Method and device for verifying structural design parameters of extruded insulated high-voltage direct-current cable

Abstract

The invention discloses a method and a device for verifying structural design parameters of an extruded insulated high-voltage direct-current cable. The method comprises the following steps: determining a conductivity model of an extruded insulating material and rated current-carrying capacity of a single direct-current cable; determining a heat source of the extruded insulated high-voltage direct-current cable according to the rated current-carrying capacity of the single direct-current cable, and calculating the thermal resistance of the extruded insulated high-voltage direct-current cable and the environmental thermal resistance; according to the heat source, the cable thermal resistance and the environment thermal resistance, the high-voltage direct-current cable insulation internal temperature is calculated, and according to the conductivity model and the high-voltage direct-current cable insulation internal temperature, the high-voltage direct-current cable insulation internal electric field is calculated; according to the internal temperature and the internal electric field of the high-voltage direct-current cable insulation, the insulation expected life of any radial position in the high-voltage direct-current cable insulation is estimated; and verifying the insulation internal temperature, the insulation internal electric field and the insulation expected life of the high-voltage direct-current cable according to preset constraint conditions to obtain a verification result.

Description

Technical Field

[0001] This invention relates to the field of extruded insulated high-voltage DC cable design technology, and more specifically, to a method and apparatus for verifying structural design parameters of extruded insulated high-voltage DC cables. Background Technology

[0002] With the large-scale development of clean wind and solar power resources in remote areas such as deep sea, desert, and Gobi, high-voltage direct current (HVDC) cables will expand their application from submarine engineering to land engineering to solve the problem of unreliable application of overhead transmission lines under harsh geological and climatic conditions, and partially replace overhead lines under extreme operating conditions.

[0003] Currently, the design methods for extruded insulated AC cables are relatively mature. Long-term theoretical and practical experience has proven that AC cable design only needs to consider the effects of long-term power frequency operating voltage, switching impulse voltage, and lightning impulse voltage, and the insulation thickness should be designed according to the power frequency and lightning impulse voltage. However, due to factors such as space charge under DC conditions and the temperature-dependent conductivity of insulating materials, the electric field distribution in the insulation layer of DC cables is much more complex than that of AC cables. Although the internal structures of AC and DC cables are basically similar, insulation design methods such as the maximum field strength method and the average field strength method, which are applicable to AC cables, are no longer applicable to DC cables. Regarding the design of the DC cable body structure, IEC and CIGRE do not mention design methods or provide specific structural parameters. While the GB / T 31489 product standard provides structural parameters for ±500kV extruded insulated DC cables, such as insulation thickness and conductor cross-section, it does not provide specific design methods or theoretical basis.

[0004] A well-designed cable structure can prevent frequent failures throughout the cable's lifespan, effectively extending its service life, reducing repair costs, and improving the reliability and economy of cable line operation. Currently, the verification of the rationality of extruded insulated DC cable structural design parameters relies heavily on type testing and pre-qualification testing of the finished cable prototypes after the design is completed. This approach suffers from drawbacks such as high cost, long processing time, and complex procedures. Furthermore, it cannot cover all environmental temperatures and fails to rigorously verify the expected service life of the cable. There is an urgent need to adopt different verification methods, provide accurate verification criteria, and promptly identify unreasonable structural designs. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method and apparatus for verifying the structural design parameters of extruded insulated high-voltage DC cables.

[0006] According to one aspect of the present invention, a method for verifying structural design parameters of extruded insulated high-voltage DC cables is provided, comprising:

[0007] Determine the conductivity model of the extruded insulation material and the rated current carrying capacity of a single DC cable;

[0008] The heat source of the extruded insulated high-voltage DC cable is determined based on the rated current carrying capacity of a single DC cable, and the thermal resistance of the extruded insulated high-voltage DC cable and the ambient thermal resistance are calculated.

[0009] The internal temperature of the high-voltage DC cable insulation is calculated based on the heat source, cable thermal resistance, and ambient thermal resistance. The internal electric field of the high-voltage DC cable insulation is also calculated based on the conductivity model and the internal temperature of the high-voltage DC cable insulation.

[0010] Based on the internal temperature and internal electric field of the high-voltage DC cable insulation, estimate the expected insulation life at any radial position inside the high-voltage DC cable insulation.

[0011] The internal temperature, internal electric field, and expected life of the high-voltage DC cable insulation were verified based on preset constraints, and the verification results were obtained.

[0012] Optionally, it also includes: if the verification result is unsuccessful, readjusting the radius and insulation thickness parameters of the cable conductor and re-verifying.

[0013] Optionally, the expression for the conductivity model includes:

[0014]

[0015] σ(E,T)=σ0exp(αT+βE)

[0016] In the formula, E is the electric field, T is the temperature, and A and B are characteristic constants that depend on the insulating material. The activation energy is q, where q is the charge of the elementary charge; k is the activation energy. b σ0 is the Boltzmann constant; σ0 is the conductivity value under the conditions of ambient temperature of 0℃ and electric field of 0kV / mm; α and β are the conductivity temperature coefficient and conductivity field strength coefficient, respectively.

[0017] Optionally, the heat source is the conductor loss per unit length, where the conductor loss per unit length is W. c The expression is:

[0018] W c =I 2 R DC =I 2 R0[1+α(θ c -20)]

[0019] In the formula, R DC R0 is the DC resistance per unit length of the conductor at 20℃, and θ is the DC resistance per unit length of the conductor. c Let α be the conductor temperature, α be the conductor's DC resistance temperature coefficient, and I be the rated current carrying capacity. The calculation expression is:

[0020]

[0021] In the formula, P and U are the rated transmission power and operating voltage of the extruded insulated high-voltage DC cable transmission project, respectively;

[0022] θ c Let be the initial temperature of the conductor, and its calculation expression is:

[0023]

[0024] In the formula, θ srd T represents the ambient temperature, and T represents the thermal resistance of the cable.

[0025] Optionally, the cable thermal resistance T is determined by the conductor shielding thermal resistance T. cs Insulation thermal resistance T i Insulation shielding thermal resistance T is Water-blocking band thermal resistance T w and outer sheath thermal resistance T o composition;

[0026] For coaxial high-voltage DC cables, the thermal resistance T of each structure x The calculation expression is:

[0027]

[0028] In the formula, ρT ,x r is the thermal resistance coefficient of the material. x,o r x,i These are the outer diameter and inner diameter of the structure, respectively.

[0029] When heat is conducted and diffused radially along the cable, the thermal resistance of the cable conductor is a series structure. The thermal resistance T of an extruded insulated high-voltage DC cable is expressed as:

[0030] T = T cs +T i +T is +T w +T o

[0031] Environmental thermal resistance T srd The calculation expression is:

[0032]

[0033] In the formula, h conv and h r These are the convective heat transfer coefficient and the radiative heat transfer coefficient, respectively; D is the cable outer diameter; T conv For convective thermal resistance; T r This is the radiative thermal resistance.

[0034] Optionally, the internal temperature of the high-voltage DC cable insulation is calculated based on the heat source, cable thermal resistance, and ambient thermal resistance, including:

[0035] The steady-state temperature difference Δθ between the inside and outside of the insulation is calculated based on the heat source. i ;

[0036] Calculate the temperature rise Δθ of the conductor relative to the environment under steady state, based on the heat source, cable thermal resistance, and ambient thermal resistance. c ;

[0037] Based on temperature rise Δθ c Calculate the conductor temperature θ under steady state c ;

[0038] According to the conductor temperature θ c and the temperature difference Δθ between the inside and outside of the insulation i Calculate the internal temperature of the insulation of the high-voltage DC cable.

[0039] Optionally, the internal temperature of the high-voltage DC cable insulation is expressed as the temperature at any radial position r of the DC cable insulation under steady-state conditions. x Temperature θ x Temperature θ x The expression is:

[0040]

[0041] In the formula, r x For the radius of any insulating position, r i r is the inner diameter of the insulation. o It is the outer diameter of the insulation.

[0042] Optionally, the radial position r of the DC cable insulation at any point in steady state can be calculated based on the conductivity model. x Electric field E x The expression is:

[0043]

[0044] In the formula, k is an intermediate calculated value, and E avg For the average electric field strength of the insulation, θ x For any radial position r of the DC cable insulation under steady state x Temperature; r i r is the inner diameter of the insulation. o It is the outer diameter of the insulation.

[0045] Optionally, the expected insulation life L at any position in the inner radial direction of the high-voltage DC cable insulation. x The calculation expression is:

[0046]

[0047] In the formula, L0(E0,θ0) represents the insulation life at voltage E0 and temperature θ0, and n is the life exponent of the insulation material; E x For any radial position r of the DC cable insulation under steady state x Electric field inside the location; θ x For any radial position r of the DC cable insulation under steady state x Temperature at the location.

[0048] Optionally, the preset constraints include:

[0049] Insulation operating temperature verification constraints:

[0050] θ x (I,θ srd ,r x )≤θ imax

[0051] In the formula, θ imax I represents the maximum allowable operating temperature; I represents the rated current carrying capacity; θ represents the maximum allowable operating temperature. srd The ambient temperature;

[0052] Insulation working field strength verification constraints:

[0053] E x (I,θ srd ,r x )≤E D

[0054] In the formula, E D For design field strength;

[0055] Insulation service life verification constraints:

[0056] L x (E x ,θ x ,r x )≥L D

[0057] In the formula, L D For design life; L x For any radial position r of the extruded insulation x Insulation expected life; E x For any radial position r of the DC cable insulation under steady state x Electric field inside the location; θ x For any radial position r of the DC cable insulation under steady state x Temperature at the location.

[0058] According to another aspect of the present invention, a device for verifying structural design parameters of extruded insulated high-voltage DC cables is provided, comprising:

[0059] The first determining module is used to determine the conductivity model of the extruded insulation material and the rated current carrying capacity of a single DC cable;

[0060] The second determining module is used to determine the heat source of the extruded insulated high-voltage DC cable based on the rated current carrying capacity of a single DC cable, and to calculate the thermal resistance of the extruded insulated high-voltage DC cable and the ambient thermal resistance.

[0061] The calculation module is used to calculate the internal temperature of the high-voltage DC cable insulation based on the heat source, cable thermal resistance, and ambient thermal resistance, and to calculate the internal electric field of the high-voltage DC cable insulation based on the conductivity model and the internal temperature of the high-voltage DC cable insulation.

[0062] The estimation module is used to estimate the expected life of the insulation at any radial position inside the insulation of a high-voltage DC cable based on the internal temperature and internal electric field.

[0063] The verification module is used to verify the internal temperature, internal electric field, and expected life of the insulation of high-voltage DC cables according to preset constraints, and obtain the verification results.

[0064] According to another aspect of the present invention, a computer-readable storage medium is provided, the storage medium storing a computer program for performing the methods described in any of the above aspects of the present invention.

[0065] According to another aspect of the present invention, an electronic device is provided, the electronic device comprising: a processor; a memory for storing executable instructions of the processor; the processor being configured to read the executable instructions from the memory and execute the instructions to implement the method described in any of the preceding aspects of the present invention.

[0066] Therefore, this invention provides a method for verifying the structural design parameters of extruded insulated high-voltage DC cables. By establishing verification criteria for insulation operating temperature limits, insulation working field strength limits, and insulation service life limits, an electrothermal coupling calculation model for extruded insulated high-voltage DC cables is constructed. The insulation temperature and electric field distribution of high-voltage DC cables under different ambient temperatures are calculated, the insulation service life is estimated, and the calculation results are compared with the design limits to verify the conductor diameter and insulation thickness parameters of extruded insulated high-voltage DC cables. Attached Figure Description

[0067] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0068] Figure 1 This is a flowchart illustrating a method for verifying structural design parameters of extruded insulated high-voltage DC cables according to an exemplary embodiment of the present invention.

[0069] Figure 2This is a schematic diagram of the approximate temperature distribution within the insulation provided by an exemplary embodiment of the present invention;

[0070] Figure 3 This is a schematic diagram of the approximate distribution of the electric field inside the insulation provided by an exemplary embodiment of the present invention;

[0071] Figure 4 This is a schematic diagram of the expected lifetime of the insulation radial position provided by an exemplary embodiment of the present invention;

[0072] Figure 5 This is a schematic diagram of the structure of the extruded insulated high-voltage DC cable structural design parameter verification device provided in an exemplary embodiment of the present invention;

[0073] Figure 6 This is the structure of an electronic device provided in an exemplary embodiment of the present invention. Detailed Implementation

[0074] Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0075] It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0076] Those skilled in the art will understand that the terms "first," "second," etc., in the embodiments of the present invention are only used to distinguish different steps, devices, or modules, and do not represent any specific technical meaning, nor do they indicate a necessary logical order between them.

[0077] It should also be understood that in the embodiments of the present invention, "multiple" can refer to two or more, and "at least one" can refer to one, two or more.

[0078] It should also be understood that any component, data or structure mentioned in the embodiments of the present invention can generally be understood as one or more unless explicitly defined or given contrary instructions in the context.

[0079] Furthermore, the term "and / or" in this invention is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this invention generally indicates that the preceding and following related objects have an "or" relationship.

[0080] It should also be understood that the description of the various embodiments in this invention emphasizes the differences between the various embodiments, and the similarities or similarities can be referred to each other. For the sake of brevity, they will not be described in detail.

[0081] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0082] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0083] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0084] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0085] The embodiments of this invention can be applied to electronic devices such as terminal devices, computer systems, and servers, and can operate together with a wide range of other general-purpose or special-purpose computing system environments or configurations. Well-known examples of terminal devices, computing systems, environments, and / or configurations suitable for use with electronic devices such as terminal devices, computer systems, and servers include, but are not limited to: personal computer systems, server computer systems, thin clients, thick clients, handheld or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, network PCs, minicomputer systems, mainframe computer systems, and distributed cloud computing environments including any of the above systems, etc.

[0086] Electronic devices such as terminal devices, computer systems, and servers can be described in the general context of computer system executable instructions (such as program modules) executed by a computer system. Typically, program modules can include routines, programs, object programs, components, logic, data structures, etc., which perform specific tasks or implement specific abstract data types. Computer systems / servers can be implemented in distributed cloud computing environments, where tasks are executed by remote processing devices linked through communication networks. In distributed cloud computing environments, program modules can reside on local or remote computing system storage media, including storage devices.

[0087] Exemplary methods

[0088] Figure 1This is a flowchart illustrating a method for verifying structural design parameters of extruded insulated high-voltage DC cables according to an exemplary embodiment of the present invention. This embodiment can be applied to electronic devices, such as... Figure 1 As shown, the method 100 for verifying the structural design parameters of extruded insulated high-voltage DC cables includes the following steps:

[0089] Step 101: Determine the conductivity model of the extruded insulation material and the rated current carrying capacity of a single DC cable;

[0090] Step 102: Determine the heat source of the extruded insulated high-voltage DC cable based on the rated current carrying capacity of a single DC cable, and calculate the thermal resistance of the extruded insulated high-voltage DC cable and the ambient thermal resistance.

[0091] Step 103: Calculate the internal temperature of the high-voltage DC cable insulation based on the heat source, cable thermal resistance, and ambient thermal resistance; and calculate the internal electric field of the high-voltage DC cable insulation based on the conductivity model and the internal temperature of the high-voltage DC cable insulation.

[0092] Step 104: Estimate the expected life of the insulation at any radial position inside the insulation of the high-voltage DC cable based on the internal temperature and internal electric field.

[0093] Step 105: Verify the internal temperature, internal electric field, and expected life of the high-voltage DC cable insulation according to the preset constraints, and obtain the verification results.

[0094] Specifically, to better address the shortcomings of existing experimental verification methods for verifying the structural design parameters of extruded insulated high-voltage DC cables, such as high cost, long processing time, complex procedures, and incomplete verification, this invention proposes a method for verifying the structural design parameters of extruded insulated high-voltage DC cables. The method includes constructing an electrothermal coupling calculation model of the extruded insulated high-voltage DC cable; determining the rated current carrying capacity of the DC cable based on the rated transmission capacity and rated operating voltage; substituting the rated current carrying capacity into the electrothermal coupling calculation model of the high-voltage DC cable; calculating the electric field and temperature distribution within the insulation of the high-voltage DC cable when transmitting the rated current carrying capacity at the operating ambient temperature; analyzing the expected lifespan of each location within the insulation under the temperature and electric field conditions; and comparing the calculated electric field, temperature, and expected insulation lifespan with design limits such as insulation design field strength, allowable long-term operating temperature, and design lifespan, thereby verifying the conductor diameter and insulation thickness parameters of the extruded insulated high-voltage DC cable.

[0095] Step (1) Determine the rated current carrying capacity.

[0096] Based on the rated transmission power P and operating voltage U of the extruded insulated high-voltage DC cable transmission project, the rated current carrying capacity I of a single DC cable is obtained, i.e.

[0097]

[0098] Step (2) Determine the conductivity model of the extruded insulating material.

[0099] The conductivity σ of the insulation material of high-voltage DC cables is related to the electric field E and the temperature T, and can be described by two models using formulas (2) and (3), namely...

[0100]

[0101] σ(E,T)=σ0exp(αT+βE) (3)

[0102] In equation (2), A and B are constants that depend on the properties of the insulating material. The activation energy is q, where q is the charge of the elementary charge; k is the activation energy. b σ0 is the Boltzmann constant. In equation (3), σ0 is the conductivity value under the conditions of ambient temperature of 0℃ and electric field of 0kV / mm, and α and β are the conductivity temperature coefficient and conductivity field strength coefficient, respectively.

[0103] For insulation materials from different suppliers, the conductivity of the insulation materials under the conditions of 0-70℃ and 0-50kV / mm is tested and then substituted into formula (2) or (3) for fitting calculation to obtain the conductivity model parameters.

[0104] Step (3) Determine the heat source of the extruded insulated high voltage DC cable based on the rated current carrying capacity.

[0105] The heat source of extruded insulated high-voltage DC cables is mainly the conductor loss per unit length (W). c It can be described as:

[0106] W c =I 2 R DC =I 2 R0[1+α(θ c -20)] (4)

[0107] In equation (4), R DC R0 is the DC resistance per unit length of the conductor at 20℃, and θ is the DC resistance per unit length of the conductor. c Let α be the conductor temperature, and α be the conductor's DC resistance temperature coefficient.

[0108] Initial temperature θ of the conductor c The following formula can be used to describe it:

[0109]

[0110] Where θ srd T represents the ambient temperature, and T represents the thermal resistance of the cable.

[0111] Step (4) Calculate the thermal resistance of the extruded insulated high voltage DC cable and the ambient thermal resistance.

[0112] The thermal resistance T of the extruded insulated high-voltage DC cable is determined by the thermal resistance T of the conductor shield. cs Insulation thermal resistance T i Insulation shielding thermal resistance T is Water-blocking band thermal resistance T w and outer sheath thermal resistance T o For a coaxial high-voltage DC cable, the thermal resistance T of each component is... x It can be described as:

[0113]

[0114] Where, ρT ,x r is the thermal resistance coefficient of the material. x,o r x,i These are the outer diameter and inner diameter of the structure, respectively.

[0115] When heat is conducted and diffused radially along the cable, the thermal resistance of the cable conductor is a series structure. The thermal resistance of an extruded insulated high-voltage DC cable can be expressed as:

[0116] T = T cs +T i +T is +T w +T o (7)

[0117] Environmental thermal resistance T srd From the convection thermal resistance T conv and radiation thermal resistance T r A parallel connection can be described as follows:

[0118]

[0119] In equation (8), h conv and h r These are the convective heat transfer coefficient and the radiative heat transfer coefficient, respectively, and D is the outer diameter of the cable.

[0120] Step (5) Calculate the internal temperature of the high voltage DC cable insulation based on the heat source, the thermal resistance of the extruded insulated high voltage DC cable, and the ambient thermal resistance.

[0121] Temperature difference Δθ between the inside and outside of the insulation under steady state i It can be represented as:

[0122] Δθ i =Wc*T i =Wc*ln((r i +d) / r i )*ρ i / 2π (9)

[0123] In equation (9), W cIt is the conductor loss per unit length, T i For insulation thermal resistance, r i ρ is the inner diameter of the insulation, d is the insulation thickness, and ρ is the inner diameter of the insulation. i It is the thermal resistance coefficient of insulation.

[0124] Temperature rise Δθ of conductor relative to ambient temperature under steady state c It can be represented as:

[0125] Δθ c =Wc(T+T) srd (10)

[0126] Then the conductor temperature θ under steady state c It can be further described as:

[0127] θ c =θ srd +Δθ c (11)

[0128] In the formula, θ srd Given the ambient temperature, the steady-state conductor temperature can be obtained through iterative calculation.

[0129] At any radial position r of DC cable insulation under steady state x Temperature θ x It can be represented as:

[0130]

[0131] In equation (10), r x For the radius of any insulating position, r i r is the inner diameter of the insulation. o It is the outer diameter of the insulation.

[0132] Step (6) Calculate the electric field inside the insulation of the high-voltage DC cable.

[0133] Based on the insulation conductivity model of formula (2), the radial conductivity r of the DC cable insulation at any position under steady state can be calculated. x electric field E x for:

[0134]

[0135] Where k is an intermediate calculated value, E avg This represents the average electric field strength of the insulation.

[0136] Step (7) Estimate the expected life of the insulation at any position in the inner radial direction of the high voltage DC cable insulation.

[0137] Based on the electrothermal life model of extruded insulation materials and the electric field E at any radial position of the insulation... x and temperature θ xThe lifetime L of the insulating material at any location can be obtained. x ,Right now:

[0138]

[0139] In the formula, L0(E0,θ0) is the insulation life at voltage E0 and temperature θ0, and n is the life index of the insulation material.

[0140] Step (8) Perform design verification based on constraints.

[0141] Insulation operating temperature verification, i.e., verification at any radial position r of the extruded insulation. x Temperature θ x Not exceeding the maximum allowable operating temperature θ imax It can be described as:

[0142] θ x (I,θ srd ,r x )≤θ imax (15)

[0143] Insulation working field strength verification, i.e., verification at any radial position r of the extruded insulation. x Field strength E x Not exceeding the design field strength E D It can be described as:

[0144] E x (I,θ srd ,r x )≤E D (16)

[0145] Insulation service life verification, i.e., extruding insulation at any radial position r. x Lifespan L x It should be no less than the design life L D It can be described as:

[0146] L x (E x ,θ x ,r x )≥L D (17)

[0147] Step (9) involves adjusting the parameters and re-verifying the extruded insulation structure designs for different purposes.

[0148] If the structural design parameters of the extruded insulated DC cable fail the temperature verification, field strength verification, and life verification, then the cable conductor radius r should be readjusted. c Parameters such as insulation thickness D are recalculated and verified according to steps (1) to (9) until the verification conditions are met.

[0149] In a specific embodiment of the present invention, to illustrate the effectiveness of the proposed method for verifying the structural design parameters of an extruded insulated high-voltage DC cable, a more detailed explanation is given using the verification of the structural design parameters of an extruded insulated DC cable used in a certain project as an example. The structural design and operation parameters of the extruded insulated DC cable used in the land section are shown in Table 1.

[0150] Table 1. Structural design parameters and operating parameters of a certain extruded insulated DC cable

[0151] Design or operating parameters numerical values Nominal cross-section (mm2) 2500 Conductor outer diameter (mm) 29 Conductor shielding thickness (mm) 2.5 Insulation layer thickness (mm) 28 Insulation shielding thickness (mm) 1.5 Buffer layer thickness (mm) 2.0 Metal sheath thickness (mm) 3.2 Sheath thickness (mm) 5.0 Maximum permissible operating temperature of insulation (°C) 70 Insulation design electric field strength (kV / mm) 24 Insulation design service life (years) 40 Operating voltage (kV) 500 Transmission capacity (MW) 2100 Operating ambient temperature (°C) 10～40

[0152] Based on the operating voltage and transmission capacity of the project, the current carrying capacity of the extruded insulated DC cable is obtained by referring to formula (1): I = 2100 * 1000 / (2 * 500) = 2100A.

[0153] The conductivity model of a certain type of XLPE insulation material adopts formula (2), and its conductivity model parameters are shown in Table 2.

[0154] Table 2 Conductivity Model Parameters for High Voltage DC Cable Insulation Materials

[0155] Taking an ambient temperature of 40℃ and a load current of 2100A as an example, referring to formulas (4), (5), (9), (10) and (11), iterative calculations can obtain the initial conductor temperature, conductor loss per unit length under steady state, insulation temperature difference, conductor temperature rise and conductor temperature, as shown in Table 3.

[0156] Table 3 Conductor Loss and Temperature

[0157] Parameter name numerical values Initial temperature of the conductor (°C) 55.7 Steady-state conductor loss per unit length (W / m) 34.04 Temperature difference between the inside and outside of the insulation under steady state (°C) 12.1 Temperature rise of conductor under steady state (°C) 26.5 Conductor temperature under steady state (°C) 66.5 Temperature of the outer side of the insulation under steady state (°C) 54.5

[0158] Based on the structural parameters of the high voltage DC cable and the thermal resistance coefficient of the corresponding materials in Table 1, the calculation results of the thermal resistance of the cable section and the thermal resistance of the cable body can be obtained by using formulas (6) and (7), as shown in Table 4.

[0159] Table 4 Thermal Resistance of Various Structures of High Voltage DC Cables

[0160] Parameter name numerical values <![CDATA[Conductor shielding thermal resistance T cs (K*m / W)]]> 0.046 <![CDATA[Thermal resistance of the insulating layer T i (K*m / W)]]> 0.354 <![CDATA[Thermal resistance T of the insulation shielding layer is (K*m / W)]]> 0.014 <![CDATA[Thermal resistance T of the water-blocking tape w (K*m / W)]]> 0.025 <![CDATA[External sheath thermal resistance T o (K*m / W)]]> 0.041 Thermal resistance of the cable body T (K*m / W) 0.479

[0161] Taking tunnel laying conditions as an example, the environmental thermal resistance can be taken as 0.3 K*m / W.

[0162] Based on the data in Tables 3 and 4, the temperature at any radial position of the insulation can be calculated using formula (12), and plotted as follows. Figure 2 As shown.

[0163] Based on the temperature distribution data within the insulation and the conductivity model parameters in Table 2, the electric field at any radial position of the insulation can be calculated using formula (13), and plotted as follows. Figure 3 As shown.

[0164] Taking the pre-qualification test conditions of ±525kV DC cable as an example, with the material life index set to 13, the life and related parameters of the DC cable that passed the pre-qualification test are shown in Table 5.

[0165] Table 5 Pre-qualification Test Conditions for High Voltage DC Cables

[0166] Parameter name numerical values Test voltage (kV) 761kV Test duration (d) 360 Average electric field strength (kV / mm) 27.19 Maximum insulation temperature (°C) 70 Lifespan Index n 13

[0167] Based on the data in Table 5 and the temperature and electric field at the radial location of the insulation, the expected lifetime at any radial location of the insulation can be calculated using formula (14), such as... Figure 4 As shown.

[0168] The operating constraints of a certain extruded insulated high-voltage DC cable are shown in Table 6.

[0169] Table 6 Operating Constraints of High Voltage DC Cables

[0170] Constraints numerical values Maximum permissible operating temperature of insulation (°C) 70 Insulation design electric field strength (kV / mm) 23.6 Minimum service life of insulation (a) 40

[0171] Figure 2 As can be seen, when the ambient temperature is 40℃, the ambient thermal resistance is 0.3K*m / W, and the load current is 2100A, the temperature at any radial position of the DC cable insulation does not exceed the maximum allowable operating temperature of 70℃.

[0172] Figure 3 As can be seen, at an ambient temperature of 40℃, an ambient thermal resistance of 0.3K*m / W, and a load current of 2100A, the electric field at any radial position of the DC cable insulation does not exceed the design field strength of 23.6kV / mm.

[0173] Figure 4 It can be seen that at an ambient temperature of 40℃, an ambient thermal resistance of 0.3K*m / W, and a load current of 2100A, the expected life of the DC cable insulation at any radial position is no less than 40 years.

[0174] Therefore, this invention provides a method for verifying the structural design parameters of extruded insulated high-voltage DC cables. By establishing verification criteria for insulation operating temperature limits, insulation working field strength limits, and insulation service life limits, an electrothermal coupling calculation model for extruded insulated high-voltage DC cables is constructed. The insulation temperature and electric field distribution of high-voltage DC cables under different ambient temperatures are calculated, the insulation service life is estimated, and the calculation results are compared with the design limits to verify the conductor diameter and insulation thickness parameters of extruded insulated high-voltage DC cables.

[0175] Exemplary device

[0176] Figure 5This is a schematic diagram of the structure of a device for verifying the structural design parameters of an extruded insulated high-voltage DC cable, provided in an exemplary embodiment of the present invention. Figure 5 As shown, the device 500 includes:

[0177] The first determining module 510 is used to determine the conductivity model of the extruded insulation material and the rated current carrying capacity of a single DC cable;

[0178] The second determining module 520 is used to determine the heat source of the extruded insulated high-voltage DC cable based on the rated current carrying capacity of a single DC cable, and to calculate the thermal resistance of the extruded insulated high-voltage DC cable and the ambient thermal resistance.

[0179] The calculation module 530 is used to calculate the internal temperature of the high-voltage DC cable insulation based on the heat source, cable thermal resistance and ambient thermal resistance, and to calculate the internal electric field of the high-voltage DC cable insulation based on the conductivity model and the internal temperature of the high-voltage DC cable insulation.

[0180] The estimation module 540 is used to estimate the expected life of the insulation at any radial position inside the insulation of the high-voltage DC cable based on the internal temperature and internal electric field of the insulation.

[0181] The verification module 550 is used to verify the internal temperature, internal electric field, and expected life of the insulation of the high-voltage DC cable according to preset constraints, and obtain the verification results.

[0182] Optionally, the device 500 further includes an adjustment module for readjusting the radius and insulation thickness parameters of the cable conductor and re-verifying if the verification result is unsuccessful.

[0183] Optionally, the expression for the conductivity model includes:

[0184]

[0185] σ(E,T)=σ0exp(αT+βE)

[0186] In the formula, E is the electric field, T is the temperature, and A and B are characteristic constants that depend on the insulating material. The activation energy is q, where q is the charge of the elementary charge; k is the activation energy. b σ0 is the Boltzmann constant; σ0 is the conductivity value under the conditions of ambient temperature of 0℃ and electric field of 0kV / mm; α and β are the conductivity temperature coefficient and conductivity field strength coefficient, respectively.

[0187] Optionally, the heat source is the conductor loss per unit length, where the conductor loss per unit length is W. c The expression is:

[0188] W c =I 2 R DC =I 2R0[1+α(θ c -20)]

[0189] In the formula, R DC R0 is the DC resistance per unit length of the conductor at 20℃, and θ is the DC resistance per unit length of the conductor. c Let α be the conductor temperature, α be the conductor's DC resistance temperature coefficient, and I be the rated current carrying capacity. The calculation expression is:

[0190]

[0191] In the formula, P and U are the rated transmission power and operating voltage of the extruded insulated high-voltage DC cable transmission project, respectively;

[0192] θ c Let be the initial temperature of the conductor, and its calculation expression is:

[0193]

[0194] In the formula, θ srd T represents the ambient temperature, and T represents the thermal resistance of the cable.

[0195] Optionally, the cable thermal resistance T is determined by the conductor shielding thermal resistance T. cs Insulation thermal resistance T i Insulation shielding thermal resistance T is Water-blocking band thermal resistance T w and outer sheath thermal resistance T o composition;

[0196] For coaxial high-voltage DC cables, the thermal resistance T of each structure x The calculation expression is:

[0197]

[0198] In the formula, ρ T,x r is the thermal resistance coefficient of the material. x,o r x,i These are the outer diameter and inner diameter of the structure, respectively.

[0199] When heat is conducted and diffused radially along the cable, the thermal resistance of the cable conductor is a series structure. The thermal resistance T of an extruded insulated high-voltage DC cable is expressed as:

[0200] T = T cs +T i +T is +T w +T o

[0201] Environmental thermal resistance T srd The calculation expression is:

[0202]

[0203] In the formula, h conv and h r These are the convective heat transfer coefficient and the radiative heat transfer coefficient, respectively; D is the cable outer diameter; T conv For convective thermal resistance; T r This is the radiative thermal resistance.

[0204] Optionally, the internal temperature of the high-voltage DC cable insulation is calculated based on the heat source, cable thermal resistance, and ambient thermal resistance, including:

[0205] The steady-state temperature difference Δθ between the inside and outside of the insulation is calculated based on the heat source. i ;

[0206] Calculate the temperature rise Δθ of the conductor relative to the environment under steady state, based on the heat source, cable thermal resistance, and ambient thermal resistance. c ;

[0207] Based on temperature rise Δθ c Calculate the conductor temperature θ under steady state c ;

[0208] According to the conductor temperature θ c and the temperature difference Δθ between the inside and outside of the insulation i Calculate the internal temperature of the insulation of the high-voltage DC cable.

[0209] Optionally, the internal temperature of the high-voltage DC cable insulation is expressed as the temperature at any radial position r of the DC cable insulation under steady-state conditions. x Temperature θ x Temperature θ x The expression is:

[0210]

[0211] In the formula, r x For the radius of any insulating position, r i r is the inner diameter of the insulation. o It is the outer diameter of the insulation.

[0212] Optionally, the radial position r of the DC cable insulation at any point in steady state can be calculated based on the conductivity model. x Electric field E x The expression is:

[0213]

[0214] In the formula, k is an intermediate calculated value, and E avg For the average electric field strength of the insulation, θ x For any radial position r of the DC cable insulation under steady state x Temperature; r i r is the inner diameter of the insulation. o It is the outer diameter of the insulation.

[0215] Optionally, the expected insulation life L at any position in the inner radial direction of the high-voltage DC cable insulation. x The calculation expression is:

[0216]

[0217] In the formula, L0(E0,θ0) represents the insulation life at voltage E0 and temperature θ0, and n is the life exponent of the insulation material; E x For any radial position r of the DC cable insulation under steady state x Electric field inside the location; θ x For any radial position r of the DC cable insulation under steady state x Temperature at the location.

[0218] Optionally, the preset constraints include:

[0219] Insulation operating temperature verification constraints:

[0220] θ x (I,θ srd ,r x )≤θ imax

[0221] In the formula, θ imax I represents the maximum allowable operating temperature; I represents the rated current carrying capacity; θ represents the maximum allowable operating temperature. srd The ambient temperature;

[0222] Insulation working field strength verification constraints:

[0223] E x (I,θ srd ,r x )≤E D

[0224] In the formula, E D For design field strength;

[0225] Insulation service life verification constraints:

[0226] L x (E x ,θ x ,r x )≥L D

[0227] In the formula, L D For design life; L x For any radial position r of the extruded insulation x Insulation expected life; E x For any radial position r of the DC cable insulation under steady state x Electric field inside the location; θ xFor any radial position r of the DC cable insulation under steady state x Temperature at the location.

[0228] Exemplary electronic devices

[0229] Figure 6 This is the structure of an electronic device provided in an exemplary embodiment of the present invention. For example... Figure 6 As shown, the electronic device 60 includes one or more processors 61 and a memory 62.

[0230] The processor 61 may be a central processing unit (CPU) or other form of processing unit with data processing and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0231] The memory 62 may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, random access memory (RAM) and / or cache memory. The non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 61 may execute the program instructions to implement the methods of the software programs of the various embodiments of the present invention described above, and / or other desired functions. In one example, the electronic device may also include an input device 63 and an output device 64, these components being interconnected via a bus system and / or other forms of connection mechanisms (not shown).

[0232] In addition, the input device 63 may also include, for example, a keyboard, a mouse, etc.

[0233] The output device 64 can output various information to the outside. The output device 64 may include, for example, a display, a speaker, a printer, and a communication network and its connected remote output devices, etc.

[0234] Of course, for the sake of simplicity, Figure 6 Only some of the components of this electronic device relevant to the present invention are shown, omitting components such as buses, input / output interfaces, etc. In addition, the electronic device may include any other suitable components depending on the specific application.

[0235] Exemplary computer program products and computer-readable storage media

[0236] In addition to the methods and apparatus described above, embodiments of the present invention may also be computer program products, which include computer program instructions that, when executed by a processor, cause the processor to perform the steps in the methods according to various embodiments of the present invention described in the "Exemplary Methods" section above.

[0237] The computer program product can be written in any combination of one or more programming languages ​​to perform the operations of the embodiments of the present invention. The programming languages ​​include object-oriented programming languages ​​such as Java and C++, as well as conventional procedural programming languages ​​such as C or similar languages. The program code can be executed entirely on the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0238] Furthermore, embodiments of the present invention may also be computer-readable storage media storing computer program instructions thereon, which, when executed by a processor, cause the processor to perform the steps of the methods according to various embodiments of the present invention described in the "Exemplary Methods" section above.

[0239] The computer-readable storage medium may be any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or any combination thereof. More specific examples (a non-exhaustive list) of readable storage media include: an electrical connection having one or more wires, a portable disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof.

[0240] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0241] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For system embodiments, since they largely correspond to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0242] The block diagrams of devices, systems, devices, and systems involved in this invention are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, systems, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0243] The methods and systems of the present invention may be implemented in many ways. For example, they may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above-described order of steps for the methods is for illustrative purposes only, and the steps of the methods of the present invention are not limited to the order specifically described above unless otherwise specifically stated. Furthermore, in some embodiments, the present invention may also be implemented as a program recorded on a recording medium, the program comprising machine-readable instructions for implementing the methods according to the present invention. Thus, the present invention also covers recording media storing programs for performing the methods according to the present invention.

[0244] It should also be noted that in the systems, apparatus, and methods of the present invention, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered equivalents of the present invention. The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the invention. Therefore, the invention is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0245] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the invention to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method for verifying structural design parameters of extruded insulated high-voltage DC cables, characterized in that, include: Determine the conductivity model of the extruded insulation material and the rated current carrying capacity of a single DC cable; The heat source of the extruded insulated high-voltage DC cable is determined based on the rated current carrying capacity of a single DC cable, and the thermal resistance of the extruded insulated high-voltage DC cable and the ambient thermal resistance are calculated. The internal temperature of the high-voltage DC cable insulation is calculated based on the heat source, the cable thermal resistance, and the ambient thermal resistance. The internal electric field of the high-voltage DC cable insulation is also calculated based on the conductivity model and the internal temperature of the high-voltage DC cable insulation. Based on the internal temperature and internal electric field of the high-voltage DC cable insulation, estimate the expected insulation life at any radial position inside the high-voltage DC cable insulation. The internal temperature, internal electric field, and expected life of the high-voltage DC cable insulation were verified according to preset constraints, and the verification results were obtained.

2. The method according to claim 1, characterized in that, Also includes: If the verification result is unsuccessful, the radius and insulation thickness parameters of the cable conductor should be readjusted and the verification should be performed again.

3. The method according to claim 1, characterized in that, The expression for the conductivity model includes: σ(E,T)=σ0exp(αT+βE) In the formula, E is the electric field, T is the temperature, and A and B are characteristic constants that depend on the insulating material. The activation energy is q, where q is the charge of the elementary charge; k is the activation energy. b σ0 is the Boltzmann constant; σ0 is the conductivity value under the conditions of ambient temperature of 0℃ and electric field of 0kV / mm; α and β are the conductivity temperature coefficient and conductivity field strength coefficient, respectively.

4. The method according to claim 1, characterized in that, The heat source is the conductor loss per unit length, and the conductor loss per unit length W c The expression is: W c =I 2 R DC =I 2 R0[1+α(θ c -20)] In the formula, R DC R0 is the DC resistance per unit length of the conductor at 20℃, and θ is the DC resistance per unit length of the conductor. c Let α be the conductor temperature, α be the conductor's DC resistance temperature coefficient, and I be the rated current carrying capacity. The calculation expression is: In the formula, P and U are the rated transmission power and operating voltage of the extruded insulated high-voltage DC cable transmission project, respectively; θ c Let be the initial temperature of the conductor, and its calculation expression is: In the formula, θ srd T represents the ambient temperature, and T represents the thermal resistance of the cable.

5. The method according to claim 1, characterized in that, The thermal resistance T of the cable is determined by the conductor shielding thermal resistance T. cs Insulation thermal resistance T i Insulation shielding thermal resistance T is Water-blocking band thermal resistance T w and outer sheath thermal resistance T o composition; For coaxial high-voltage DC cables, the thermal resistance T of each structure x The calculation expression is: In the formula, ρT ,x r is the thermal resistance coefficient of the material. x,o r x,i These are the outer diameter and inner diameter of the structure, respectively. When heat is conducted and diffused radially along the cable, the thermal resistance of the cable conductor is a series structure. The thermal resistance T of an extruded insulated high-voltage DC cable is expressed as: T=T cs +T i +T is +T w +T o The environmental thermal resistance T srd The calculation expression is: In the formula, h conv and h r These are the convective heat transfer coefficient and the radiative heat transfer coefficient, respectively; D is the cable outer diameter; T conv For convective thermal resistance; T r This is the radiative thermal resistance.

6. The method according to claim 1, characterized in that, The internal temperature of the high-voltage DC cable insulation is calculated based on the heat source, the cable thermal resistance, and the ambient thermal resistance, including: Calculate the steady-state temperature difference Δθ between the inside and outside of the insulation based on the heat source. i ; Calculate the temperature rise Δθ of the conductor relative to the ambient temperature under steady state based on the heat source, the cable thermal resistance, and the ambient thermal resistance. c ; According to the temperature rise Δθ c Calculate the conductor temperature θ under steady state c ; According to the conductor temperature θ c and the temperature difference Δθ between the inside and outside of the insulation i Calculate the internal temperature of the insulation of the high-voltage DC cable.

7. The method according to claim 6, characterized in that, The internal temperature of the high-voltage DC cable insulation is expressed as r at any radial position of the DC cable insulation under steady-state conditions. x Temperature θ x Temperature θ x The expression is: In the formula, r x For the radius of any insulating position, r i r is the inner diameter of the insulation. o It is the outer diameter of the insulation.

8. The method according to claim 3, characterized in that, Based on the conductivity model, the radial position r of the DC cable insulation at any point under steady state is calculated. x Electric field E x The expression is: In the formula, k is an intermediate calculated value, and E avg For the average electric field strength of the insulation, θ x For any radial position r of the DC cable insulation under steady state x Temperature; r i r is the inner diameter of the insulation. o It is the outer diameter of the insulation.

9. The method according to claim 1, characterized in that, The expected insulation life L at any position in the inner radial direction of the high-voltage DC cable insulation x The calculation expression is: In the formula, L0(E0,θ0) represents the insulation life at voltage E0 and temperature θ0, and n is the life exponent of the insulation material; E x For any radial position r of the DC cable insulation under steady state x Electric field inside the location; θ x For any radial position r of the DC cable insulation under steady state x Temperature at the location.

10. The method according to claim 1, characterized in that, The preset constraints include: Insulation operating temperature verification constraints: i x (I,θ srd ,r x )≤θ imax In the formula, θ imax I represents the maximum allowable operating temperature; I represents the rated current carrying capacity; θ represents the maximum allowable operating temperature. srd The ambient temperature; Insulation working field strength verification constraints: E x (I,θ srd ,r x )≤E D In the formula, E D For design field strength; Insulation service life verification constraints: L x (E x ,i x ,r x )≥L D In the formula, L D For design life; L x For any radial position r of the extruded insulation x Insulation expected life; E x For any radial position r of the DC cable insulation under steady state x Electric field inside the location; θ x For any radial position r of the DC cable insulation under steady state x Temperature at the location.

11. A device for verifying structural design parameters of extruded insulated high-voltage DC cables, characterized in that, include: The first determining module is used to determine the conductivity model of the extruded insulation material and the rated current carrying capacity of a single DC cable; The second determining module is used to determine the heat source of the extruded insulated high-voltage DC cable based on the rated current carrying capacity of a single DC cable, and to calculate the thermal resistance of the extruded insulated high-voltage DC cable and the ambient thermal resistance. The calculation module is used to calculate the internal temperature of the high-voltage DC cable insulation based on the heat source, the cable thermal resistance, and the ambient thermal resistance, and to calculate the internal electric field of the high-voltage DC cable insulation based on the conductivity model and the internal temperature of the high-voltage DC cable insulation. The estimation module is used to estimate the expected life of the insulation at any radial position inside the insulation of a high-voltage DC cable based on the internal temperature and internal electric field. The verification module is used to verify the internal temperature, internal electric field, and expected life of the insulation of the high-voltage DC cable according to preset constraints, and to obtain the verification results.

12. A computer-readable storage medium, characterized in that, The storage medium stores a computer program for performing the method described in any one of claims 1-10.

13. An electronic device, characterized in that, The electronic device includes: processor; Memory used to store the processor's executable instructions; The processor is configured to read the executable instructions from the memory and execute the instructions to implement the method described in any one of claims 1-10.

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