A structure and method for increasing the current carrying capacity of submarine cables at the landing section by utilizing tidal cooling

Abstract

The present invention discloses a structure and method for increasing the current carrying capacity of a submarine cable in a landing section by utilizing tidal cooling in the field of submarine cable casing structure technology. The structure comprises a cable casing buried in a sand layer between high and low tide levels of seawater, wherein both ends of the cable casing are respectively connected to a seawater area and a cable landing trench, and the landing section of the underwater cable is arranged in the cable casing. The inner cavity of the cable casing is divided into a plurality of seawater storage areas by concrete blocking blocks arranged at fixed intervals along the cable laying path, and a water seepage channel is provided on the outer wall of the cable casing corresponding to each seawater storage area. At each high tide, seawater will seep into the cable casing to replenish the seawater in the pipe. After the tide recedes, the seawater in the pipe will slowly seep out and be lost, but will be replenished in time at each high tide. Therefore, the submarine cable is always in flowing seawater, and the flowing seawater can take away heat in time, so that the submarine cable is almost in a constant temperature environment. The heat dissipation conditions are better than those of the submarine cable directly buried in the middle of the sea.

Description

Technical Field

[0001] The present invention relates to the technical field of submarine cable casing structures, and in particular to a structure and method for increasing the current carrying capacity of a submarine cable at a landing section by utilizing tidal cooling. Background Art

[0002] In order to achieve "carbon peak and carbon neutrality", China's offshore wind power has developed rapidly, the wind farm capacity is getting larger and larger, and the offshore distance is getting farther and farther. The required submarine cable voltage level is getting higher and higher, and the cross-section is getting larger and larger. As the main artery of offshore wind power, in order to ensure output reliability, submarine cables are generally required to be produced as whole as possible. However, the heat dissipation conditions of the landing section of the submarine cable are poor, and the current carrying capacity is generally lower than that of the mid-sea section. The cross-section selection of the submarine cable is controlled by the landing section. The proportion of the landing section in the entire submarine cable path is very small. The overall enlargement of the submarine cable cross-section caused by this is obviously uneconomical.

[0003] The current carrying capacity of a submarine cable is mainly controlled by conditions such as the cable's own losses, the external ambient temperature, and the soil thermal resistance coefficient. Therefore, when the structural type of the submarine cable is selected and the external ambient temperature and soil thermal resistance are certain, soil replacement measures are considered to reduce the thermal resistance coefficient, accelerate soil heat dissipation, and increase the current carrying capacity of the submarine cable to meet the transmission capacity requirements of the wind farm. However, this measure can only reduce the soil thermal resistance coefficient to 1.2K·m / w, which is still a large difference compared to the thermal resistance coefficient of 0.7K·m / w in the mid-sea section. Moreover, this solution cannot be adopted below the high tide level due to the scouring effect of seawater. Therefore, the heat dissipation problem of the direct-buried casing protection section below the high tide level has not been solved so far.

[0004] Based on this, the present invention designs a structure and method for utilizing tidal cooling to increase the current carrying capacity of the submarine cable at the landing section to solve the above problems. Summary of the Invention

[0005] The purpose of the invention is to provide a structure and method for increasing the current carrying capacity of submarine cables in the landing section by utilizing tidal cooling to solve the above technical problems.

[0006] To achieve the above-mentioned objectives, the invention provides the following technical solutions: a structure and method for increasing the current carrying capacity of a submarine cable in the landing section by utilizing tidal cooling, comprising a cable sheath buried in a sand layer between high and low tide levels of the seawater, the two ends of the cable sheath being connected to the seawater area and the cable landing trench respectively, the landing section of the underwater cable being arranged in the cable sheath, the inner cavity of the cable sheath being divided into several seawater storage areas by concrete sealing blocks arranged at fixed intervals along the direction of the cable laying path, and a water seepage channel being provided on the outer wall of the cable sheath corresponding to each of the seawater storage areas.

[0007] Preferably, the cable sheath is arranged in an inclined shape with a slope of 1 to 2 degrees, and the end close to the sea water area is the low-potential end.

[0008] Preferably, the cable sleeve is composed of a plurality of unit sections connected end to end, and gaps are left at the joints between the unit sections to form the water seepage channel.

[0009] Preferably, the unit segment integral structure is composed of an intermediate tube and a large-diameter spherical end and a small-diameter spherical end located at both ends of the intermediate tube, and the outer diameter of the small-diameter spherical end is smaller than the inner diameter of the large-diameter spherical end.

[0010] Preferably, the port diameters of the large-diameter spherical end and the small-diameter spherical end are respectively smaller than their inner diameters.

[0011] Preferably, the unit section is composed of two symmetrical upper and lower halves, and mounting ear plates are provided on the left and right sides of the half surfaces of the unit section.

[0012] A method for increasing the current carrying capacity of a submarine cable at a landing section by utilizing tidal cooling, comprising the following steps:

[0013] Step S10: Select the inner diameter of the cable casing according to the outer diameter of the selected submarine cable, and the inner diameter of the cable casing is twice the outer diameter of the submarine cable;

[0014] Step S20: Designing the cable casing slope: The landing section of the submarine cable is between low tide and high tide, with a slope of 1 to 2 degrees, and the buried depth of the submarine cable in the landing section is not less than 1 meter;

[0015] Step S30: Design of the spacing of concrete plugging blocks: To ensure that all submarine cables within the plugging spacing are immersed in seawater, the height difference within the spacing should be less than half the inner diameter of the cable casing, and the slope should be 1.2 degrees;

[0016] Step S40: Prefabricating a concrete plugging module according to the cable casing unit section structure, wherein the height of the prefabricated concrete plugging module is half the height of the cable casing unit section;

[0017] Step S50: digging a trench for laying cables according to the slope, with a trench depth of no less than 1m and a trench width of 1:1;

[0018] Step S60: The submarine cable begins to land and is laid into the excavated trench;

[0019] Step S70: Start installing the cable casing from the low tide end to the high tide end. According to the principle of 5m plugging interval in step S30, concrete plugging is performed starting from the first section of the cable casing at the low tide end.

[0020] Preferably, the specific construction operation steps of step S70 are:

[0021] Step a: Use machinery to lift the submarine cable to an appropriate height above the ground;

[0022] Step b: Install half of the cable bushing unit section and half of the plugging module;

[0023] Step c: Place the submarine cable in the installed half-piece plugging module;

[0024] Step d: Install the other half of the plugging module and clamp the submarine cable between the plugging modules;

[0025] Step e: Install the other half of the cable bushing unit, but do not tighten the bolts, and mark it;

[0026] Step f: Complete the installation of the first 5m interval and plugging, and start the installation of the second 5m interval;

[0027] Step g: After all cable casings are installed, pour concrete into the marked cable casings that need to be sealed;

[0028] Step h: This completes the installation of the cable sleeve and plug.

[0029] Compared with the prior art, the invention has the following beneficial effects:

[0030] The heat dissipation protective casing structure of the submarine cable landing section of the present invention is used in the section from low tide to high tide. After the submarine cable is laid and the casing is installed, concrete is filled and sealed in the middle casing section at certain intervals. After the cable casing and the sealing are installed, the casing is filled with water when a high tide arrives, and then the original sand is backfilled to restore the original state. After adopting this device structure, seawater will seep into the cable casing every time the tide rises, replenishing the seawater in the pipe. After the tide recedes, the seawater in the pipe will slowly seep out and be lost, but it will be replenished in time with each high tide. Therefore, the submarine cable is always in the flowing seawater, and the flowing seawater can take away the heat in time, so that the submarine cable is in an almost constant temperature environment. The heat dissipation conditions are better than those of the submarine cable directly buried in the middle of the sea. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 This is a schematic diagram of the overall paving structure of the present invention;

[0033] Figure 2 This is a schematic diagram of the half-surface structure of a unit section of the invented cable casing;

[0034] Figure 3 The present invention is a schematic diagram of the cross-sectional structure of a unit section of a cable sheath.

[0035] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0036] 1-sand layer, 2-cable casing, 21-concrete sealing block, 211-intermediate pipe, 212-large-diameter spherical end, 213-small-diameter spherical end, 22-seawater storage area, 23-seepage channel, 3-seawater area, 4-cable landing trench, 5-undersea cable. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0038] See also Figure 1 The invention provides a technical solution: a structure and method for increasing the current carrying capacity of a submarine cable in the landing section by using tidal cooling, comprising a cable casing 2 buried in a sand layer 1 between high and low tide levels of seawater, with both ends of the cable casing 2 connected to a seawater area 3 and a cable landing trench 4, respectively. The landing section of an underwater cable 5 is laid in the cable casing 2, and the inner cavity of the cable casing 2 is divided into a plurality of seawater storage areas 22 by concrete blocking blocks 21 arranged at fixed intervals along the cable laying path, and a water seepage channel 23 is provided on the outer wall of the cable casing 2 corresponding to each seawater storage area 22. Every time the tide rises, seawater will seep into the seawater storage area 22 through the water seepage channel 23 to replenish the seawater in the pipe. After the tide recedes, the seawater in the pipe will slowly seep away, but it will be replenished in time every time the tide rises. Therefore, the submarine cable is always in flowing seawater, and the flowing seawater can take away heat in time, so that the submarine cable is in an almost constant temperature environment. The heat dissipation conditions are better than those of the submarine cable directly buried in the mid-sea section.

[0039] The cable casing 2 is laid out with a slope of 1 to 2 degrees, with the end close to the seawater area 3 being the low-potential end, which is consistent with the characteristic that the cable landing trench 4 is located higher than the sand layer 1.

[0040] like Figure 2-3As shown, the cable sleeve 2 is composed of a plurality of unit sections 21 connected end to end. In this case, the unit section 21 is made of ductile iron. The unit section 21 has a certain weight and adopts a segmented end-to-end connection structure, which can be easily installed and carried. A gap is left at the connection between the unit sections 21 and the unit sections 21 to form a water seepage channel 23 for infiltrating seawater; the unit section 21 is composed of an intermediate tube 211 of an integral structure and a large-diameter spherical end 212 and a small-diameter spherical end 213 located at both ends of the intermediate tube 211. When the unit section 21 is connected, the small-diameter spherical end 213 is embedded in the large-diameter spherical end 212 of the next unit section 21 to form a nested connection structure. The outer diameter of the small-diameter spherical end 213 is smaller than the inner diameter of the large-diameter spherical end 212, so that the large-diameter spherical end 212 and the small-diameter spherical end 213 are connected. After the end head 213 is fitted, a gap can be left to form a water seepage channel 23; the port diameters of the large-diameter spherical end head 212 and the small-diameter spherical end head 213 are respectively smaller than their inner diameters, so that after the installation centers of the large-diameter spherical end head 212 and the small-diameter spherical end head 213 coincide with each other and are fitted, the two have a certain overlapping part, so that the entire cable sheath 2 forms a serpentine pipe structure with a certain degree of bending freedom, and even if the later laying route has a certain degree of bending, it will not cause a fault at the connection point to form a gap; the unit section 21 is composed of two symmetrical upper and lower halves, so that the small-diameter spherical end head 213 can be embedded in the large-diameter spherical end head 212, and it is convenient for local disassembly and maintenance in the later stage, and mounting ear plates 214 are provided on the left and right sides of the half surface of the unit section 21 for cooperating with bolts to fasten the upper and lower half unit sections 21.

[0041] Working principle example:

[0042] The key factor in ensuring that the submarine cable in the casing is always immersed in seawater is the design of the spacing. The maximum distance of the spacing needs to be converted according to the landing slope. Considering the inconvenience of shallow construction and the unsatisfactory sealing effect of the casing top, the height difference within the spacing needs to be less than half of the inner diameter of the cable casing. In this way, it can be ensured that when the water storage height at the lower end has not reached the pipe diameter, the seawater has basically submerged the submarine cable at the higher side. The groove slope needs to be designed in combination with the selected cable casing diameter. The specific steps are as follows:

[0043] (1) Select the inner diameter of the cable casing according to the outer diameter of the selected submarine cable. According to the regulations, the inner diameter of the cable casing is twice the outer diameter of the submarine cable. At present, the most commonly used cables for offshore wind power are three-core AC submarine cables with voltage levels of 35kV, 110kV, 220kV, and 500kV, and DC submarine cables with voltage levels of ±200kV, ±320kV, ±400kV, and ±535kV. The outer diameter of the 35kV three-core submarine cable is approximately between 111mm and 166mm, and the outer diameter of the 110kV three-core submarine cable is approximately between 192mm and 23 The outer diameter of 220kV three-core submarine cable is approximately between 244mm and 277mm, the outer diameter of 110kV single-core submarine cable is between 108mm and 137mm, the outer diameter of 220kV single-core submarine cable is between 136mm and 176mm, the outer diameter of 500kV single-core submarine cable is between 153mm and 184mm, and the outer diameter of DC submarine cable is between 104mm and 200mm. Therefore, the inner diameter of the selected casing is between 216mm and 554mm.

[0044] (2) Slope design: For direct burial laying, the burial depth is also a limiting factor for current carrying capacity. Taking into account the need for protection depth, the shallowest burial depth of shallow submarine cables is generally about 1m. After adopting this patented design, the influence of burial depth can be ignored. However, considering the earthwork, the slope design needs to be combined with the landing terrain design. According to experience, the shallow section is relatively gentle, with a slope of about 1 to 2 degrees, that is, a change of 0.17 to 0.35 meters every 10 meters;

[0045] (3) Spacing design: Based on the principle that the height difference within the spacing is less than half of the inner diameter of the cable casing, the slope is designed to be 1.2 degrees. Based on the smallest casing inner diameter (216mm), the maximum spacing is 5m (rounded up). Based on the largest casing inner diameter (554mm), the maximum spacing is 13m (rounded up). The above slope, spacing, and submarine cable burial depth can be adjusted according to the specific conditions of the project.

[0046] (4) Before the construction of the submarine cable, a concrete plugging module is prefabricated according to the structure of the submarine cable casing unit. The height of the module is half the height of the submarine cable casing unit. The number of modules is based on the needs of the project.

[0047] (5) Before landing the submarine cable, a trench must be dug according to the slope. The trench depth should not be less than 1m, and the trench width should be excavated at a slope of 1:1.

[0048] (6) After the trench is excavated, the submarine cable begins to land and be laid into the excavated trench;

[0049] (7) Install the cable casing from the low tide end to the high tide end. According to the principle of 5m plugging interval in step S30, concrete plugging is performed starting from the first section of the cable casing at the low tide end. The specific construction steps are as follows:

[0050] a. Use machinery to lift the submarine cable to an appropriate height from the ground;

[0051] b. Install half of the submarine cable casing unit section and half of the plugging module;

[0052] c. Place the submarine cable in the installed half-piece blocking module;

[0053] d. Install the other half of the plugging module and clamp the submarine cable between the plugging modules;

[0054] e. Install the other half of the submarine cable casing unit, but do not tighten the bolts, and mark them;

[0055] f. Complete the installation of the first 5m interval and plugging, and start the installation of the second 5m interval;

[0056] g. After all cable casings are installed, pour concrete into the marked cable casings that need to be sealed;

[0057] h. The installation of cable casing and plugging is now complete;

[0058] i. Wait for a high tide, and when the tide begins to recede, backfill the original sand and soil as the tide recedes to ensure that the casing is basically filled with seawater at this time, restoring the original landform of the beach. This completes the construction of this method.

[0059] Based on the above embodiments, the technical benefits that this device can bring are:

[0060] (1) Without increasing the construction cost, the operation environment of the submarine cable in the landing section is improved, the heat dissipation environment of the submarine cable is improved, the current carrying capacity of the submarine cable is increased by 30%, the bottleneck problem of the current carrying capacity of the submarine cable in the landing section is solved, and the cross-section of the entire submarine cable is reduced;

[0061] (2) The landing section accounts for a very small proportion of the entire submarine cable path, but in previous projects, it caused the entire submarine cable cross-section to be enlarged, resulting in a significant increase in project investment. The adoption of this patent can solve this problem, significantly reduce project investment, and increase project economic benefits;

[0062] (3) The invention is intended for use in future long-distance, large-capacity offshore wind power. Since the amount of electrical energy transmitted by submarine cables is enormous, the landing section of the submarine cables requires a better heat dissipation environment. This patent will better reflect its economic benefits.

[0063] In the description of the invention, it should be understood that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inside", "front", "center", "both ends", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on the invention.

[0064] In the invention, unless otherwise clearly stipulated and limited, the terms such as "installation", "setting", "connection", "fixation", "screw-on" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the invention according to the specific circumstances.

[0065] While embodiments of the invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and alterations may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A structure that utilizes tidal cooling to increase the current carrying capacity of a submarine cable at the landing section, characterized by: The invention comprises a cable casing (2) buried in a sand layer (1) between high and low tide levels of seawater, wherein both ends of the cable casing (2) are connected to a seawater area (3) and a cable landing trench (4), respectively, and a landing section of an underwater cable (5) is arranged in the cable casing (2). The inner cavity of the cable casing (2) is divided into a plurality of seawater storage areas (22) by concrete blocking blocks (21) arranged at fixed intervals along the cable laying path, and a water seepage channel (23) is provided on the outer wall of the cable casing (2) corresponding to each of the seawater storage areas (22); The cable sleeve (2) is composed of a plurality of unit sections (21) connected end to end, and gaps are left at the connection points between the unit sections (21) to form the water seepage channel (23).

2. The structure for increasing the current carrying capacity of submarine cables at the landing section by utilizing tidal cooling according to claim 1 is characterized in that: The cable casing (2) is arranged in an inclined shape with a slope of 1 to 2 degrees, and the end close to the seawater area (3) is a low-potential end.

3. The structure for increasing the current carrying capacity of submarine cables at the landing section by utilizing tidal cooling according to claim 1 is characterized in that: The unit section (21) is composed of an integrated intermediate tube (211) and a large-diameter spherical end (212) and a small-diameter spherical end (213) located at both ends of the intermediate tube (211). The outer diameter of the small-diameter spherical end (213) is smaller than the inner diameter of the large-diameter spherical end (212).

4. The structure for increasing the current carrying capacity of submarine cables at the landing section by utilizing tidal cooling according to claim 3 is characterized in that: The port diameters of the large-diameter spherical end (212) and the small-diameter spherical end (213) are both smaller than their inner diameters.

5. The structure for increasing the current carrying capacity of submarine cables at the landing section by utilizing tidal cooling according to claim 1 is characterized in that: The unit section (21) is composed of two symmetrical upper and lower halves, and mounting ear plates (214) are provided on the left and right sides of the opposite halves of the unit section (21).

6. A method for increasing the current carrying capacity of a submarine cable at the landing section by utilizing tidal cooling, utilizing the structure for increasing the current carrying capacity of a submarine cable at the landing section by utilizing tidal cooling as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: step S10: Select the inner diameter of the cable casing according to the outer diameter of the selected submarine cable. The inner diameter of the cable casing should be twice the outer diameter of the submarine cable. Step S20: Designing the cable casing slope: The landing section of the submarine cable is between low tide and high tide, with a slope of 1 to 2 degrees, and the buried depth of the submarine cable in the landing section is not less than 1 meter; Step S30: Design of the spacing of concrete plugging blocks: To ensure that all submarine cables within the plugging spacing are immersed in seawater, the height difference within the spacing should be less than half the inner diameter of the cable casing, and the slope should be 1.2 degrees; Step S40: Prefabricating a concrete plugging module according to the cable casing unit section structure, wherein the height of the prefabricated concrete plugging module is half the height of the cable casing unit section; Step S50: digging a trench for laying cables according to the slope, with a trench depth of no less than 1m and a trench width of 1:1; Step S60: The submarine cable begins to land and is laid into the excavated trench; Step S70: Start installing the cable casing from the low tide end to the high tide end. According to the principle of 5m plugging interval in step S30, concrete plugging is performed starting from the first section of the cable casing at the low tide end.

7. The method of increasing the current carrying capacity of submarine cables at the landing section by utilizing tidal cooling according to claim 6, characterized in that: The specific construction operation steps of step S70 are: Step a: Use machinery to lift the submarine cable to an appropriate height above the ground; Step b: Install half of the cable bushing unit section and half of the plugging module; Step c: Place the submarine cable in the installed half-piece plugging module; Step d: Install the other half of the plugging module and clamp the submarine cable between the plugging modules; Step e: Install the other half of the cable bushing unit, but do not tighten the bolts, and mark it; Step f: Complete the installation of the first 5m interval and plugging, and start the installation of the second 5m interval; Step g: After all cable casings are installed, pour concrete into the marked cable casings that need to be sealed; Step h: This completes the installation of the cable sleeve and plug.

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