sheath layer.

[0034] Example 3

[0035] S1. Dissolve 5 g of maleic anhydride-grafted polyethylene with a grafting rate of 8%, 0.5 g of terephthalaldehyde, and 0.075 g of potassium carbonate in 500 mL of water. Add 50 g of aluminum hydroxide and stir and mix at 500 rpm for 40 min, then filter and dry to obtain the modified metal hydroxide.

[0036] S2. Mix 50 parts of ethylene-vinyl acetate copolymer, 40 parts of ethylene-butene copolymer, 30 parts of bimodal terpolymer, 90 parts of silica, 50 parts of modified metal hydroxide, 5 parts of polyethylene wax, and 3 parts of antioxidant 1010 evenly, then transfer them to an internal mixer for mixing. After the temperature reaches 160 °C, transfer them to a single-screw extruder and extrude at 170 °C outside the steel tape armor layer to obtain the sheath layer.

[0037] Example 4

[0038] S1. Dissolve 5 g of maleic anhydride-grafted polyethylene with a grafting rate of 8%, 1 g of phthalaldehyde, and 0.05 g of potassium carbonate in 500 mL of water. Add 40 g of aluminum hydroxide and stir and mix at 500 rpm for 30 min, then filter and dry to obtain the modified metal hydroxide.

[0039] S2. Mix 40 parts of ethylene-vinyl acetate copolymer, 30 parts of ethylene-butene copolymer, 20 parts of bimodal terpolymer, 50 parts of carbon black, 30 parts of silica, 40 parts of modified metal hydroxide, 4 parts of stearic acid, and 2 parts of antioxidant 1010 evenly, then transfer them to an internal mixer for kneading. After the temperature reaches 160°C, transfer them to a single-screw extruder and extrude at 170°C on the outside of the steel tape armor layer to obtain the sheath layer.

[0040] Example 5

[0041] S1. Dissolve 5 g of maleic anhydride grafted polyethylene with a grafting rate of 8%, 1.5 g of phthalaldehyde, and 0.05 g of potassium carbonate in 500 mL of water. Add 40 g of aluminum hydroxide and stir and mix at 500 rpm for 30 min, then filter and dry to obtain the modified metal hydroxide.

[0042] S2. Mix 40 parts of ethylene-vinyl acetate copolymer, 30 parts of ethylene-butene copolymer, 20 parts of bimodal terpolymer, 50 parts of carbon black, 30 parts of silica, 40 parts of modified metal hydroxide, 4 parts of stearic acid, and 2 parts of antioxidant 1010 evenly, then transfer them to an internal mixer for kneading. After the temperature reaches 160°C, transfer them to a single-screw extruder and extrude at 170°C on the outside of the steel tape armor layer to obtain the sheath layer.

[0043] Example 6

[0044] S1. Dissolve 5 g of maleic anhydride grafted polyethylene with a grafting rate of 8%, 2 g of phthalaldehyde, and 0.05 g of potassium carbonate in 500 mL of water. Add 40 g of aluminum hydroxide and stir and mix at 500 rpm for 30 min, then filter and dry to obtain the modified metal hydroxide.

[0045] S2. Mix 40 parts of ethylene-vinyl acetate copolymer, 30 parts of ethylene-butene copolymer, 20 parts of bimodal terpolymer, 50 parts of carbon black, 30 parts of silica, 40 parts of modified metal hydroxide, 4 parts of stearic acid, and 2 parts of antioxidant 1010 evenly, then transfer them to an internal mixer for kneading. After the temperature reaches 160°C, transfer them to a single-screw extruder and extrude at 170°C on the outside of the steel tape armor layer to obtain the sheath layer.

[0046] Example 7

[0047] S1. Dissolve 5 g of maleic anhydride grafted polyethylene with a grafting rate of 8%, 2.5 g of phthalaldehyde, and 0.05 g of potassium carbonate in 500 mL of water. Add 40 g of aluminum hydroxide and stir and mix at 500 rpm for 30 min, then filter and dry to obtain the modified metal hydroxide.

[0048] S2. Mix 40 parts of ethylene-vinyl acetate copolymer, 30 parts of ethylene-butene copolymer, 20 parts of bimodal terpolymer, 50 parts of carbon black, 30 parts of silica, 40 parts of modified metal hydroxide, 4 parts of stearic acid, and 2 parts of antioxidant 1010 evenly, then transfer them to an internal mixer for mixing. After the temperature reaches 160°C, transfer them to a single-screw extruder and extrude at 170°C outside the steel tape armor layer to obtain a sheath layer.

[0049] Example 8

[0050] S1. Dissolve 5 g of maleic anhydride-grafted polyethylene with a grafting rate of 1.2%, 1.5 g of phthalaldehyde, and 0.05 g of potassium carbonate in 500 mL of water. Add 40 g of aluminum hydroxide and stir and mix at 500 rpm for 30 min, then filter and dry to obtain a modified metal hydroxide.

[0051] S2. Mix 40 parts of ethylene-vinyl acetate copolymer, 30 parts of ethylene-butene copolymer, 20 parts of bimodal terpolymer, 50 parts of carbon black, 30 parts of silica, 40 parts of modified metal hydroxide, 4 parts of stearic acid, and 2 parts of antioxidant 1010 evenly, then transfer them to an internal mixer for mixing. After the temperature reaches 160°C, transfer them to a single-screw extruder and extrude at 170°C outside the steel tape armor layer to obtain a sheath layer.

[0052] Comparative Example 1

[0053] Mix 40 parts of ethylene-vinyl acetate copolymer, 5 parts of maleic anhydride-grafted polyethylene with a grafting rate of 8%, 0.5 part of phthalaldehyde, 0.05 part of potassium carbonate, 30 parts of ethylene-butene copolymer, 20 parts of bimodal terpolymer, 50 parts of carbon black, 30 parts of silica, 40 parts of metal hydroxide, 4 parts of stearic acid, and 2 parts of antioxidant 1010 evenly, then transfer them to an internal mixer for mixing. After the temperature reaches 160°C, transfer them to a single-screw extruder and extrude at 170°C outside the steel tape armor layer to obtain a sheath layer.

[0054] Comparative Example 2

[0055] S1. Dissolve 5 g of maleic anhydride-grafted polyethylene with a grafting rate of 8% in 500 mL of water. Add 40 g of aluminum hydroxide and stir and mix at 500 rpm for 30 min, then filter and dry to obtain a modified metal hydroxide.

[0056] S2. Mix 40 parts of ethylene-vinyl acetate copolymer, 30 parts of ethylene-butene copolymer, 20 parts of bimodal terpolymer, 50 parts of carbon black, 30 parts of silica, 40 parts of modified metal hydroxide, 4 parts of stearic acid, and 2 parts of antioxidant 1010 evenly, then transfer them to an internal mixer for mixing. After the temperature reaches 160°C, transfer them to a single-screw extruder and extrude at 170°C outside the steel tape armor layer to obtain a sheath layer.

[0057] Comparative Example 3

[0058] 40 parts of ethylene-vinyl acetate copolymer, 5 parts of maleic anhydride grafted polyethylene with a grafting rate of 8%, 30 parts of ethylene-butene copolymer, 20 parts of bimodal terpolymer, 50 parts of carbon black, 30 parts of silica, 40 parts of metal hydroxide, 4 parts of stearic acid, and 2 parts of antioxidant 1010 were mixed evenly and then transferred to an internal mixer for mixing. After the temperature reached 160 °C, it was transferred to a single-screw extruder and extruded at 170 °C outside the steel tape armor layer to obtain a sheath layer.

[0059] The sheath layers obtained in Examples 1 to 8 and Comparative Examples 1 to 3 were cut into dumbbell specimens according to the method in GB / T 2951.11-2008 for testing the tensile strength and elongation at break, and the test results were recorded in Table 1.

[0060] Table 1 Tensile strength and elongation at break of the sheath layer

[0061]

[0062] As can be seen from Table 1, the tensile strength of the sheath layer provided by the present invention is above 14.5 N / mm 2 ² or more, and the elongation at break is above 527%, having good mechanical properties.

[0063] Compared with Comparative Examples 1 to 3, the tensile strength and elongation at break of the sheath layers prepared by adding metal hydroxides modified with maleic anhydride grafted polyethylene, aromatic aldehyde, and potassium carbonate in Examples 1 to 8 are higher than those in Comparative Examples 1 to 3, indicating that using metal hydroxides modified with maleic anhydride grafted polyethylene, aromatic aldehyde, and potassium carbonate as flame retardants can improve the mechanical properties of the sheath material.

[0064] The tensile strength and elongation at break of the sheath layers obtained in Examples 4 to 6 are higher than those in Examples 1 and 7, indicating that the mass ratio of metal hydroxide, maleic anhydride grafted polyethylene, aromatic aldehyde, and potassium carbonate of 30 to 50:5:1 to 2:0.025 to 0.075 can further improve the mechanical properties of the sheath material.

[0065] The fire-resistant medium-voltage power cables obtained in Example 5 were subjected to various performance tests. When tested according to GB / T 31248-2014, the test specimens consisted of 4 cables (average outer diameter 59 mm), each 3.5 mm long. The cables were installed at intervals, the heat source was 20.5 kW, and the fire supply time was 20 min; other test samples were prepared according to the relevant standard requirements, and the test results were recorded in Table 2.

[0066] Table 2 Various properties of the fire-resistant medium-voltage power cable

[0067]

[0068] As can be seen from Table 2, the combustion performance of the medium-voltage power cable provided by the present invention meets the B1 (d2, t0, a1) level in GB 31247-2014 "Classification of the Combustion Performance of Cables and Optical Fibre Cables".

[0069] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A fireproof medium voltage power cable, characterized in that: It includes, from inside to outside, a conductor, a conductor shielding layer, a cross-linked polyethylene insulation layer, an insulation shielding layer, a metal shielding layer, a fire-resistant wrapping layer, an oxygen-isolating layer, a steel belt armoring layer and a sheathing layer, wherein a fire-resistant filler is arranged between the metal shielding layer and the fire-resistant wrapping layer; The sheath layer is made of a low-smoke, halogen-free, flame-retardant polyolefin material, which includes the following components in parts by weight: 30-50 parts of ethylene-vinyl acetate copolymer, 20-40 parts of ethylene-butene copolymer, 10-30 parts of bimodal ternary polymer, 70-90 parts of filler, 30-50 parts of modified metal hydroxide, 3-5 parts of lubricant, and 1-3 parts of antioxidant, wherein the modified metal hydroxide is obtained by modifying metal hydroxide by maleic anhydride grafted polyethylene, aromatic aldehyde and potassium carbonate; After the components of the low-smoke halogen-free flame-retardant polyolefin material are uniformly mixed, they are transferred to an internal mixer for mixing. After the temperature reaches 160° C., they are transferred to a single-screw extruder and extruded at 170° C. onto the outside of the steel belt armor layer to obtain a sheath layer.

2. A fireproof medium voltage power cable according to claim 1, characterized in that: The conductor is a copper conductor.

3. A fireproof medium voltage power cable according to claim 1, characterized in that: The metal shielding layer is a copper tape shielding layer.

4. A fireproof medium voltage power cable according to claim 1, characterized in that: The raw materials of the modified metal hydroxide include metal hydroxide, maleic anhydride grafted polyethylene, aromatic aldehyde and potassium carbonate in a mass ratio of 30-50:5:1-2:0.025-0.

075.

5. A fireproof medium voltage power cable according to claim 4, characterized in that: The metal hydroxide includes one or both of magnesium hydroxide and aluminum hydroxide; the aromatic aldehyde includes one or both of o-phthalaldehyde and terephthalaldehyde.

6. A fireproof medium voltage power cable according to claim 4, characterized in that: The preparation method of the modified metal hydroxide comprises the following steps: mixing maleic anhydride grafted polyethylene, aromatic aldehyde, potassium carbonate and solvent, adding metal hydroxide, continuing to mix, filtering and drying to obtain the modified metal hydroxide.

7. A fireproof medium voltage power cable according to claim 4, characterized in that: The grafting rate of the maleic anhydride grafted polyethylene is 8%.

8. A fireproof medium voltage power cable according to claim 1, characterized in that: The filler includes one or both of carbon black and white carbon black.

9. A fireproof medium voltage power cable according to claim 1, characterized in that: The lubricant includes one or both of polyethylene wax and stearic acid.

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