A power cable for high-speed rail vehicles based on polyolefin insulation

Abstract

A power cable for high-speed rail vehicles based on a polyolefin insulation layer, the structure of which is: from the inside to the outside, it is a conductor, a semi-conductive tape layer, an insulating layer, a barrier tape layer, a braided shielding layer and a sheath layer; the conductor is composed of a plurality of tinned copper wire bundles, which are then twisted to form a conductor; the semi-conductive tape layer is composed of a wrapped semi-conductive tape; the insulating layer is composed of an extruded polyolefin insulation material; the barrier tape layer is composed of a low-smoke halogen-free flame-retardant tape; the braided shielding layer is braided by tinned copper wires; the sheath layer is composed of an extruded low-smoke halogen-free flame-retardant sheath material; the polyolefin insulation material is made of syndiotactic polypropylene as the base resin, ultra-high molecular weight polyethylene as the modified resin, nanopowder with high bandgap width, high critical breakdown electric field and small dielectric constant as the modifier, and a compound antioxidant. This cable has the characteristics of better salt spray resistance, low temperature resistance, high flame retardancy, low toxicity, high oil resistance, and environmental protection.

Description

Technical Field

[0001] The technical solution relates to the field of cable technology, in particular to power cables for high-speed rail vehicles. Background Art

[0002] With the independent research and development of the new generation of standard EMU "Fuxing", our EMU manufacturing technology has been further improved. The current CR400AF EMU can run at a speed of 350km / h. Due to the complex operating environment of the train, including the extremely cold Northeast, the hot Hainan, and the humid coastal cities, the requirements for parts have also been raised. The cables need to meet the requirements of salt spray resistance, low toxicity, environmental protection, low temperature resistance, high flame retardancy, etc. These requirements put forward specific requirements for the cable materials used in the cables, that is, the cable materials with corresponding functions must be used, and the products must be manufactured using existing production equipment.

[0003] During the design and production process, it was found that due to the use of functional cable materials, it was not possible to obtain the product simply by replacing the materials. The main reason was that the electrical insulation performance and mechanical protection performance of the functional cable materials were quite different from those of the existing cable materials, and the thickness of the functional layer and the inner and outer adjacent relationship of the functional layer needed to be redesigned. This also required the conductor structure to be redesigned, because the conductor structure has the greatest impact on the cable's tensile strength, bending and other properties, and the conductor is also the core factor of the cable's conductive performance.

[0004] Therefore, the research and development of power cables for new high-speed rail vehicles is of great significance. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, this technical solution proposes a power cable for high-speed rail vehicles, the conductor adopts the sixth type of tinned copper super-soft conductor, the insulation adopts high-electricity halogen-free flame-retardant polyolefin material, and the sheath adopts salt spray-resistant, low-temperature-resistant, environmentally friendly low-smoke halogen-free flame-retardant material. The cable structure is:

[0006] A power cable for high-speed rail vehicles based on a polyolefin insulation layer, the structure of which is: from the inside to the outside, it is a conductor 1, a semi-conductive tape layer 2, an insulating layer 3, an isolation tape layer 4, a braided shielding layer 5 and a sheath layer 6;

[0007] The conductor 1 is characterized in that a plurality of tinned copper wires are bundled into strands, and the strands are then twisted to form a conductor;

[0008] The semi-conductive tape layer 2 is composed of a conductor wrapped with a semi-conductive tape;

[0009] The insulating layer 3 is composed of extruded polyolefin insulating material;

[0010] The isolation tape layer 4 is composed of a wrapped low-smoke halogen-free flame retardant tape;

[0011] The braided shielding layer 5 is braided from tinned copper wires;

[0012] The sheath layer 6 is made of extruded low-smoke halogen-free flame-retardant sheath material;

[0013] The conductor is made of tinned copper conductor of type 6 specified in IEC60228;

[0014] The wrapping tape overlap rate of the semi-conductive tape layer is 40% to 45%;

[0015] The braiding density of the braided shielding layer is not less than 80%;

[0016] The polyolefin insulating material is prepared by using syndiotactic polypropylene as base resin, ultra-high molecular weight polyethylene as modified resin, nanometer powder with high bandgap width, high critical breakdown electric field and small dielectric constant as modifier, and a compound antioxidant.

[0017] The bundling direction of the tinned copper monofilaments of the strands is left-handed, and the bundled pitch-diameter ratio is 30 to 35 times; the bundled strands are then twisted according to the pitch-diameter ratio of 8 to 10.

[0018] According to the mass percentage, the formula of the polyolefin insulation material is:

[0019] Syndiotactic polypropylene 70-90 parts

[0020] Ultra-high molecular weight polyethylene 10-30 parts

[0021] Modifier 1-3 parts

[0022] Antioxidant 0.5-2 parts

[0023] The number average molecular weight of ultra-high molecular weight polyethylene is 600,000 to 7,000,000, and the density is 0.930 to 0.970 g / cm 3 ;

[0024] The bandgap width of the modifier is ≥3.2eV, the breakdown field strength of the material is ≥45kV / mm, and the dielectric constant is ≤2.1 at room temperature;

[0025] The antioxidant is a compound antioxidant prepared by compounding any one of antioxidant 300, antioxidant 1076, antioxidant 1035 and antioxidant 1330 with antioxidant 802.

[0026] The applicable relationship between ultra-high molecular weight polyethylene and syndiotactic polypropylene is:

[0027] The number average molecular weight of the ultra-high molecular weight polyethylene is 6*10 5 ~2*10 6 , then: the mass fraction of syndiotactic polypropylene is 85-90 parts, and the mass fraction of ultra-high molecular weight polyethylene is 10-15 parts;

[0028] The number average molecular weight of the ultra-high molecular weight polyethylene is 2*10 6 ~3*10 6 , then: the mass fraction of syndiotactic polypropylene is 80-85 parts, and the mass fraction of ultra-high molecular weight polyethylene is 15-20 parts;

[0029] The number average molecular weight of the ultra-high molecular weight polyethylene is 3*10 6 ~5*10 6 , then: the mass fraction of syndiotactic polypropylene is 75-80 parts, and the mass fraction of ultra-high molecular weight polyethylene is 20-25 parts;

[0030] The number average molecular weight of the ultra-high molecular weight polyethylene is 5*10 6 ~7*10 6 , then: the mass fraction of syndiotactic polypropylene is 70-75 parts, and the mass fraction of ultra-high molecular weight polyethylene is 25-30 parts;

[0031] The modifier is one of nano-silicon dioxide aerogel powder, nano-titanium dioxide or nano-silicon carbide;

[0032] In the compound antioxidant: the mass of antioxidant 802 is 2 parts; the mass of antioxidant 300, antioxidant 1076, antioxidant 1035 or antioxidant 1330 is 3 parts.

[0033] The insulating material uses syndiotactic polypropylene as the base resin, which can improve the overall temperature resistance level of the material and meet higher operating temperatures without cross-linking; at the same time, the low-temperature resistance of the material is better than that of the material using isotactic and atactic polypropylene as the base resin.

[0034] Compared with conventional polyethylene (including low-density, medium-density and high-density polyethylene), ultra-high molecular weight polyethylene has better low-temperature resistance (low-temperature resistance can reach -169°C). At the same time, compared with conventional toughening and modified resins used to improve low-temperature resistance, this solution has a higher melting point, ensuring the overall temperature resistance level of the material. In addition, the addition of ultra-high molecular weight polyethylene has significantly improved the thermal aging performance of the insulation material made of polypropylene, which has poor thermal aging performance, and further improved the low-temperature resistance of polypropylene insulation materials.

[0035] Specific modifiers further improve the insulating electrical properties of polypropylene cable insulation.

[0036] The compounded antioxidants 300#, 1076, 1035, 1330, and 802 significantly improve the thermal aging performance of the material, which is far superior to the performance requirements of conventional polypropylene cable insulation materials. The relatively unstable helical conformation of polypropylene (PP) and the tertiary carbon atoms in the structure are more sensitive to oxidation. From processing to use, it is easy to be oxidized and degraded by heat, oxygen and light. Hindered phenol and thiophenol antioxidants can capture free radicals, terminate chain reactions, and decompose hydroperoxides. After theoretical analysis and experimental exploration, the preferred antioxidants are antioxidant 300#, antioxidant 1076, antioxidant 1035, antioxidant 1330 and antioxidant 802.

[0037] The insulating layer made of the above polyolefin insulating material has excellent insulation and protection properties for the conductor. Together with the semi-conductive tape layer, braided shielding layer and sheath layer, the cable is suitable for the power supply system of high-speed railway EMU vehicles in extremely cold areas and humid coastal environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a schematic diagram of a radial cross section of the cable of this embodiment;

[0039] Figure 2 Schematic diagram of the structure of the conductor and single conductive tape portion of the cable of this embodiment;

[0040] In the figure: conductor 1, semi-conductive tape layer 2, insulating layer 3, isolation tape layer 4, braided shielding layer 5, and sheath layer 6. DETAILED DESCRIPTION

[0041] The technical solution is further described below in conjunction with the accompanying drawings and specific implementation methods:

[0042] like Figure 1 , a power cable for high-speed rail vehicles based on a polyolefin insulation layer, the structure of which is: from the inside to the outside, a conductor 1, a semi-conductive tape layer 2, an insulating layer 3, a barrier tape layer 4, a braided shielding layer 5 and a sheath layer 6;

[0043] The conductor 1 is composed of a plurality of tinned copper wires bundled into strands, which are then twisted to form a conductor; the bundling direction of the tinned copper monofilaments of the strands is left-handed, and the bundled pitch-diameter ratio is 30 to 35 times; the bundled strands are then twisted at a pitch-diameter ratio of 8 to 10. Bundling the conductors first and then twisting them can improve the flexibility and tightness of the conductors.

[0044] The semi-conductive tape layer 2 is composed of a conductor wrapped with a semi-conductive tape; the wrapping of the semi-conductive tape can play a role in homogenizing the electric field, so that the cable has good electrical properties.

[0045] The insulating layer 3 is formed by extrusion of polyolefin insulating material;

[0046] The isolation tape layer 4 is composed of a wrapped low-smoke halogen-free flame retardant tape; since the wrapped flame retardant tape has good flame retardant properties, the flame retardancy of the cable is improved;

[0047] The braided shielding layer 5 is braided with tinned copper wires; the copper wire braiding structure is not conducive to the bending of the cable, but in order to improve the electromagnetic compatibility of the cable, tinned copper wires must be used for braiding. This cable adopts a specific braiding structure, combined with other structural designs of the cable, to overcome the negative impact of the copper wire braiding structure on the bending of the cable;

[0048] The sheath layer 6 is made of extruded low-smoke halogen-free flame-retardant sheath material.

[0049] In this example: the conductor material is tinned copper conductor of type 6 specified in IEC60228; the conductor area is 95mm 2

[0050] In the stranded wire, the bundle pitch of the tinned copper monofilament is 50 mm, and the bundle pitch diameter ratio of the stranded wire is 12;

[0051] In the conductor, there are three layers of strands from the inside to the outside, the inner layer is 1 strand, the middle layer is 6 strands, and the outer layer is 12 strands;

[0052] When the conductor is twisted again: 1+6 strands layer: the twisting cage speed is 115.2rpm, and the strand bundle pitch is 75mm; 12 strands layer: the twisting cage speed is 84rpm, and the strand bundle pitch is 132mm.

[0053] The above process structure is adopted to make the conductor twisting more compact and round, effectively solving the problem of loose conductors.

[0054] A layer of semi-conductive terylone tape is used for wrapping, and the wrapping tape overlap rate is 40% to 45%. During wrapping, the wrapping head speed is 325r / min, the wrapping tape width is 25mm, and the wrapping pitch is 28mm. With this wrapping structure, the semi-conductive tape wrapping is relatively flat, without bulges, and without leakage problems.

[0055] The nominal thickness of the insulation layer is 3.00mm, the average thickness is not less than the nominal thickness, and the thinnest thickness is not less than 3.00mm×90%-0.1mm. With this insulation structure, the electrical performance of the cable meets the use requirements and has good electrical resistance.

[0056] During production, the screw speed of the rubber extruder for insulation extrusion is 35r / min, the production steam pressure is 15.6bar, and the production speed is 23m / mim. Under this process condition, the insulation extrusion is relatively smooth, the stability of the insulation thickness is relatively good, and the degree of insulation cross-linking is high.

[0057] The overlap rate of the low-smoke zero-halogen tape of the isolation tape layer 4 is 25% to 30%. During wrapping, the speed of the wrapping head is 283r / min, and the width of the wrapping tape is 30mm.

[0058] Tinned copper wire is used for braiding. The nominal diameter of the tinned copper wire is 0.28 mm, and the braiding angle (the angle between the braided wire and the center line of the cable core) is 27 0 , the weaving density is 82%.

[0059] The above structure enables the cable to have good shielding performance. The above process enables the braided wire of the cable to be relatively stable, and there will be no problem of the braided wire wiping back and forming a lantern when the sheath is extruded.

[0060] The nominal thickness of the sheath layer is 1.8 mm, the average thickness is not less than the nominal thickness, and the thinnest thickness is not less than 1.80 mm×85%-0.1 mm. In this example, the sheath material is a sheath material of grade XH-31D.

[0061] In order to verify the applicability relationship between ultra-high molecular weight polyethylene and syndiotactic polypropylene, as well as other ratio relationships in the formula, the following formula was used for trial production of insulating materials, and 5 groups of cable samples were trial-produced using the following formula for inspection.

[0062]

[0063] The use of the above thickness of sheath (and sheath material) makes the cable have good halogen-free flame retardant performance, the cable meets the low temperature resistance requirements, effectively protects the cable, and controls the overall outer diameter of the cable. This grade of salt spray resistant, low temperature resistant, environmentally friendly low smoke halogen-free flame retardant sheath material has good salt spray resistance, low temperature resistance, low toxicity, low smoke halogen-free flame retardant, high oil resistance, and good environmental performance.

[0064] The specially made insulating layer of the present invention has the advantages of low temperature resistance, low smoke and halogen-free flame retardancy, flexibility and excellent electrical properties.

[0065] Compared with the existing technology, the technical performance of this cable is better and can fully meet the following technical requirements:

[0066] 1. The maximum long-term allowable operating temperature of the cable conductor is 125℃.

[0067] 2. When laying cables, the ambient temperature shall not be lower than -15°C; when using cables, the ambient temperature shall not be lower than -55°C.

[0068] 3. Insulation tensile strength 13.2Mpa, insulation elongation at break 420%.

[0069] 4. Aging of insulation air box: (158℃±1, 168h)

[0070] The change rate of tensile strength after insulation aging is -11%, and the change rate of elongation at break after insulation aging is -12%.

[0071] 5. The sheath tensile strength is 14.2Mpa, and the insulation elongation at break is 230%.

[0072] 6. Sheath air box aging: (158℃±1, 168h)

[0073] The change rate of tensile strength of the sheath after aging is -10%, and the change rate of elongation at break of the sheath after aging is -11%.

[0074] 7. Sheath-55 low temperature stretching: 35%.

[0075] 8. The mineral oil resistance of the sheath meets the requirements (100°C, 72h). The change rate of tensile strength after oil resistance is +2%, and the change rate of elongation at break after oil resistance is -17%.

[0076] 9. The fuel oil resistance of the sheath meets the requirements (70°C, 168h), the change rate of tensile strength after oil resistance is -13%, and the change rate of elongation at break after oil resistance is -21%.

[0077] 10. Cable power frequency AC withstand voltage test:

[0078] The cable insulation can withstand 6.5kV, 5min power frequency AC voltage without breakdown.

[0079] 11. Cable salt spray resistance test (70°C, 168h):

[0080] The change rate of insulation tensile strength is -2%, and the change rate of insulation elongation at break is -3%;

[0081] The change rate of sheath tensile strength is -3%, and the change rate of sheath breaking elongation is -5%.

[0082] 12. Smoke density test: minimum light transmittance 85%

[0083] 13. Single vertical burning test: passed

[0084] 14. Cable bundle flame retardant Class A test: passed

[0085] 15. Toxicity index: 3

[0086] 16. The cable complies with RoHS2.0 and REACH environmental protection requirements.

Claims

1. A power cable for high-speed rail vehicles based on a polyolefin insulation layer, the structure of which is: from the inside to the outside, it is a conductor, a semi-conductive tape layer, an insulating layer, a separation tape layer, a braided shielding layer and a sheath layer; Its characteristic is that the conductor is composed of a plurality of tinned copper wires bundled into strands, which are then twisted to form a conductor; The semi-conductive tape layer is composed of a conductor wrapped with a semi-conductive tape; The insulation layer is made of extruded polyolefin insulation material; The isolation tape layer is composed of wrapped low-smoke halogen-free flame-retardant tape; The braided shield is made of tinned copper wires; The sheath layer is made of extruded low-smoke halogen-free flame-retardant sheath material; The conductor is made of tinned copper conductor of type 6; The wrapping tape overlap rate of the semi-conductive tape layer is 40% to 45%; The braiding density of the braided shielding layer is not less than 80%; The polyolefin insulating material is made of syndiotactic polypropylene as a base resin, ultra-high molecular weight polyethylene as a modified resin, nano powder with a high band gap, a high critical breakdown electric field and a small dielectric constant as a modifier, and a compound antioxidant; The formula of the polyolefin insulation material is calculated by mass: Syndiotactic polypropylene 70-90 parts Ultra-high molecular weight polyethylene 10-30 parts Modifier 1-3 parts Antioxidant 0.5-2 parts The number average molecular weight of ultra-high molecular weight polyethylene is 600,000 to 7,000,000, and the density is 0.930 to 0.970 g / cm 3 ; The bandgap width of the modifier is ≥3.2eV, the breakdown field strength of the material is ≥45kV / mm, and the dielectric constant is ≤2.1 at room temperature; The antioxidant is a compound antioxidant prepared by compounding any one of antioxidant 300, antioxidant 1076, antioxidant 1035 and antioxidant 1330 with antioxidant 802; The applicable relationship between ultra-high molecular weight polyethylene and syndiotactic polypropylene is: The number average molecular weight of the ultra-high molecular weight polyethylene is 6*10 5 ~2*10 6 , then: the mass fraction of syndiotactic polypropylene is 85-90 parts, and the mass fraction of ultra-high molecular weight polyethylene is 10-15 parts; The number average molecular weight of the ultra-high molecular weight polyethylene is 2*10 6 ~3*10 6 , then: the mass fraction of syndiotactic polypropylene is 80-85 parts, and the mass fraction of ultra-high molecular weight polyethylene is 15-20 parts; The number average molecular weight of the ultra-high molecular weight polyethylene is 3*10 6 ~5*10 6 , then: the mass fraction of syndiotactic polypropylene is 75-80 parts, and the mass fraction of ultra-high molecular weight polyethylene is 20-25 parts; The number average molecular weight of the ultra-high molecular weight polyethylene is 5*10 6 ~7*10 6 , then: the mass fraction of syndiotactic polypropylene is 70-75 parts, and the mass fraction of ultra-high molecular weight polyethylene is 25-30 parts; The modifier is one of nano-silicon dioxide aerogel powder, nano-titanium dioxide or nano-silicon carbide; In the compound antioxidant: the mass of antioxidant 802 is 2 parts; the mass of antioxidant 300, antioxidant 1076, antioxidant 1035 or antioxidant 1330 is 3 parts.

2. The high-speed rail vehicle power cable based on a polyolefin insulation layer according to claim 1, Its characteristics are The bundling direction of the tinned copper monofilaments of the strands is left-handed, and the bundled pitch-diameter ratio is 30 to 35 times; the bundled strands are then twisted at a pitch-diameter ratio of 8 to 10.

3. The high-speed rail vehicle power cable based on a polyolefin insulation layer according to claim 1, Its characteristics are The cross-sectional area of ​​the conductor is 95mm 2 ,but: In the stranded wire, the bundle pitch of the tinned copper monofilament is 50 mm, and the bundle pitch diameter ratio of the stranded wire is 12; In the conductor, there are three layers of strands from the inside to the outside, the inner layer is 1 strand, the middle layer is 6 strands, and the outer layer is 12 strands; When the conductor is twisted again: 1+6 strands layer: the twisting cage speed is 115.2rpm, and the strand bundle pitch is 75mm; 12 strands layer: the twisting cage speed is 84rpm, and the strand bundle pitch is 132mm.

4. The high-speed rail vehicle power cable based on a polyolefin insulation layer according to claim 1, Its characteristics are The semi-conductive tape is a semi-conductive terephthalate tape; during wrapping, the speed of the wrapping head is 325r / min, the width of the wrapping tape is 25mm, and the wrapping pitch is 28mm.

5. The high-speed rail vehicle power cable based on a polyolefin insulation layer according to claim 1, Its characteristics are The nominal thickness of the insulation layer is 3.00mm, the average thickness is not less than the nominal thickness, and the thickness at the thinnest point is not less than 3.00mm×90%-0.1mm; The insulating layer is produced by using a rubber extruder to extrude polyolefin insulation material onto the outside of the conductor. The screw speed of the rubber extruder is 35r / min, the production steam pressure is 15.6bar, and the production speed is 23m / mim.

6. The high-speed rail vehicle power cable based on a polyolefin insulation layer according to claim 1, Its characteristics are Use a layer of low-smoke halogen-free tape for wrapping, with the overlap rate of the wrapping tape being 25% to 30%. When wrapping, the speed of the wrapping head is 283r / min and the width of the wrapping tape is 30mm.

7. The high-speed rail vehicle power cable based on a polyolefin insulation layer according to claim 1, Its characteristics are Tinned copper wire is used for weaving, the nominal diameter of the tinned copper wire is 0.28mm, the braiding angle, that is, the angle between the braided wire and the cable axis, is 27°, and the braiding density is 82%.

8. The high-speed rail vehicle power cable based on a polyolefin insulation layer according to claim 1, Its characteristics are The nominal thickness of the sheath layer is 1.8mm, the average thickness is not less than the nominal thickness, and the thickness at the thinnest point is not less than 1.80mm×85%-0.1mm.

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