Radiation-resistant medium-voltage fire-resistant leading flexible cable for motor and manufacturing method of radiation-resistant medium-voltage fire-resistant leading flexible cable

Abstract

The invention belongs to the technical field of cable production, and provides a radiation-resistant medium-voltage fire-resistant leading flexible cable for a motor and a manufacturing method thereof.The radiation-resistant medium-voltage fire-resistant leading flexible cable comprises at least one cable core, the cable core comprises a stranded conductor and an insulating wire core layer, the stranded conductor is wrapped by an inner shielding layer and an insulating layer, and the insulating layer is wrapped by an outer shielding layer. The inner shielding layer and the insulating layer are vulcanized to obtain the insulating wire core layer; a first high-flame-retardant wrapping tape, an inner sheath layer and an oxygen barrier layer are sequentially arranged outside the insulating wire core layer in a wrapping manner; a ceramic mica tape and a second high-flame-retardant wrapping tape are arranged outside the oxygen barrier layer in a wrapping mode, and an outer sheath layer which is subjected to extrusion, vulcanization and cross-linking treatment is arranged outside the second high-flame-retardant wrapping tape.

Description

Technical Field

[0001] The present invention belongs to the technical field of cable production, and particularly relates to a radiation-resistant medium-voltage fire-resistant connecting flexible cable for motors and a manufacturing method thereof. Background Art

[0002] The statements in this part only provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] Cables used in or near nuclear islands need to meet the requirements of flame retardancy, low smoke, halogen-free, and non-corrosive gases. Cables with special uses require fire resistance even more. Cables used in nuclear islands must pass the LOCA test (radiation resistance test). According to the newly formulated "General Requirements for 1E-Class Cables in Nuclear Power Plants" standard in China, Class K1 cables should pass the design basis event test, and the cumulative irradiation dose should reach at least 850 kGy; Class K2 cables should pass the design basis event test, and the cumulative irradiation dose should reach at least 250 kGy. In a nuclear power environment with strict requirements, the design and development of products are even more important. Therefore, relevant research on cable structure and manufacturing is required. Summary of the Invention

[0004] To solve the above problems, the present invention proposes a radiation-resistant medium-voltage fire-resistant connecting flexible cable for motors and a manufacturing method thereof. The cable structure and materials are improved to obtain a new type of fire-resistant, flame-retardant, and radiation-resistant radiation-resistant medium-voltage fire-resistant connecting flexible cable for motors to meet the harsh requirements of the service environment of long-life fire-resistant cables.

[0005] According to some embodiments, the first solution of the present invention provides a radiation-resistant medium-voltage fire-resistant connecting flexible cable for motors, adopting the following technical solution:

[0006] A radiation-resistant medium-voltage fire-resistant connecting flexible cable for motors includes at least one cable core. The cable core includes a stranded conductor and an insulated core layer. An inner shielding layer and an insulating layer are wrapped around the stranded conductor. The inner shielding layer and the insulating layer are vulcanized to obtain the insulated core layer; a first highly flame-retardant tape, an inner sheath layer, and an oxygen barrier layer are sequentially wrapped around the insulated core layer; a ceramicized mica tape and a second highly flame-retardant tape are wrapped around the oxygen barrier layer, and an extruded and vulcanized cross-linked outer sheath layer is provided outside the second highly flame-retardant tape.

[0007] As a further technical limitation, the inner shielding layer and the insulating layer adopt a double-layer co-extrusion process and are composed of a halogen-free semi-conductive inner shielding material and a halogen-free ethylene propylene rubber insulating material stacked together.

[0008] As a further technical limitation, a semi-conductive Teflon tape is overlapped and wrapped between the stranded conductor and the inner shielding layer.

[0009] As a further technical limitation, the stranded conductor is stranded by tinned copper wires.

[0010] As a further technical limitation, the oxygen barrier layer is made of extruded ceramicized low-smoke, halogen-free, flame-retardant and fire-resistant polyolefin.

[0011] As a further technical limitation, the outer sheath layer is made of halogen-free, flame-retardant rubber sheath material.

[0012] According to some embodiments, the second solution of the present invention provides a manufacturing method of a radiation-resistant medium-voltage fire-resistant lead soft cable for motors, adopting the following technical solutions:

[0013] A manufacturing method of a radiation-resistant medium-voltage fire-resistant lead soft cable for motors. Tape wrapping is performed on the stranded conductor in the cable core to obtain an insulated wire core layer obtained by vulcanization treatment of the inner shielding layer and the insulating layer. Wrapping treatment is performed on the insulated wire core layer to obtain a first highly flame-retardant tape, an inner sheath layer and an oxygen barrier layer. A ceramicized mica tape and a second highly flame-retardant tape are wrapped outside the oxygen barrier layer, and an extruded, combined and vulcanized cross-linked outer sheath layer is provided outside the second highly flame-retardant tape to obtain a radiation-resistant medium-voltage fire-resistant lead soft cable for motors.

[0014] As a further technical limitation, the stranded conductor is stranded by tinned copper wires, and the stranding pitch is set to be 16 to 22 times the outer diameter of the stranded conductor.

[0015] As a further technical limitation, the stranding direction of the outermost layer of the stranded conductor is set to be right-handed, and the stranding directions of adjacent layers are opposite.

[0016] As a further technical limitation, the insulated wire core layer is obtained by vulcanization treatment of the inner shielding layer and the insulating layer. During the vulcanization process, the pressure of the heating steam in the vulcanization pipeline is controlled at 0.8 to 1.1 MPa, and the water level of the cooling water is controlled at 25 to 30 meters.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] The present invention adopts a double-layer co-extrusion technology, and the extrusion quality is good, making the interface between the inner shielding layer and the insulating layer smooth and tight, greatly improving the performance of the cable; the inner shielding layer plays a role in uniforming the electric field and preventing local discharge caused by the generation of gaps between the insulating layer and the conductor; removing the outer shielding layer and the copper tape in the conventional cable can prevent local discharge caused by the generation of gaps between the insulating layer and the copper tape shielding;

[0019] The insulating layer in the present invention adopts ethylene-propylene rubber insulating material, ensuring that the service life of the cable reaches the design life of 60 years of nuclear power plants, ensuring reliable electrical performance and being more stable during use; at the same time, making the cable core have flame-retardant performance and radiation-resistant performance. Description of the Drawings

[0020] The accompanying drawings forming a part of this embodiment are used to provide a further understanding of this embodiment. The illustrative embodiments and descriptions thereof of this embodiment are used to explain this embodiment and shall not constitute an improper limitation to this embodiment.

[0021] Figure 1 It is a schematic structural diagram of a radiation-resistant medium-voltage fire-resistant lead soft cable for a motor in Embodiment 1 of the present invention;

[0022] Wherein, 1. stranded conductor; 2. semi-conductive Teflon tape; 3. inner shielding layer; 4. insulating layer; 5. first high flame-retardant tape; 6. inner sheath layer; 7. oxygen barrier layer; 8. ceramizable mica tape; 9. second high flame-retardant tape; 10. outer sheath layer. Detailed implementation manners

[0023] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0024] It should be noted that the following detailed descriptions are all exemplary and are intended to provide a further description of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0025] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary implementation manners according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0026] In the present invention, terms such as "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "side", "bottom", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only relationship terms determined for the convenience of describing the structural relationship of each component or element of the present invention and do not specifically refer to any component or element of the present invention and should not be construed as a limitation to the present invention.

[0027] In the present invention, terms such as "fixed connection", "connected", "connection", etc. should be understood in a broad sense, indicating that it can be a fixed connection, an integral connection or a detachable connection; it can be directly connected or indirectly connected through an intermediate medium. For relevant scientific research or technical personnel in this field, the specific meanings of the above terms in this invention can be determined according to specific circumstances and should not be construed as a limitation to the present invention.

[0028] Without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0029] Example 1

[0030] Example 1 of the present invention introduces a radiation-resistant medium-voltage fire-resistant connecting flexible cable for motors.

[0031] As Figure 1 A radiation-resistant medium-voltage fire-resistant connecting flexible cable for motors as shown in the figure includes a stranded conductor 1. A semiconductive Teflon tape 2 is wound around the outer wall of the stranded conductor 1. A double-layer co-extrusion inner shield layer 3 made of a halogen-free semiconductive inner shield material and an insulation layer 4 made of a medium-voltage halogen-free ethylene propylene rubber insulating material are provided. Externally, a first high-flame-retardant tape 5, an inner sheath layer 6 made of a high-flame-retardant oxygen barrier polyolefin, an oxygen barrier layer 7 made of a ceramifiable low-smoke halogen-free flame-retardant and fire-resistant polyolefin, a ceramifiable mica tape 8, a second high-flame-retardant tape 9, and an outer sheath layer 10 made of a halogen-free flame-retardant rubber sheath material are sequentially arranged.

[0032] In this embodiment, the stranded conductor 1 is a stranded tinned round conductor to improve the flexibility of the cable. During the stranding process, the conductor stranding should be uniform and tight, without missing strands or jumper wires; the surface of the stranded conductor should be smooth, free of oil, moisture, and burrs, and there should be no uneven outer diameter; the whole stranded conductor is not allowed to be welded, but single wires are allowed to be welded, and the welded part should be annealed, and the annealing distance on both sides is not less than 25 mm; the stranded joint should be smooth, firm, and round, and there should be no obvious protrusion at the joint, and the distance between adjacent joints should not be less than 300 mm.

[0033] As one or more implementation manners, a semiconductive Teflon tape 2 is wound around the stranded conductor 1 in this embodiment to prevent the inner shield material from being affected during the double-layer co-extrusion due to the strands of the stranded conductor 1, which affects the partial discharge test. The requirements for the connection of the semiconductive Teflon tape 2 during production are as follows: The two ends of the joint should be cut into 45° beveled edges, and there is no overlap and seamless splicing at both ends. Then, double-sided tape is adhered to the inner sides at both ends, and the tape is adhered to the conductor at the same time. At the interface, 1 - 2 layers of special black tape provided by the manufacturer are wound and should be flat and firm. The winding length is not less than 10 mm on both sides of the joint; the tape width can be selected according to the actual situation; the winding length can be adjusted according to the outer diameter of the wire core; the winding layer number is 1 - 2 layers. The outer diameter of the winding part is not greater than the outer diameter of the winding + 0.3 mm and there is no bulging phenomenon allowed.

[0034] In this embodiment, the inner shielding layer 3 and the insulating layer 4 adopt a double-layer co-extrusion process. During the double-layer co-extrusion process, the extrusion temperature shown in Table 1 is adopted, and it is formed by stacking a halogen-free semiconductive inner shield material and a halogen-free ethylene propylene rubber insulating material; the following points should be noted during production: Before feeding, the head (especially the dead corners) and the screw must be cleaned thoroughly. It must not be co-extruded with materials of different grades to prevent the cable performance from being unqualified. The materials need to be pumped into the barrel and must not be directly poured with the outer packaging bag to prevent foreign objects from entering the barrel, causing the cable surface to be uneven and other problems. Before feeding, it should be checked and confirmed that the materials are free of foreign objects and the anti-foreign object measures are complete.

[0035] Table 1 Extrusion Temperature

[0036]

[0037] The present invention adopts a double-layer co-extrusion technology with good extrusion quality, making the interface between the inner shielding and the insulation smooth and tight, greatly improving the cable performance; the inner shielding layer plays a role in uniforming the electric field and preventing local discharge caused by the generation of gaps between the insulation layer and the conductor; removing the outer shielding layer and copper tape in the conventional cable can prevent local discharge caused by the generation of gaps between the insulation layer and the copper tape shielding;

[0038] The insulating layer in the present invention adopts an ethylene propylene rubber insulating material, ensuring that the service life of the cable reaches the design life of 60 years of the nuclear power plant, ensuring reliable electrical performance and being more stable during use; at the same time, enabling the cable core to have flame retardant performance and radiation resistance.

[0039] Embodiment 2

[0040] Embodiment 2 of the present invention introduces a manufacturing method of a radiation-resistant medium-voltage fire-resistant lead soft cable for motors.

[0041] A manufacturing method of a radiation-resistant medium-voltage fire-resistant lead soft cable for motors, used to manufacture the radiation-resistant medium-voltage fire-resistant lead soft cable introduced in Embodiment 1, includes conductor material selection - conductor winding - extrusion of inner shielding and insulating layers - vulcanization cross-linking treatment - winding - double-layer oxygen barrier layer - tape winding - vulcanization cross-linking treatment of the outer sheath layer; specifically: tape winding is performed on the stranded conductor in the cable core to obtain an insulated wire core layer vulcanized by the inner shielding layer and the insulating layer, winding treatment is performed on the insulated wire core layer to obtain a first highly flame-retardant tape, an inner sheath layer and an oxygen barrier layer, a ceramicized mica tape and a second highly flame-retardant tape are wound outside the oxygen barrier layer, and an extruded and vulcanized cross-linked outer sheath layer is arranged outside the second highly flame-retardant tape to obtain a radiation-resistant medium-voltage fire-resistant lead soft cable for motors.

[0042] As one or more embodiments, the stranded conductor is made of tinned copper wires, and the stranding pitch is set to be 16 to 22 times the outer diameter of the stranded conductor; the stranding direction of the outermost layer of the stranded conductor is set to be right-handed, and the stranding directions of adjacent layers are opposite; the insulated wire core layer is obtained by vulcanizing the inner shield layer and the insulating layer. During the vulcanization process, the pressure of the heating steam in the vulcanization pipe is controlled at 0.8 to 1.1 MPa, and the water level of the cooling water is controlled at 25 m to 30 m.

[0043] To ensure that the service life of the radiation-resistant medium-voltage fire-resistant lead soft cable for motors reaches 60 years and the cable has halogen-free, low-smoke, flame-retardant, fire-resistant, low-toxic, and strong radiation-resistant properties, and can be applicable to the harsh use environment of nuclear power plants, the corresponding cable materials and structural designs in the above implementation solutions are adopted for the cable.

[0044] The radiation-resistant medium-voltage fire-resistant lead soft cable for motors manufactured in this embodiment shall meet the following technical indicators and parameters:

[0045] (1) Electrical properties

[0046] DC resistance of conductor at 20°C: It shall meet the requirements of the conductor in IEC 60228:2004 standard.

[0047] Insulation resistance constant at 20°C and 90°C: The minimum insulation resistance constant Ki ≥ 3670 MΩ·km at 20°C, and the minimum insulation resistance constant Ki ≥ 3.67 MΩ·km at 90°C.

[0048] Voltage test: Adopt power frequency AC voltage test of 42 kV, the voltage application time shall be not less than 5 min, applied between the conductor and the metal shield, and the insulation shall not break down.

[0049] Partial discharge test: The cable shall be subjected to partial discharge test, and the test sensitivity shall be 10 pC or better.

[0050] The voltage is applied between the conductor and the metal shield. The test voltage shall be gradually increased to 2U0 and maintained for 10 s, and then slowly decreased to 1.73U0. At 1.73U0, there shall be no detectable discharge exceeding the declared test sensitivity generated by the cable under test.

[0051] 4h voltage test: A power frequency AC voltage of 48 kV shall be applied between the cable conductor and the shield for 4 h. The voltage shall be gradually increased to the specified value. The insulation shall not break down.

[0052] (2) Mechanical and physical properties of insulation and sheath

[0053] Insulation elongation test: The insulation treatment conditions are air temperature 250°C, load time 15 min, and mechanical stress 20 N / cm 2 , and the elongation rate under load is required to be controlled within the range of 50% to 100%

[0054] Mechanical property test before and after insulation aging: The tensile strength before aging should be not less than 8.5 N / mm 2 , and the elongation at break should be not less than 200%. The change rates of tensile strength and elongation at break after aging should not be greater than ±30%. The aging conditions are temperature (135 ± 3)°C and time 168 h.

[0055] Insulation water absorption test: The weight increase should not be greater than 5 mg / cm 2 , the test temperature is (85 ± 2)°C, and the time is 336 h.

[0056] Sheath thermal elongation test: The sheath treatment conditions are air temperature 200°C, load time 15 min, and mechanical stress 20 N / cm 2 , and the elongation rate under load is required to be controlled within the range of 50% - 100%.

[0057] Mechanical property test before and after sheath aging: The tensile strength before aging should be not less than 8.5 N / mm 2 , and the elongation at break should be not less than 200%. The change rate of tensile strength after aging should not be greater than ±30% and the change rate of elongation at break should not be greater than ±40%. The aging conditions are temperature (100 ± 2)°C and time 168 h.

[0058] Sheath oil resistance test: The change rate of tensile strength should not be greater than ±40%, the test temperature is (100 ± 2)°C, and the time is 24 h.

[0059] Sheath low-temperature tensile test: The elongation at break should not be less than 20%, and the test temperature is (-15 ± 2)°C.

[0060] Sheath low-temperature impact test: There should be no cracks on the sheath after impact, and the test temperature is (-15 ± 2)°C.

[0061] Combustion test:

[0062] Vertical burning test of bunched cables (Type B): The height reached by the charred part should not be greater than 2.5 m.

[0063] Test for gases evolved during combustion: The amount of halogen acid gas released from the insulation and sheath should not be greater than 5 mg / g, the pH value of the insulation and sheath should not be less than 4.3, and the conductivity of the insulation and sheath should not be greater than 10 μS / mm.

[0064] Difference in oxygen index of insulation and sheath at 20°C and 80°C: It should not be greater than 2.

[0065] Insulation and sheath toxicity index test: The toxicity indices should not be greater than 5.

[0066] Cable combustion smoke density test: The light transmittance should not be less than 60%.

[0067] (3) Special Bending Test (Seismic Test)

[0068] Using 7 times the outer diameter of the cable as the bending diameter, bend it forward and backward 3 times, and then conduct the test. The voltage test voltage of the finished cable is 21 kV, and the time is not less than 5 min. It is required that the insulation shall not break down.

[0069] (4) Compatibility Test of Finished Cable

[0070] The change rates of tensile strength and elongation at break of the insulation and sheath before and after 168 h of aging shall not be greater than ±40%.

[0071] (5) Evaluation of Cable Time Behavior

[0072] Normal operating condition thermal aging simulation test (accelerated thermal aging test equivalent to 60 years of operation): Aging temperature 155 °C, time 956.9 h.

[0073] Irradiation aging simulation test under normal operating conditions: The irradiation aging test under normal operating conditions shall be carried out on the finished cable specimen and the insulated conductor core specimen in air. The dose rate shall not be greater than 1 Mrad / h, and the cumulative γ irradiation dose of the cable is 37.5 Mrad.

[0074] Bundle combustion test (Class B): The height reached by the charred part shall not be greater than 2.5 m.

[0075] (5) Fire Resistance Test

[0076] Single burner fire supply, the flame temperature is about 950 °C, the fire supply time is 180 min, no breakdown. 15 min after stopping the fire supply, no breakdown. After cooling, check the integrity of the specimen, no breakdown.

[0077] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and modifications.

[0078] The above are only the preferred embodiments of this example and are not used to limit this example. For those skilled in the art, this example can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this example shall be included within the protection scope of this example.

Claims

1. A radiation-resistant medium-voltage fire-resistant lead-in flexible cable for motors, characterized in that, It includes at least one cable core, and the cable core includes a stranded conductor and an insulating core layer. An inner shield layer and an insulating layer are wrapped around the stranded conductor, and the inner shield layer and the insulating layer are vulcanized to obtain the insulating core layer; a first highly flame-retardant tape, an inner sheath layer and an oxygen barrier layer are sequentially wrapped around the insulating core layer; a ceramized mica tape and a second highly flame-retardant tape are wrapped around the oxygen barrier layer, and an extruded, vulcanized and cross-linked outer sheath layer is provided outside the second highly flame-retardant tape.

2. A radiation-resistant medium-voltage fire-resistant lead soft cable for motors as described in claim 1, characterized in that, The inner shield layer and the insulating layer adopt a double-layer co-extrusion process and are formed by stacking a halogen-free semi-conductive inner shield material and a halogen-free ethylene-propylene rubber insulating material.

3. A radiation-resistant medium-voltage fire-resistant lead-in flexible cable for motors, characterized in that, A semi-conductive Teflon tape with overlapping wrapping is provided between the stranded conductor and the inner shield layer.

4. A radiation-resistant medium-voltage fire-resistant lead-in flexible cable for an electric motor as described in claim 1, characterized in that, The stranded conductor is stranded by tinned copper wires.

5. A radiation-resistant medium-voltage fire-resistant lead-in flexible cable for motors, characterized in that, The oxygen barrier layer is made of extruded ceramized low-smoke halogen-free flame-retardant and fire-resistant polyolefin.

6. The radiation-resistant medium-voltage fire-resistant lead soft cable for a motor according to claim 1, wherein, The outer sheath layer is made of a halogen-free flame-retardant rubber sheath material.

7. A manufacturing method of a radiation-resistant medium-voltage fire-resistant lead soft cable for an electric motor, which is used to manufacture the radiation-resistant medium-voltage fire-resistant lead soft cable for an electric motor as described in any one of claims 1-6, characterized in that, The stranded conductor in the cable core is wrapped with a tape to obtain an insulating core layer obtained by vulcanizing the inner shield layer and the insulating layer. The insulating core layer is wrapped to obtain a first highly flame-retardant tape, an inner sheath layer and an oxygen barrier layer. A ceramized mica tape and a second highly flame-retardant tape are wrapped around the oxygen barrier layer, and an extruded, vulcanized and cross-linked outer sheath layer is provided outside the second highly flame-retardant tape to obtain a radiation-resistant medium-voltage fire-resistant lead-in flexible cable for motors.

8. The manufacturing method of a radiation-resistant medium-voltage fire-resistant lead-in flexible cable for an electric motor as described in claim 7, characterized in that, The stranded conductor is stranded by tinned copper wires, and the stranding pitch is set to be 16 to 22 times the outer diameter of the stranded conductor.

9. The manufacturing method of a radiation-resistant medium-voltage fire-resistant lead-in flexible cable for motors as described in claim 7, characterized in that, The stranding direction of the outermost layer of the stranded conductor is set to be right-handed, and the stranding directions of adjacent layers are opposite.

10. The manufacturing method of a radiation-resistant medium-voltage fire-resistant lead soft cable for motors as described in claim 7, characterized in that, The insulating core layer is obtained by vulcanizing the inner shield layer and the insulating layer. During the vulcanization process, the pressure of the heating steam in the vulcanization pipe is controlled at 0.8 to 1.1 MPa, and the water level of the cooling water is controlled at 25 to 30 meters.

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