Heat-resistant light-weight cross-linked polyethylene insulated cable and preparation method thereof

Abstract

The invention relates to the technical field of insulated cables, in particular to a heat-resistant light-weight crosslinked polyethylene insulated cable which sequentially comprises a conductor, an insulating layer, a shielding layer and a sheath layer from inside to outside. The raw materials of the insulating layer comprise a heat-conducting filler, a corona-resistant filler, a compatilizer and crosslinked polyethylene; wherein the corona-resistant filler is prepared from modified microfibrillated cellulose, nano strontium titanate and a coupling agent; the preparation method of the cable comprises the following steps: S1, dividing the raw materials of the insulating layer into an insulating material A, an insulating material B and an insulating material C; s2, coating an insulating layer; s3, coating a sheath layer to obtain an insulated cable; according to the invention, the corona-resistant filler can prevent space charge accumulation and significantly inhibit the starting and destruction effects of corona, and the insulating layer is divided into three layers to improve the partial discharge resistance of the cable.

Description

Technical Field

[0001] This invention relates to the field of insulated cable technology, specifically to a heat-resistant, lightweight cross-linked polyethylene insulated cable and its preparation method. Background Technology

[0002] Cross-linked polyethylene insulated power cables are power cables that use cross-linked polyethylene (XLPE) as the insulation layer. They are mainly used in fixed laying scenarios of power distribution networks or industrial equipment with a rated power frequency voltage of 0.6 / 1kV and below, covering environments such as overhead, indoor, tunnel, and cable trench. The upper limit of its long-term operating temperature is 90℃, and the maximum withstand temperature during short circuit is 250℃ (lasting ≤5 seconds). The laying environment temperature must be ≥0℃, and the minimum bending radius is not less than 15 times the outer diameter of the cable.

[0003] This cable utilizes a cross-linking process to transform polyethylene into a three-dimensional network structure, possessing both chemical stability and high-temperature resistance, resulting in higher current carrying capacity and mechanical strength compared to traditional cables. However, cross-linked polyethylene has inherent limitations in its corona resistance: cross-linked polyethylene insulated cables have poor resistance to partial discharge, and prolonged partial discharge accelerates insulation degradation; furthermore, impurities, pores, and other defects within the cable insulation, or discontinuities in the semi-conductive shielding layer, can easily cause electric field concentration, potentially triggering partial discharge and leading to treeing discharge (electrical treeing, water treeing), thus affecting the cable's insulation performance.

[0004] Therefore, this invention aims to design a heat-resistant, lightweight cross-linked polyethylene insulated cable and a preparation method to improve the above-mentioned problems. Summary of the Invention

[0005] To address the above problems, this invention provides a heat-resistant, lightweight cross-linked polyethylene insulated cable and its preparation method.

[0006] A heat-resistant, lightweight cross-linked polyethylene insulated cable, comprising, from the inside out, a conductor, an insulation layer, a shielding layer, and a sheath layer; The raw materials for the insulating layer include thermally conductive filler, corona-resistant filler, compatibilizer, and cross-linked polyethylene in a mass ratio of 1:2~3:0.5:10; The corona-resistant filler comprises modified microfibrillated cellulose, nano-strontium titanate, and a coupling agent in a mass ratio of 1:0.5:0.05~0.08.

[0007] Furthermore, the conductor is a copper conductor.

[0008] Note: Copper conductors have high current carrying capacity, reliable connection, good mechanical strength, low voltage loss, and excellent stability.

[0009] Furthermore, the sheath layer is made of cross-linked polyethylene.

[0010] Note: Cross-linked polyethylene has excellent heat resistance, good insulation properties, strong mechanical properties, and resistance to chemical corrosion, which can effectively protect cables.

[0011] Furthermore, the shielding layer is made of aluminum foil.

[0012] Note: Aluminum foil has good electrical conductivity and high flexibility, and can effectively shield external electromagnetic interference.

[0013] Furthermore, the thermally conductive filler is silicon dioxide with a particle size of 3~5μm.

[0014] Note: Silica can form thermally conductive paths in cross-linked polyethylene, increasing the overall thermal conductivity of the insulation layer and helping to dissipate heat during cable operation.

[0015] Furthermore, the compatibilizer is polyethylene grafted with maleic anhydride.

[0016] Note: Polyethylene grafted with maleic anhydride has a large molecular weight, which can more effectively transfer stress and improve the impact resistance of the cable.

[0017] Furthermore, the preparation method of the corona-resistant filler is as follows: Microfibrillated cellulose is treated with argon plasma at a power of 220-250W for 2-3 minutes to obtain modified microfibrillated cellulose. The modified microfibrillated cellulose, nano-strontium titanate, and coupling agent are then mixed in a specific ratio at a temperature of 50-60℃ for 20-30 minutes to obtain a mixture. The mixture was added to deionized water at a solid-liquid ratio of 1g:20~25ml and ultrasonically dispersed for 1~2h with an ultrasonic power of 150~180W. Ozone was then introduced into the deionized water at a rate of 1500~1600mg / h. The obtained product was filtered, washed and dried in sequence to obtain a corona-resistant filler.

[0018] Explanation: After argon plasma treatment, the surface of microfibrillated cellulose generates more active sites, enhancing its reactivity and binding ability with subsequently added nano-strontium titanate and coupling agent. During subsequent mixing and ultrasonic dispersion, ultrasonic cavitation effectively breaks up the agglomeration of nano-strontium titanate, ensuring uniform dispersion. The functional groups of the coupling agent can hydrolyze and bind to the hydroxyl groups on the cellulose surface, while the functional groups at the other end interact with the surface of nano-strontium titanate, forming a stable filler. Ozone combined with ultrasonic etching significantly improves the surface roughness of the mixture, which is beneficial for increasing the bonding force between the corona-resistant filler and cross-linked polyethylene. In the corona-resistant filler obtained in this way, nano-strontium titanate can effectively capture and uniformly disperse high-energy charges that accelerate under a high electric field, preventing the accumulation of space charge and significantly inhibiting the initiation and destructive effects of corona, thereby extending the service life of the cable. The combination of microfibrillated cellulose and nano-strontium titanate enhances thermal conductivity, aids in heat dissipation, and improves the current carrying capacity and long-term thermal stability of the cable.

[0019] A method for preparing a heat-resistant, lightweight cross-linked polyethylene insulated cable as described in any of the above methods includes the following steps: S1. Weigh the raw materials for the insulation layer according to the specified ratio. Then, divide the thermally conductive filler into 3 parts in a mass ratio of 0.7~0.9:1:1, divide the corona-resistant filler into 3 parts in a mass ratio of 1.5~1.8:1.2:1, divide the compatibilizer into 3 parts in a mass ratio of 1.2~1.4:1:0.8, and divide the cross-linked polyethylene into 3 parts in a mass ratio of 1.2~1.4:1:1. After dividing the raw materials according to the above proportions, prepare insulating material A, insulating material B and insulating material C respectively; The mass ratio of corona-resistant filler in insulating material A, insulating material B, and insulating material C is 1.5~1.8:1.2:1; The mass ratio of thermally conductive filler in insulating material A, insulating material B, and insulating material C is 0.7~0.9:1:1; The mass ratio of the compatibilizer in insulating material A, insulating material B, and insulating material C is 1.2~1.4:1:0.8; The mass ratio of cross-linked polyethylene in insulation material A, insulation material B, and insulation material C is 1.2~1.4:1:1; S2. Insulating material A, insulating material B and insulating material C are sequentially extruded and coated onto the surface of the conductor using a twin-screw mixer to obtain an insulating layer. S3. The shielding layer and the sheath layer are extruded sequentially onto the surface of the insulation layer using a twin-screw mixer to obtain an insulated cable.

[0020] Further, in S2, the mixing temperature of the extrusion coating is 180~190℃, the mixing time is 10~15min, and the extrusion temperature is 150~160℃; in S3, the mixing temperature of the extrusion coating is 170~175℃, the mixing time is 5~10min, and the extrusion temperature is 110~120℃.

[0021] Note: The above temperature allows for better coating of the insulation and sheath materials, resulting in a stable cable.

[0022] Compared with existing cross-linked polyethylene insulated cables, the advantages of this invention are: (1) This invention uses modified microfibrillated cellulose, nano-strontium titanate, and coupling agent as corona-resistant fillers. After being treated with argon plasma, the surface of the modified microfibrillated cellulose generates more active sites, which enhances its reactivity and binding ability with the subsequently added nano-strontium titanate and coupling agent. In the subsequent mixing and ultrasonic dispersion, ultrasonic cavitation can effectively break the agglomeration of nano-strontium titanate and make it uniformly dispersed. The functional groups of the coupling agent can be hydrolyzed and combined with the hydroxyl groups on the surface of cellulose, while the functional groups at the other end combine with the nano-strontium titanate. Strontium surface treatment forms a stable filler, and ozone combined with ultrasonic etching significantly improves the surface roughness of the mixture, which is beneficial to increasing the bonding force between the corona-resistant filler and cross-linked polyethylene. In the corona-resistant filler obtained in this way, nano-strontium titanate can effectively capture and uniformly disperse high-energy charges that accelerate under high electric fields, prevent the accumulation of space charges, and significantly inhibit the initiation and destructive effects of corona, thereby extending the service life of the cable. The combination of microfibrillated cellulose and nano-strontium titanate enhances thermal conductivity, helps heat dissipation, and improves the current carrying capacity and long-term thermal stability of the cable.

[0023] (2) The present invention divides the insulation layer into three layers, forming a sandwich structure with gradually changing performance from the inside to the outside. Insulation material A is the inner layer, with a high proportion of corona-resistant filler, which can more effectively uniform the electric field on the conductor surface and suppress corona generation. Insulation material C is the outer layer, with a relatively high proportion of cross-linked polyethylene, which ensures the overall insulation strength and mechanical protection, and can significantly improve the cable's resistance to partial discharge and long-term electrical life.

[0024] (3) The present invention adjusts the proportion of cross-linked polyethylene according to the mass of corona-resistant filler in each insulating material, which can ensure that there is enough polymer matrix to wrap in the insulating layer with a large proportion of corona-resistant filler to prevent interface defects; and provides sufficient insulating medium in the insulating layer with a large proportion of corona-resistant filler. This helps to maintain the flexibility and processability of the material while maintaining excellent corona resistance, reduce internal stress, and improve the stability of the cable under thermal cycling or mechanical vibration. Attached Figure Description

[0025] Figure 1This is a comparison chart of the results of Experiment Example 1 of this invention; Figure 2 This is a comparison chart of the results of Experiment Example 2 of this invention; Figure 3 This is a comparison chart of the results of Experiment Example 3 of this invention. Detailed Implementation

[0026] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0027] Example 1: A heat-resistant and lightweight cross-linked polyethylene insulated cable, comprising, from the inside out, a conductor, an insulation layer, a shielding layer, and a sheath layer; the conductor is a copper conductor, the sheath layer is made of cross-linked polyethylene, and the shielding layer is made of aluminum foil; The raw materials of the insulating layer include thermally conductive filler, corona-resistant filler, compatibilizer, and cross-linked polyethylene in a mass ratio of 1:2.5:0.5:10. The thermally conductive filler is silicon dioxide with a particle size of 3.5~4.5μm, and the compatibilizer is polyethylene grafted with maleic anhydride. The corona-resistant filler comprises modified microfibrillated cellulose, nano-strontium titanate, and silane coupling agent (KH-550) in a mass ratio of 1:0.5:0.07. The preparation method of the corona-resistant filler is as follows: Microfibrillated cellulose was treated with argon plasma at a power of 235W for 2.5 minutes to obtain modified microfibrillated cellulose. The modified microfibrillated cellulose, nano-strontium titanate, and coupling agent were then mixed in a specific ratio at a temperature of 55°C for 25 minutes to obtain a mixture. The mixture was added to deionized water at a solid-liquid ratio of 1g:23ml and ultrasonically dispersed for 1.5h with an ultrasonic power of 165W. Ozone was then introduced into the deionized water at a rate of 1550mg / h. The obtained product was filtered, washed and dried sequentially. The washing was done with deionized water, and the drying temperature was 60℃ for 30 minutes to obtain the corona-resistant filler.

[0028] Example 2: A method for preparing a heat-resistant, lightweight cross-linked polyethylene insulated cable as described in Example 1, comprising the following steps: S1. Weigh the raw materials for the insulation layer according to the specified ratio, then divide the thermally conductive filler into 3 parts by mass ratio of 0.8:1:1, divide the corona-resistant filler into 3 parts by mass ratio of 1.6:1.2:1, divide the compatibilizer into 3 parts by mass ratio of 1.3:1:0.8, and divide the cross-linked polyethylene into 3 parts by mass ratio of 1.3:1:1. After dividing the raw materials according to the above proportions, prepare insulating material A, insulating material B and insulating material C respectively; The mass ratio of corona-resistant filler in insulating material A, insulating material B, and insulating material C is 1.6:1.2:1. The mass ratio of the thermally conductive filler in insulating material A, insulating material B, and insulating material C is 0.8:1:1; The mass ratio of the compatibilizer in insulating material A, insulating material B, and insulating material C is 1.3:1:0.8; The mass ratio of cross-linked polyethylene in insulation material A, insulation material B, and insulation material C is 1.3:1:1; S2. Insulating material A, insulating material B and insulating material C are sequentially extruded and coated onto the surface of the copper conductor using a twin-screw mixer to obtain an insulating layer; the extrusion coating mixing temperature is 185℃, the mixing time is 13min, and the extrusion temperature is 155℃. S3. The shielding layer and the sheath layer are sequentially extruded onto the surface of the insulation layer using a twin-screw mixer. The extrusion mixing temperature is 172°C, the mixing time is 8 minutes, and the extrusion temperature is 115°C to obtain the insulated cable.

[0029] Example 3: The difference between this example and Example 1 is that the raw materials of the insulating layer include thermally conductive filler, corona-resistant filler, compatibilizer, and cross-linked polyethylene in a mass ratio of 1:2:0.5:10, and the thermally conductive filler is silicon dioxide with a particle size of 3~3.5μm.

[0030] Example 4: The difference between this example and Example 1 is that the raw materials of the insulating layer include thermally conductive filler, corona-resistant filler, compatibilizer, and cross-linked polyethylene in a mass ratio of 1:3:0.5:10, and the thermally conductive filler is silicon dioxide with a particle size of 4.5~5μm.

[0031] Example 5: This example differs from Example 1 in that the corona-resistant filler comprises modified microfibrillated cellulose, nano-strontium titanate, and silane coupling agent (KH-550) in a mass ratio of 1:0.5:0.05.

[0032] Example 6: The difference between this example and Example 1 is that the corona-resistant filler includes modified microfibrillated cellulose, nano-strontium titanate, and silane coupling agent (KH-550) in a mass ratio of 1:0.5:0.08.

[0033] Example 7: The difference between this example and Example 1 is that the microfibrillated cellulose is treated with argon plasma at a power of 220W for 2 minutes to obtain modified microfibrillated cellulose.

[0034] Example 8: The difference between this example and Example 1 is that the microfibrillated cellulose is treated with argon plasma at a power of 250W for 3 minutes to obtain modified microfibrillated cellulose.

[0035] Example 9: This example differs from Example 1 in that the modified microfibrillated cellulose, nano-strontium titanate, and coupling agent are mixed in a certain proportion, the mixing temperature is 50°C, and the mixing time is 20 min to obtain a mixture.

[0036] Example 10: This example differs from Example 1 in that the modified microfibrillated cellulose, nano-strontium titanate, and coupling agent are mixed in a certain proportion, the mixing temperature is 60°C, and the mixing time is 30 min to obtain a mixture.

[0037] Example 11: This example differs from Example 1 in that the mixture is added to deionized water at a solid-liquid ratio of 1g:20ml and ultrasonically dispersed for 1h with an ultrasonic power of 150W. Ozone is also introduced into the deionized water at a rate of 1500mg / h.

[0038] Example 12: This example differs from Example 1 in that the mixture is added to deionized water at a solid-liquid ratio of 1g:25ml and ultrasonically dispersed for 2 hours with an ultrasonic power of 180W. Ozone is also introduced into the deionized water at a rate of 1600mg / h.

[0039] Example 13: This example differs from Example 2 in that the thermally conductive filler is divided into 3 parts by mass ratio of 0.7:1:1, the corona-resistant filler is divided into 3 parts by mass ratio of 1.5:1.2:1, the compatibilizer is divided into 3 parts by mass ratio of 1.2:1:0.8, and the cross-linked polyethylene is divided into 3 parts by mass ratio of 1.4:1:1. The mass ratio of the corona-resistant filler in insulating materials A, B, and C is 1.5:1.2:1; the mass ratio of the thermally conductive filler in insulating materials A, B, and C is 0.7:1:1; the mass ratio of the compatibilizer in insulating materials A, B, and C is 1.2:1:0.8; and the mass ratio of the cross-linked polyethylene in insulating materials A, B, and C is 1.4:1:1.

[0040] Example 14: This example differs from Example 2 in that the thermally conductive filler is divided into 3 parts by mass ratio of 0.9:1:1, the corona-resistant filler is divided into 3 parts by mass ratio of 1.8:1.2:1, the compatibilizer is divided into 3 parts by mass ratio of 1.4:1:0.8, and the cross-linked polyethylene is divided into 3 parts by mass ratio of 1.2:1:1. The mass ratio of the corona-resistant filler in insulating materials A, B, and C is 1.8:1.2:1; the mass ratio of the thermally conductive filler in insulating materials A, B, and C is 0.9:1:1; the mass ratio of the compatibilizer in insulating materials A, B, and C is 1.4:1:0.8; and the mass ratio of the cross-linked polyethylene in insulating materials A, B, and C is 1.2:1:1.

[0041] Example 15: This example differs from Example 2 in that, in S2, the mixing temperature of the extrusion coating is 180°C, the mixing time is 10 min, and the extrusion temperature is 150°C; in S3, the mixing temperature of the extrusion coating is 170°C, the mixing time is 5 min, and the extrusion temperature is 110°C.

[0042] Example 16: This example differs from Example 2 in that, in S2, the mixing temperature of the extrusion coating is 190°C, the mixing time is 15 min, and the extrusion temperature is 160°C; in S3, the mixing temperature of the extrusion coating is 175°C, the mixing time is 10 min, and the extrusion temperature is 120°C.

[0043] Experimental Example: The description of this experimental example is based on the scheme described in Example 2, and aims to illustrate the practical application effect of the present invention.

[0044] The corona resistance of the cross-linked polyethylene insulated cables obtained in each embodiment was tested to prove that the cross-linked polyethylene insulated cables obtained by the present invention have excellent performance. The corona resistance test method is as follows: apply 10kV to the cable and test the total time it takes for the cable to break down under high voltage. The longer the total time, the better the corona resistance.

[0045] Investigation 1: Investigate the effect of the raw material ratio of cross-linked polyethylene insulated cables on the corona resistance of the cables.

[0046] Depend on Figure 1 The results show that, compared with Examples 1 and 3 to 6, a small proportion of corona-resistant filler and a small or large proportion of modified microfibrillated cellulose will shorten the total time. In Example 4, the proportion of corona-resistant filler is larger than that in Example 1, but the extension of the total time is less than that of the increase in the amount of corona-resistant filler. Therefore, from an economic point of view, the parameters of Example 1 are relatively better.

[0047] Investigation 2: Investigate the effect of the preparation of corona-resistant filler on the corona resistance of cables.

[0048] Depend on Figure 2 The results show that, compared with Examples 1 and 7 to 12, too small or too large parameters for argon plasma treatment, too small or too large parameters for mixture preparation, and too small or too large parameters for ozone ultrasound will shorten the total time. Therefore, from a comprehensive perspective, the parameters of Example 1 are relatively better.

[0049] Investigation 3: Investigate the effect of preparation method on the corona resistance of cable.

[0050] Depend on Figure 3 The results show that, compared with Examples 2 and 13 to 16, both excessively small or large proportions of corona-resistant filler in each insulating material and excessively small or large basic coating parameters will shorten the total time. Therefore, from a comprehensive perspective, the parameter effect of Example 1 is relatively better.

[0051] In addition, the present invention also tested the thermal aging performance of the cable. Before aging, the tensile strength of the cable was 38.8 MPa and the elongation at break was 448%; after aging, the tensile strength of the cable decreased by 0.32% and the elongation at break decreased by 2.63%. In summary, the cross-linked polyethylene insulated cable prepared by this invention has excellent heat resistance and corona resistance.

Claims

1. A heat-resistant, lightweight cross-linked polyethylene insulated cable, characterized in that, From the inside out, it includes the conductor, insulation layer, shielding layer, and sheath layer; The raw materials for the insulating layer include thermally conductive filler, corona-resistant filler, compatibilizer, and cross-linked polyethylene in a mass ratio of 1:2~3:0.5:10; The corona-resistant filler comprises modified microfibrillated cellulose, nano-strontium titanate, and a coupling agent in a mass ratio of 1:0.5:0.05~0.

08.

2. The heat-resistant, lightweight cross-linked polyethylene insulated cable as described in claim 1, characterized in that, The conductor is a copper conductor.

3. The heat-resistant, lightweight cross-linked polyethylene insulated cable as described in claim 1, characterized in that, The sheath layer is made of cross-linked polyethylene.

4. The heat-resistant, lightweight cross-linked polyethylene insulated cable as described in claim 1, characterized in that, The shielding layer is made of aluminum foil.

5. The heat-resistant, lightweight cross-linked polyethylene insulated cable as described in claim 1, characterized in that, The thermally conductive filler is silicon dioxide with a particle size of 3~5μm.

6. The heat-resistant, lightweight cross-linked polyethylene insulated cable as described in claim 1, characterized in that, The compatibilizer is polyethylene grafted with maleic anhydride.

7. The heat-resistant, lightweight cross-linked polyethylene insulated cable as described in claim 1, characterized in that, The preparation method of the corona-resistant filler is as follows: Microfibrillated cellulose is treated with argon plasma at a power of 220-250W for 2-3 minutes to obtain modified microfibrillated cellulose. The modified microfibrillated cellulose, nano-strontium titanate, and coupling agent are then mixed in a specific ratio at a temperature of 50-60℃ for 20-30 minutes to obtain a mixture. The mixture was added to deionized water at a solid-liquid ratio of 1g:20~25ml and ultrasonically dispersed for 1~2h with an ultrasonic power of 150~180W. Ozone was then introduced into the deionized water at a rate of 1500~1600mg / h. The obtained product was filtered, washed and dried in sequence to obtain a corona-resistant filler.

8. A method for preparing a heat-resistant, lightweight cross-linked polyethylene insulated cable as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Weigh the raw materials for the insulation layer according to the specified ratio. Then, divide the thermally conductive filler into 3 parts in a mass ratio of 0.7~0.9:1:1, divide the corona-resistant filler into 3 parts in a mass ratio of 1.5~1.8:1.2:1, divide the compatibilizer into 3 parts in a mass ratio of 1.2~1.4:1:0.8, and divide the cross-linked polyethylene into 3 parts in a mass ratio of 1.2~1.4:1:

1. After dividing the raw materials according to the above proportions, prepare insulating material A, insulating material B and insulating material C respectively; The mass ratio of corona-resistant filler in insulating material A, insulating material B, and insulating material C is 1.5~1.8:1.2:1; The mass ratio of thermally conductive filler in insulating material A, insulating material B, and insulating material C is 0.7~0.9:1:1; The mass ratio of the compatibilizer in insulating material A, insulating material B, and insulating material C is 1.2~1.4:1:0.8; The mass ratio of cross-linked polyethylene in insulation material A, insulation material B, and insulation material C is 1.2~1.4:1:1; S2. Insulating material A, insulating material B and insulating material C are sequentially extruded and coated onto the surface of the conductor using a twin-screw mixer to obtain an insulating layer. S3. The shielding layer and the sheath layer are extruded sequentially onto the surface of the insulation layer using a twin-screw mixer to obtain an insulated cable.

9. The method for preparing a heat-resistant, lightweight cross-linked polyethylene insulated cable as described in claim 1, characterized in that, In S2, the mixing temperature of the extrusion coating is 180~190℃, the mixing time is 10~15min, and the extrusion temperature is 150~160℃; in S3, the mixing temperature of the extrusion coating is 170~175℃, the mixing time is 5~10min, and the extrusion temperature is 110~120℃.

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