A cable for a flexible direct power supply system

Abstract

The utility model belongs to cable technical field, concretely relates to a cable for flexible direct power supply system, including many wire cores, filling layer, tape layer, fire barrier layer, armoring layer and outer sheath, the utility model discloses realized electromagnetic compatibility and the dual consideration of fire safety, through making armoring layer by single side rolling grain metal band vertical package formation, effectively suppressed the common mode electromagnetic interference of bipolar direct current system, simultaneously with fire barrier layer together formed the double fireproof mechanism of physical and chemical combination, greatly promoted cable use safety stability.

Description

Technical Field

[0001] This utility model belongs to the field of cable technology, specifically relating to a cable for a flexible DC power supply system. Background Technology

[0002] With the rapid development of new energy power generation (such as photovoltaic power generation and energy storage systems) and high-voltage direct current (HVDC) power distribution systems for data centers, flexible DC power supply systems are gradually becoming an important development direction to replace traditional AC power supply systems due to their significant advantages in transmission efficiency, loss control, and network flexibility. Especially in medium-voltage DC application scenarios such as DC ±375V, flexible DC systems can better adapt to the dynamic characteristics of new energy access and data center loads, and have good engineering application prospects.

[0003] In the actual deployment of flexible DC power supply systems, the system wiring method is one of the key factors affecting its performance and reliability. Currently, the industry mostly uses the traditional single-pole structure design for DC cables, which performs well in single-pole power supply systems.

[0004] However, when applied to a bipolar symmetrical power supply DC system, the close proximity of the positive and negative cables can cause their magnetic fields to couple, easily leading to severe common-mode electromagnetic interference. This interference threatens the operational stability of sensitive loads such as precision servers and storage devices within data centers, thus affecting the overall electromagnetic compatibility (EMC) performance of the system.

[0005] In addition, as a critical information infrastructure, data centers have strict requirements for the safety and fire resistance of their power supply lines; however, traditional cable flame-retardant designs often focus on the flame retardancy of a single material or structural protection, and their protection capabilities are poor when facing fire risks caused by external fire sources or internal electrical faults. Utility Model Content

[0006] The purpose of this invention is to provide a cable for a flexible DC power supply system, which solves the technical problems of common-mode electromagnetic interference caused by magnetic field coupling and poor fire resistance in existing cables.

[0007] This utility model discloses a cable for a flexible DC power supply system, comprising: Multiple wire cores, each wire core comprising a conductor and an insulating layer covering the conductor; A filler layer that fills the gaps between the multiple said wire cores; A wrapping layer is wrapped around the filler layer; A fire-resistant layer is wrapped around the outer layer of the wrapping tape; The armor layer is formed by longitudinally wrapping a single-sided corrugated metal strip around the fireproof layer. The single-sided corrugated metal strip is an aluminum strip or a copper strip, with the corrugated side facing the inside of the cable and the smooth side facing the outside of the cable, and there is an overlapping area at the edge of the longitudinal wrapping. The outer sheath is extruded over the armor layer.

[0008] This application achieves a balance between electromagnetic compatibility and fire safety. By making the armor layer longitudinally wrapped with single-sided corrugated metal strips, it effectively suppresses common-mode electromagnetic interference of bipolar DC systems. At the same time, together with the fireproof layer, it forms a dual fireproof mechanism that combines physical and chemical methods, thereby greatly improving the safety and stability of the cable.

[0009] Based on the above technical solution, the solution of this application can be further improved as follows: Preferably, the corrugated shape of the single-sided corrugated metal strip is a sine wave or a trapezoidal wave; with this solution, the trapezoidal wave can provide stable mechanical protection; the sine wave has better flexibility and a smoother surface, which helps to reduce stress concentration and improve the bending performance of the cable.

[0010] Preferably, the thickness t of the single-sided corrugated metal strip is 0.2mm to 0.8mm, the corrugation pitch e is 4mm to 6mm, and the corrugation depth h is 0.04mm to 0.2mm; when the corrugation shape is trapezoidal, its inclination angle α is 45° to 70°; this scheme balances the cable's flexibility, shielding effectiveness, mechanical strength, and manufacturing processability.

[0011] Preferably, the ratio of the insulation layer thickness to the conductor diameter is ≤0.30; by adopting this solution, a balance between high flexibility, bending resistance, and electrical reliability of the cable can be achieved.

[0012] Preferably, the conductor consists of three strands twisted together with a twist pitch ratio of 10 to 15, and the cross-section of the cable is circular. This design ensures that the conductors are tightly twisted, the stress distribution of the single filaments is more uniform when bent, the fatigue resistance is stronger, and it has a synergistic effect with the thickness of the insulation layer, which helps to ensure that the cable has both good electrical and mechanical properties, as well as high flexibility and bending resistance.

[0013] Preferably, the conductor consists of two parallel wires, and the cable cross-section is rectangular, with the corner thickness being 10% to 25% greater than the side thickness. This design allows for close arrangement in space-constrained environments, significantly improving space utilization. It also facilitates uniform current distribution in high-frequency and high-current applications, and enables full-coverage shielding to enhance electromagnetic interference resistance. Furthermore, its square design provides good pressure resistance, prevents rolling during installation, and facilitates fixing. The thickened corners effectively improve the electric field distribution, eliminate discharge risks, and ensure long-term insulation reliability for medium-voltage DC applications.

[0014] Preferably, the longitudinal edge of the single-sided corrugated metal strip is sealed by laser welding; this solution eliminates the electromagnetic leakage path caused by edge gaps, significantly improves the shielding effectiveness of the cable, and also eliminates the penetration path of water vapor from the edge, thus achieving the waterproof function of the cable.

[0015] Preferably, the overlapping area of ​​the single-sided corrugated metal strip is coated with waterproof adhesive, or the troughs of the corrugated surface are filled with phosphorus-nitrogen-based expanding water-blocking gel. This solution can effectively block the longitudinal penetration of water vapor, greatly enhance the cable's resistance to water vapor intrusion and the internal dryness during long-term operation, and ensure the reliability of the insulation system.

[0016] Preferably, both the fire-resistant layer and the outer sheath are made of halogen-free, low-smoke, flame-retardant polyolefin material. Using this solution, it can be combined with the armor layer to form a triple "thermal barrier," achieving a dual fire-resistant mechanism of physical flame isolation by the armor layer + chemical flame retardancy by the fire-resistant layer and the outer sheath, thus achieving multiple flame retardancy in the finished cable.

[0017] Preferably, the single-sided corrugated metal strip undergoes surface passivation treatment; this method delays internal metal oxidation and prevents electrochemical corrosion.

[0018] Through the above technical solution, this utility model achieves the following beneficial effects: 1. This application achieves a dual balance between electromagnetic compatibility and fire safety. By making the armor layer longitudinally wrapped with single-sided corrugated metal strips, it effectively suppresses common-mode electromagnetic interference of bipolar DC systems. At the same time, it forms a dual fireproof mechanism combining physical and chemical methods together with the fireproof layer, thereby greatly improving the safety and stability of the cable. 2. This application eliminates the electromagnetic leakage path caused by edge gaps by using laser welding to seal the longitudinal edge of the single-sided corrugated metal strip, significantly improving the shielding effectiveness of the cable and also eliminating the penetration path of water vapor from the edge, thus achieving the waterproof function of the cable. 3. This application effectively blocks the longitudinal penetration of water vapor by coating the overlapping area with waterproof adhesive and / or filling the troughs of the ribbed surface with phosphorus-nitrogen-based expanding water-blocking gel, which greatly enhances the cable's resistance to water vapor intrusion and the internal dryness during long-term operation, thus ensuring the reliability of the insulation system. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the cable used in the flexible DC power supply system according to Embodiment 1 of this application; Figure 2 This is a schematic diagram of the cable used in the flexible DC power supply system according to Embodiment 2 of this application; Figure 3 A schematic diagram of a cross section when the groove shape of a single-sided corrugated metal strip is a sine wave; Figure 4 A schematic diagram of the cross section when the groove shape of a single-sided corrugated metal strip is a trapezoidal wave; Explanation of reference numerals in the attached figures: 1. Core wire; 2. Filler layer; 3. Wrapping layer; 4. Fireproof layer; 5. Armor layer; 6. Outer sheath. Detailed Implementation

[0021] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0022] In this application, unless otherwise expressly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0023] To better understand the above technical solutions, the following will provide a detailed description of the technical solutions in conjunction with the accompanying drawings and specific embodiments.

[0024] Example 1: like Figure 1 As shown, this embodiment discloses a cable for a flexible DC power supply system, used in a bipolar flexible DC power supply system as a power transmission carrier for both positive and negative poles. Its specific structure includes: multiple conductors 1, a filling layer 2, a wrapping layer 3, a fireproof layer 4, an armor layer 5, and an outer sheath 6.

[0025] The conductor 1 includes a conductor 11 and an insulation layer 12 covering the conductor 11. The conductor 11 is used to carry current and can be made of type 2 round copper or aluminum, which has excellent conductivity. The insulation layer 12 is made of cross-linked polyethylene (XLPE) insulation material extruded, and the dielectric strength of cross-linked polyethylene (XLPE) at a rated voltage of 375V must be ≥15kV / mm.

[0026] The filler layer 2 fills the gaps between multiple wire cores 1, keeping the cross-section of the cable round, ensuring structural stability and roundness, and avoiding unevenness in subsequent processing. A non-hygroscopic filler compatible with the insulation layer 12 can be used, and it should be ensured that it is tight and without gaps during filling.

[0027] The wrapping layer 3 is wrapped around the filler layer 2 to bind the core 1 and the filler layer 2 together to form a stable and non-loose cable core, providing a flat base for the subsequent wrapping of the fireproof layer 4 and the armor layer 5. It can be made of halogen-free, low-smoke, high flame-retardant glass fiber wrapping tape, which has excellent flame-retardant properties, high tensile strength and tear strength, as well as good corrosion resistance and insulation properties.

[0028] The fire-resistant layer 4 is wrapped around the wrapping layer 3. It can isolate the cable core from the armor layer 5, prevent the cable core from being crushed or damaged by the armor layer 5, and also achieve chemical flame retardancy.

[0029] The armor layer 5 is formed by longitudinally wrapping a single-sided corrugated metal strip around the fireproof layer 4. The single-sided corrugated metal strip is made of aluminum or copper, with the corrugated side facing the inside of the cable and the smooth side facing the outside of the cable. There is an overlap area at the edge of the longitudinal wrapping, which is preferably ≥5mm. This ensures electrical continuity and mechanical integrity and avoids shielding breaks.

[0030] It should be noted that, regarding electromagnetic compatibility: Single-sided corrugated aluminum strip can achieve high-frequency interference suppression: First, the high conductivity of aluminum (61% IACS) makes it an excellent electromagnetic wave reflector. When high-frequency electromagnetic waves (≥100MHz) are incident, the induced eddy currents generated on the surface of the aluminum strip will form a reverse magnetic field. According to Lenz's law, the reverse magnetic field generated by the eddy currents can reflect most of the electromagnetic energy. Second, the skin effect concentrates the high-frequency current on the surface of the aluminum. The skin depth of aluminum decreases sharply with increasing frequency (δ=√(2 / ωμσ)), which means that even a 0.1mm thick aluminum strip can effectively shield GHz-level interference. Finally, the corrugated structure can reduce transfer impedance and reduce common-mode noise transmission through multi-point contact of the crests. Single-sided corrugated copper strip can suppress low-frequency magnetic fields (<1MHz): First, the weak permeability of copper induces eddy currents, and the reverse magnetic field formed by these eddy currents can partially cancel the original magnetic field; simultaneously, the high resistivity of copper (5.5×10⁻⁻⁶) 8 (Ω·m) can convert more magnetic field energy into Joule heat dissipation, while the uneven surface of the corrugated structure can avoid local overheating by breaking up the eddy current path.

[0031] It should be noted that, regarding fire safety: First, the smooth surface of the single-sided corrugated metal strip can reflect some of the radiant heat, and the air layer formed by its high-density corrugated structure can further delay heat conduction based on its low thermal conductivity (about 0.024 W / m·K), thus forming a "thermal barrier" effect. Secondly, aluminum has a melting point of 660°C, and copper has a melting point of approximately 900°C. Therefore, in the early stages of a fire (300–600°C), the armor layer 5 can still maintain the integrity of the cable structure and prevent the flames from directly eroding the cable core.

[0032] The outer sheath 6 is extruded over the armor layer 5 to provide the final protective barrier, ensuring that the cable maintains good performance in a variety of harsh environments.

[0033] This invention achieves a balance between electromagnetic compatibility and fire safety. By making the armor layer 5 longitudinally wrapped with single-sided corrugated metal strip, it effectively suppresses common-mode electromagnetic interference of the bipolar DC system. At the same time, together with the fireproof layer 4, it forms a dual fireproof mechanism that combines physical and chemical methods, thereby greatly improving the safety and stability of the cable.

[0034] In this embodiment, as Figure 3 and Figure 4 As shown, the corrugated shape of single-sided corrugated metal strip is a sine wave or trapezoidal wave, which has good machinability and ensures product consistency and quality reliability. It should be noted that trapezoidal waves provide stable mechanical protection and are suitable for direct burial applications with higher requirements for pressure resistance and rigidity; sine waves have better flexibility and a smoother surface, which helps reduce stress concentration and improves the bending performance of cables, making them suitable for applications with high requirements for bending radius.

[0035] In this embodiment, as Figure 3 and Figure 4 As shown, the thickness t of the single-sided corrugated metal strip is 0.2mm to 0.8mm, the corrugation pitch e is 4mm to 6mm, and the corrugation depth h is 0.04mm to 0.2mm; when the corrugation shape is trapezoidal, its inclination angle a is 45° to 70°.

[0036] The above design balances cable flexibility, shielding effectiveness, mechanical strength, and manufacturability.

[0037] In this embodiment, as Figure 3 and Figure 4 As shown, the ratio of the thickness of the insulation layer 12 to the diameter of the conductor 11 is ≤0.30, which can achieve a balance between high flexibility, bending resistance and electrical reliability of the cable.

[0038] In this embodiment, as Figure 1As shown, there are three wire cores 1, which are the positive pole, negative pole and grounding wire respectively, and they are twisted together. The twisting pitch ratio is 10 to 15, and the cross-section of the cable is circular.

[0039] The above design ensures that the conductors are tightly stranded, the stress distribution of the single filaments is more uniform when bent, the fatigue resistance is stronger, and it works synergistically with the thickness of the insulation layer 12, which helps to ensure that the cable has both good electrical and mechanical properties, as well as high flexibility and bending resistance.

[0040] Example 2: like Figure 2 As shown, this embodiment discloses a cable for a flexible DC power supply system. The difference between this cable and the first embodiment is that the core 1 consists of two parallel wires, the cable cross-section is rectangular, and the thickness of the corners is 10% to 25% greater than the thickness of the sides.

[0041] When installation space is limited by height (such as in flat cable trays, building mezzanines, or elevator shafts), square cables can be arranged more closely to optimize cross-sectional area utilization and reduce space waste. In high-frequency or high-current applications, the edges of square cables can distribute current density more evenly, and for power applications with high shielding requirements, the shielding layer of square cables is easier to fully cover, reducing electromagnetic interference (EMI). In addition, square cables are less prone to deformation under vertical pressure, and in fixed installations (such as pre-embedded installations in buildings), the square design prevents the cable from rolling in the tray and facilitates fixation.

[0042] It should be noted that the thickness of the corners of the square cable is 10% to 25% greater than that of the sides. This effectively improves the electric field distribution at the corners, fundamentally eliminating the electric field concentration caused by the angular structure, and ensuring the long-term insulation reliability and service life of the cable under medium-voltage DC conditions.

[0043] Example 3: This embodiment discloses a cable for a flexible direct power supply system, which differs from Embodiment 1 or Embodiment 2 in that the longitudinal edge of the single-sided corrugated metal strip is sealed by laser welding.

[0044] The above design eliminates electromagnetic leakage paths caused by edge gaps, significantly improves the cable's shielding effectiveness, and also prevents moisture from penetrating through the edges, thus achieving the cable's waterproof function.

[0045] In this embodiment, the overlapping area of ​​the single-sided corrugated metal strip is coated with waterproof adhesive and / or the troughs of the corrugated surface are filled with phosphorus-nitrogen-based expanding water-blocking gel.

[0046] Specifically, the overlapping areas of the single-sided corrugated metal strips are coated with waterproof adhesive, which fills and bonds the microscopic gaps between the metal strips, thereby preventing liquid water and water vapor from slowly and persistently penetrating through the mechanical seams.

[0047] Specifically, the troughs of the corrugated surface of the single-sided corrugated metal strip are filled with phosphorus-nitrogen-based expandable water-blocking gel. When water vapor enters, it immediately expands upon contact with water, thereby adaptively and tightly blocking all trough gaps, thus completely cutting off the subsequent propagation path of moisture. Furthermore, its "phosphorus-nitrogen-based" chemical properties resonate with the phosphorus-nitrogen-based flame retardant in the outer sheath, enabling it to better respond to flame-retardant functions. Its chemical properties are also relatively mild, with low corrosivity to the metal strip of the armor layer 5, which helps to extend the service life of the cable.

[0048] The above design effectively blocks the longitudinal penetration of water vapor, greatly enhancing the cable's resistance to water vapor intrusion and its internal dryness during long-term operation, thus ensuring the reliability of the insulation system.

[0049] In this embodiment, as Figure 3-4 As shown, both the fire-resistant layer 4 and the outer sheath 6 are made of halogen-free, low-smoke, flame-retardant polyolefin material. Based on the four-fold protection system of "heat absorption and cooling - gas phase inhibition - solid phase barrier - smoke control", it achieves chemical flame retardancy and achieves high flame retardancy in the finished cable, with bromine and chlorine content (expressed as HCl) not exceeding 0.5%, pH value not less than 4.3, electrical conductivity not exceeding 10μS / mm, fluorine content not exceeding 0.1%, smoke concentration transmittance not less than 60%, combustion drips / particles d0 grade, smoke toxicity t0 grade, and corrosivity a1 grade. The endothermic decomposition of metal hydroxides in the sheath material consumes combustion heat and releases water vapor to dilute oxygen; phosphorus and nitrogen-based flame retardants interrupt the chain reaction by capturing gaseous free radicals, while nano-clay and carbonizing agents form a dense ceramic carbon layer (thermal conductivity <0.3W / m·K) in the condensed phase, effectively isolating heat and oxygen; at the same time, smoke suppressants such as zinc molybdate catalyze the deep oxidation of smoke particles, controlling the smoke density (NBS) below 40.

[0050] Through the above design, it can be combined with the armor layer 5 to form a triple "thermal barrier", realizing a triple fire isolation mechanism of physical flame isolation by the armor layer 4 + fireproof layer 4 and chemical flame retardancy by the outer sheath 6, thereby achieving multiple flame retardancy of the finished cable.

[0051] In this embodiment, as Figure 3-4 As shown, the surface passivation treatment of single-sided corrugated metal strip can generate an inert protective film on the surface of the metal strip, which can more effectively isolate the metal substrate from external water vapor, oxygen and corrosive media, thereby delaying internal metal oxidation and preventing electrochemical corrosion.

[0052] Numerous specific details are set forth in this specification. However, it will be understood that embodiments of this invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0053] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model, and they should all be covered within the scope of the claims and specification of this utility model.

Claims

1. A cable for a flexible DC power supply system, characterized in that, include: Multiple wire cores, each wire core comprising a conductor and an insulating layer covering the conductor; A filler layer that fills the gaps between the multiple said wire cores; A wrapping layer is wrapped around the filler layer; A fire-resistant layer is wrapped around the outer layer of the wrapping tape; The armor layer is formed by longitudinally wrapping a single-sided corrugated metal strip around the fireproof layer. The single-sided corrugated metal strip is made of aluminum or copper, with the corrugated side facing the inside of the cable and the smooth side facing the outside of the cable, and has an overlapping area at the edge of the longitudinal wrapping. The overlapping area of ​​the single-sided corrugated metal strip is coated with waterproof adhesive and / or the troughs of the corrugated surface are filled with phosphorus-nitrogen-based expanding water-blocking gel. The outer sheath is extruded over the armor layer.

2. The cable for a flexible DC power supply system according to claim 1, characterized in that, The single-sided corrugated metal strip has a corrugated shape that is either sinusoidal or trapezoidal.

3. The cable for a flexible DC power supply system according to claim 2, characterized in that, The thickness t of the single-sided corrugated metal strip is 0.2mm to 0.8mm, the corrugation pitch e is 4mm to 6mm, and the corrugation depth h is 0.04mm to 0.2mm; when the corrugation shape is trapezoidal, its inclination angle a is 45° to 70°.

4. The cable for a flexible DC power supply system according to claim 1, characterized in that, The ratio of the insulation layer thickness to the conductor diameter is ≤0.

30.

5. The cable for a flexible DC power supply system according to claim 1, characterized in that, The cable consists of three wires twisted together, with a twist pitch ratio of 10 to 15, and the cross-section of the cable is circular.

6. The cable for a flexible DC power supply system according to claim 1, characterized in that, The cable consists of two wires arranged in parallel. The cable has a rectangular cross-section, and the thickness at the corners is 10% to 25% greater than the thickness at the sides.

7. The cable for a flexible DC power supply system according to claim 1, characterized in that, The longitudinal edge of the single-sided corrugated metal strip is sealed by laser welding.

8. The cable for a flexible DC power supply system according to claim 1, characterized in that, Both the fire-resistant layer and the outer sheath are made of halogen-free, low-smoke, flame-retardant polyolefin material.

9. The cable for a flexible DC power supply system according to claim 1, characterized in that, The surface passivation treatment of the single-sided corrugated metal strip.

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