Multi-effect protection type alternating current traction power supply cable for electrified railway

Abstract

The invention discloses a multi-effect protection type alternating current traction power supply cable for an electrified railway, which comprises a guide core, and a co-extrusion shielding layer, a water-blocking wrapping layer, a sparsely-wound shielding layer, an isolation sleeve, a flame-retardant wrapping layer, an armor layer, a flame-retardant inner sheath and a rat-proof and termite-proof weather-proof outer sheath which are sequentially arranged outside the guide core from inside to outside, the flame-retardant inner sheath is formed by extruding a flame-retardant inner sheath material; the flame-retardant inner protection material is prepared from the following components in parts by weight: 40 to 60 parts of a resin base material, 6 to 10 parts of a phosphorus flame retardant, 25 to 45 parts of an inorganic hydroxide flame retardant, 1 to 3 parts of a free radical inhibition type flame-retardant synergist, 0.5 to 1.5 parts of a crosslinking char-forming type flame-retardant synergist, 0.5 to 2.5 parts of a nano-structure type flame-retardant smoke suppressant and 0.25 to 0.75 part of a metal oxide type flame-retardant smoke suppressant, the cable can overcome the defects that an existing traction power supply cable for the electrified railway is low in flame retardant grade, poor in protection performance and prone to being influenced by environmental factors, and is very suitable for high-voltage power supply scenes of closed space places such as subways and high-speed rails.

Description

Technical Field

[0001] This invention relates to the technical field of cables, and in particular to the technical field of AC traction power supply cables for electrified railways. Background Technology

[0002] With the rapid development of electrified railways, subways and high-speed rail have become important choices for urban and intercity travel. Electrified railway AC traction power supply cables are high-voltage AC cables specifically used in the traction power supply system of electrified railways. Examples include a new type of electrified railway cable and its manufacturing process (publication number CN112420249A) and a single-phase AC cross-linked insulated cable for electrified railways (publication number CN102881371A). Their core function is to transmit electrical energy to the traction locomotives of electrified railways.

[0003] Electrified railways operate primarily in enclosed spaces, placing extremely high demands on the performance of traction power cables. However, current market products based on GB / T... Electrified railway traction power supply cables manufactured according to the 28427-2012 standard generally only achieve a ZC flame retardant rating (which is prone to problems such as burning drips, rapid flame spread, highly toxic and corrosive smoke in the event of a fire), making it difficult to meet the needs of safe evacuation of personnel and protection of equipment in confined spaces. In addition, existing cables also have deficiencies in their protective structure design. Specifically, firstly, existing cable products usually do not have specific protection against rodent and ant infestation, and the cable sheath is easily damaged by rodents and ants in the complex laying environment along railway lines (which can lead to exposure of the internal core and even power supply failure). Secondly, the outer sheath of traditional cables is mostly a single-layer structure, which is poor in terms of scratch resistance, aging resistance and bending performance. After long-term use, it is prone to cracking and falling off, which will affect the service life and power supply stability of the cable. Thirdly, the water-blocking and shielding structures of existing cables are not tightly combined. Moisture intrusion can easily cause water treeing aging of the core, which can lead to electrical breakdown and threaten the safe operation of the traction power supply system.

[0004] In summary, developing a 27.5kV AC traction power supply cable for electrified railways with a high flame retardant rating (flame retardant B1 grade), reliable protection performance, and stable power supply capability has become one of the key requirements for solving current technical pain points. Summary of the Invention

[0005] This invention provides a flame-retardant B1-grade 27.5kV AC traction power supply cable for electrified railways. Through innovative structural design and material formulation, it can achieve high flame retardancy, rodent and termite resistance, weather resistance, and water-blocking shielding while ensuring power supply stability. It overcomes the shortcomings of existing electrified railway traction power supply cables, such as low flame retardancy, poor protection performance, and susceptibility to environmental factors. It is very suitable for high-voltage power supply scenarios in enclosed spaces such as subways and high-speed railways.

[0006] To achieve the above objectives, this invention proposes a multi-effect protection type AC traction power supply cable for electrified railways, comprising a conductor core and, from the inside out, a co-extruded shielding layer, a water-blocking wrapping layer, a loosely wound shielding layer, an isolation sleeve, a flame-retardant wrapping layer, an armor layer, a flame-retardant inner sheath, and a rodent- and termite-resistant weather-resistant outer sheath, all arranged sequentially outside the conductor core. The flame-retardant inner sheath is formed by extrusion of a flame-retardant inner sheath material, which comprises 40-60 parts by weight of a resin base material, 6-10 parts by weight of a phosphorus-based flame retardant, 25-45 parts by weight of an inorganic hydroxide flame retardant, 1-3 parts by weight of a free radical inhibiting flame retardant synergist, 0.5-1.5 parts by weight of a cross-linked carbon-forming flame retardant synergist, 0.5-2.5 parts by weight of a nanostructured flame retardant and smoke suppressant, and 0.25-0.75 parts by weight of a metal oxide flame retardant and smoke suppressant.

[0007] Preferably, the conductor core is made of several copper conductors pressed together, and the conductor cross-sectional area is 150-400 mm². 2 The compression coefficient is 0.90 to 0.93.

[0008] Preferably, the co-extruded shielding layer comprises a conductor shielding layer, an insulating layer, and an insulating shielding layer arranged sequentially from the inside out. The conductor shielding layer is formed by extrusion of semi-conductive polyethylene material and its thickness is controlled between 0.8 and 1.2 mm. The insulating layer is formed by extrusion of cross-linked polyethylene material and its thickness is controlled between 11 and 12 mm. The insulating shielding layer is formed by extrusion of semi-conductive polyethylene material and its thickness is controlled between 0.6 and 1.0 mm.

[0009] Preferably, the water-blocking wrapping layer is a semi-conductive water-blocking wrapping tape wrapped around the co-extruded shielding layer, with a wrapping overlap rate of 25-35% and a wrapping layer number of 1-3 layers.

[0010] Preferably, the loosely wound shielding layer is made of several copper wires with a diameter of 0.8 to 1.0 mm loosely wound together, and the average gap between the copper wires is no more than 4 mm.

[0011] Preferably, the isolation sleeve is a high-density polyethylene sleeve extruded outside the loosely wound shielding layer, and the extrusion thickness is controlled between 2.0 and 2.5 mm.

[0012] Preferably, the flame-retardant wrapping layer is a halogen-free, low-smoke, flame-retardant fiberglass tape wrapped around the isolation sleeve, with a bandwidth of 40-60 mm, a wrapping overlap rate of 40-50%, and 1-3 wrapping layers.

[0013] Preferably, the armor layer is formed by loosely winding several non-magnetic aluminum wires with a diameter of 1.5 to 3.5 mm, and the armor pitch is controlled at 100 to 150 mm.

[0014] Preferably, the flame-retardant inner protective material further includes 0.25 to 0.75 parts by weight of a processing lubricant and 0.25 to 0.75 parts by weight of a processing release agent.

[0015] Preferably, the resin substrate is formed by mixing 15-25 parts by weight of ethylene-vinyl acetate copolymer resin and 25-35 parts by weight of linear low-density polyethylene; the phosphorus-based flame retardant is melamine polyphosphate; the inorganic hydroxide flame retardant is formed by mixing 10-14 parts by weight of aluminum hydroxide and 20-30 parts by weight of magnesium hydroxide; the free radical inhibiting flame retardant synergist is ammonium molybdate; the cross-linked carbon-forming flame retardant synergist is 4,4'-diaminodiphenylmethane; the nanostructured flame retardant and smoke suppressant is organically modified nano-montmorillonite; the metal oxide flame retardant and smoke suppressant is active zinc oxide; the processing lubricant is polyethylene wax; the processing release agent is zinc stearate; and the rodent-resistant and weather-resistant outer sheath is a polyamide sheath extruded outside the flame-retardant inner sheath. The extrusion thicknesses of the flame-retardant inner sheath and the rodent-resistant and weather-resistant outer sheath are 3.1-3.4 mm and 0.7-0.9 mm, respectively.

[0016] The beneficial effects of this invention are: 1) Multi-layer composite flame retardant system: This invention uses a multi-layer composite structure of "semi-conductive resistive water layer + halogen-free low-smoke flame retardant fiberglass tape wrapping layer + low-smoke halogen-free high flame retardant sheath", combined with an innovative sheath material formula. During combustion, there are no drips, low smoke density, low smoke toxicity and weak corrosiveness. It can significantly reduce the total heat release, heat release rate and smoke release rate, and achieve the B1 flame retardant level in GB31247-2014 (far higher than the ZC flame retardant performance in the existing GB / T 28427-2012 standard). This meets the fire safety requirements of confined spaces and buys valuable time for personnel evacuation and equipment protection in confined space fire scenarios such as subways and high-speed railways. 2) Double-layer composite sheath structure: This invention combines a low-smoke halogen-free, high flame-retardant sheath with a polyamide (nylon 12) sheath inside and out. This retains the low-smoke halogen-free characteristics to reduce the release of toxic fumes during combustion, while the polyamide material simultaneously enhances the cable's resistance to rodents and insects, scratches, and aging. The double-layer tight bonding structure also improves the cable's bending performance, enabling the cable to adapt to the complex railway laying environment (resisting the corrosion of the complex environment along the railway line and avoiding cable damage caused by rodents and insects or external scratches). This solves the problem of insufficient protection of traditional single-layer sheaths and effectively extends the service life of the cable. 3) Stable electrical and mechanical performance: In this invention, the application of the three-layer co-extrusion process reduces interface defects between the conductor shielding layer, the insulation layer and the insulation shielding layer, and improves the electrical insulation performance of the cable; the non-magnetic aluminum wire armor structure not only ensures mechanical protection capabilities, but also avoids eddy current and hysteresis losses, which can be adapted to the electromagnetic environment of single-core high-voltage cables and ensure the stability of 27.5kV AC traction power supply. 4) Strong adaptability: In this invention, the overall cable structure design takes into account flame retardancy, protection and electrical performance, while also having good bending performance, which can adapt to complex laying environments such as railway tunnels and bridges, thereby providing a reliable guarantee for the safe and stable operation of electrified railway traction power supply systems.

[0017] The features and advantages of the present invention will be described in detail through embodiments and in conjunction with the accompanying drawings. Attached Figure Description

[0018] Figure 1 This is a front view of the multi-effect protection type AC traction power supply cable for electrified railways according to the present invention; In the diagram: 1-Conductor core, 2-Conductor shielding layer, 3-Insulation layer, 4-Insulation shielding layer, 5-Water-blocking wrapping layer, 6-Loose wrapping shielding layer, 7-Isolation sleeve, 8-Flame-retardant wrapping layer, 9-Armor layer, 10-Flame-retardant inner sheath, 11-Rodent-proof and weather-resistant outer sheath. Detailed Implementation

[0019] See Figure 1 This invention discloses a multi-effect protection type AC traction power supply cable for electrified railways, including a conductor core 1 and, from the inside out, a co-extruded shielding layer, a water-blocking wrapping layer 5, a loosely wound shielding layer 6, an isolation sleeve 7, a flame-retardant wrapping layer 8, an armor layer 9, a flame-retardant inner sheath 10, and a rodent-proof and weather-resistant outer sheath 11.

[0020] The conductor core 1 is made of several Class 2 round copper conductors conforming to GB / T 3956 standard, which are tightly pressed together, and the conductor cross-sectional area is 400 mm². 2The compression coefficient is 0.91; this design allows the conductor 1 to have excellent conductivity (ensuring stable conductivity), thereby meeting the current carrying requirements of 27.5kV AC traction power supply.

[0021] The co-extruded shielding layer comprises, from the inside out, a conductor shielding layer 2, an insulation layer 3, and an insulation shielding layer 4. The conductor shielding layer 2 is formed by extrusion of semi-conductive polyethylene material with a thickness controlled at 1.0 mm. The insulation layer 3 is formed by extrusion of cross-linked polyethylene material with a thickness controlled at 11.5 mm (meeting the insulation requirements of 27.5 kV high voltage). The insulation shielding layer 4 is formed by extrusion of semi-conductive polyethylene material with a thickness controlled at 0.9 mm. The conductor shielding layer 2, insulation layer 3, and insulation shielding layer 4 are formed using a three-layer co-extrusion process (i.e., formed in one step using a three-layer co-extrusion equipment). The three layers are tightly bonded, which can effectively reduce interface defects and improve the electrical insulation performance of the cable, thereby ensuring the safety of 27.5 kV high voltage power supply.

[0022] The water-blocking wrapping layer 5 is a semi-conductive water-blocking tape wrapped around the co-extruded shielding layer with a wrapping overlap rate of 30% and a wrapping layer of 1. The water-blocking wrapping layer 5 is fixed by wrapping, which can effectively prevent water from entering the cable (ensuring water blocking effect), prevent electrical breakdown caused by water tree aging, and does not affect the shielding performance. It can also block the spread of flames to a certain extent in the event of a fire.

[0023] The loosely wound shielding layer 6 is made of 80 soft copper wires with a diameter of 0.895mm, with an average gap of no more than 4mm between the copper wires. In addition, the tension needs to be controlled to be uniform during the wrapping process to ensure that the gap between the copper wires is consistent, thus achieving the dual functions of waterproofing and shielding. The loosely wound shielding layer 6 can effectively shield the electromagnetic interference generated during the operation of the cable and ensure the electromagnetic compatibility of the traction power supply system.

[0024] The isolation sleeve 7 is a high-density polyethylene sleeve extruded outside the loosely wound shielding layer 6, and the extrusion thickness is controlled at 2.0 mm (the isolation sleeve 7 is covered on the outside of the copper wire shielding layer by extrusion process, and it is necessary to ensure that the surface of the isolation sleeve 7 is smooth and free of bubbles); the isolation sleeve 7 can isolate the copper wire shielding layer located inside it from the outer structure, thereby avoiding mutual influence between different materials, and at the same time providing a stable support foundation for the subsequent structure.

[0025] The flame-retardant wrapping layer 8 is a halogen-free, low-smoke, flame-retardant fiberglass tape wrapped around the isolation sleeve 7, with a width of 50mm, a wrapping overlap rate of 40%, and one wrapping layer. The halogen-free, low-smoke, flame-retardant fiberglass tape has excellent flame-retardant properties, which can slow down the spread of fire in the event of a fire. At the same time, it blocks the gas generated by the thermal decomposition of the cross-linked core, preventing the gas from leaking out and expanding, which would cause the outer sheath material to fall off, thus enhancing the stability of the cable in a fire. In addition, after wrapping, hot air treatment can be used (hot air temperature of 120-160℃; hot air pressure of 0.2-0.4 MPa; hot air distance of 20-40 mm; the treatment speed needs to be synchronized with the production line, usually controlled at 5-15 m / min; the treatment method is to blow the annular hot air evenly onto the wrapping surface to ensure full circumference heating), thereby enhancing the adhesion between the halogen-free, low-smoke, flame-retardant fiberglass tape and the isolation sleeve 7.

[0026] The armor layer 9 is formed by loosely winding several non-magnetic circular aluminum wires with a diameter of 2.5mm and the armor pitch is controlled at 120mm. During armoring, the tension of the aluminum wires needs to be controlled to ensure that the armor layer is tight and uniform (without looseness). This design can, on the one hand, protect the internal core from external compression and stretching by the armor layer 9, thereby improving the mechanical protection performance of the cable. On the other hand, since the armor layer 9 has non-magnetic properties, it can avoid eddy current and hysteresis losses, and is perfectly adapted to the electromagnetic environment of single-core high-voltage cables.

[0027] The flame-retardant inner sheath 10 is formed by extrusion of a flame-retardant inner sheath material, which comprises 19 parts by weight of ethylene-vinyl acetate copolymer resin, 30 parts by weight of linear low-density polyethylene, 8 parts by weight of phosphorus-based flame retardant (melamine polyphosphate), 12 parts by weight of aluminum hydroxide, 25 parts by weight of magnesium hydroxide, 2 parts by weight of free radical inhibiting flame retardant synergist (ammonium molybdate), and 1 part by weight of cross-linked char-forming flame retardant synergist (4,4'- The composition includes 1.5 parts of a nanostructured flame retardant and smoke suppressant (organically modified nano-montmorillonite), 0.5 parts of a metal oxide flame retardant and smoke suppressant (active zinc oxide), 0.5 parts of a processing lubricant (polyethylene wax, molecular weight 1000-3000), and 0.5 parts of a processing release agent (zinc stearate). The flame-retardant inner sheath material is mixed and granulated using a twin-screw extruder, then extruded onto the outside of the armor layer 9 with an extrusion thickness of 3.1 mm. The flame-retardant inner sheath 10 uses a newly formulated low-smoke, halogen-free, high-flame-retardant material. This material uses a mixture of ethylene-vinyl acetate copolymer resin and magnesium hydroxide linear low-density polyethylene as the base raw material, compounded with melamine polyphosphate, aluminum hydroxide and magnesium hydroxide as flame retardants, and innovatively added ammonium molybdate and 4,4'-diaminodiphenylmethane as special additives as flame retardant synergists. At the same time, organic modified nano-montmorillonite and active zinc oxide are added as flame retardant and smoke suppressant. With this design, the char content of the combustion residue can be improved through comprehensive char formation technology, and the smoke toxicity, corrosiveness and smoke density during combustion can be improved through the low smoke halogen-free material system, thereby meeting the ZA flame retardant performance in GB / T 19666-2019 and the B1 level (d0, t0, a1) flame retardant rating in GB31247-2014.

[0028] The rodent-proof and weather-resistant outer sheath 11 is a polyamide sheath extruded outside the flame-retardant inner sheath 10. The rodent-proof and weather-resistant outer sheath 11 is made of medical-grade nylon 12 material, extruded simultaneously with the flame-retardant inner sheath 10 via tandem extrusion, with an extrusion thickness of 0.7 mm. During extrusion, the temperature needs to be controlled between 230 and 250°C to ensure a tight bond between the two sheaths without delamination. This tight bonding structure of the double sheaths gives the cable good bending performance, making it suitable for the complex laying environment of railways. Furthermore, the rodent-proof and weather-resistant outer sheath 11 possesses excellent rodent-proof properties, scratch resistance, and aging resistance.

[0029] The performance of the multi-effect protection AC traction power supply cable for electrified railways prepared in this embodiment was tested, and the results are as follows: 1) Flame retardant performance: Meets the requirements of Class B1 in GB 31247-2014, with a combustion dripping level of d0 (no combustion dripping within 1200 seconds), a smoke toxicity level of t0, a corrosiveness level of a1 (conductivity 1.4μs / mm, pH=5.8), and a minimum light transmittance of 82% during combustion; 2) Rodent-proof performance: Rodent-proof test was conducted according to JB / T 10696.10-2011. After the test, there were no tooth marks on the surface of the protective layer, which meets the requirements. 3) Termite resistance: The termite resistance test was conducted according to JB / T 10696.9-2011 using the group method. After the test, there were no tooth marks on the cable surface, and the termite infestation level was 1. 4) Electrical performance: Partial discharge quantity ≤5pC at 1.73U0 (48kV) voltage, insulation resistance ≥1000MΩ, meeting the requirements of 27.5kV AC traction power supply; 5) Mechanical properties: When the bending radius is 12 times the outer diameter of the cable, the cable does not crack or delaminate; after the scratch resistance test, the sheath is not damaged.

[0030] The above embodiments are illustrative of the present invention and are not intended to limit the present invention. Any simple modifications to the present invention are within the scope of protection of the present invention.

Claims

1. Multi-effect protective electrified railway AC traction power supply cable, characterized in that: The cable comprises a core (1), a co-extrusion shielding layer, a water-blocking wrapping layer (5), a sparse wrapping shielding layer (6), an isolation sleeve (7), a flame-retardant wrapping layer (8), an armored layer (9), a flame-retardant inner sheath (10) and a rodent-proof and ant-ant weather-proof outer sheath (11) arranged outside the core (1) in sequence from inside to outside, wherein the flame-retardant inner sheath (10) is formed by extrusion coating of a flame-retardant inner sheath material, and the flame-retardant inner sheath material comprises 40-60 parts of resin base material, 6-10 parts of phosphorus flame retardant, 25-45 parts of inorganic hydroxide flame retardant, 1-3 parts of free radical inhibition type flame-retardant synergist, 0.5-2.5 parts of nano-structure type flame-retardant smoke suppressant, and 0.25-0.75 parts of metal oxide type flame-retardant smoke suppressant.

2. A multi-effect shielded electrified railway AC traction power supply cable according to claim 1, characterized in that: The lead core (1) is made of several copper conductors with a tight pressing and a conductor cross-sectional area of 150-400 mm 2 and a tight pressing coefficient of 0.90-0.

93.

3. The multi-effect shielded electrified railway AC traction power supply cable according to claim 1, characterized in that: The co-extrusion shielding layer has a conductor shielding layer (2), an insulation layer (3) and an insulation shielding layer (4) arranged outside in sequence from inside to outside, wherein the conductor shielding layer (2) is formed by extrusion coating of semi-conductive polyethylene material and the thickness is controlled to be 0.8-1.2 mm, the insulation layer (3) is formed by extrusion coating of cross-linked polyethylene material and the thickness is controlled to be 11-12 mm, and the insulation shielding layer (4) is formed by extrusion coating of semi-conductive polyethylene material and the thickness is controlled to be 0.6-1.0 mm.

4. The multi-effect shielded electrified railway AC traction power supply cable according to claim 1, characterized in that: The water-blocking wrapping layer (5) is a semi-conductive water-blocking tape wrapped outside the co-extrusion shielding layer, and the wrapping overlap rate is 25-35% and the wrapping layer number is 1-3.

5. The multi-effect shielded electrified railway AC traction power supply cable according to claim 1, characterized in that: The sparse wrapping shielding layer (6) is formed by sparse wrapping of copper wires with a diameter of 0.8-1.0 mm, and the average gap of the copper wires is not greater than 4 mm.

6. The multi-effect shielded electrified railway AC traction power supply cable according to claim 1, characterized in that: The isolation sleeve (7) is a high-density polyethylene sleeve extruded outside the sparse wrapping shielding layer (6), and the extrusion thickness is controlled to be 2.0-2.5 mm.

7. The multi-effect shielded electrified railway AC traction power supply cable according to claim 1, characterized in that: The flame-retardant wrapping layer (8) is a halogen-free low-smoke flame-retardant glass fiber tape wrapped outside the isolation sleeve (7), and the tape width is 40-60 mm, the wrapping overlap rate is 40-50%, and the wrapping layer number is 1-3.

8. The multi-effect shielded electrified railway AC traction power supply cable according to claim 1, characterized in that: The armored layer (9) is formed by sparse wrapping of non-magnetic aluminum wires with a diameter of 1.5-3.5 mm, and the armored pitch is controlled to be 100-150 mm.

9. A multi-effect shielded electrified railway AC traction power supply cable according to any of claims 1 to 8, characterized in that: The flame-retardant inner sheath material further comprises 0.25-0.75 parts of processing lubricating aid and 0.25-0.75 parts of processing release aid.

10. A multi-effect shielded electrified railway AC traction power supply cable according to claim 9, characterized in that: The resin base material is formed by mixing 15-25 parts of ethylene-vinyl acetate copolymer resin and 25-35 parts of linear low density polyethylene, the phosphorus flame retardant is melamine polyphosphate, the inorganic hydroxide flame retardant is formed by mixing 10-14 parts of aluminum hydroxide and 20-30 parts of magnesium hydroxide, the free radical inhibition type flame retardant synergist is ammonium molybdate, the crosslinking carbonization type flame retardant synergist is 4,4'-diaminodiphenyl methane, the nano structure type flame retardant smoke suppressant is organic modified nano montmorillonite, the metal oxide type flame retardant smoke suppressant is active zinc oxide, the processing lubricating aid is polyethylene wax, the processing release aid is zinc stearate, the rat and termite proof weather resistant outer sheath (11) is a polyamide sheath extruded outside the flame retardant inner sheath (10), the extrusion thickness of the flame retardant inner sheath (10) and the rat and termite proof weather resistant outer sheath (11) is 3.1-3.4 mm and 0.7-0.9 mm respectively.

Images