Crosslinked polyethylene insulated medium and high voltage power cables

Abstract

The present invention relates to the technical field of power cables, and provides a cross-linked polyethylene insulated medium and high voltage power cable, which includes a conductor core, a filling rope, a wrapping layer, a flame retardant layer, and an armor layer; the armor layer includes a first wrapping tape located on the inner layer and having the same stranding direction as the conductor core, and a second wrapping tape located on the outer layer and having the opposite stranding direction to the conductor core. The first wrapping tape and the second wrapping tape are alternately wound along the length direction of the cable to form a positive wrapping part and a negative wrapping part that alternately circulate along the length of the cable; by changing the structure of the armor layer, the performance of the cable can be improved in terms of increased transported alternating current and / or reduced cross-sectional area of the electrical conductor. The cyclic reversal of the stranding direction of the cable core and / or the winding direction of the armor wires along the length of the cable improves the mechanical properties of the cable and reduces the hysteresis and eddy current losses in the cable.

Description

Technical Field

[0001] The present invention relates to the technical field of power cables, and in particular to a cross-linked polyethylene insulated medium and high voltage power cable. Background Art

[0002] Power cables are cables used to transmit and distribute electrical energy. They can be divided into low voltage, medium voltage, high voltage, and extra-high voltage cables according to voltage levels. In addition, they can be divided into AC cables and DC cables according to current systems. In order to improve the mechanical strength of medium and high voltage power cables, one or more cable cores are usually surrounded by at least one layer of armor in the form of metal wires. The armor is constructed to strengthen the cable structure while maintaining appropriate flexibility. However, armored cables have the defect that the current carrying capacity is much smaller than that of non-armored cables under the same operating temperature and the same environmental conditions because the loss of conventional armor materials is too large.

[0003] Studies have shown that reducing losses in armored cables makes it possible to increase the permissible current rating, thereby reducing the cross-section of the conductor and / or increasing the amount of current carried by the cable conductor, and can reduce the size of the cable and the amount of material required to manufacture the cable and increase the power carried by the cable. Summary of the invention

[0004] The present invention aims to provide a cross-linked polyethylene insulated medium and high voltage power cable in view of the defects of the prior art, comprising:

[0005] A wire core, wherein the plurality of wire cores are tangential to each other and twisted with each other;

[0006] A filling rope is filled in the twisted gap of the core and is wound around the sheath together with the core to form a circular cross section;

[0007] A flame retardant layer, coated on the outer wall of the wrapping layer;

[0008] An armor layer wrapped around the outer wall of the flame retardant layer;

[0009] An isolation layer, extruded on the outer wall of the armor layer;

[0010] An outer sheath, extruded and wrapped around the outer wall of the isolation layer;

[0011] The armor layer includes a first wrapping tape located in an inner layer and having the same twisting direction as the core, and a second wrapping tape located in an outer layer and having an opposite twisting direction to the core, and the first wrapping tape and the second wrapping tape are alternately wound along the length direction of the cable to form a forward wrapping portion and a reverse wrapping portion that alternately circulate along the length of the cable;

[0012] The wrapping pitch of the second wrapping tape is greater than the twisting pitch of the core, and the wrapping pitch of the first wrapping tape is smaller than the wrapping pitch of the second wrapping tape.

[0013] Furthermore, the first wrapping tape and the second wrapping tape both include a braided tape and at least two armor ropes. The armor ropes are arranged parallel to the length direction of the braided tape and are braided and connected by the braided tape to form the wrapping tape.

[0014] Furthermore, the armored rope comprises a metal rope with a circular or polygonal cross-section.

[0015] Furthermore, the braided belt is formed by cross-braiding a plurality of aramid yarns into an aramid yarn braided belt, and two adjacent armor ropes are connected by the aramid yarn braided belt.

[0016] Furthermore, the braiding density of the aramid yarn braided belt is 90% to 95%, and the axial angle between the braided yarns in the aramid yarn braided belt and the cable is ≤30°.

[0017] Furthermore, the wire core includes a conductor twisted into a circular cross-section, an insulating shielding layer extruded on the outer wall of the conductor, and a metal shielding layer coated on the outer wall of the insulating shielding layer.

[0018] Furthermore, the flame retardant layer and the isolation layer both include a ceramic silicone rubber layer, the thickness of the flame retardant layer is 0.8 mm-1.5 mm, and the thickness of the isolation layer is 0.2 mm-1.4 mm.

[0019] Furthermore, the outer sheath comprises a low-smoke halogen-free flame-retardant polyolefin outer sheath with an oxygen index OI ≥ 36%, and the extrusion thickness of the low-smoke halogen-free flame-retardant polyolefin outer sheath is 1.8 mm-5.0 mm.

[0020] Furthermore, the outer sheath has at least two channels opened along the length direction of the cable inside, a reinforcing core is passed through the channels, and the inner diameter of the channels is greater than the outer diameter of the reinforcing core.

[0021] Furthermore, the reinforcing core includes a fiber filament and six steel wires, which are twisted into a circular cross-sectional shape using a regular 1+6 twisting method.

[0022] Compared with the prior art, the cross-linked polyethylene insulated medium and high voltage power cable of the present invention has the following significant advantages:

[0023] 1. The cross-linked polyethylene insulated medium and high voltage power cable proposed by the present invention can improve the performance of the cable in terms of increased AC current transported and / or reduced conductor cross-sectional area by changing the structure of the armor layer. The cyclic reversal of the twisting direction of the cable core and / or the winding direction of the armor wire along the length of the cable improves the mechanical properties of the cable (compared with a structure with overall co-directional laying), and reduces the hysteresis and eddy current losses in the cable (compared with a structure with overall reverse laying);

[0024] 2. The cross-linked polyethylene insulated medium and high voltage power cable of the present invention can limit the pitch between adjacent metal ropes by adding aramid silk braided belts, thereby preventing deformation of the metal ropes when the cable is bent and laid, and improving the stability of the armor layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are not intended to be drawn to scale. In the accompanying drawings, each identical or nearly identical component shown in each figure may be represented by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the present invention will now be described by way of example and with reference to the accompanying drawings.

[0026] Figure 1 It is an axial view of a medium- and high-voltage power cable shown in an embodiment of the present invention.

[0027] Figure 2 It is a schematic cross-sectional view of a medium- and high-voltage power cable shown in an embodiment of the present invention.

[0028] Figure 3 3 is a schematic diagram comparing the winding direction of the armor layer and the twisting direction of the core shown in an embodiment of the present invention.

[0029] In the figure, the meanings of the various reference numerals are as follows:

[0030] 1. Wire core; 11. Conductor; 12. Insulation shielding layer; 13. Metal shielding layer; 2. Filling rope; 3. Wrapping layer; 4. Flame retardant layer; 5. Armor layer; 6. Isolation layer; 7. Outer sheath; 71. Channel; 8. Strengthening core. DETAILED DESCRIPTION

[0031] In order to better understand the technical content of the present invention, specific embodiments are given and described as follows in conjunction with the accompanying drawings.

[0032] Combination Figure 1-3 The cross-linked polyethylene insulated medium and high voltage power cable of the illustrated embodiment comprises a core 1 , a filling rope 2 , a wrapping layer 3 , a flame retardant layer 4 , an armor layer 5 , an isolation layer 6 and an outer sheath 7 .

[0033] Among them, the wire core 1, multiple wire cores 1 are tangent to each other and twisted together, and the wire core 1 includes a conductor 11 twisted into a circular cross-section, an insulating shielding layer 12 extruded on the outer wall of the conductor 11, and a metal shielding layer 13 coated on the outer wall of the insulating shielding layer 12.

[0034] Furthermore, the conductor 11 is formed by twisting a plurality of pure oxygen-free copper ultrafine wires in a regular manner of 1+6+12. The oxygen-free copper ultrafine wires have strong flexibility and good bending resistance, and the conductor 11 has good flexibility and bending resistance.

[0035] The insulating shielding layer 12 includes a conductor shielding layer, an insulating layer and an insulating shielding layer which are sequentially coated from the inside to the outside in a three-layer co-extrusion manner.

[0036] Among them, the conductor shielding layer and the insulating shielding layer are both made of semi-conductive shielding materials, which can eliminate the air gap on the surface of the conductive core and improve the ability to resist local discharge and tree discharge. When the temperature of the cable suddenly rises (the core heats up), the high temperature will not immediately impact the insulating layer due to the isolation of the inner semi-conductive shielding layer, which reduces the temperature rise of the insulating layer to a certain extent and protects the main insulation, so it has a thermal barrier effect. The insulating layer is made of cross-linked polyethylene insulation material, which has unique insulation properties, excellent mechanical properties and heat resistance.

[0037] Specifically, three layers of the insulating shielding layer 12 are co-extruded on the outer wall of the conductor 11 to form an insulating conductor core.

[0038] As an optional example, the metal shielding layer 13 is made of copper tape, which is wrapped around the outer wall of the insulating core to form the metal shielding layer 13. The number of wrapped layers of the copper tape is 1-2, and the wrapping overlap rate is greater than 20%.

[0039] Furthermore, the filling rope 2 is filled in the twisted gap of the wire core 1, and is wound around the sheath 3 together with the wire core 1 to form a cable core with a circular cross-section.

[0040] Among them, the filling rope 2 is made of glass fiber rope, which has high strength, high modulus, low shrinkage, no deformation, non-flammability, and good thermal insulation performance. It is filled in the twisted gap of the core 1 as a filling material, which not only makes the cross-section of the cable after cabling more round, but also has good flame retardant properties.

[0041] Furthermore, the wrapping layer 3 is made of elastic non-woven fabric and wrapped around the outer wall of the filling rope 2, mainly used to wrap the wire core 1 and the filling rope 2 together to form a cable core with a circular cross-section, and the wrapping overlap rate is greater than 20%.

[0042] Furthermore, the flame retardant layer 4 is coated on the outer wall of the wrapping layer 3; the flame retardant layer 4 is made of ceramic silicone rubber material and is extruded on the outer wall of the wrapping layer 3 by an extruder, and the thickness of the flame retardant layer 4 is 0.8mm-1.5mm.

[0043] Optionally, the ceramic silicone rubber material uses vibration-proof ceramic silicone rubber, including the following components by mass: 20-100 parts of methyl vinyl silicone rubber, 20-800 parts of end-vinyl-capped methyl vinyl silicone rubber, 20-80 parts of fumed silica, 0.5-5 parts of platinum flame retardant, 2-8 parts of structural control agent, 5-10 parts of coupling agent, 10-500 parts of mineral silicate, 5-200 parts of magnesium hydroxide, 2-50 parts of zinc oxide, and 2-50 parts of zinc borate. It can form a hard shell when burning, overcome other mechanical strength damage such as abnormal vibration at the fire scene, protect the burned cable from damage, and maintain electrical signal transmission.

[0044] Furthermore, the armor layer 5 is wrapped around the outer wall of the flame retardant layer 4 .

[0045] In a preferred embodiment, Figure 3 As shown, the armor layer 5 includes a first wrapping tape located in the inner layer with the same twisting direction as the core 1 and a second wrapping tape located in the outer layer with the opposite twisting direction to the core 1. The first wrapping tape and the second wrapping tape are alternately wound along the length direction of the cable to form a forward wrapping portion 501 and a reverse wrapping portion 502 that alternate along the length of the cable.

[0046] Specifically, the first wrapping tape and the second wrapping tape each include a plurality of metal ropes with circular cross-sections. The forward wrapping portion 501 and the reverse wrapping portion 502 are formed by spirally winding the metal ropes along the length direction of the cable through a wrapping machine. In an optional embodiment, the outer diameter of the metal rope is 2mm-3mm.

[0047] In an optional embodiment, the metal rope can be a steel wire rope. Since the steel wire rope has good radial compression resistance, it is wrapped around the outer wall of the flame retardant layer 4 to form a spiral armor layer 5. The radial compression resistance is achieved through the spiral structure, so that the cable has good radial compression resistance after being cabled, and provides armor protection for the cable after being formed.

[0048] In summary of the above embodiments, the present invention divides the armor layer 5 into a forward winding part 501 and a reverse winding part 502. Compared with the case where the twisting direction of the core 1 is the same as the wrapping direction of the armor layer 5, and the twisting direction of the core 1 is opposite to the winding direction of the armor layer 5 along the length of the cable, the performance of the cable can be improved in terms of increased transported AC current and / or reduced conductor cross-sectional area. The cyclic reversal of the twisting direction of the cable core and / or the winding direction of the armor wire along the length of the cable improves the mechanical properties of the cable (compared with a structure with overall unidirectional laying) and reduces the hysteresis and eddy current losses in the cable (compared with a structure with overall reverse laying).

[0049] Since the bending radius in the direction opposite to the twisting direction of the wire core 1 and the winding direction of the metal rope is larger than the bending radius in the direction identical to the twisting direction of the wire core 1 and the winding direction of the metal rope, if the twisting direction of the wire core 1 is opposite to the winding direction of the metal rope, the pitches of the two are the same, which will cause the reverse wrapping portion 502 to be difficult to bend, affecting the bending and laying of the cable during use.

[0050] Furthermore, the first wrapping tape is spirally wound on the outer wall of the cable core by a wrapping machine, in the same direction as the twisting direction of the core 1, and the wrapping pitch is greater than the twisting pitch of the core 1; the second wrapping tape is spirally wound on the outer wall of the first wrapping tape by a wrapping machine, in the opposite direction to the wrapping direction of the first wrapping tape, and the wrapping pitch is greater than the wrapping pitch of the first wrapping tape.

[0051] In this way, by setting the wrapping pitch of the wrapping tape in the armor layer 5, after the cable is protected by the armor layer 5, the winding pitch of the reverse wrapping part is greater than the winding pitch of the unidirectional wrapping part, and the winding pitch of the reverse wrapping part is greater than the twisting pitch of the core 1, so that the cable can be easier to bend after being formed while having the mechanical property of radial compression resistance, which is convenient for bending and laying of the cable.

[0052] During the cable laying process, due to the influence of cable traction and bending, the winding pitch of the metal rope may be deformed, resulting in the pitch between the local metal ropes of the armor layer 5 becoming larger. If the metal rope cannot be reset, the local metal ropes will be tightly squeezed together, which will cause the local armor of the cable to be harder, affecting the bending and laying of the cable. In addition, the increase in the pitch of the local metal ropes will cause the cable to partially lose armor protection.

[0053] In an optional embodiment, in order to limit the pitch between adjacent metal ropes, the first wrapping tape and the second wrapping tape both include a braided tape 52 and at least two armored ropes 51, the armored ropes 51 are arranged parallel to the length direction of the braided tape 52, and are braided and connected by the braided tape 52 to form a wrapping tape.

[0054] Optionally, the armor rope 51 includes a metal rope with a circular or polygonal cross-section; the braided belt 52 is formed by cross-braiding a plurality of aramid yarns into an aramid yarn braided belt, and two adjacent armor ropes 51 are connected by the aramid yarn braided belt.

[0055] In a specific embodiment, during weaving, a plurality of aramid filaments are first cross-woven into an aramid filament braided belt through a braiding machine. During the weaving process, a plurality of parallel distributed steel wire ropes are added at equal intervals along the width direction of the braided belt. Each steel wire rope extends along the length direction of the braided belt. Two adjacent steel wire ropes are connected by weaving the braided belt and, together with the braided belt, are woven by the braiding machine to form a composite braided belt.

[0056] Among them, the composite braided belt is arranged to be distributed in the width direction of the braided belt in an alternating structure of aramid wire braided belt-metal rope-aramid wire braided belt-metal rope-aramid wire braided belt-metal rope; the braiding density of the aramid wire braided belt is 90% to 95%, and the axial angle between the braided wire in the aramid wire braided belt and the cable is ≤30°.

[0057] In summary of the above embodiments, the distance between two adjacent metal ropes is limited by an aramid wire braided belt, and the two adjacent metal ropes are connected by high-density and small-angle braiding, which effectively limits the pitch of the metal ropes and prevents the pitch of the metal ropes from changing when the cable is bent and laid, resulting in local compactness or local relaxation, thereby improving the armor stability of the armor layer 5. Aramid wire has good mechanical strength and tensile strength and is light in weight. When used as a braided wire to connect metal ropes, it improves the tensile strength of the cable after molding to a certain extent, and enhances the safety of vertical laying of the cable after molding.

[0058] Furthermore, in order to prevent the metal ropes of the armor layer 5 from repeatedly rubbing against the outer sheath and causing wear of the outer sheath when the cable is bent and laid, Figure 2 and Figure 3 As shown, an isolation layer 6 is extruded on the outer wall of the armor layer 5 .

[0059] Specifically, the isolation layer 6 is made of ceramic silicone rubber material with a thickness of 0.2mm-0.4mm; the ceramic silicone rubber layer forms a hard shell when burning, which can overcome other mechanical strength damage such as abnormal vibration at the fire scene, protect the burned cable from damage, and maintain electrical signal transmission; using ceramic silicone rubber material as the isolation layer 6, on the one hand, can isolate the armor layer 5 and the outer sheath 7 so that the two will not be in direct contact and avoid wear, and on the other hand, through the use of ceramic silicone rubber material, the flame retardant performance of the cable can be improved, and in the event of a fire, the communication time of the cable can be extended.

[0060] Furthermore, the outer sheath 7 is extruded onto the outer wall of the isolation layer 6 .

[0061] Specifically, the outer sheath 7 includes a low-smoke halogen-free flame-retardant polyolefin outer sheath with an oxygen index OI ≥ 36%, and the extruded thickness of the low-smoke halogen-free flame-retardant polyolefin outer sheath is 1.8mm-5.0mm; it has good wear resistance, tensile strength and flame retardant properties. As an outer sheath, it can provide good protection for the internal structure of the cable.

[0062] Furthermore, in order to improve the tensile strength of the cable, Figure 2 As shown, at least two channels 71 are provided inside the outer sheath 7 along the length direction of the cable. A reinforcing core 8 is passed through the channels 71 , and the inner diameter of the channels 71 is greater than the outer diameter of the reinforcing core 8 .

[0063] like Figure 2 and Figure 3 As shown, in the present embodiment, six channels 71 are provided, and a reinforcing core 8 is passed through each channel 71. Since the inner diameter of the channel 71 is larger than the outer diameter of the reinforcing core 8, when the cable is laid in a bent manner, the reinforcing core 8 has axial movement space in the channel 71, thereby preventing the reinforcing core 8 from bending in the channel 71 and causing bulging of the outer sheath 7.

[0064] In an optional embodiment, the reinforcing core 8 includes one fiber filament and six steel wires, which are twisted into a circular cross-section using a regular twisting method of 1+6.

[0065] In order to prevent the reinforcing core 8 from wearing the outer sheath 7, a layer of rubber sleeve can be extruded on the outer wall of the reinforcing core 8. On the one hand, it can prevent the twisted structure of the reinforcing core 8 from becoming loose. On the other hand, it can prevent the metal wire from piercing or wearing the outer sheath 7, causing wear or damage to the outer sheath 7, thereby enhancing the safety and stability of the outer sheath 7.

[0066] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. A cross-linked polyethylene insulated medium and high voltage power cable, characterized in that, it comprises: a conductor core (1), multiple said conductor cores (1) being tangent to each other pairwise and twisted together; a filling rope (2), filled in the twisting gaps of the conductor cores (1), and being wound and fixed together with the conductor cores (1) by a wrapping layer (3) to form a circular cross-section; a flame retardant layer (4), covering the outer wall of the wrapping layer (3); an armor layer (5), wound around the outer wall of the flame retardant layer (4); an isolation layer (6), extruded on the outer wall of the armor layer (5); an outer sheath (7), extruded on the outer wall of the isolation layer (6); wherein, the armor layer (5) includes a first wrapping tape located in the inner layer with the same twisting direction as the conductor cores (1) and a second wrapping tape located in the outer layer with the opposite twisting direction to the conductor cores (1), the first wrapping tape and the second wrapping tape are alternately wound along the length direction of the cable to form a forward wrapping part (501) and a reverse wrapping part (502) that cycle and alternate along the length of the cable; the wrapping pitch of the second wrapping tape is greater than the twisting pitch of the conductor cores (1), and the wrapping pitch of the first wrapping tape is less than the wrapping pitch of the second wrapping tape; the first wrapping tape and the second wrapping tape both include a braided tape (52) and at least two armor ropes (51), the armor ropes (51) are arranged parallel to the length direction of the braided tape (52), and are braided and connected by the braided tape (52) to form a wrapping tape; the braided tape (52) is formed by cross-braiding multiple strands of aramid filaments into an aramid filament braided tape, and adjacent two of the armor ropes (51) are connected by the aramid filament braided tape.

2. The cross-linked polyethylene insulated medium and high voltage power cable according to claim 1, characterized in that, the armor rope (51) includes a metal rope with a circular or polygonal cross-section.

3. The cross-linked polyethylene insulated medium and high voltage power cable according to claim 1, characterized in that, the braiding density of the aramid filament braided tape is 90% - 95%, and the included angle between the braiding filaments in the aramid filament braided tape and the axial direction of the cable ≤ 30°.

4. The cross-linked polyethylene insulated medium and high voltage power cable according to claim 1, characterized in that, the conductor core (1) includes a conductor (11) twisted into a circular cross-section, an insulation shielding layer (12) extruded on the outer wall of the conductor (11), and a metal shielding layer (13) covering the outer wall of the insulation shielding layer (12).

5. The cross-linked polyethylene insulated medium and high voltage power cable according to claim 1, characterized in that, both the flame retardant layer (4) and the isolation layer (6) include a ceramized silicone rubber layer, the thickness of the flame retardant layer (4) is 0.8 mm - 1.5 mm, and the thickness of the isolation layer (6) is 0.2 mm - 0.4 mm.

6. The cross-linked polyethylene insulated medium and high voltage power cable according to any one of claims 1 - 5, characterized in that, the outer sheath (7) includes a low-smoke and halogen-free flame retardant polyolefin outer protective layer with an oxygen index OI ≥ 36%, and the extrusion thickness of the low-smoke and halogen-free flame retardant polyolefin outer protective layer is 1.8 mm - 5.0 mm.

7. The cross-linked polyethylene insulated medium and high voltage power cable according to claim 6, characterized in that, at least two channels (71) are provided inside the outer sheath (7) along the length direction of the cable, a strengthening core (8) is disposed in the channels (71), and the inner diameter of the channels (71) is larger than the outer diameter of the strengthening core (8).

8. The cross-linked polyethylene insulated medium and high voltage power cable according to claim 7, characterized in that, the strengthening core (8) comprises one fiber wire and six steel wires, and is stranded into a circular cross-section by a regular stranding method of 1+6.

Images