Optical fiber composite flame-retardant medium-voltage cable and preparation method thereof

Abstract

The invention discloses an optical fiber composite flame-retardant medium-voltage cable and a preparation method thereof. The cable comprises an outer sheath, a plurality of conductor assemblies which are arranged in the outer sheath at equal intervals in a surrounding manner, and an optical fiber assembly. The method comprises the following steps: S1, preparing an ethylene propylene rubber material; s2, first-stage co-extrusion; S3, second-stage vulcanization; and S4, carrying out second-stage co-extrusion. Structures and components of sheath layers in the conductor assembly and the optical fiber assembly are reasonably selected, the comprehensive cable suitable for medium-voltage cables is finally formed, the comprehensive cable has good flame-retardant and electromagnetic shielding effects, an insulating heat-conducting carrier BN and TiO2 of a flame retardant aid are compounded, the comprehensive performance of high heat conduction and high flame retardance can be achieved, and the comprehensive cable is suitable for being used for medium-voltage cables. The solid phase content of the coating used as the conductor assembly is slightly higher than that of the coating used as the optical fiber assembly, and for a medium-voltage cable, good insulation and temperature resistance effects can be achieved without using a mica tape.

Description

Technical Field

[0001] The invention relates to the technical field of cable manufacturing, and in particular to an optical fiber composite flame-retardant medium-voltage cable and a preparation method thereof. Background Art

[0002] Optical composite medium voltage cable is a special cable that combines optical fiber communication and power transmission functions. It is often used in scenarios where power and data need to be transmitted simultaneously. Its core function is to combine medium voltage power transmission and optical signal transmission in the same cable, which can not only supply power but also realize information exchange. It is suitable for power systems, industrial parks, urban infrastructure and other fields.

[0003] The structure of this type of cable is divided into a power transmission layer and an optical communication layer. The power transmission layer is usually composed of a conductor, an insulation layer, a shielding layer, and a sheath. The conductor is made of copper or aluminum and is responsible for transmitting medium voltage currents from 6kV to 35kV; the insulation layer uses cross-linked polyethylene or ethylene propylene rubber to ensure the safety of power transmission; the shielding layer is used to evenly distribute the electric field; and the outer sheath protects the internal structure from environmental erosion. The optical communication layer contains an optical fiber unit, which is composed of multiple optical fiber bundles. The outer layer is wrapped with a loose tube to buffer mechanical stress, and the outer layer is superimposed with a water-blocking material and a metal armor layer to prevent moisture penetration and physical damage.

[0004] When manufacturing and using this type of cable, anti-electromagnetic interference and flame retardant performance are the first issues to be considered. With its good performance conditions, EPDM can be used as the main material for the outer sheath of optical fiber composite medium voltage cable, but its processing performance and cost and other factors restrict its good promotion and application. The invention patent with patent publication number CN106117825A discloses a preparation method of ethylene propylene rubber insulated chloroprene rubber sheathed cable sheath material, comprising the following steps: mixing ethylene propylene rubber, chloroprene rubber, hydrogenated nitrile rubber, fluororubber, and styrene butadiene rubber for 1-2 minutes; adding modified quicklime, coumarone resin, calcined clay, nano titanium dioxide, bentonite, hollow microspheres, zirconium oxide, RF-90 resin, microcrystalline cellulose, thiuram disulfide, and hexamethylenetetramine, mixing evenly and then discharging, the mixing temperature is 105-110°C; adding antioxidant RD, antioxidant H, antioxidant 4010NA, operating oil, pine tar, and dibutyl phthalate, mixing evenly, adding benzoyl peroxide and aluminum hydroxide for vulcanization, the vulcanization temperature is 158-163°C, the vulcanization time is 1-2 minutes, and the discharging is cooled to obtain the ethylene propylene rubber insulated chloroprene rubber sheathed cable sheath material. However, this method does not make targeted optimization for the application of optical fiber composite medium voltage cables. Summary of the invention

[0005] In view of the above problems, the present invention provides an optical fiber composite flame-retardant medium voltage cable and a preparation method thereof.

[0006] The technical solution of the present invention is:

[0007] An optical fiber composite flame-retardant medium voltage cable comprises an outer sheath, a plurality of conductor components arranged around the outer sheath at equal intervals, and an optical fiber component;

[0008] The conductor assembly includes, from inside to outside, a copper conductor, a PP shielding layer, a first EPDM rubber insulation layer, and a conductor sheath;

[0009] The optical fiber assembly comprises a plurality of optical fiber bundles arranged around at equal intervals, a PBT sheath is disposed outside the optical fiber bundle, an optical fiber sheath is disposed outside the PBT sheath, and a second ethylene propylene rubber insulation layer is commonly disposed outside each of the optical fiber sheaths;

[0010] A filling layer is arranged outside the conductor assembly and the optical fiber assembly, an armor layer is arranged outside the filling layer, and an outer sheath is arranged outside the armor layer.

[0011] Furthermore, the conductor sheath and the optical fiber sheath are both cross-linked polyethylene sheaths.

[0012] Description: Cross-linked polyethylene sheath is a commonly used material in cable sheaths. It has certain insulation, temperature resistance and corrosion resistance. It can play a good auxiliary insulation and flame retardant effect when used in conductor sheaths and optical fiber sheaths of medium voltage cables.

[0013] Furthermore, a filling medium is provided between the PBT sheath and the second EPDM rubber insulation layer, the filling medium is a fully dry filling medium, and the filling layer is a polypropylene filler.

[0014] Description: The overall strength of the cable is ensured by the internal filler of the optical fiber components and the PET points inside the cable.

[0015] Furthermore, the armor layer is a tinned copper wire braided armor tape, and the outer sheath is a PVC sheath.

[0016] Description: The overall mechanical strength of the cable is improved by setting the armor layer.

[0017] Furthermore, there are three conductor assemblies and six optical fiber bundles.

[0018] The present invention also provides a method for preparing an optical fiber composite flame-retardant medium voltage cable, comprising the following steps:

[0019] S1. Preparation of EPDM rubber material:

[0020] S1-1, mixing: take 100-120 parts of EPDM rubber particles by weight, put them in an open mill for plasticizing, and then thin pass them. After thin passing, add 1-2 parts of antioxidant, 0.5-0.7 parts of RF-90 resin and 0.3-0.5 parts of calcined clay in sequence after rolling. Cut left and right several times, then add 110-130 parts of carbon black, 60-70 parts of paraffin oil, 3-4 parts of vulcanizing agent and 1-2 parts of vulcanizing agent in sequence. Cut left and right several times, roll with triangles several times and thin pass again to obtain a mixed rubber.

[0021] S1-2, one-stage vulcanization: vulcanizing the mixed rubber at 170-180° C. for 5-6 minutes to obtain an EPDM rubber material;

[0022] S2, one-stage co-extrusion:

[0023] S2-1, conductor assembly extrusion: extruding a PP shielding layer outside the copper conductor, then extruding the EPDM rubber material outside the PP shielding layer, and electrostatically coating the outside of the extruded EPDM rubber material to obtain a first EPDM rubber insulation layer;

[0024] S2-2, extrusion of optical fiber components: extruding a PBT sheath outside the optical fiber bundle, extruding an optical fiber sheath outside the PBT sheath, then filling the outer surface of each optical fiber sheath with a medium and extruding the EPDM rubber material, and electrostatically coating the outer surface of the extruded EPDM rubber material to obtain a second EPDM rubber insulation layer;

[0025] S3, two-stage vulcanization: vulcanize the first EPDM rubber insulation layer of the conductor assembly and the second EPDM rubber insulation layer of the optical fiber assembly under the steam conditions of 170-180°C and 0.5-1MPa for 7-8 minutes;

[0026] S4, two-stage co-extrusion: then extrude a conductor sheath outside the first EPDM rubber insulation layer to obtain a conductor assembly, extrude a filling layer outside several conductor assemblies and outside the second EPDM rubber insulation layer of the optical fiber assembly, and cover the filling layer with an armor layer, and then extrude an outer sheath outside the armor layer.

[0027] Furthermore, in the S1, the roller spacing of the open mill during plasticating is 1 mm, and the roller spacing of the open mill is adjusted to 2 mm after plasticating, the number of left and right cutting knives is 3 times, the number of thin passes is 3 times, the number of triangle packages is 6 times, and the roller spacing of the open mill is adjusted to 4 mm when making triangle packages.

[0028] Note: By optimizing the specific parameters of the mixing mill, it is ensured that the rubber is dispersed quickly, evenly and with high shear efficiency during mixing.

[0029] Furthermore, when the coating is applied in S2, the coating is prepared by:

[0030] Nano-TiO2 and nano-BN are placed in anhydrous ethanol and ultrasonically dispersed and mixed for 30 to 60 minutes to obtain a coating liquid. The solid content of the coating liquid is 10 to 20%. 2 The particle size of nano-BN is 20-200nm. In the first EPDM insulating layer, nano-TiO 2 The addition amount of nano-BN is 0.75-1wt% of the EPDM rubber material. In the second EPDM rubber insulating layer, the addition amount of nano-TiO 2 The addition amount of is 0.25-0.5wt% of the EPDM rubber material, and the addition amount of nano BN is 0.5-1wt% of the EPDM rubber material;

[0031] The spraying method is: fix the conductor component or optical fiber component on the roller, use the spray needle to spray the coating liquid onto the surface of the extruded EPDM rubber material, the spraying distance is 5 to 10 cm, a positive voltage of 10±1kV is applied to the spray needle, a negative voltage of 10±1kV is applied to the roller, and the spray needle advances at a speed of 3 to 6mm / min.

[0032] Description: By adding a coating on the surface of the EPDM insulation layer, the flame retardant effect of the cable can be further improved. The insulating thermal conductive carrier BN and the flame retardant additive TiO 2 The compound can achieve the comprehensive performance of high thermal conductivity + high flame retardancy.

[0033] Furthermore, in the S4, the temperature of the die head during the whole process of the two-stage co-extrusion is 75°C to 80°C, the temperature of the front section of the body is 70°C to 75°C, the temperature of the rear section of the body is 65°C to 70°C, and the screw cooling method of the rubber extruder is water cooling.

[0034] Description: By optimizing the temperature control during the second-stage extrusion, it is ensured that the conductor component, the optical fiber component and the filling layer of the cable are well bonded during the second-stage extrusion.

[0035] The beneficial effects of the present invention are:

[0036] (1) The fiber-optic composite flame-retardant medium-voltage cable of the present invention is equipped with a conductor assembly and an optical fiber assembly, and the structure and components of the sheath layer in the conductor assembly and the optical fiber assembly are reasonably selected according to the application conditions of the medium-voltage cable, thereby finally forming a comprehensive cable suitable for use in medium-voltage cables, which has good flame-retardant and electromagnetic shielding effects.

[0037] (2) In the preparation method of a fiber-optic composite flame-retardant medium-voltage cable of the present invention, the conductor component and the optical fiber component are prepared independently. The two components use an EPDM rubber insulation layer with a coating to improve their thermal conductivity and flame retardancy. At the same time, two-stage vulcanization is carried out simultaneously, and finally co-extruded into a mold. On the premise of having good flame retardancy and electromagnetic shielding effects, the mechanical strength is also greatly improved, especially when used in 8.7 / 15kV power systems, it can exert good practical use effects.

[0038] (3) In the preparation method of the optical fiber composite flame-retardant medium-voltage cable of the present invention, the ethylene-propylene rubber insulation layer of the conductor component and the optical fiber component is adjusted differently, so that the coatings of the two components have different component contents, wherein the insulating heat-conducting carrier BN and the flame retardant additive TiO 2 The compound can achieve the comprehensive performance of high thermal conductivity and high flame retardancy. The solid content of the coating as a conductor component is slightly higher than that of the coating as an optical fiber component. For medium-voltage cables, good insulation and temperature resistance can be achieved without the use of mica tape. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the overall structure of an optical fiber composite flame-retardant medium-voltage cable of the present invention;

[0040] Figure 2 A schematic structural diagram of an optical fiber assembly in an optical fiber composite flame-retardant medium voltage cable of the present invention;

[0041] Figure 3 Comparison chart of thermal conductivity of each case in Experimental Example 1 of the present invention.

[0042] Among them, 1-conductor assembly, 11-copper conductor, 12-PP shielding layer, 13-first EPDM rubber insulation layer, 14-conductor sheath, 2-optical fiber assembly, 21-optical fiber bundle, 22-PBT sheath, 23-optical fiber sheath, 24-second EPDM rubber insulation layer, 25-filling medium, 3-outer sheath, 4-filling layer, 5-armor layer, DETAILED DESCRIPTION

[0043] Example 1

[0044] An optical fiber composite flame-retardant medium voltage cable comprises an outer sheath 3, three conductor components 1 arranged around the outer sheath 3 at equal intervals, and an optical fiber component 2;

[0045] The conductor assembly 1 includes, from the inside to the outside, a copper conductor 11, a PP shielding layer 12, a first EPDM rubber insulation layer 13, and a conductor sheath 14;

[0046] The optical fiber assembly 2 includes 6 optical fiber bundles 21 which are equally spaced and arranged around each other. A PBT sheath 22 is provided outside the optical fiber bundle 21. An optical fiber sheath 23 is provided outside the PBT sheath 22. A second EPDM rubber insulation layer 24 is provided outside each optical fiber sheath 23. A filling medium 25 is provided between the PBT sheath 22 and the second EPDM rubber insulation layer 24. The filling medium 25 is a fully dry filling medium 25. Both the conductor sheath 14 and the optical fiber sheath 23 are cross-linked polyethylene sheaths.

[0047] A filling layer 4 is provided outside the conductor component 1 and the optical fiber component 2. The filling layer 4 is a polypropylene filler. An armor layer 5 is provided outside the filling layer 4. An outer sheath 3 is provided outside the armor layer 5. The armor layer 5 is a tinned copper wire braided armor tape. The outer sheath 3 is a PVC sheath.

[0048] Example 2

[0049] This embodiment is a method for preparing an optical fiber composite flame-retardant medium voltage cable of embodiment 1, comprising the following steps:

[0050] S1. Preparation of EPDM rubber material:

[0051] S1-1, mixing: 110 parts of ethylene propylene rubber particles are taken by mass, placed in an open mill for plasticizing, and thin-passed 3 times after plasticizing. The roller spacing of the open mill is 1 mm during plasticizing. After plasticizing, the roller spacing of the open mill is adjusted to 2 mm. After thin-passing and rolling, 1 part of antioxidant, 0.6 part of RF-90 resin and 0.4 part of calcined clay are added in sequence. After cutting with a knife 3 times, 120 parts of carbon black, 65 parts of paraffin oil, 4 parts of vulcanizing agent and 2 parts of co-vulcanizing agent are added in sequence. Cut with a knife 3 times, make triangle packages 6 times and thin-passed again 3 times. When making triangle packages, the roller spacing of the open mill is adjusted to 4 mm to obtain a mixed rubber;

[0052] S1-2, one-stage vulcanization: vulcanize the mixed rubber at 175°C for 5 minutes to obtain EPDM rubber material;

[0053] S2, one-stage co-extrusion:

[0054] S2-1, extrusion of the conductor component 1: extruding a PP shielding layer 12 outside the copper conductor 11, then extruding an EPDM rubber material outside the PP shielding layer 12, and electrostatically coating the outside of the extruded EPDM rubber material to obtain a first EPDM rubber insulation layer 13;

[0055] S2-2, extrusion of optical fiber assembly 2: extruding a PBT sheath 22 outside the optical fiber bundle 21, extruding an optical fiber sheath 23 outside the PBT sheath 22, then filling the outside of each optical fiber sheath 23 with a medium 25 and extruding an EPDM rubber material, and electrostatically coating the outside of the extruded EPDM rubber material to obtain a second EPDM rubber insulation layer 24;

[0056] When applying the coating, the coating is prepared by:

[0057] Nano-TiO 2 and nano-BN were placed in anhydrous ethanol and ultrasonically dispersed and mixed for 40 minutes to obtain a coating liquid. The solid content of the coating liquid was 15%, and the nano-TiO 2 The particle size of the nano-BN is 100 nm. In the first EPDM rubber insulating layer 13, the nano-TiO 2 The amount of nano-BN added is 0.6wt% of the EPDM rubber material, the amount of nano-TiO added is 0.8wt% of the EPDM rubber material, and in the second EPDM rubber insulating layer 24, the amount of nano-BN added is 0.8wt%. 2 The addition amount of is 0.4wt% of the EPDM rubber material, and the addition amount of nano BN is 0.7wt% of the EPDM rubber material;

[0058] The spraying method is as follows: fix the conductor component 1 or the optical fiber component 2 on the roller, use the spray needle to spray the coating liquid onto the surface of the extruded EPDM rubber material, the spraying distance is 6 cm, a positive voltage of 10 kV is applied to the spray needle, a negative voltage of 10 kV is applied to the roller, and the spray needle advances at a speed of 5 mm / min;

[0059] S3, two-stage vulcanization: vulcanize the first ethylene propylene rubber insulation layer 13 of the conductor component 1 and the second ethylene propylene rubber insulation layer 24 of the optical fiber component 2 at 175° C. and 0.8 MPa steam conditions for 7 minutes;

[0060] S4, two-stage co-extrusion: then extrude the conductor sheath 14 outside the first EPDM rubber insulation layer 13 to obtain the conductor assembly 1, extrude the filling layer 4 outside the several conductor assemblies 1 and the second EPDM rubber insulation layer 24 of the optical fiber assembly 2, and coat the armor layer 5 outside the filling layer 4, and then extrude the outer sheath 3 outside the armor layer 5. During the whole process of the two-stage co-extrusion, the head temperature is 77°C, the front section temperature of the body is 72°C, the rear section temperature of the body is 68°C, and the screw cooling method of the rubber extruder is water cooling.

[0061] Example 3

[0062] The difference between this embodiment and embodiment 2 is that:

[0063] S1-1. Mixing: 100 parts of EPDM rubber particles are taken by mass and placed in an open mill for plasticizing. After plasticizing, thin-pass is performed 3 times. The roller spacing of the open mill is 1 mm during plasticizing. After plasticizing, the roller spacing of the open mill is adjusted to 2 mm. After thin-passing and rolling, 1 part of antioxidant, 0.5 part of RF-90 resin and 0.3 part of calcined clay are added in sequence. After cutting with a knife left and right 3 times, 110 parts of carbon black, 60 parts of paraffin oil, 3 parts of vulcanizing agent and 1 part of vulcanizing aid are added in sequence. Cut with a knife left and right 3 times, make triangle packages 6 times and thin-pass again 3 times. When making triangle packages, the roller spacing of the open mill is adjusted to 4 mm to obtain a mixed rubber.

[0064] Example 4

[0065] The difference between this embodiment and embodiment 2 is that:

[0066] S1-1. Mixing: 120 parts by mass of ethylene propylene rubber granules are placed in an open mill for plasticizing. After plasticizing, thin-pass the mill three times. The roller spacing of the open mill is 1 mm during plasticizing. After plasticizing, the roller spacing of the open mill is adjusted to 2 mm. After thin-passing and rolling, 2 parts of antioxidant, 0.7 parts of RF-90 resin and 0.5 parts of calcined clay are added in sequence. After cutting left and right for 3 times, 130 parts of carbon black, 70 parts of paraffin oil, 4 parts of vulcanizing agent and 2 parts of vulcanizing aid are added in sequence. Cut left and right for 3 times, make triangle packages 6 times and thin-pass the mill again for 3 times. When making triangle packages, the roller spacing of the open mill is adjusted to 4 mm to obtain a mixed rubber.

[0067] Example 5

[0068] The difference between this embodiment and embodiment 2 is that:

[0069] S1-2, one-stage vulcanization: vulcanize the mixed rubber at 170°C for 6 minutes to obtain EPDM rubber material.

[0070] Example 6

[0071] The difference between this embodiment and embodiment 2 is that:

[0072] S1-2, one-stage vulcanization: vulcanize the mixed rubber at 180°C for 5 minutes to obtain EPDM rubber material.

[0073] Example 7

[0074] The difference between this embodiment and embodiment 2 is that:

[0075] When applying the coating, the coating is prepared by:

[0076] Nano-TiO 2 and nano-BN were placed in anhydrous ethanol and ultrasonically dispersed for 30 minutes to obtain a coating solution. The solid content of the coating solution was 10%. 2 The particle size of the nano-BN is 20 nm. In the first EPDM rubber insulating layer 13, the nano-TiO 2 The amount of nano-BN added is 0.75wt% of the EPDM rubber material. In the second EPDM rubber insulating layer 24, the amount of nano-TiO 2 The added amount of is 0.25wt% of the EPDM rubber material, and the added amount of nano BN is 0.5wt% of the EPDM rubber material.

[0077] Example 8

[0078] The difference between this embodiment and embodiment 2 is that:

[0079] When applying the coating, the coating is prepared by:

[0080] Nano-TiO 2 and nano-BN were placed in anhydrous ethanol and ultrasonically dispersed for 60 minutes to obtain a coating solution. The solid content of the coating solution was 12%. 2 The particle size of the nano-BN is 50 nm. In the first EPDM rubber insulating layer 13, the nano-TiO 2 The amount of nano-BN added is 0.85wt% of the EPDM rubber material. In the second EPDM rubber insulating layer 24, the amount of nano-TiO 2 The added amount of is 0.3wt% of the EPDM rubber material, and the added amount of nano BN is 0.6wt% of the EPDM rubber material.

[0081] Example 9

[0082] The difference between this embodiment and embodiment 2 is that:

[0083] When applying the coating, the coating is prepared by:

[0084] Nano-TiO 2 and nano-BN were placed in anhydrous ethanol and ultrasonically dispersed for 60 minutes to obtain a coating solution. The solid content of the coating solution was 18%. 2 The particle size of the nano-BN is 150nm. In the first EPDM rubber insulating layer 13, the nano-TiO 2 The amount of nano-BN added is 0.8wt% of the EPDM rubber material. In the second EPDM rubber insulating layer 24, the amount of nano-TiO 2 The added amount of is 0.45wt% of the EPDM rubber material, and the added amount of nano BN is 0.8wt% of the EPDM rubber material.

[0085] Example 10

[0086] The difference between this embodiment and embodiment 2 is that:

[0087] When applying the coating, the coating is prepared by:

[0088] Nano-TiO 2 and nano-BN were placed in anhydrous ethanol and ultrasonically dispersed for 60 minutes to obtain a coating solution. The solid content of the coating solution was 20%. 2 The particle size of the nano-BN is 200 nm. In the first EPDM rubber insulating layer 13, the nano-TiO 2The amount of nano-BN added is 0.75wt% of the EPDM rubber material, the amount of nano-TiO added is 1wt% of the EPDM rubber material, and in the second EPDM rubber insulating layer 24, the amount of nano-BN added is 1wt% of the EPDM rubber material. 2 The added amount of is 0.5wt% of the EPDM rubber material, and the added amount of nano BN is 1wt% of the EPDM rubber material.

[0089] Embodiment 11

[0090] The difference between this embodiment and embodiment 2 is that:

[0091] The coating spraying method is as follows: fix the conductor component 1 or the optical fiber component 2 on the roller, use a spray needle to spray the coating liquid onto the surface of the extruded EPDM rubber material, the spraying distance is 5 cm, a positive voltage of 9 kV is applied to the spray needle, a negative voltage of 9 kV is applied to the roller, and the spray needle advances at a speed of 3 mm / min.

[0092] Example 12

[0093] The difference between this embodiment and embodiment 2 is that:

[0094] The coating spraying method is as follows: fix the conductor component 1 or the optical fiber component 2 on the roller, use a spray needle to spray the coating liquid onto the surface of the extruded EPDM rubber material, the spraying distance is 10 cm, a positive voltage of 11 kV is applied to the spray needle, a negative voltage of 11 kV is applied to the roller, and the spray needle advances at a speed of 6 mm / min.

[0095] Embodiment 13

[0096] The difference between this embodiment and embodiment 2 is that:

[0097] S3, two-stage vulcanization: vulcanize the first ethylene propylene rubber insulation layer 13 of the conductor component 1 and the second ethylene propylene rubber insulation layer 24 of the optical fiber component 2 under the steam conditions of 170° C. and 0.5 MPa for 7 minutes.

[0098] Embodiment 14

[0099] The difference between this embodiment and embodiment 2 is that:

[0100] S3, two-stage vulcanization: vulcanize the first ethylene propylene rubber insulation layer 13 of the conductor component 1 and the second ethylene propylene rubber insulation layer 24 of the optical fiber component 2 under the steam condition of 180° C. and 1 MPa for 8 minutes.

[0101] Embodiment 15

[0102] The difference between this embodiment and embodiment 2 is that:

[0103] S4, two-stage co-extrusion: then extrude the conductor sheath 14 outside the first EPDM rubber insulation layer 13 to obtain the conductor assembly 1, extrude the filling layer 4 outside the several conductor assemblies 1 and the second EPDM rubber insulation layer 24 of the optical fiber assembly 2, and coat the armor layer 5 outside the filling layer 4, and then extrude the outer sheath 3 outside the armor layer 5. During the whole process of the two-stage co-extrusion, the head temperature is 75°C, the front section temperature of the body is 70°C, the rear section temperature of the body is 65°C, and the screw cooling method of the rubber extruder is water cooling.

[0104] Example 16

[0105] The difference between this embodiment and embodiment 2 is that:

[0106] S4, two-stage co-extrusion: then extrude the conductor sheath 14 outside the first EPDM rubber insulation layer 13 to obtain the conductor assembly 1, extrude the filling layer 4 outside the several conductor assemblies 1 and the second EPDM rubber insulation layer 24 of the optical fiber assembly 2, and coat the armor layer 5 outside the filling layer 4, and then extrude the outer sheath 3 outside the armor layer 5. During the whole process of the two-stage co-extrusion, the head temperature is 80°C, the front section temperature of the body is 75°C, and the rear section temperature of the body is 70°C. The screw cooling method of the rubber extruder is water cooling.

[0107] Experimental Example 1

[0108] First, we separately explore the thermal conductivity of the first EPDM rubber insulation layer 13 of the present invention, taking Examples 2 and 7 to 10 as examples, and comparing them with the EPDM rubber insulation layer without coating as Comparative Example 1. The results are as follows: Figure 3 shown.

[0109] It can be seen that the thermal conductivity is related to the nano-TiO 2 The relationship between the content of nano-BN and the content of solid phase is correlated to a certain extent. With the increase of the mass fraction of solid phase content, the thermal conductivity of the first EPDM rubber insulation layer 13 increases first and then decreases. This may be due to the fact that when the mass fraction of the insulating thermal conductive carrier nano-BN is low, the nano-TiO 2 The contact area between the nano-BN and the first EPDM rubber insulating layer 13 is relatively small or even non-contacting, and an effective heat conduction path cannot be formed, so that the thermal conductivity of the first EPDM rubber insulating layer 13 increases slowly; with the increase of the mass fraction of the solid phase content, the nano-TiO 2 A large amount of contact begins between the nano-BN and the insulating layer 13 to form a thermal conductive network. Therefore, in Example 2, the thermal conductivity of the first EPDM rubber insulating layer 13 is the largest. At this time, when the mass fraction of the solid phase content continues to increase, the thermal conductivity decreases, because the thermal conductive network has become complete, and continuing to increase the solid phase content only accumulates on the original thermal conductive network and cannot form a new thermal conductive channel. Therefore, continuing to increase the solid phase content will reduce the thermal conductivity and the thermal conductive performance will decrease.

[0110] Example 2

[0111] Subsequently, we explored various parameter indicators of the cable of the present invention and compared them with the required standard values ​​of the medium voltage cable. Among them, the mechanical properties were tested by a universal testing machine, the sample was a standard dumbbell type, the fixture spacing was 50mm, and the width of the middle narrow strip was 4mm; the breakdown performance test is an effective and direct method to identify the insulation strength of electrical insulating materials, which is of decisive significance for judging whether electrical insulating materials can be used; the experimental instrument uses a test system composed of a high-voltage DC power supply, an AC power supply and an experimental transformer operating box to test the DC and AC breakdown field strengths of the cable; the test cable length is 5m, taking Examples 2 to 6 as examples (the parameter adjustments in Examples 2 to 6 are all adjusted within a reasonable range, only to increase the number of test groups, and will not affect the final performance parameters), and compared with Comparative Example 2, in Comparative Example 2, the first EPDM rubber insulation layer 13 and the second EPDM rubber insulation layer 24 in Example 2 of the present invention are replaced with mica tape, and the rest are the same, and the results are shown in Table 1.

[0112] Table 1 Performance parameters of cables in various cases

[0113]

[0114]

[0115] It can be seen that the optical fiber composite flame-retardant medium voltage cable of the present invention successfully completed various tests, while in Comparative Example 2, the first EPDM rubber insulation layer 13 and the second EPDM rubber insulation layer 24 in Example 2 were replaced with mica tape, and the voltage test was not passed. This is because for the optical fiber conductor, its outer diameter is small and the heat dissipation is slow, and the heat is relatively concentrated. At high temperature, the insulation resistance of the mica tape decreases, resulting in the breakdown of the optical fiber core; at the same time, the mica tape insulated wrapped cable itself has a large water content, and its thermal weight loss is more than twice that of the first EPDM rubber insulation layer 13 and the second EPDM rubber insulation layer 24 of the present invention, resulting in a small insulation resistance value between the cores after production, which easily leads to failure to pass the tensile strength test.

[0116] In summary, the optical fiber composite flame-retardant medium-voltage cable of the present invention can be put into use normally, and has accumulated valuable experience for the design and production of cables with larger specifications and more complex structures in the future.

Claims

1. An optical fiber composite flame-retardant medium voltage cable, characterized in that: It comprises an outer sheath (3), a plurality of conductor components (1) arranged in a surrounding manner at equal intervals inside the outer sheath (3), and an optical fiber component (2); The conductor assembly (1) comprises, from the inside to the outside, a copper conductor (11), a PP shielding layer (12), a first ethylene propylene rubber insulation layer (13), and a conductor sheath (14); The optical fiber assembly (2) comprises a plurality of optical fiber bundles (21) arranged in a surrounding manner at equal intervals, a PBT sheath (22) is provided outside the optical fiber bundle (21), an optical fiber sheath (23) is provided outside the PBT sheath (22), and a second ethylene propylene rubber insulation layer (24) is commonly provided outside each of the optical fiber sheaths (23); A filling layer (4) is provided outside the conductor component (1) and the optical fiber component (2), an armor layer (5) is provided outside the filling layer (4), and an outer sheath (3) is provided outside the armor layer (5).

2. The optical fiber composite flame-retardant medium voltage cable according to claim 1, characterized in that: The conductor sheath (14) and the optical fiber sheath (23) are both cross-linked polyethylene sheaths.

3. The optical fiber composite flame-retardant medium voltage cable according to claim 1, characterized in that: A filling medium (25) is provided between the PBT sheath (22) and the second EPDM rubber insulation layer (24); the filling medium (25) is a fully dry filling medium (25); and the filling layer (4) is a polypropylene filler.

4. The optical fiber composite flame-retardant medium voltage cable according to claim 1, characterized in that: The armor layer (5) is a tinned copper wire braided armor tape, and the outer sheath (3) is a PVC sheath.

5. The optical fiber composite flame-retardant medium voltage cable according to claim 1, characterized in that: There are three conductor components (1) and six optical fiber bundles (21).

6. A method for preparing an optical fiber composite flame-retardant medium voltage cable according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Preparation of EPDM rubber material: S1-1, mixing: take 100-120 parts of EPDM rubber particles by weight, put them in an open mill for plasticizing, and then thin pass them. After thin passing, add 1-2 parts of antioxidant, 0.5-0.7 parts of RF-90 resin and 0.3-0.5 parts of calcined clay in sequence after rolling. Cut left and right several times, then add 110-130 parts of carbon black, 60-70 parts of paraffin oil, 3-4 parts of vulcanizing agent and 1-2 parts of vulcanizing agent in sequence. Cut left and right several times, roll with triangles several times and thin pass again to obtain a mixed rubber. S1-2, one-stage vulcanization: vulcanizing the mixed rubber at 170-180° C. for 5-6 minutes to obtain an EPDM rubber material; S2, one-stage co-extrusion: S2-1, extrusion of the conductor assembly (1): extruding a PP shielding layer (12) on the outside of the copper conductor (11), then extruding the EPDM rubber material on the outside of the PP shielding layer (12), and electrostatically coating the outside of the extruded EPDM rubber material to obtain a first EPDM rubber insulation layer (13); S2-2, extrusion of optical fiber assembly (2): extruding a PBT sheath (22) outside the optical fiber bundle (21), extruding an optical fiber sheath (23) outside the PBT sheath (22), then filling each optical fiber sheath (23) with a medium (25) and extruding the EPDM rubber material, and electrostatically coating the extruded EPDM rubber material to obtain a second EPDM rubber insulation layer (24); S3, two-stage vulcanization: vulcanizing the first ethylene propylene rubber insulation layer (13) of the conductor component (1) and the second ethylene propylene rubber insulation layer (24) of the optical fiber component (2) under steam conditions of 170-180° C. and 0.5-1 MPa for 7-8 minutes; S4, two-stage co-extrusion: then, a conductor sheath (14) is extruded outside the first EPDM rubber insulation layer (13) to obtain a conductor assembly (1), a filling layer (4) is extruded outside the plurality of conductor assemblies (1) and outside the second EPDM rubber insulation layer (24) of the optical fiber assembly (2), and an armor layer (5) is coated outside the filling layer (4), and then an outer sheath (3) is extruded outside the armor layer (5).

7. The method for preparing a fiber composite flame-retardant medium voltage cable according to claim 6, characterized in that: In the S1, the roller spacing of the open mill during plastication is 1 mm, and the roller spacing of the open mill is adjusted to 2 mm after plastication. The number of left and right cutters is 3 times, the number of thin passes is 3 times, the number of triangle packages is 6 times, and the roller spacing of the open mill is adjusted to 4 mm when making triangle packages.

8. The method for preparing a fiber composite flame-retardant medium voltage cable according to claim 6, characterized in that: When the coating is applied in S2, the coating is prepared by: Nano-TiO2 and nano-BN are placed in anhydrous ethanol and ultrasonically dispersed and mixed for 30 to 60 minutes to obtain a coating liquid, wherein the solid content of the coating liquid is 10 to 20%, and the particle sizes of the nano-TiO2 and nano-BN are 20 to 200 nm. In the first EPDM insulating layer (13), the amount of nano-TiO2 added is 0.5 to 0.75 wt% of the EPDM material, and the amount of nano-BN added is 0.75 to 1 wt% of the EPDM material. In the second EPDM insulating layer (24), the amount of nano-TiO2 added is 0.25 to 0.5 wt% of the EPDM material, and the amount of nano-BN added is 0.5 to 1 wt% of the EPDM material. The spraying method is as follows: fixing the conductor component (1) or the optical fiber component (2) on a roller, and using a spray needle to spray the coating liquid onto the surface of the extruded EPDM rubber material, the spraying distance is 5 to 10 cm, a positive voltage of 10±1 kV is applied to the spray needle, a negative voltage of 10±1 kV is applied to the roller, and the spray needle advances at a speed of 3 to 6 mm / min.

9. The method for preparing a fiber composite flame-retardant medium voltage cable according to claim 6, characterized in that: In the S4, the temperature of the die head during the whole process of the two-stage co-extrusion is 75°C-80°C, the temperature of the front section of the body is 70-75°C, the temperature of the rear section of the body is 65-70°C, and the screw cooling method of the rubber extruder is water cooling.

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