Water-tree-resistant medium-voltage power cable

Abstract

The invention relates to the technical field of power cables, and provides a water-tree-resistant medium-voltage power cable which comprises a conductor, an insulating layer, an insulating shielding layer, a waterproof layer, a metal shielding layer and an outer sheath layer. Wherein the insulating layer is prepared from the following raw materials in parts by weight: 73-85 parts of polypropylene, 0.5-1.5 parts of an initiator, 5-15 parts of a water-tree-resistant auxiliary agent and 3-4 parts of a lubricant. Polypropylene is adopted to replace traditional cross-linked polyethylene, and molecules of polypropylene are arranged more tightly, so that moisture permeation can be effectively blocked, and the possibility of water tree formation is reduced; the water-tree-resistant auxiliary agent can effectively prevent water from permeating and can also play a certain role in stabilizing the polypropylene matrix, and through the technical scheme, the problem that in the related technology, a cable insulation layer is extremely prone to water tree aging is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power cables, and in particular to a water-tree resistant medium-voltage power cable. Background Art

[0002] With the continuous advancement of urban power grid construction and the continued growth in industrial electricity demand, medium-voltage power cables are increasingly widely used in distribution networks. Medium-voltage power cables operate in complex and changing environments for long periods of time, particularly when laid underground, in moist soil, or underwater. They are highly susceptible to moisture intrusion. Moisture vapor easily penetrates the conductors and insulation, forming tree-like structures in the insulation layer. These trees continue to grow and spread, severely weakening the cable's insulation performance and ultimately causing cable breakdown, power outages, and even significant economic losses and safety hazards.

[0003] Currently, conventional medium-voltage power cables mostly use cross-linked polyethylene (XLPE) as the insulation material. XLPE has been widely used in power cables due to its excellent electrical, mechanical, and processability. However, XLPE is inherently hydroscopic, and under the combined effects of electric fields and moisture, its insulation layer is highly susceptible to water treeing. Furthermore, the moisture-proof design of traditional medium-voltage cables primarily relies on physical barriers such as metal sheaths or aluminum-plastic composite tapes. However, during installation and operation, mechanical stress, thermal expansion, and contraction can easily cause microscopic damage to the sheath, allowing moisture to gradually penetrate the insulation layer. This is particularly true in high-humidity environments such as direct underground burial, tunnels, and coastal locations. When the cable insulation material comes into contact with moisture, the electric field can easily trigger water tree growth. Therefore, given these challenges, there is an urgent need for a water-tree-resistant medium-voltage power cable to meet the growing demands of power cable technology. Summary of the Invention

[0004] The present invention provides a water-tree resistant medium-voltage power cable, which solves the problem in the related art that the cable insulation layer is very susceptible to water tree aging.

[0005] The technical solutions of the present invention are as follows: The present invention provides a water-tree-resistant medium-voltage power cable, comprising a conductor, an insulation layer, an insulation shielding layer, a water-blocking layer, a metal shielding layer, and an outer sheath layer. The insulation layer comprises the following raw materials in parts by weight: 73-85 parts of polypropylene, 0.5-1.5 parts of an initiator, 5-15 parts of an anti-water-tree additive, and 3-4 parts of a lubricant.

[0006] As a further technical solution, the conductor is made of oxygen-free copper rod.

[0007] As a further technical solution, the material of the water-blocking layer is an aluminum-plastic composite water-blocking tape.

[0008] As a further technical solution, the material of the metal shielding layer is a braided copper mesh.

[0009] As a further technical solution, the insulating shielding layer is semi-conductive polyethylene, which includes the following raw materials in parts by weight: 63-71 parts of polyethylene and 12-18 parts of carbon black.

[0010] In the present invention, the insulating shielding layer adopts a composite material of semi-conductive polyethylene and carbon black, which optimizes the electric field distribution and reduces the risk of partial discharge.

[0011] As a further technical solution, the material of the outer sheath layer is polyvinyl chloride.

[0012] As a further technical solution, the initiator is one of dicumyl peroxide and tert-butylcumyl peroxide.

[0013] As a further technical solution, the lubricant is one of polyethylene wax, zinc stearate and epoxidized soybean oil.

[0014] In the present invention, polypropylene is used as the material for the insulation layer. Since polypropylene has a higher degree of crystallinity than polyethylene and its molecules are arranged more tightly, it is more difficult for moisture to diffuse into the interior of the insulation layer, which can improve the cable's anti-water treeing performance to a certain extent; the aluminum-plastic composite water-blocking tape is the core material for radial water blocking in power cables, which can further improve the cable's anti-water treeing performance.

[0015] As a further technical solution, the anti-water tree additive is prepared by the following steps: Step A1: At room temperature, in a dry three-necked flask equipped with a constant pressure dropping funnel, a magnetic stirrer, and a condenser, anhydrous toluene is used as a reaction solvent, and pentaerythritol is used as a reaction raw material. After the two are mixed, phosphorus trichloride is added to the flask using a constant pressure dropping funnel. After the addition is complete, a magnetic stirrer is used to stir for 10-20 minutes, and the device is heated until the temperature reaches 80°C. The temperature is maintained and refluxed for 4 hours. After the reaction is complete, anhydrous toluene and excess phosphorus trichloride are removed by rotary evaporation to obtain an auxiliary intermediate product A; In step A1, pentaerythritol and phosphorus trichloride react in a molar ratio of 1:2, and phosphorus trichloride is slightly excessive to ensure sufficient reaction; the reaction formula is as follows:

[0016] Step A2, under room temperature, in a dry three-necked flask equipped with a constant pressure dropping funnel, a magnetic stirrer and a condenser, anhydrous toluene is used as the reaction solvent, the auxiliary intermediate product A and pentafluorophenol are used as the reaction raw materials, the three are mixed, and then sodium hydroxide is mixed with deionized water. After the solution is configured into a solution, it is slowly added dropwise to the flask using a constant pressure dropping funnel. After the addition is completed, a magnetic stirrer is used to stir for 5-10 minutes, and the device is heated until the reaction temperature stabilizes at 65 ° C. The reaction is maintained at the temperature for 4 hours. After the reaction is completed, it is filtered, and after rotary evaporation using a rotary evaporator, it is purified by column chromatography to obtain the auxiliary intermediate product B; In step A2, sodium hydroxide is used as a base catalyst to catalyze the reaction between pentafluorophenol and the auxiliary intermediate product A; the reaction formula is as follows:

[0017] Step A3, under room temperature, in a dry three-necked flask equipped with a constant pressure dropping funnel, a magnetic stirrer and a condenser, anhydrous toluene is used as the reaction solvent, the auxiliary intermediate product B and 4-hydroxystyrene are used as the reaction raw materials, the three are mixed, and then sodium hydroxide is mixed with deionized water. After preparing a solution, it is slowly added dropwise to the flask using a constant pressure dropping funnel. After the addition is completed, use a magnetic stirrer and stir for 6-8 minutes, then heat the device until the reaction temperature stabilizes at 70°C, maintain the temperature for 6 hours, and after the reaction is completed, filter, use a rotary evaporator for rotary evaporation, and purify by column chromatography to obtain an anti-water tree auxiliary agent; In step A3, the auxiliary intermediate product B reacts with 4-hydroxystyrene. The reaction principle is the same as that in step A2. The reaction formula is as follows:

[0018] The anti-water treeing agent prepared by the present invention has multiple C-F bonds introduced into its molecule. Due to the high bond energy of the C-F bonds, they are extremely difficult to break under the action of electric fields and moisture. The hydrophobicity of the C-F bonds creates a "lotus effect" on the surface of the insulating material, preventing moisture from wetting or penetrating the interior, effectively blocking moisture penetration and improving the anti-water treeing performance of the substrate. In addition, a benzene ring is introduced into the molecule of the anti-water treeing agent. The benzene ring, as a hydrophobic group, can further improve the anti-water treeing performance of the substrate. In addition, the phosphite structure introduced into the molecule can absorb free radicals, reduce the aging effect of water treeing, and further improve the anti-water treeing performance of the substrate. Finally, an unsaturated double bond is introduced at one end of the molecule. This group can cross-link with the polypropylene matrix under the action of an initiator, thereby connecting the small molecule anti-water treeing agent to the large molecule polypropylene matrix, improving the migration resistance of the anti-water treeing agent and making the performance of the anti-water treeing agent more stable.

[0019] As a further technical solution, the ratio of anhydrous toluene, pentaerythritol, and phosphorus trichloride in step A1 is 100 mL: 13.0-14.0 g: 29.5-30.5 g, for example, it can be 100 mL: 13.0 g: 29.5 g, 100 mL: 13.2 g: 30 g, 100 mL: 13.6 g: 30.2 g, 100 mL: 14.0 g: 30.5 g, preferably 100 mL: 13.6 g: 30.2 g.

[0020] As a further technical solution, the ratio of anhydrous toluene, auxiliary intermediate product A, pentafluorophenol, sodium hydroxide and deionized water in step A2 is 120mL:26.0~26.5g:18.0~18.5g:4.0g:15mL, for example, it can be 120mL:26.0g:18.0g:4.0g:15mL, 120mL:26.5g:18.0g:4.0g:15mL, 120mL:26.0g:18.5g:4.0g:15mL, 120mL:26.5g:18.3g:4.0g:15mL, 120mL:26.5g:18.5g:4.0g:15mL, preferably 120mL:26.5g:18.3g:4.0g:15mL.

[0021] As a further technical solution, the ratio of anhydrous toluene, auxiliary intermediate product B, 4-hydroxystyrene, sodium hydroxide and deionized water in step A3 is 150mL:41.0~41.5g:12.0g:4.0g:15mL, for example, it can be 150mL:41.0g:12.0g:4.0g:15mL, 150mL:41.1g:12.0g:4.0g:15m L, 150mL:41.2g:12.0g:4.0g:15mL, 150mL:41.3g:12.0g:4.0g:15mL, 150mL:41.4g:12.0g:4.0g:15mL, 150mL:41.5g:12.0g:4.0g:15mL, preferably 150mL:41.1g:12.0g:4.0g:15mL.

[0022] As a further technical solution, the water-tree resistant medium-voltage power cable is manufactured by the following steps: An oxygen-free copper rod is drawn into a thin copper wire through a wire drawing machine, and a plurality of thin copper wires are twisted to obtain a conductor. After polypropylene is dried, it is mixed with diisopropyl benzene peroxide, an anti-water tree additive and epoxy soybean oil as an insulating layer material. Polyethylene and carbon black are then mixed as an insulating shielding layer material. The two materials are respectively added into two extruders for melt blending. The materials are extruded and coated on the surface of the conductor through double-die co-extrusion to form an insulating layer and an insulating shielding layer. The insulating shielding layer is wrapped with an aluminum-plastic composite water-blocking tape to form a water-blocking layer. The water-blocking layer is then wrapped with a braided copper mesh to form a metal shielding layer. Finally, polyvinyl chloride is extruded and coated on the surface of the metal shielding layer through an extruder to form an outer sheath layer to prepare an anti-water-tree medium-voltage power cable.

[0023] The working principle and beneficial effects of the present invention are: 1. The insulating layer of the present invention uses polypropylene instead of traditional cross-linked polyethylene. The molecules of polypropylene are more tightly arranged, which can effectively block water penetration and reduce the possibility of water tree formation. The anti-water tree additive is introduced into the insulating layer. The anti-water tree additive can effectively prevent water penetration and also play a certain role in stabilizing the polypropylene matrix. 2. The cable adopts a multi-layer structure design, including an insulating shielding layer, a water-blocking layer and a metal shielding layer, which blocks moisture intrusion from a physical level. The combination of the water-blocking layer and the metal shielding layer further improves the radial and longitudinal waterproof capabilities of the cable; In summary, the cable prepared by the present invention has excellent anti-water treeing performance, is suitable for humid environments, and has important application value in the field of power cable technology. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0025] In the following examples and comparative examples, polypropylene is model T30S; commercially available ordinary cross-linked polyethylene is model YJ-35; and commercially available water-tree resistant cross-linked polyethylene is produced by Zhejiang Wanma Polymer Materials Group Co., Ltd. and is model TR-YJ-66.

[0026] Example 1 Preparation of anti-water tree additives: Step A1, at room temperature, in a dry three-necked flask equipped with a constant pressure dropping funnel, a magnetic stirrer and a condenser, 100 mL of anhydrous toluene was used as the reaction solvent, 13.6 g of pentaerythritol was used as the reaction raw material, the two were mixed, and then 30.2 g of phosphorus trichloride was added to the flask using a constant pressure dropping funnel. After the addition was complete, a magnetic stirrer was used to stir for 20 minutes, and the device was heated until the temperature reached 80 ° C. The temperature was maintained and refluxed for 4 hours. After the reaction was completed, anhydrous toluene and excess phosphorus trichloride were removed by rotary evaporation to obtain an auxiliary intermediate product A; Step A2, at room temperature, in a dry three-necked flask equipped with a constant pressure dropping funnel, a magnetic stirrer and a condenser, 120 mL of anhydrous toluene was used as the reaction solvent, 26.5 g of the auxiliary intermediate product A and 18.3 g of pentafluorophenol were used as the reaction raw materials. After the three were mixed, 4.0 g of sodium hydroxide was mixed with 15 mL of deionized water. After the solution was configured, it was slowly added dropwise to the flask using a constant pressure dropping funnel. After the addition was complete, a magnetic stirrer was used and stirred for 10 minutes. The device was heated until the reaction temperature stabilized at 65 ° C. The reaction was maintained at temperature for 4 hours. After the reaction was completed, it was filtered, and after rotary evaporation using a rotary evaporator, it was purified by column chromatography to obtain the auxiliary intermediate product B; Step A3, under room temperature, in a dry three-necked flask equipped with a constant pressure dropping funnel, a magnetic stirrer and a condenser, 150 mL of anhydrous toluene was used as the reaction solvent, 41.1 g of the auxiliary intermediate product B and 12.0 g of 4-hydroxystyrene were used as the reaction raw materials, and after the three were mixed, 4.0 g of sodium hydroxide was mixed with 15 mL of deionized water. After the solution was prepared, it was slowly added dropwise to the flask using a constant pressure dropping funnel. After the addition was completed, a magnetic stirrer was used and stirred for 8 minutes. The device was heated until the reaction temperature stabilized at 70 ° C. The reaction was maintained at the temperature for 6 hours. After the reaction was completed, it was filtered, and after rotary evaporation using a rotary evaporator, it was purified by column chromatography to obtain an anti-water tree additive; A water-tree resistant medium-voltage power cable is manufactured by the following steps: An oxygen-free copper rod is drawn into a thin copper wire through a wire drawing machine, and a plurality of thin copper wires are twisted to obtain a conductor. 73g of polypropylene is dried and mixed with 0.5g of diisopropyl benzene peroxide, 5g of an anti-water tree agent and 4g of epoxy soybean oil as an insulating layer material. 63g of polyethylene and 12g of carbon black are mixed as an insulating shielding layer material. The two materials are respectively added into two extruders for melt blending. The materials are extruded and coated on the surface of the conductor through double-die co-extrusion to form an insulating layer and an insulating shielding layer. The insulating shielding layer is wrapped with an aluminum-plastic composite water-blocking tape to form a water-blocking layer. The water-blocking layer is then wrapped with a braided copper mesh to form a metal shielding layer. Finally, polyvinyl chloride is extruded and coated on the surface of the metal shielding layer through an extruder to form an outer sheath layer to prepare an anti-water-tree medium-voltage power cable.

[0027] Example 2 Preparation of anti-water tree additives: Step A1, at room temperature, in a dry three-necked flask equipped with a constant pressure dropping funnel, a magnetic stirrer and a condenser, 100 mL of anhydrous toluene was used as the reaction solvent, 13.0 g of pentaerythritol was used as the reaction raw material, the two were mixed, and then 29.5 g of phosphorus trichloride was added to the flask using a constant pressure dropping funnel. After the addition was complete, a magnetic stirrer was used to stir for 20 minutes, and the device was heated until the temperature reached 80 ° C. The temperature was maintained and refluxed for 4 hours. After the reaction was completed, anhydrous toluene and excess phosphorus trichloride were removed by rotary evaporation to obtain an auxiliary intermediate product A; Step A2, at room temperature, in a dry three-necked flask equipped with a constant pressure dropping funnel, a magnetic stirrer and a condenser, 120 mL of anhydrous toluene was used as the reaction solvent, 26.0 g of the auxiliary intermediate product A and 18.0 g of pentafluorophenol were used as the reaction raw materials. After the three were mixed, 4.0 g of sodium hydroxide was mixed with 15 mL of deionized water. After the solution was configured, it was slowly added dropwise to the flask using a constant pressure dropping funnel. After the addition was completed, a magnetic stirrer was used and stirred for 10 minutes. The device was heated until the reaction temperature stabilized at 65 ° C. The reaction was maintained at the temperature for 4 hours. After the reaction was completed, it was filtered, and after rotary evaporation using a rotary evaporator, it was purified by column chromatography to obtain the auxiliary intermediate product B; Step A3, under room temperature, in a dry three-necked flask equipped with a constant pressure dropping funnel, a magnetic stirrer and a condenser, 150 mL of anhydrous toluene was used as the reaction solvent, 41.0 g of the auxiliary intermediate product B and 12.0 g of 4-hydroxystyrene were used as the reaction raw materials, and after the three were mixed, 4.0 g of sodium hydroxide was mixed with 15 mL of deionized water. After the solution was prepared, it was slowly added dropwise to the flask using a constant pressure dropping funnel. After the addition was completed, a magnetic stirrer was used to stir for 8 minutes, and the device was heated until the reaction temperature stabilized at 70 ° C. The temperature was maintained for 6 hours. After the reaction was completed, it was filtered, and after rotary evaporation using a rotary evaporator, it was purified by column chromatography to obtain an anti-water tree additive; A water-tree resistant medium-voltage power cable is manufactured by the following steps: An oxygen-free copper rod is drawn into a thin copper wire through a wire drawing machine, and a plurality of thin copper wires are twisted to obtain a conductor. 79g of polypropylene is dried and mixed with 1.0g of tert-butyl peroxide isopropyl benzene, 10g of an anti-water tree agent and 4g of zinc stearate as an insulating layer material. 70g of polyethylene and 15g of carbon black are mixed as an insulating shielding layer material. The two materials are respectively added into two extruders for melt blending. The materials are extruded and coated on the surface of the conductor through double-die co-extrusion to form an insulating layer and an insulating shielding layer. The insulating shielding layer is wrapped with an aluminum-plastic composite water-blocking tape to form a water-blocking layer. The water-blocking layer is then wrapped with a braided copper mesh to form a metal shielding layer. Finally, polyvinyl chloride is extruded and coated on the surface of the metal shielding layer through an extruder to form an outer sheath layer to prepare an anti-water-tree medium-voltage power cable.

[0028] Example 3 Preparation of anti-water tree additives: Step A1, at room temperature, in a dry three-necked flask equipped with a constant pressure dropping funnel, a magnetic stirrer and a condenser, 100 mL of anhydrous toluene was used as the reaction solvent, 14.0 g of pentaerythritol was used as the reaction raw material, the two were mixed, and then 30.5 g of phosphorus trichloride was added to the flask using a constant pressure dropping funnel. After the addition was complete, a magnetic stirrer was used to stir for 20 minutes, and the device was heated until the temperature reached 80 ° C. The temperature was maintained and refluxed for 4 hours. After the reaction was completed, anhydrous toluene and excess phosphorus trichloride were removed by rotary evaporation to obtain an auxiliary intermediate product A; Step A2, at room temperature, in a dry three-necked flask equipped with a constant pressure dropping funnel, a magnetic stirrer and a condenser, 120 mL of anhydrous toluene was used as the reaction solvent, 26.5 g of the auxiliary intermediate product A and 18.5 g of pentafluorophenol were used as the reaction raw materials. After the three were mixed, 4.0 g of sodium hydroxide was mixed with 15 mL of deionized water. After the solution was configured, it was slowly added dropwise to the flask using a constant pressure dropping funnel. After the addition was completed, a magnetic stirrer was used and stirred for 10 minutes. The device was heated until the reaction temperature stabilized at 65 ° C. The reaction was maintained at temperature for 4 hours. After the reaction was completed, it was filtered, and after rotary evaporation using a rotary evaporator, it was purified by column chromatography to obtain the auxiliary intermediate product B; Step A3, under room temperature, in a dry three-necked flask equipped with a constant pressure dropping funnel, a magnetic stirrer and a condenser, 150 mL of anhydrous toluene was used as the reaction solvent, 41.5 g of the auxiliary intermediate product B and 12.0 g of 4-hydroxystyrene were used as the reaction raw materials, and after the three were mixed, 4.0 g of sodium hydroxide was mixed with 15 mL of deionized water. After the solution was prepared, it was slowly added dropwise to the flask using a constant pressure dropping funnel. After the addition was completed, a magnetic stirrer was used to stir for 8 minutes, and the device was heated until the reaction temperature stabilized at 70 ° C. The reaction was maintained at the temperature for 6 hours. After the reaction was completed, it was filtered, and after rotary evaporation using a rotary evaporator, it was purified by column chromatography to obtain an anti-water tree additive; A water-tree resistant medium-voltage power cable is manufactured by the following steps: An oxygen-free copper rod is drawn into a thin copper wire through a wire drawing machine, and a plurality of thin copper wires are twisted to obtain a conductor. 85g of polypropylene is dried and mixed with 1.5g of tert-butyl peroxide isopropyl benzene, 15g of an anti-water treeing agent and 4g of epoxy soybean oil as an insulating layer material. 71g of polyethylene and 18g of carbon black are mixed as an insulating shielding layer material. The two materials are respectively added into two extruders for melt blending. The materials are extruded and coated on the surface of the conductor through double-die co-extrusion to form an insulating layer and an insulating shielding layer. The insulating shielding layer is wrapped with an aluminum-plastic composite water-blocking tape to form a water-blocking layer. The water-blocking layer is then wrapped with a braided copper mesh to form a metal shielding layer. Finally, polyvinyl chloride is extruded and coated on the surface of the metal shielding layer through an extruder to form an outer sheath layer to prepare an anti-water-treeing medium-voltage power cable.

[0029] Comparative Example 1 The only difference between this comparative example and Example 1 is that in this comparative example, the insulating layer material is replaced with an equal amount of commercially available ordinary cross-linked polyethylene.

[0030] Comparative Example 2 The only difference between this comparative example and Example 1 is that in this comparative example, the insulating layer material is replaced with an equal amount of commercially available water-tree resistant cross-linked polyethylene.

[0031] Comparative Example 3 The only difference between this comparative example and Example 1 is that no anti-water treeing agent is added in this comparative example.

[0032] Only the insulating layer materials of Examples 1-3 and Comparative Example 3 were prepared separately, and then the anti-water treeing effect of the insulating layer materials of Examples 1-3 and Comparative Example 1-3 was measured using the IEC / TS61956 standard; The measured results are shown in the following table:

[0033] As can be seen from the above table, the insulating layer material prepared in the embodiment of the present invention has excellent water tree resistance and is higher than that of the comparative example. Therefore, using it as one of the components of the cable makes the present invention suitable for humid environments and has important application value in the field of power cable technology.

[0034] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A water-tree resistant medium-voltage power cable comprising a conductor, an insulating layer, an insulating shielding layer, a water-blocking layer, a metal shielding layer and an outer sheath layer, characterized in that: The material of the insulating layer includes the following raw materials in parts by weight: 73-85 parts of polypropylene, 0.5-1.5 parts of initiator, 5-15 parts of anti-water tree additive and 3-4 parts of lubricant.

2. The water-tree resistant medium voltage power cable according to claim 1, characterized in that: The anti-water tree additive is prepared by the following steps: Step A1: After mixing anhydrous toluene and pentaerythritol, phosphorus trichloride was added, stirred, and refluxed at 80° C. for 4 hours. The reaction was completed to obtain an auxiliary intermediate product A; Step A2: Anhydrous toluene, auxiliary intermediate product A, and pentafluorophenol were mixed, and a solution of sodium hydroxide and deionized water was added, stirred, and reacted at 65° C. for 4 hours. The reaction was completed to obtain auxiliary intermediate product B; Step A3: Anhydrous toluene, the intermediate product B, and 4-hydroxystyrene were mixed, and a solution of sodium hydroxide and deionized water was added. The mixture was stirred and reacted at 70° C. for 6 hours. The reaction was completed to obtain an anti-water treeing additive.

3. The water-tree resistant medium voltage power cable according to claim 2, characterized in that: In step A1, the ratio of anhydrous toluene, pentaerythritol, and phosphorus trichloride is 100 mL: 13.0-14.0 g: 29.5-30.5 g.

4. The water-tree resistant medium voltage power cable according to claim 2, characterized in that: In step A2, the ratio of anhydrous toluene, auxiliary intermediate product A, pentafluorophenol, sodium hydroxide and deionized water is 120 mL: 26.0-26.5 g: 18.0-18.5 g: 4.0 g: 15 mL.

5. The water-tree resistant medium voltage power cable according to claim 2, characterized in that: In step A3, the ratio of anhydrous toluene, auxiliary intermediate product B, 4-hydroxystyrene, sodium hydroxide and deionized water is 150 mL:41.0~41.5 g:12.0 g:4.0 g:15 mL.

6. The water-tree resistant medium voltage power cable according to claim 1, characterized in that: The material of the water-blocking layer is an aluminum-plastic composite water-blocking tape.

7. The water-tree resistant medium voltage power cable according to claim 1, characterized in that: The insulating shielding layer is made of semi-conductive polyethylene, which comprises the following raw materials in parts by weight: 63-71 parts of polyethylene and 12-18 parts of carbon black.

8. The water-tree resistant medium voltage power cable according to claim 1, characterized in that: The material of the outer sheath layer is polyvinyl chloride.

9. The water-tree resistant medium voltage power cable according to claim 1, characterized in that: The initiator is one of dicumyl peroxide and tert-butyl cumyl peroxide.

10. The water-tree resistant medium voltage power cable according to claim 1, characterized in that: The lubricant is one of polyethylene wax, zinc stearate and epoxidized soybean oil.

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