High-voltage submarine cable conductor temperature calculation method considering harmonic current influence

Abstract

The invention relates to a high-voltage submarine cable conductor temperature calculation method considering harmonic current influence, and belongs to the technical field of cable conductor temperature calculation and current-carrying capacity regulation and control. The problem that conductor temperature evaluation is inaccurate due to the fact that harmonic current is ignored in an existing cable temperature calculation method is solved, and the influence of harmonic waves on the submarine cable operation state in the long-distance power transmission environment cannot be comprehensively represented. According to the technical scheme, the method comprises the steps of establishing an electromagnetic thermal coupling model, calculating volume loss density of power frequency and harmonic current, setting boundary conditions according to a midsea section laying scene, carrying out multi-physics field simulation to obtain conductor temperature, and verifying effectiveness through experiments. The method can accurately quantify the influence of the harmonic current component and content on submarine cable conductor heating, and guarantees the long-term stable operation of the large-capacity offshore wind power connected into the high-voltage submarine cable.

Description

Technical Field

[0001] This invention belongs to the field of cable conductor temperature calculation and current carrying capacity control technology, and relates to a method for calculating the conductor temperature of high-voltage submarine cables that takes into account the influence of harmonic current. Background Technology

[0002] Submarine cables, as key transmission channels connecting offshore wind farms to the mainland power grid, play a vital role in achieving efficient transmission of clean energy and ensuring the stable operation of power grids on isolated islands. With the large-scale integration of large-capacity offshore wind power, the harmonic problems generated during grid-connected operation of wind farms are becoming increasingly prominent. Among these, the 5th, 7th, 11th, and 13th harmonic current components are particularly significant.

[0003] During long-distance high-voltage submarine cable transmission, the presence of harmonic currents significantly affects the cable's heating characteristics. Harmonic currents enhance the conductor's skin effect and proximity effect, increasing the cable's volume loss density and causing a rise in conductor temperature. Excessive conductor temperature rise not only directly limits the actual transmission capacity of the submarine cable but also accelerates the aging of cross-linked polyethylene (XLPE) insulation material, reducing insulation performance and threatening the safe operation of the submarine cable.

[0004] Current cable temperature calculation methods primarily focus on heating characteristics under power frequency conditions. For example, existing patents propose conductor temperature calculation formulas based on the influence of sheath circulating current, or assess cable current carrying capacity by establishing a finite element model of the temperature field. Other methods construct multiphysics coupling models, considering the relationship between material parameters and temperature to calculate cable temperature distribution. While these methods achieve cable conductor temperature calculation to some extent, none fully consider the impact of harmonic currents on cable heating characteristics.

[0005] In actual offshore wind power grid-connected scenarios, changes in harmonic current content and frequency composition significantly alter the heating characteristics of submarine cables. Traditional methods, by neglecting the additional heating effect of harmonic currents, struggle to accurately reflect the true temperature changes of conductors in long-distance submarine cables under harmonic influences. This leads to current-carrying capacity assessments deviating from actual operating conditions, failing to provide a valid basis for ensuring the safe operation of submarine cables.

[0006] Therefore, there is an urgent need for a method to calculate the conductor temperature of high-voltage submarine cables that can take into account the influence of harmonic currents, accurately quantify the degree of influence of the components and content of harmonic currents on conductor temperature, and provide technical support for the scientific regulation of the current carrying capacity of submarine cables in power grids with a high proportion of new energy sources. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a method for calculating the conductor temperature of high-voltage submarine cables that takes into account the influence of harmonic currents.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A method for calculating the conductor temperature of a high-voltage submarine cable that takes into account the influence of harmonic currents includes the following steps: Calculate the volume loss density of high-voltage submarine cables under the influence of power frequency current and harmonic current. A high-voltage submarine cable conductor temperature calculation model considering the influence of harmonic currents is established based on the aforementioned volume loss density. The conductor temperature of the high-voltage submarine cable is calculated using the aforementioned high-voltage submarine cable conductor temperature calculation model.

[0009] Furthermore, the step of calculating the volume loss density of the high-voltage submarine cable under the influence of power frequency current and harmonic current includes: Calculate the total electromagnetic loss of the high-voltage submarine cable based on the electromagnetic field control equation; Based on the total electromagnetic loss, calculate the volume loss density under the influence of power frequency current and the volume loss density under the influence of harmonic current respectively. The total volume loss density is obtained by superimposing the volume loss density under the influence of the power frequency current and the volume loss density under the influence of the harmonic current.

[0010] Furthermore, the electromagnetic field control equation is as follows:

[0011] in, The electric field intensity vector, For AC angular frequency, The magnetic vector potential, For vector differential operators, The magnetic field strength vector. It is the current density vector. Magnetic flux density For electrical conductivity, j The imaginary unit, It is the electric displacement vector.

[0012] Furthermore, the total electromagnetic loss is calculated using the electromagnetic-thermal coupling equation:

[0013] in, For material density, For fluid velocity vector, This refers to the specific heat capacity of the material under normal pressure. This represents the total electromagnetic loss. For the temperature of the submarine cable, For resistive loss, For hysteresis loss, Thermal conductivity, It is the complex conjugate of the electric field intensity vector. It is the complex conjugate of the magnetic field strength vector.

[0014] Furthermore, the volumetric loss density under the influence of the power frequency current Volume loss density under the influence of harmonic current The calculation formula is:

[0015] in, The total electromagnetic loss of the submarine cable under the influence of power frequency current. The total electromagnetic loss of the submarine cable due to the influence of harmonic currents. This represents the cross-sectional area of ​​the submarine cable conductor. The thickness outside the electromagnetic field.

[0016] Furthermore, the step of establishing a high-voltage submarine cable conductor temperature calculation model based on the volume loss density, taking into account the influence of harmonic currents, includes: substituting the total volume loss density as a heat source into the heat conduction equation:

[0017] in, Thermal conductivity, The temperature of the submarine cable after harmonic superposition.

[0018] Furthermore, the step of calculating the conductor temperature of the high-voltage submarine cable using the high-voltage submarine cable conductor temperature calculation model includes: setting the boundary conditions for laying the high-voltage submarine cable in the middle of the sea; performing multi-physics field calculations based on the boundary conditions, where electromagnetic field and temperature field are coupled; and outputting the conductor temperature of the high-voltage submarine cable.

[0019] Furthermore, the boundary conditions include a first type of boundary condition, a second type of boundary condition, and a third type of boundary condition; the first type of boundary condition is the soil subsurface boundary temperature, calculated using the following formula:

[0020] in, x , y For spatial coordinates, Physical boundary of an object The wall temperature distribution function on the surface, Physical boundary of an object The pre-defined wall temperature function; the second type of boundary condition is the normal heat flux density, calculated using the following formula:

[0021] in, For heat flux density, n For the boundary The normal direction; the third type of boundary condition is the convective heat transfer boundary condition between seawater and soil, and the calculation formula is:

[0022] in, The convective heat transfer coefficient is... This refers to the seawater temperature.

[0023] Furthermore, the components of the harmonic current include at least one of 250Hz, 350Hz, 550Hz and 650Hz; the content of the harmonic current is 5% to 20%.

[0024] Furthermore, the input parameters of the high-voltage submarine cable conductor temperature calculation model include power frequency current, harmonic current components, harmonic current content, seawater temperature, and burial depth; the output parameter of the high-voltage submarine cable conductor temperature calculation model is the high-voltage submarine cable conductor temperature.

[0025] The beneficial effects of this invention are as follows: (1) This invention is the first to incorporate the additional heating effect generated by harmonic current into the temperature calculation system of high-voltage submarine cable conductors. By calculating the volume loss density under power frequency current and harmonic current conditions, a complete electromagnetic-thermal coupling model is established. This method can accurately characterize the influence mechanism of different harmonic components and contents on the temperature of submarine cable conductors, and solves the problem of temperature assessment deviation caused by neglecting harmonic current in traditional methods.

[0026] (2) By establishing a multi-physics coupling calculation model, this invention fully considers the synergistic effects of environmental factors such as seawater temperature and burial depth with harmonic currents, and can more accurately reflect the heating characteristics of submarine cable conductors under actual operating conditions. This provides a reliable technical basis for the dynamic control of submarine cable current carrying capacity in high-capacity offshore wind power access scenarios, and effectively avoids capacity waste or overheating risks caused by inaccurate conductor temperature estimation.

[0027] (3) The conductor temperature calculation method provided by this invention can detect abnormal temperature rise caused by harmonic current in a timely manner, providing key parameters for the insulation status assessment and remaining life prediction of submarine cables. By providing early warning of potential overheating risks, the safety and reliability of high-voltage submarine cable operation can be significantly improved, and the service life of the equipment can be extended.

[0028] (4) This method provides an important reference for the selection of submarine cables and the formulation of operation strategies in power grid systems with a high proportion of new energy sources. Based on this invention, engineers can accurately assess the temperature distribution of submarine cables under different harmonic environments, optimize the overall design scheme of offshore wind power grid connection systems, and improve the economy and stability of system operation.

[0029] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 Flowchart of a rapid calculation method for conductor temperature of cross-linked polyethylene submarine cables; Figure 2 Schematic diagram of boundary conditions for laying submarine cables in the middle of the sea; Figure 3 shows the simulation cloud map of the temperature distribution of AC submarine cable affected by different harmonic current components; Figure 3(a) is 250Hz; Figure 3(b) is 350Hz; Figure 3(c) is 550Hz; Figure 3(d) is 650Hz. Detailed Implementation

[0031] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0032] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0033] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present 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, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0034] This invention provides a method for calculating the conductor temperature of high-voltage submarine cables that takes into account the influence of harmonic currents, mainly including the following four steps: Step 1: Based on the long-term heating characteristics of high-voltage submarine cables, calculate the volume loss density of high-voltage submarine cables under power frequency current and harmonic current conditions, and establish a high-voltage submarine cable conductor temperature calculation model that takes into account the influence of harmonic current. Step 2: Based on the actual laying scenario of the high-voltage submarine cable in the middle of the sea, set the corresponding control equations and boundary conditions, carry out multi-physics field calculations of the electromagnetic field and temperature field coupling of the high-voltage submarine cable considering the influence of harmonic current, and obtain numerical calculation results of the conductor temperature of the submarine cable with different harmonic components. Step 3: Verify the effectiveness of the high-voltage submarine cable conductor temperature calculation method that takes into account the influence of harmonic currents; Step 4: Using specific power frequency current, harmonic current composition and content, seawater temperature, and burial depth as inputs, calculate the conductor temperature of the high-voltage submarine cable.

[0035] Step 1: Based on the long-term heating characteristics of high-voltage submarine cables, calculate the volume loss density of high-voltage submarine cables under power frequency current and harmonic current conditions, and establish a calculation model for the conductor temperature of high-voltage submarine cables affected by harmonic current.

[0036] When current flows through the submarine cable conductor, an electromagnetic field is generated. Electromagnetic losses occur between the conductor and the cross-linked polyethylene (XLPE) insulation material. The heat generated by these electromagnetic losses affects the temperature field distribution around the submarine cable, impacting the heating of the conductor and reducing the long-term current carrying capacity of the cable. The electromagnetic field control equation for the submarine cable is shown in equation (1): (1) In equation (1), E The electric field intensity vector, ω Let A be the alternating angular frequency and A be the magnetic vector potential. H It is the magnetic field strength vector; J It is the current density vector; B Let T be the magnetic flux density. σ S is the electrical conductivity, in S / m; D It is the electric displacement vector.

[0037] The electromagnetic-thermal coupling equation is shown in equation (2): (2) In equation (2), ρ This refers to the material density, expressed in kg / m³. 3 ; C Specific heat capacity of the material at normal pressure, expressed in J / (kg·℃); Q a Total electromagnetic loss, in watts (W). T The temperature of the submarine cable is expressed in °C. T The maximum value is the temperature of the submarine cable conductor; Q r This refers to resistance loss, measured in watts (W). Q m This represents hysteresis loss, measured in W.

[0038] After calculating the total electromagnetic loss, the volume loss density under the influence of power frequency current and harmonic current is calculated separately, as shown in equation (3): (3) In equation (3), q v1 This refers to the volumetric loss density of submarine cables under the influence of power frequency current, expressed in W / m. 3 , q v2 This represents the volumetric loss density of submarine cables under the influence of harmonic currents, expressed in W / m. 3 , Q a1 The total electromagnetic loss of the submarine cable under the influence of power frequency current is expressed in watts (W). Q a2 The total electromagnetic loss of the submarine cable under the influence of harmonic current is expressed in W, S is the cross-sectional area of ​​the submarine cable conductor, and d is the outside thickness of the electromagnetic field in meters.

[0039] The volume loss density of the power frequency current and harmonic current is superimposed, and the total volume loss density is used as the heat source of the submarine cable. The conductor temperature after the power frequency current is superimposed with the harmonic current is calculated as shown in Equation (4).

[0040] (4) In equation (4), k Thermal conductivity, T a The temperature of the submarine cable after harmonic superposition is expressed in °C. T a The maximum value is the temperature of the submarine cable conductor when the power frequency current is superimposed with the harmonic current.

[0041] Step 2: Based on the actual laying scenario of the high-voltage submarine cable in the sea, set the corresponding control equations and boundary conditions, carry out multi-physics field calculations of the electromagnetic field and temperature field coupling of the high-voltage submarine cable considering the influence of harmonic current, and obtain numerical calculation results of the conductor temperature of the submarine cable with different harmonic components.

[0042] Based on a simulation model of direct burial of a 500kV AC submarine cable in the submarine, this study analyzes the influence of harmonic current superimposed with power frequency current on the temperature distribution of the high-voltage AC submarine cable in the submarine section under rated current carrying capacity. A schematic diagram of the boundary conditions for laying the submarine cable in the submarine section is shown below. Figure 2 As shown.

[0043] The first type of boundary condition is the soil subsurface boundary temperature, and its calculation formula is shown in equation (5).

[0044] (5) In equation (5), f(x, y)|Γ is the wall temperature of the physical boundary Γ of the object. In this simulation, the temperature of the bottom layer of soil is set to 283 K.

[0045] The second type of boundary condition is the normal heat flux density, and the calculation formula is shown in equation (6).

[0046] (6) In equation (6), q 2 represents heat flux density, set to 0; k represents thermal conductivity.

[0047] The third type of boundary condition is the convective heat transfer boundary condition between air and soil, as shown in equation (7): (7) In equation (7), α The convective heat transfer coefficient is expressed in W / (m²). 2 The convective heat transfer coefficient between seawater and soil is 200 W / (m²). 2 ·K); T f The value represents seawater temperature, expressed in Kelvin (K). The simulation model uses a seawater temperature of 293 K and a burial depth of 1.5 m.

[0048] The temperature calculation model of the submarine cable conductor considering harmonics proposed in the first step was used as the governing equation. After setting the corresponding boundary conditions and performing mesh generation, the temperature distribution of the submarine cable under power frequency and different harmonic frequencies was calculated using the "frequency domain-steady state" solver of the finite element simulation model of the direct burial of the submarine cable in the middle section. Among them, the harmonic frequencies of the submarine cable were set to 250Hz, 350Hz, 550Hz and 650Hz respectively. The rated current carrying capacity of the submarine cable under pure power frequency conditions was 2000A. The harmonic current and power frequency current were calculated as shown in Equation (8).

[0049] (8) In equation (8), I a This indicates the actual operating current carrying capacity of the submarine cable. I h This indicates the power frequency current of the submarine cable. h This indicates the content of harmonic current.

[0050] Considering a 5% harmonic current content, the power frequency current is set to 1997A and the harmonic current to 99.85A; considering a 10% harmonic current content, the power frequency current is set to 1990A and the harmonic current to 199A; considering a 15% harmonic current content, the power frequency current is set to 1978A and the harmonic current to 297A; considering a 20% harmonic current content, the power frequency current is set to 1961A and the harmonic current to 392A. The volumetric loss density of the submarine cable under power frequency and harmonic current conditions is calculated separately. The volumetric loss densities of the submarine cable under the two conditions are superimposed using an interpolation function and placed at the submarine cable conductor as a heat source. The simulation cloud map of the influence of different harmonic current components on the temperature distribution of the AC submarine cable conductor under different harmonic current contents is shown in Figure 3.

[0051] Figure 3 shows the simulation cloud map of the temperature distribution of AC submarine cable affected by different harmonic current components; Figure 3(a) is 250Hz (5% harmonic current content); Figure 3(b) is 350Hz (10% harmonic current content); Figure 3(c) is 550Hz (15% harmonic current content); Figure 3(d) is 650Hz (20% harmonic current content); Based on the temperature distribution cloud map of submarine cable in Figure 3, the calculated temperature of submarine cable conductors with different harmonic components is obtained, as shown in Table 1.

[0052] Table 1. Calculation results of conductor temperature of submarine cable with different harmonic components at rated current carrying capacity under seawater temperature of 20℃ and burial depth of 1.5m.

[0053] Step 3: Verify the effectiveness of the high-voltage submarine cable conductor temperature calculation method that takes into account the influence of harmonic currents.

[0054] In the actual operation scenario of the submarine section of an ultra-high voltage submarine cable, a thin rod-shaped sensor was installed at the cable conductor. The sensor was elastically fixed to the cable conductor using a special fixing device. The temperature of the cable conductor was measured. The calculation results of the cable conductor temperature in the second step were compared and analyzed with the experimental results, as shown in Table 2, to verify the effectiveness of the high voltage submarine cable conductor temperature calculation method that takes into account the influence of harmonic current.

[0055] Table 2 Comparison of Calculated and Experimental Results of Conductor Temperature of Submarine Cables with Different Harmonic Components and Rated Current Carrying Capacity

[0056] By comparing and analyzing the calculated and experimental results of the conductor temperature of submarine cable under the influence of harmonics, the error is less than 6%, and the calculation error of the conductor temperature of high-voltage submarine cable considering the influence of harmonic current is within a reasonable range.

[0057] Step 4: Using specific power frequency current, harmonic current composition and content, seawater temperature, and burial depth as inputs, calculate the conductor temperature of the high-voltage submarine cable.

[0058] The high-voltage submarine cable conductor temperature calculation model that takes into account the influence of harmonic currents is used as the control equation for finite element simulation. The boundary conditions are determined according to the cable laying conditions. The power frequency current, harmonic current composition and content, seawater temperature, and burial depth are used as input quantities, and the conductor temperature is used as the output quantity. The conductor temperature that takes into account the influence of harmonic currents is calculated accurately and quickly.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. 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 be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for calculating the conductor temperature of a high-voltage submarine cable considering the influence of harmonic currents, characterized in that: Includes the following steps: Calculate the volume loss density of high-voltage submarine cables under the influence of power frequency current and harmonic current. A high-voltage submarine cable conductor temperature calculation model considering the influence of harmonic currents is established based on the aforementioned volume loss density. The conductor temperature of the high-voltage submarine cable is calculated using the aforementioned high-voltage submarine cable conductor temperature calculation model.

2. The method for calculating the conductor temperature of a high-voltage submarine cable considering the influence of harmonic currents according to claim 1, characterized in that: The steps for calculating the volume loss density of high-voltage submarine cables under the influence of power frequency current and harmonic current include: Calculate the total electromagnetic loss of the high-voltage submarine cable based on the electromagnetic field control equation; Based on the total electromagnetic loss, calculate the volume loss density under the influence of power frequency current and the volume loss density under the influence of harmonic current respectively. The total volume loss density is obtained by superimposing the volume loss density under the influence of the power frequency current and the volume loss density under the influence of the harmonic current.

3. The method for calculating the conductor temperature of high-voltage submarine cables considering the influence of harmonic currents according to claim 2, characterized in that: The electromagnetic field control equation is: in, The electric field intensity vector, For AC angular frequency, The magnetic vector potential, For vector differential operators, The magnetic field strength vector. It is the current density vector. Magnetic flux density For electrical conductivity, j The imaginary unit, It is the electric displacement vector.

4. The method for calculating the conductor temperature of a high-voltage submarine cable considering the influence of harmonic currents according to claim 2, characterized in that: The total electromagnetic loss is calculated using the electromagnetic-thermal coupling equation: in, For material density, v For fluid velocity vector, This refers to the specific heat capacity of the material under normal pressure. This represents the total electromagnetic loss. For the temperature of the submarine cable, For resistive loss, For hysteresis loss, Thermal conductivity, It is the complex conjugate of the electric field intensity vector. It is the complex conjugate of the magnetic field strength vector.

5. The method for calculating the conductor temperature of a high-voltage submarine cable considering the influence of harmonic currents according to claim 2, characterized in that: Volume loss density under the influence of power frequency current Volume loss density under the influence of harmonic current The calculation formula is: in, The total electromagnetic loss of the submarine cable under the influence of power frequency current. The total electromagnetic loss of the submarine cable due to the influence of harmonic currents. This represents the cross-sectional area of ​​the submarine cable conductor. The thickness outside the electromagnetic field.

6. The method for calculating the conductor temperature of a high-voltage submarine cable considering the influence of harmonic currents according to claim 1, characterized in that: The steps for establishing a high-voltage submarine cable conductor temperature calculation model based on the volume loss density, taking into account the influence of harmonic currents, include: substituting the total volume loss density as a heat source into the heat conduction equation. in, Thermal conductivity, The temperature of the submarine cable after harmonic superposition.

7. The method for calculating the conductor temperature of a high-voltage submarine cable considering the influence of harmonic currents according to claim 1, characterized in that: The steps for calculating the conductor temperature of the high-voltage submarine cable using the high-voltage submarine cable conductor temperature calculation model include: setting boundary conditions for laying the high-voltage submarine cable in the middle of the sea; performing multi-physics field calculations based on the boundary conditions, where electromagnetic and temperature fields are coupled; and outputting the conductor temperature of the high-voltage submarine cable.

8. The method for calculating the conductor temperature of a high-voltage submarine cable considering the influence of harmonic currents according to claim 7, characterized in that: The boundary conditions include a first type of boundary condition, a second type of boundary condition, and a third type of boundary condition; the first type of boundary condition is the subsurface soil boundary temperature, calculated using the following formula: in, x , y For spatial coordinates, Physical boundary of an object The wall temperature distribution function on the surface, Physical boundary of an object The pre-defined wall temperature function; the second type of boundary condition is the normal heat flux density, calculated using the following formula: in, For heat flux density, n For the boundary The normal direction; the third type of boundary condition is the convective heat transfer boundary condition between seawater and soil, and the calculation formula is: in, The convective heat transfer coefficient is... This refers to the seawater temperature.

9. The method for calculating the conductor temperature of a high-voltage submarine cable considering the influence of harmonic currents according to claim 1, characterized in that: The harmonic current comprises at least one of 250Hz, 350Hz, 550Hz and 650Hz; the content of the harmonic current is 5% to 20%.

10. The method for calculating the conductor temperature of a high-voltage submarine cable considering the influence of harmonic currents according to claim 1, characterized in that: The input parameters of the high-voltage submarine cable conductor temperature calculation model include power frequency current, harmonic current components, harmonic current content, seawater temperature, and burial depth; the output parameter of the high-voltage submarine cable conductor temperature calculation model is the high-voltage submarine cable conductor temperature.

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