Conductor coating submarine cable current-carrying capacity prediction method based on thermal resistance theory

Abstract

The invention relates to the technical field of submarine cable current-carrying capacity prediction, in particular to a conductor coated submarine cable current-carrying capacity prediction method based on a thermal resistance theory, which comprises the following steps: lead sleeves and armors at two ends of a conductor uncoated steel wire submarine cable are short-circuited and are respectively connected with two different grounding points of a test site through grounding leads; processing the conductor copper wire coated aluminum alloy armored submarine cable prototype by the same method; raising the temperature of the submarine cable under a preset current value of a test loop, setting the current of the test loop as a test current value, obtaining and recording submarine cable characteristic data, adjusting the test current value and repeatedly recording multiple groups of data; calculating the thermal resistance of each part based on the multiple groups of submarine cable characteristic data and a thermal circuit formula, and calculating the dielectric loss; and inputting the thermal resistance and the dielectric loss of each part into a preset submarine cable current-carrying capacity prediction model to obtain the submarine cable current-carrying capacity output by the submarine cable current-carrying capacity prediction model, and solving the problems in the prior art that the submarine cable current-carrying capacity prediction method is easy to be interfered by the external environment, large in measurement error and low in reliability.

Description

Technical Field

[0001] This invention relates to the field of submarine cable current carrying capacity prediction technology, and in particular to a method for predicting the current carrying capacity of conductor-coated submarine cables based on thermal resistance theory. Background Technology

[0002] Submarine cable current carrying capacity, as a core indicator of its power transmission capacity, directly impacts the efficiency and safety of energy transmission. Accurately determining the current carrying capacity ensures stable operation within the cable's design lifespan, preventing serious problems such as overheating, insulation aging, and even short circuits caused by overload. This not only guarantees the continuity of energy transmission but also reduces the enormous repair costs and the risk of energy supply interruptions due to faults. Against the backdrop of continuously rising energy demand and the booming development of new energy industries such as offshore wind power, precise testing and optimization of submarine cable current carrying capacity are of great significance for improving the efficiency of marine energy development and utilization and promoting the green energy transition.

[0003] However, existing methods for testing the current-carrying capacity of submarine cables still have problems, especially in the testing of air-laid submarine cables. Due to the fluidity of air, its heat dissipation is complex and variable, making it difficult to accurately control and simulate. This makes accurately measuring the temperature distribution around the submarine cable extremely difficult. Furthermore, the accuracy of commonly used thermocouples is insufficient. When measuring the temperature of the submarine cable conductor, they are easily affected by external environmental interference, resulting in large measurement errors. This makes it difficult to accurately control the current to stabilize the conductor temperature at 90 degrees Celsius. Inaccurate conductor temperature directly affects the accuracy of current-carrying capacity calculations, reducing the reliability of the current-carrying capacity results obtained from these measurements. Summary of the Invention

[0004] The purpose of this invention is to provide a method for predicting the current carrying capacity of conductor-coated submarine cables based on thermal resistance theory, which solves the problems of existing technologies such as susceptibility to external environmental interference, large measurement errors, and low reliability.

[0005] To achieve the above objectives, this invention provides a method for predicting the current carrying capacity of conductor-coated submarine cables based on thermal resistance theory, comprising the following steps: Short-circuit the lead sleeves and armor at both ends of the uncoated steel wire submarine cable, and connect them to two different grounding points at the test site through grounding leads. Treat the prototype copper wire coated aluminum alloy armored submarine cable in the same way. The submarine cable is heated to the preset current value of the test circuit. After reaching the target temperature, the current of the test circuit is set to the test current value. When the conductor temperature stabilizes, the characteristic data of the submarine cable is acquired and recorded. The test current value is adjusted and multiple sets of data are recorded repeatedly. The thermal resistance of each part is calculated based on multiple sets of submarine cable characteristic data and thermal circuit formulas, and the dielectric loss is also calculated. The thermal resistance and dielectric loss of each component are input into the preset submarine cable current carrying capacity prediction model to obtain the submarine cable current carrying capacity output by the submarine cable current carrying capacity prediction model.

[0006] In some embodiments of this application, shorting the lead sheaths and armor at both ends of the uncoated steel wire submarine cable includes: When using the lead pipe welding method to complete the lead sleeve short joint, the cutting edges of the lead sleeve and the sheath at both ends of the joint are treated symmetrically. A lead pipe with an inner diameter slightly larger than the outer diameter of the lead sleeve, a length that can cover the joint and form an effective overlap with the original lead sleeves at both ends is selected. The lead pipe is placed on the submarine cable joint. One end of the lead pipe is welded to the lead sleeve of the submarine cable body using an oxyhydrogen flame and lead welding rod. After welding, the lead pipe is pulled out using a pull die with an inner diameter decreasing in sequence until the outer diameter of the lead pipe is consistent with the lead sheath. Then the other end of the lead pipe is welded. For armored short-joints, a connecting sleeve welding method is used. The wrapping unit outside the armored steel wire at the end of the submarine cable is stripped to expose the steel wire. A connecting sleeve with a length of 8-15cm, with a raised middle section and connecting sections on both sides, is selected. The first section of the connecting sleeve is inserted into the end of the first submarine cable, so that the armored steel wire is wrapped around the outer circumference of the first section, and the end of the steel wire is welded to the side wall of the middle section. The armored steel wire of the second submarine cable is passed through the corresponding through hole of the pitch disc. By rotating the pitch disc, its original pitch is restored, and then the steel wire is wrapped around the outer circumference of the second section of the connecting sleeve. After the excess steel wire is cut off, its end is welded to the other side wall of the middle section, thus completing the short-joint between the lead sheath and the armor at both ends of the submarine cable.

[0007] In some embodiments of this application, the uncoated steel wire submarine cable uses copper wire conductors and steel wire armor, has a length of 15m, and a conductor cross-section of 1000mm². 2 ; The prototype submarine cable with copper wire conductor coating and aluminum alloy armor uses copper wire conductor coating and aluminum alloy wire armor. It is 15m long and has a conductor cross-section of 1000mm². 2 .

[0008] In some embodiments of this application, the preset current value of the test circuit is 2500A, and the test current value is 500A.

[0009] In some embodiments of this application, the submarine cable characteristic data includes conductor temperature, sheath temperature, armor temperature, ambient temperature, sheath circulation current, and armor circulation current.

[0010] In some embodiments of this application, adjusting the test current value and repeatedly recording multiple sets of data includes: The test circuit current was increased to 700A and 900A respectively. The conductor temperature, sheath temperature, armor temperature, ambient temperature, sheath circulating current and armor circulating current data at each temperature measurement point were measured and recorded. A feature data table was generated based on the measurement data.

[0011] In some embodiments of this application, the thermal resistance of each part is calculated based on multiple sets of submarine cable characteristic data and thermal circuit formulas, and the dielectric loss is calculated as follows: Calculate conductor loss The expression is: ; ; in, This refers to alternating current in a high-voltage conductor. The AC resistance per unit length of the high-voltage conductor at operating temperature. The DC resistance per unit length of the high-voltage conductor at operating temperature. For skin effect factor, The proximity effect factor; Calculate the total loss of the metal sheath and armor. : ; ; in, The parallel equivalent resistance of the sheath and armor. The resistance per unit length of the submarine cable's metal sheath at the highest operating temperature. The resistance of the armor sheath per unit length of the submarine cable at the highest operating temperature. and These are respectively sheath impedance and steel wire impedance; For AC submarine cables armored with non-magnetic materials, calculate the proportion of sheath loss to conductor loss. and the proportion of armor loss to conductor loss The expression is: ; ; in, Total loss of metal sheath and armor The proportion of conductor loss; For AC submarine cables armored with magnetic materials, calculate the proportion of sheath loss to conductor loss. and the proportion of armor loss to conductor loss The expression is: ; In some embodiments, the calculations for coated and uncoated conductor copper wires, and for magnetic and non-magnetic armor, are combined in pairs. The main difference lies in the loss calculation. The armor loss under different conditions is shown below. The difference between coated and uncoated conductor copper wires is mainly in the calculation of AC current. Different AC currents affect conductor losses, and ultimately affect the current carrying capacity calculation. The formula for the AC current of uncoated submarine cables is: Before calculating the AC submarine cable resistance, the DC submarine cable resistance must be calculated first. At the highest stable operating temperature, the DC submarine cable resistance per unit length is: ; ; in, The DC resistance of the conductor at 20℃; The resistivity of the conductor at 20℃; L is the unit length in meters; S is the nominal cross-sectional area of ​​the conductor. The maximum operating temperature for maintaining stable operation of submarine cables is measured in degrees Celsius. Typically, the maximum operating temperature for AC submarine cables is 90°C. α is the mass temperature coefficient of the conductor at 20°C.

[0012] At the highest stable operating temperature, the resistance per unit length of AC submarine cable is: ; ; ; Where R is the AC resistance of the conductor at the highest stable operating temperature, in Ω; The DC resistance of a conductor at its highest stable operating temperature, expressed in Ω; X s The skin effect coefficient; The power frequency is 50Hz; the coefficient is set to 1 according to the IEC60287 standard.

[0013] It is important to understand that for the calculation of AC current of coated submarine cables, ys approaches 0, so we take ys equal to 0 for approximate calculation.

[0014] The thermal resistance of each part is calculated using the following expression: ; in, These are the thermal resistances between the single conductor and the metal sheath, the inner lining thermal resistance between the metal sheath and the armor, the outer sheath thermal resistance of the submarine cable, and the thermal resistance between the surface of the submarine cable and the surrounding medium. 、 、 、 These are conductor temperature, sheath temperature, armor temperature, and ambient temperature, respectively. Calculate the three sets of test data based on the feature data table. The data accuracy was corrected using a weighted average method to obtain the corrected single set of thermal resistance data.

[0015] In some embodiments of this application, thermal resistance data and dielectric loss of each component are input into a preset submarine cable current carrying capacity prediction model to obtain the submarine cable current carrying capacity output by the submarine cable current carrying capacity prediction model. I The expression is: .

[0016] The advantages and beneficial effects of this invention compared to the prior art are: This invention only requires measuring the temperature of the conductor, armor, sheath, and ambient temperature measurement points of the test submarine cable under three fixed currents, as well as the circulating current on the sheath and armor, to calculate the current carrying capacity. The short measurement time solves the problem of difficulty in controlling the current to stabilize the conductor temperature at 90 degrees Celsius when measuring the current carrying capacity of air-laid submarine cables in traditional methods. Furthermore, the weighted average method is used to correct the data accuracy of the three sets of test data, effectively reducing test errors and increasing the reliability and accuracy of the prediction results.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for predicting the current carrying capacity of a conductor-coated submarine cable based on thermal resistance theory, as described in an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of a single-core 220kV submarine cable with steel wire armor, without conductor coating, in an embodiment of the present invention. Figure 3 This is a schematic diagram of the structure of a single-core 220kV conductor copper wire coated with aluminum alloy armored submarine cable in this embodiment of the invention. Figure 4 This is a schematic diagram of the test circuit arrangement for measuring current in an embodiment of the present invention; Figure 5 This is a schematic diagram of the temperature measurement points inside the test hall in an embodiment of the present invention; Figure 6 This is a schematic diagram of a directly buried temperature measuring point in an embodiment of the present invention. Detailed Implementation

[0019] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" 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 mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0021] like Figure 1 As shown, this invention provides a method for predicting the current carrying capacity of conductor-coated submarine cables based on thermal resistance theory, comprising the following steps: Short-circuit the lead sleeves and armor at both ends of the uncoated steel wire submarine cable, and connect them to two different grounding points at the test site through grounding leads. Treat the prototype copper wire coated aluminum alloy armored submarine cable in the same way. The submarine cable is heated to the preset current value of the test circuit. After reaching the target temperature, the current of the test circuit is set to the test current value. When the conductor temperature stabilizes, the characteristic data of the submarine cable is acquired and recorded. The test current value is adjusted and multiple sets of data are recorded repeatedly. The thermal resistance of each part is calculated based on multiple sets of submarine cable characteristic data and thermal circuit formulas, and the dielectric loss is also calculated. The thermal resistance and dielectric loss of each component are input into the preset submarine cable current carrying capacity prediction model to obtain the submarine cable current carrying capacity output by the submarine cable current carrying capacity prediction model.

[0022] In some embodiments of this application, shorting the lead sheaths and armor at both ends of the uncoated steel wire submarine cable includes: When using the lead pipe welding method to complete the lead sleeve short joint, the cutting edges of the lead sleeve and the sheath at both ends of the joint are treated symmetrically. A lead pipe with an inner diameter slightly larger than the outer diameter of the lead sleeve, a length that can cover the joint and form an effective overlap with the original lead sleeves at both ends is selected. The lead pipe is placed on the submarine cable joint. One end of the lead pipe is welded to the lead sleeve of the submarine cable body using an oxyhydrogen flame and lead welding rod. After welding, the lead pipe is pulled out using a pull die with an inner diameter decreasing in sequence until the outer diameter of the lead pipe is consistent with the lead sheath. Then the other end of the lead pipe is welded. For armored cable short-switching, a connecting sleeve welding method is used. The outer covering of the armored steel wire at the end of the submarine cable is removed to expose the wire. A connecting sleeve with a length of 8-15cm, featuring a raised middle section and connecting sections on both sides, is selected. The first section of the connecting sleeve is inserted into the end of the first submarine cable, allowing the armored steel wire to fit around the outer circumference of the first section. The end of the steel wire is then welded to the side wall of the middle section. The armored steel wire of the second submarine cable is passed through the corresponding through hole of the pitch disc. By rotating the pitch disc, its original pitch is restored. The steel wire is then fitted around the outer circumference of the second section of the connecting sleeve. After removing excess steel wire, its end is welded to the other side wall of the middle section, completing the short-switching of the lead sheaths and armor at both ends of the submarine cable. When burying the grounding wire in the soil, after the lead sheaths and armor at both ends of each test object are short-switched, the grounding lead is led out to the ground surface. The conductor cross-section of the grounding lead is not less than 250 mm². 2 .

[0023] In some embodiments of this application, such as Figure 2 As shown, the uncoated steel wire submarine cable uses copper wire conductors and steel wire armor, has a length of 15m, and a conductor cross-section of 1000mm². 2 ; like Figure 3 As shown, the prototype submarine cable with copper wire conductor coating and aluminum alloy armor uses copper wire conductor coating and aluminum alloy wire armor, with a length of 15m and a conductor cross-section of 1000mm². 2 .

[0024] In some embodiments of this application, the preset current value of the test circuit is 2500A, and the test current value is 500A.

[0025] In some embodiments of this application, the submarine cable characteristic data includes conductor temperature, sheath temperature, armor temperature, ambient temperature, sheath circulation current, and armor circulation current.

[0026] In some embodiments of this application, adjusting the test current value and repeatedly recording multiple sets of data includes: The test circuit current was increased to 700A and 900A respectively. The conductor temperature, sheath temperature, armor temperature, ambient temperature, sheath circulating current and armor circulating current data at each temperature measurement point were measured and recorded. A feature data table was generated based on the measurement data.

[0027] In one specific embodiment, the test site layout is as follows: Figure 4As shown, a DC servo motor is connected in series with the intermediate transformer, and then connected in parallel with the remaining 8 transformers. The 9 transformers induce current in the test circuit. Different samples are connected by conductors, and a special copper lug is used to crimp the copper conductors at both ends. The outer sheath of the lead sleeve at both ends of the sample is cut open, exposing part of the lead sleeve. The armor at both ends of the sample is peeled off, removing the asphalt adhering to the surface to expose the armor wires. Grounding stakes are driven in according to the grounding point layout diagram. Thermocouples are arranged at various locations on the sample according to the sample temperature measurement point layout diagram to measure the temperature at different locations, and the current inductance is used to measure the circuit current.

[0028] In one specific embodiment, a total of 20 temperature monitoring points are set up, and the distribution of the temperature monitoring points is as follows: On both sides of the test submarine cable section, a set of temperature measuring points is set at 1 / 3L (L is the length of the intact part of the test submarine cable section) and 1 / 2L from the end of the middle submarine cable section. Each set of temperature measuring points contains three conductor thermocouples, for a total of 12 temperature measuring points. In the intermediate test section of the submarine cable, a set of temperature measuring points is set at the midpoint, including three conductor thermocouples, a metal sheath thermocouple and a metal armor layer thermocouple. Conductor temperature measuring points are set at each end 1m away, for a total of 7 temperature measuring points. An ambient temperature measuring point is set 3m above the center of the test circuit inside the test hall. When buried in the soil, a surface temperature measuring point is set at the ground surface at the center of the test circuit. The distribution of each measuring point is as follows: Figure 5 and Figure 6 As shown.

[0029] Before the test, ensure good contact between the thermocouple and the measured point, and take proper heat insulation and recovery measures for the conductor temperature measurement point. The temperature difference between any two points of the three conductor temperature measurement points at the same location should not exceed ±2℃. The average temperature of these three points, Tca, is taken as the temperature value of the conductor. The ambient temperature should be recorded throughout the test.

[0030] In some embodiments of this application, the thermal resistance of each part is calculated based on multiple sets of submarine cable characteristic data and thermal circuit formulas, and the dielectric loss is calculated as follows: Calculate conductor loss The expression is: ; ; in, This refers to alternating current in a high-voltage conductor. The AC resistance per unit length of the high-voltage conductor at operating temperature. The DC resistance per unit length of the high-voltage conductor at operating temperature. For skin effect factor, The proximity effect factor; Calculate the total loss of the metal sheath and armor. : ; ; in, The parallel equivalent resistance of the sheath and armor. The resistance per unit length of the submarine cable's metal sheath at the highest operating temperature. The resistance of the armor sheath per unit length of the submarine cable at the highest operating temperature. and These are sheathed reactors and steel wire reactors, respectively. For AC submarine cables armored with non-magnetic materials, calculate the proportion of sheath loss to conductor loss. and the proportion of armor loss to conductor loss The expression is: ; ; in, Total loss of metal sheath and armor The proportion of conductor loss; For AC submarine cables armored with magnetic materials, calculate the proportion of sheath loss to conductor loss. and the proportion of armor loss to conductor loss The expression is: ; The thermal resistance of each part is calculated using the following expression: ; in, These are the thermal resistances between the single conductor and the metal sheath, the inner lining thermal resistance between the metal sheath and the armor, the outer sheath thermal resistance of the submarine cable, and the thermal resistance between the surface of the submarine cable and the surrounding medium. 、 、 、 These are conductor temperature, sheath temperature, armor temperature, and ambient temperature, respectively. Calculate the three sets of test data based on the feature data table. The data accuracy was corrected using a weighted average method to obtain the corrected single set of thermal resistance data.

[0031] In some embodiments of this application, thermal resistance data and dielectric loss of each component are input into a preset submarine cable current carrying capacity prediction model to obtain the submarine cable current carrying capacity output by the submarine cable current carrying capacity prediction model. I The expression is: .

[0032] This invention only requires measuring the temperature of the conductor, armor, sheath, and ambient temperature measurement points of the test submarine cable under three fixed currents, as well as the circulating current on the sheath and armor, to calculate the current carrying capacity. The short measurement time solves the problem of difficulty in controlling the current to stabilize the conductor temperature at 90 degrees Celsius when measuring the current carrying capacity of air-laid submarine cables in traditional methods. Furthermore, the weighted average method is used to correct the data accuracy of the three sets of test data, effectively reducing test errors and increasing the reliability and accuracy of the prediction results.

[0033] In this application, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. In case of any inconsistency, the meaning set forth in this specification or derived from the content described herein shall prevail. Furthermore, the terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit the scope of this application.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for predicting the current carrying capacity of conductor-coated submarine cables based on thermal resistance theory, characterized in that, Includes the following steps: Short-circuit the lead sleeves and armor at both ends of the uncoated steel wire submarine cable, and connect them to two different grounding points at the test site through grounding leads. Treat the prototype copper wire coated aluminum alloy armored submarine cable in the same way. The submarine cable is heated to the preset current value of the test circuit. After reaching the target temperature, the current of the test circuit is set to the test current value. When the conductor temperature stabilizes, the characteristic data of the submarine cable is acquired and recorded. The test current value is adjusted and multiple sets of data are recorded repeatedly. The thermal resistance of each part is calculated based on multiple sets of submarine cable characteristic data and thermal circuit formulas, and the dielectric loss is also calculated. The thermal resistance and dielectric loss of each component are input into the preset submarine cable current carrying capacity prediction model to obtain the submarine cable current carrying capacity output by the submarine cable current carrying capacity prediction model.

2. The method for predicting the current carrying capacity of conductor-coated submarine cables based on thermal resistance theory according to claim 1, characterized in that, The method of short-switching the lead sheaths and armor at both ends of the conductor-uncoated steel wire submarine cable includes: When using the lead pipe welding method to complete the lead sleeve short joint, the cutting edges of the lead sleeve and the sheath at both ends of the joint are treated symmetrically. A lead pipe with an inner diameter slightly larger than the outer diameter of the lead sleeve, a length that can cover the joint and form an effective overlap with the original lead sleeves at both ends is selected. The lead pipe is placed on the submarine cable joint. One end of the lead pipe is welded to the lead sleeve of the submarine cable body using an oxyhydrogen flame and lead welding rod. After welding, the lead pipe is pulled out using a pull die with an inner diameter decreasing in sequence until the outer diameter of the lead pipe is consistent with the lead sheath. Then the other end of the lead pipe is welded. For armored short-joints, a connecting sleeve welding method is used. The wrapping unit outside the armored steel wire at the end of the submarine cable is stripped to expose the steel wire. A connecting sleeve with a length of 8-15cm, with a raised middle section and connecting sections on both sides, is selected. The first section of the connecting sleeve is inserted into the end of the first submarine cable, so that the armored steel wire is wrapped around the outer circumference of the first section, and the end of the steel wire is welded to the side wall of the middle section. The armored steel wire of the second submarine cable is passed through the corresponding through hole of the pitch disc. By rotating the pitch disc, its original pitch is restored, and then the steel wire is wrapped around the outer circumference of the second section of the connecting sleeve. After the excess steel wire is cut off, its end is welded to the other side wall of the middle section, thus completing the short-joint between the lead sheath and the armor at both ends of the submarine cable.

3. The method for predicting the current carrying capacity of conductor-coated submarine cables based on thermal resistance theory according to claim 2, characterized in that, The uncoated steel wire submarine cable uses copper wire conductors and steel wire armor, has a length of 15m, and a conductor cross-section of 1000mm². 2 ; The prototype submarine cable with copper wire coated and aluminum alloy armor uses copper wire conductor coating and aluminum alloy wire armor, with a length of 15m and a conductor cross-section of 1000mm². 2 .

4. The method for predicting the current carrying capacity of conductor-coated submarine cables based on thermal resistance theory according to claim 3, characterized in that, The preset test circuit has a current value of 2500A, and the test current value is 500A.

5. The method for predicting the current carrying capacity of conductor-coated submarine cables based on thermal resistance theory according to claim 4, characterized in that, The submarine cable characteristic data includes conductor temperature, sheath temperature, armor temperature, ambient temperature, sheath circulation current, and armor circulation current.

6. The method for predicting the current carrying capacity of a conductor-coated submarine cable based on thermal resistance theory according to claim 5, characterized in that, The process of adjusting the test current value and repeatedly recording multiple sets of data includes: The test circuit current was increased to 700A and 900A respectively. The conductor temperature, sheath temperature, armor temperature, ambient temperature, sheath circulating current and armor circulating current data at each temperature measurement point were measured and recorded. A feature data table was generated based on the measurement data.

7. The method for predicting the current carrying capacity of conductor-coated submarine cables based on thermal resistance theory according to claim 6, characterized in that, The calculation of thermal resistance for each part based on multiple sets of submarine cable characteristic data and thermal circuit formulas, and the calculation of dielectric loss, include: Calculate conductor loss The expression is: ； ； in, This refers to alternating current in a high-voltage conductor. The AC resistance per unit length of the high-voltage conductor at operating temperature. The DC resistance per unit length of the high-voltage conductor at operating temperature. For skin effect factor, The proximity effect factor; Calculate the total loss of the metal sheath and armor. : ； ； in, The parallel equivalent resistance of the sheath and armor. The resistance per unit length of the submarine cable's metal sheath at the highest operating temperature. The resistance of the armor sheath per unit length of the submarine cable at the highest operating temperature. and These are respectively sheath impedance and steel wire impedance; For AC submarine cables armored with non-magnetic materials, calculate the proportion of sheath loss to conductor loss. and the proportion of armor loss to conductor loss The expression is: ； ； in, Total loss of metal sheath and armor The proportion of conductor loss; For AC submarine cables armored with magnetic materials, calculate the proportion of sheath loss to conductor loss. and the proportion of armor loss to conductor loss The expression is: ； The thermal resistance of each part is calculated using the following expression: ； in, These are the thermal resistances between the single conductor and the metal sheath, the inner lining thermal resistance between the metal sheath and the armor, the outer sheath thermal resistance of the submarine cable, and the thermal resistance between the surface of the submarine cable and the surrounding medium. 、 、 、 These are conductor temperature, sheath temperature, armor temperature, and ambient temperature, respectively. Calculate the three sets of test data based on the feature data table. The data accuracy was corrected using a weighted average method to obtain the corrected single set of thermal resistance data.

8. The method for predicting the current carrying capacity of a conductor-coated submarine cable based on thermal resistance theory according to claim 7, characterized in that, The thermal resistance data and dielectric loss of each component are input into a preset submarine cable current carrying capacity prediction model to obtain the submarine cable current carrying capacity output by the submarine cable current carrying capacity prediction model. I The expression is: 。

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