A reduced-order method and device for a power distribution network three-core armored power cable carrier wave model

Abstract

This application provides a method and apparatus for reducing the order of a carrier model for a three-core armored power cable in a distribution network. The method includes: obtaining a 7th-order multi-conductor transmission line carrier model of the three-core armored power cable in the distribution network; obtaining the 7th-order unit-length impedance matrix from the 7th-order multi-conductor transmission line carrier model; reconstructing the 7th-order unit-length impedance matrix according to the Carson-Clem formula to obtain a reconstructed 7th-order unit-length impedance matrix; constructing a 7th-order multi-conductor transmission line carrier model based on the reconstructed 7th-order unit-length impedance matrix; constructing a 5th-order multi-conductor transmission line carrier model based on the first global method, the Carson-Clem formula, and the reconstructed 7th-order multi-conductor transmission line carrier model; and constructing a 4th-order multi-conductor transmission line carrier model based on the 5th-order multi-conductor transmission line carrier model. By reducing the order of the 7th-order multi-conductor transmission line carrier model in two steps, the complexity of the carrier model and the computational load are reduced.

Description

Technical Field

[0001] This application relates to the field of cable carrier technology, specifically to a method and apparatus for reducing the order of a three-core armored power cable carrier model in a power distribution network. Background Technology

[0002] As a crucial component of the smart grid, the construction of an efficient, fast, flexible, and economical distribution communication network has long been a bottleneck hindering the rapid development of the smart distribution network. Power line communication (PLC) technology in the distribution network relies on the existing network topology to build communication channels, enabling power communication and offering significant advantages such as low investment, wide coverage, high flexibility, and network reliability. Furthermore, with the rapid development of Orthogonal Frequency Division Multiplexing (OFDM) technology, PLC technology has made significant progress in communication speed, anti-interference capabilities, and adaptive capabilities, meeting the business needs of smart distribution networks and becoming an important component of smart distribution network communication methods.

[0003] Compared to overhead lines, power cables offer significant advantages such as reliable operation, low maintenance costs, and minimal land occupation for underground installations, making them the preferred choice for new and renovated power distribution networks. However, the complex cross-sectional structure of power cables results in a more complex carrier signal model within them.

[0004] Currently, carrier communication models based on Multi-conductor Transmission Line (MTL) theory primarily focus on low-voltage indoor cables and overhead lines in distribution networks to analyze their transmission characteristics. However, the structural parameters of power cables in distribution networks, which use power cables as transmission channels, differ significantly from those of low-voltage indoor cables and overhead lines, thus limiting the applicability of related research. While some exploration has been conducted in power cable carrier communication for distribution networks based on MTL theory, these studies mainly use the three-phase cable cores as the transmission medium and do not consider the influence of shielding and armor layers.

[0005] In existing technologies, considering the lower voltage level of distribution networks compared to transmission networks, and the excellent heat resistance, mechanical properties, electrical properties, and aging resistance of cross-linked polyethylene (XLPE) power cables, XLPE three-core armored power cables are typically the preferred choice for distribution networks. Distribution networks commonly use XLPE three-core armored power cables, which generally consist of a complex seven-layer structure from the outside in: outer sheath, armor layer, inner lining, filler layer, phase shielding layer, phase insulation layer, and phase core layer. When high-frequency carrier signals are transmitted using distribution network three-core armored power cables as the transmission medium, due to the complex cross-sectional structure of the cables, the conductive layers (three-phase cores, three-phase shielding layer, and armor layer) are mutually coupled. Therefore, the carrier model of the distribution network three-core armored power cable is a 7th-order multi-conductor transmission line model. Applying a bottom-up modeling method inevitably makes the carrier model of the distribution network three-core armored power cable more complex, reducing the speed of carrier analysis and increasing the computational load of the model. Summary of the Invention

[0006] To address the aforementioned technical problems, this application is proposed. Embodiments of this application provide a method and apparatus for reducing the order of a carrier wave model for a three-core armored power cable in a distribution network. This solves the problem that existing models of three-core armored power cables in distribution networks are complex, reducing the speed of carrier wave analysis and increasing the computational load of the model.

[0007] According to one aspect of this application, a method for reducing the order of a carrier wave model of a three-core armored power cable in a distribution network is provided, comprising:

[0008] Obtain the 7th-order multi-conductor transmission line carrier model of a three-core armored power cable in a power distribution network;

[0009] Obtain the 7th order unit length impedance matrix in the 7th order multi-conductor transmission line carrier model;

[0010] The 7th-order unit length impedance matrix is ​​reconstructed according to the Carson-Clem formula to obtain the reconstructed 7th-order unit length impedance matrix.

[0011] Based on the reconstructed 7th order unit length impedance matrix, the 7th order multi-conductor transmission line carrier model is constructed to obtain the reconstructed 7th order multi-conductor transmission line carrier model.

[0012] Based on the first overall method, the Carson-Clem formula, and the reconstructed 7th-order multi-conductor transmission line carrier model, a 5th-order multi-conductor transmission line carrier model is constructed.

[0013] Based on the 5th-order multi-conductor transmission line carrier model, a 4th-order multi-conductor transmission line carrier model is constructed.

[0014] In one embodiment, obtaining the 7th-order multi-conductor transmission line carrier model of the cable includes:

[0015] Obtain a 7th-order multi-conductor transmission line carrier model for a three-core armored power cable in a power distribution network; wherein the differential equation of the 7th-order multi-conductor transmission line carrier model is:

[0016] in, U is the 7th order voltage column vector of the cable, I is the 7th order current column vector of the cable, Z7 is the 7th order impedance matrix per unit length of the cable, Y7 is the 7th order admittance matrix per unit length of the cable, R7 is the 7th order resistance matrix per unit length, L7 is the 7th order inductance matrix per unit length, G7 is the 7th order conductance matrix per unit length, C7 is the 7th order capacitance matrix per unit length, and ω is the angular frequency of the carrier signal.

[0017] In one embodiment, obtaining the 7th-order unit-length impedance matrix in the 7th-order multi-conductor transmission line carrier model includes:

[0018] Obtain the 7th-order unit-length impedance matrix in the 7th-order multi-conductor transmission line carrier model; wherein, the expression for the 7th-order unit-length impedance matrix is:

[0019] Wherein, subscript X represents the cable core, subscript P represents the cable shielding layer, subscript K represents the cable armor layer, superscript s represents the self-impedance, m1 represents the coaxial mutual impedance, and m0 represents the non-coaxial mutual impedance.

[0020] In one embodiment, reconstructing the 7th-order unit-length impedance matrix according to the Carson-Clem formula to obtain the reconstructed 7th-order unit-length impedance matrix includes:

[0021] According to the Carson-Clem formula, the mutual impedance between each phase core of the cable and the corresponding shielding layer is equal to the self-impedance of the shielding layer.

[0022] According to the Carson-Clem formula, the non-coaxial mutual impedance between each phase core of the cable and the shielding layer of other phases is equal to the non-coaxial mutual impedance of each phase shielding layer.

[0023] Based on the fact that the mutual impedance between each phase core of the cable and the corresponding shielding layer is equal to the self-impedance of the shielding layer, and that the non-coaxial mutual impedance between each phase core of the cable and the shielding layers of other phases is equal to the non-coaxial mutual impedance of the shielding layers of each phase, the 7th-order unit-length impedance matrix is ​​reconstructed to obtain the reconstructed 7th-order unit-length impedance matrix; wherein, the expression of the reconstructed 7th-order unit-length impedance matrix is:

[0024]

[0025] In one embodiment, constructing a fifth-order multi-conductor transmission line carrier model based on the first overall method, the Carson-Clem formula, and the reconstructed seventh-order multi-conductor transmission line carrier model includes:

[0026] According to the first overall method, the three-phase shielding layer of the cable is treated as a whole to obtain the overall shielding layer of the cable;

[0027] Based on the overall shielding layer of the cable, the mutual impedance between the overall shielding layer of the cable and each phase core of the cable is obtained, the mutual impedance between the overall shielding layer of the cable and the armor layer of the cable is, and the self-impedance of the overall shielding layer of the cable is obtained.

[0028] Based on the mutual impedance between the overall shielding layer of the cable and the cores of each phase of the cable, the mutual impedance between the overall shielding layer of the cable and the armor layer of the cable, the self-impedance of the overall shielding layer of the cable, the Carson-Clem formula, and the reconstructed 7th-order multi-conductor transmission line carrier model, the 5th-order multi-conductor transmission line carrier model is constructed.

[0029] In one embodiment, the construction of the 5th-order multi-conductor transmission line carrier model, based on the mutual impedance between the overall shielding layer of the cable and each phase core of the cable, the mutual impedance between the overall shielding layer of the cable and the armor layer of the cable, the self-impedance of the overall shielding layer of the cable, the Carson-Clem formula, and the reconstructed 7th-order multi-conductor transmission line carrier model, includes:

[0030] According to the Carson-Clem formula, the mutual impedance between the overall shielding layer and the armor layer of the cable is equal to the self-impedance of the armor layer of the cable.

[0031] Based on the mutual impedance between the overall shielding layer and the armor layer of the cable being equal to the self-impedance of the armor layer, the mutual impedance between the overall shielding layer and each phase core of the cable, the mutual impedance between the overall shielding layer and the armor layer of the cable, the self-impedance of the overall shielding layer, and the reconstructed 7th-order multi-conductor transmission line carrier model, the 5th-order multi-conductor transmission line carrier model is constructed.

[0032] In one embodiment, constructing a fourth-order multi-conductor transmission line carrier model based on the fifth-order multi-conductor transmission line carrier model includes:

[0033] Based on the second overall method, the Carson-Clem formula, and the fifth-order multi-conductor transmission line carrier model, the fourth-order multi-conductor transmission line carrier model is constructed.

[0034] In one embodiment, constructing the fourth-order multi-conductor transmission line carrier model based on the second overall method, the Carson-Clem formula, and the fifth-order multi-conductor transmission line carrier model includes:

[0035] According to the second integral method, the conductive protective layer of the cable is treated as a whole to obtain an integral conductive protective layer;

[0036] Based on the overall conductive protective layer, the equivalent radius of the cable's shielding layer and the radius of the cable's armor layer are obtained;

[0037] The equivalent radius of the cable is obtained based on the equivalent radius of the cable's shielding layer and the radius of the cable's armor layer.

[0038] Based on the equivalent radius of the cable, the Carson-Clem formula, and the fifth-order multi-conductor transmission line carrier model, the fourth-order multi-conductor transmission line carrier model is constructed.

[0039] In one embodiment, constructing a fourth-order multi-conductor transmission line carrier model based on the fifth-order multi-conductor transmission line carrier model includes:

[0040] Obtain the equivalent load impedance matrix of the cable extending to the distribution network terminal in the 5th order multi-conductor transmission line carrier model;

[0041] Based on the equivalent load impedance matrix of the cable extending to the distribution network terminal, the rank of the equivalent load impedance matrix of the cable extending to the distribution network terminal is obtained as 4.

[0042] Based on the fact that the rank of the equivalent load impedance matrix of the cable extending to the distribution network terminal is 4, a linear transformation is performed on the equivalent load impedance matrix of the cable extending to the distribution network terminal to obtain the transformed equivalent load impedance matrix.

[0043] Based on the equivalent load impedance matrix and the 5th-order multi-conductor transmission line carrier model, the 4th-order multi-conductor transmission line carrier model is constructed.

[0044] According to another aspect of this application, a device for reducing the order of a carrier model of a three-core armored power cable in a distribution network is provided, comprising: a 7th-order acquisition module for acquiring a 7th-order multi-conductor transmission line carrier model of a three-core armored power cable in a distribution network; an impedance matrix acquisition module for acquiring a 7th-order unit-length impedance matrix in the 7th-order multi-conductor transmission line carrier model; a reconstruction module for reconstructing the 7th-order unit-length impedance matrix according to the Carson-Clem formula to obtain a reconstructed 7th-order unit-length impedance matrix; a construction module for constructing the 7th-order multi-conductor transmission line carrier model according to the reconstructed 7th-order unit-length impedance matrix to obtain a reconstructed 7th-order multi-conductor transmission line carrier model; a 5th-order construction module for constructing a 5th-order multi-conductor transmission line carrier model according to a first overall method, the Carson-Clem formula, and the reconstructed 7th-order multi-conductor transmission line carrier model; and a 4th-order construction module for constructing a 4th-order multi-conductor transmission line carrier model according to the 5th-order multi-conductor transmission line carrier model.

[0045] This application provides a method and apparatus for reducing the order of a carrier wave model for a three-core armored power cable in a distribution network. The method includes: obtaining a 7th-order multi-conductor transmission line carrier wave model of the three-core armored power cable in the distribution network; obtaining the 7th-order unit-length impedance matrix in the 7th-order multi-conductor transmission line carrier wave model; reconstructing the 7th-order unit-length impedance matrix according to the Carson-Clem formula to obtain a reconstructed 7th-order unit-length impedance matrix; constructing a 7th-order multi-conductor transmission line carrier wave model based on the reconstructed 7th-order unit-length impedance matrix; constructing a 5th-order multi-conductor transmission line carrier wave model based on the first global method, the Carson-Clem formula, and the reconstructed 7th-order multi-conductor transmission line carrier wave model; and constructing a 4th-order multi-conductor transmission line carrier wave model based on the 5th-order multi-conductor transmission line carrier wave model. By reducing the order of the 7th-order multi-conductor transmission line carrier wave model twice, i.e., reducing the 7th-order multi-conductor transmission line carrier wave model to 4th order, the complexity of the carrier wave model is significantly reduced, the computational load is reduced, and the analysis speed is improved. Attached Figure Description

[0046] The above and other objects, features, and advantages of this application will become more apparent from the more detailed description of the embodiments of this application in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same components or steps.

[0047] Figure 1 This is a flowchart illustrating the method for reducing the order of a three-core armored power cable carrier model in a power distribution network, provided in an exemplary embodiment of this application.

[0048] Figure 2 This is a cross-sectional view of a three-core armored power cable for power distribution networks provided in an exemplary embodiment of this application.

[0049] Figure 3 This is a schematic diagram of the structure of a reduction device for a three-core armored power cable carrier model in a power distribution network provided in an exemplary embodiment of this application.

[0050] Figure 4 This is a schematic diagram of the structure of a reduction device for a three-core armored power cable carrier model in a power distribution network, provided in another exemplary embodiment of this application.

[0051] Figure 5 This is a structural diagram of an electronic device provided in an exemplary embodiment of this application. Detailed Implementation

[0052] Hereinafter, exemplary embodiments according to this application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments of this application. It should be understood that this application is not limited to the exemplary embodiments described herein.

[0053] Figure 1 This is a flowchart illustrating the method for reducing the order of a three-core armored power cable carrier model in a power distribution network, provided in an exemplary embodiment of this application. Figure 2 This is a cross-sectional view of a three-core armored power cable for a power distribution network provided in an exemplary embodiment of this application. Figure 1-2 As shown, the method for reducing the order of the three-core armored power cable carrier wave model in the distribution network includes:

[0054] Step 110: Obtain the 7th-order multi-conductor transmission line carrier model of the three-core armored power cable of the distribution network.

[0055] In this embodiment, from an insulation perspective, the voltage level of the distribution network is lower than that of the transmission network, and XLPE power cables have good heat resistance, mechanical properties, electrical properties, and aging resistance. Therefore, XLPE three-core armored power cables are usually the preferred choice for distribution network power cables. Commonly used XLPE three-core armored power cables in distribution networks can be roughly divided into seven layers from the outside in: outer sheath, armor layer, inner lining layer, filler layer, phase shielding layer, phase insulation layer, and phase core layer. Among these, the armor layer, phase shielding layer, and phase conductive layer are conductive, while the other layers mainly serve to resist aging, corrosion, and moisture, prevent deformation, and provide electrical insulation. When a high-frequency carrier signal is transmitted using a distribution network three-core armored power cable as the transmission medium, since the power cable is typically a three-core armored structure, its three-phase cores, three-phase shielding layer, and armor layer are coupled together. Therefore, the carrier model of the distribution network three-core armored power cable is a 7th-order multi-conductor transmission line model.

[0056] Step 120: Obtain the 7th order unit length impedance matrix in the 7th order multi-conductor transmission line carrier model.

[0057] In this embodiment of the application, the 7th-order unit length impedance matrix can be reconstructed by obtaining the 7th-order unit length impedance matrix in the 7th-order multi-conductor transmission line carrier model.

[0058] Step 130: Reconstruct the 7th-order unit length impedance matrix according to the Carson-Clem formula to obtain the reconstructed 7th-order unit length impedance matrix.

[0059] In this embodiment, for the frequency range of the high-frequency carrier signal, the elements of the impedance matrix per unit length of the three-core armored power cable in the distribution network can be calculated using the Carson-Clem formula. The Carson-Clem formula for calculating the self-impedance and mutual impedance per unit length of each conductor layer of the cable is as follows:

[0060]

[0061]

[0062] Where i and j represent the cable core, shielding layer, and armor layer of a three-core armored power cable for power distribution networks, respectively, and r... i D represents the resistance per unit length of each conductor layer of the cable (Ω), f represents the carrier signal frequency (Hz), and D CA Let Carson's depth (m) be the value, where... Where, ρ g Let d′ be the soil resistivity (Ω·m). i Indicates d′ i =2G MR G MRd represents the geometric mean radius (m) of each conductor layer of the cable. ij This represents the geometric distance between conductors i and j, in meters (m).

[0063] Step 140: Based on the reconstructed 7th order unit length impedance matrix, construct a 7th order multi-conductor transmission line carrier model to obtain the reconstructed 7th order multi-conductor transmission line carrier model.

[0064] In this embodiment, a 7th-order multi-conductor transmission line carrier model is constructed by jointly using the reconstructed 7th-order unit-length impedance matrix and the 7th-order unit-length admittance matrix. The 7th-order unit-length admittance matrix is ​​a sparse matrix, specifically represented as follows:

[0065] ;

[0066] Among them, Y XP Y represents the admittance between each phase core of the cable and its corresponding shielding layer. PP Indicates the admittance between the various shielding layers of the cable, Y PK Y represents the admittance between the cable's shield and armor layers. KE This indicates the admittance between the cable's armor layer and ground.

[0067] Step 150: Construct a fifth-order multi-conductor transmission line carrier model based on the first global method, the Carson-Clem formula, and the reconstructed seventh-order multi-conductor transmission line carrier model.

[0068] To prevent power cables from getting damp, water-blocking tape is usually wrapped around both the inside and outside of the shielding layer. However, in the actual production of XLPE three-core armored power cables commonly used in distribution networks, water-blocking tape is not required outside the shielding layer to ensure sufficient contact between the three-phase metallic shielding layers. Therefore, when the shielding layers of a three-core armored power cable in a distribution network are in contact with each other, the three-phase shielding layers can be considered as a single unit when the high-frequency carrier signal is transmitted through the power cable. Thus, the carrier model of a three-core armored power cable in a distribution network can be reduced to a 5th-order multi-conductor transmission line model.

[0069] Step 160: Construct a fourth-order multi-conductor transmission line carrier model based on the fifth-order multi-conductor transmission line carrier model.

[0070] In this embodiment, with the gradual promotion of power cables in distribution networks, distribution networks using power cables as the transmission medium typically adopt a closed-loop design and open-loop operation. During normal operation, its network topology presents a radial pattern, characterized by multiple cascades and branches, with one ring main unit installed on each distribution branch. This topology offers high power supply reliability and flexibility in power supply switching.

[0071] To ensure the electrical safety of power cables and prevent personal injury and equipment damage caused by insulation faults, the armor layers of power cables are typically grounded at both ends during operation. To avoid electromagnetic noise crosstalk between the inner and outer shielding layers, prevent large leakage currents caused by core insulation damage, and prevent induced overvoltages due to three-phase current imbalance, the shielding layers of power cables are typically grounded at both ends during operation. In summary, considering the structure of the distribution network with ring main units for power flow distribution, the shielding and armoring layers (collectively referred to as conductive protective layers) of the power cables in the distribution network are usually directly connected to the grounding electrode of the ring main unit for grounding.

[0072] Therefore, when a carrier signal is transmitted through a three-core armored power cable in a distribution network, and the carrier channel model is analyzed using the branch addition method, the power cable extending to the distribution transformer at the distribution network terminal can be considered as an equivalent load. In other words, based on the analysis of the carrier signal transmission characteristics, a fourth-order multi-conductor transmission line carrier model can be constructed from a fifth-order multi-conductor transmission line carrier model.

[0073] Furthermore, when considering the equivalent fourth-order carrier model analysis based on the conductive protective layer of the three-core armored power cable in the distribution network as a whole, its equivalent cross-sectional diagram can be equivalent to... Figure 2 The main changes in the equivalent 4th-order unit length parameter matrix compared to the 5th-order unit length parameter matrix are: 1) the order of the unit length parameter matrix is ​​reduced to 4th; 2) the elements related to the conductive protective layer in the unit length impedance matrix of three-core armored power cables in the distribution network need to be equivalently obtained. Therefore, based on the unit length parameter matrices of different cable forms, a 4th-order multi-conductor transmission line carrier model can be constructed according to the 5th-order multi-conductor transmission line carrier model.

[0074] This application provides a method for reducing the order of a carrier wave model for a three-core armored power cable in a distribution network. The method includes: obtaining a 7th-order multi-conductor transmission line carrier wave model of the three-core armored power cable in the distribution network; obtaining the 7th-order unit-length impedance matrix from the 7th-order multi-conductor transmission line carrier wave model; reconstructing the 7th-order unit-length impedance matrix according to the Carson-Clem formula to obtain a reconstructed 7th-order unit-length impedance matrix; constructing a 7th-order multi-conductor transmission line carrier wave model based on the reconstructed 7th-order unit-length impedance matrix; constructing a 5th-order multi-conductor transmission line carrier wave model based on the first global method, the Carson-Clem formula, and the reconstructed 7th-order multi-conductor transmission line carrier wave model; and constructing a 4th-order multi-conductor transmission line carrier wave model based on the 5th-order multi-conductor transmission line carrier wave model. By reducing the order of the 7th-order multi-conductor transmission line carrier wave model twice, i.e., reducing the 7th-order multi-conductor transmission line carrier wave model to 4th order, the complexity of the carrier wave model is significantly reduced, the computational load is reduced, and the analysis speed is improved.

[0075] In one embodiment, step 110 can be specifically implemented as: obtaining a 7th-order multi-conductor transmission line carrier model of a three-core armored power cable in a distribution network; wherein, the differential equation of the 7th-order multi-conductor transmission line carrier model is:

[0076] in, U is the 7th order voltage column vector of the three-core armored power cable in the distribution network, I is the 7th order current column vector of the cable, Z7 is the 7th order impedance matrix per unit length of the cable, Y7 is the 7th order admittance matrix per unit length of the cable, R7 is the 7th order resistance matrix per unit length, L7 is the 7th order inductance matrix per unit length, G7 is the 7th order conductance matrix per unit length, C7 is the 7th order capacitance matrix per unit length, and ω is the angular frequency of the carrier signal.

[0077] In one embodiment, step 120 may specifically be implemented as: obtaining the 7th-order unit length impedance matrix in the 7th-order multi-conductor transmission line carrier model; wherein, the expression for the 7th-order unit length impedance matrix is:

[0078] In this context, the subscript X represents the cable core, the subscript P represents the cable shield, the subscript K represents the cable armor, the superscript s represents the self-impedance, m1 represents the coaxial mutual impedance, and m0 represents the non-coaxial mutual impedance.

[0079] In this embodiment of the application, dashed lines are added to the above formula to facilitate the differentiation of the parameters of the cable core, shielding layer and armor layer.

[0080] In one embodiment, step 130 may be specifically implemented as follows: according to the Carson-Clem formula, the mutual impedance between each phase core of the cable and the corresponding shielding layer of each phase core is equal to the self-impedance of the shielding layer.

[0081] According to the Carson-Clem formula, the non-coaxial mutual impedance between each phase core and the shielding layer of other phases of the three-core armored power cable in the distribution network is equal to the non-coaxial mutual impedance of each phase shielding layer.

[0082] Based on the principle that the mutual impedance between each phase core and the corresponding shielding layer of a three-core armored power cable in a distribution network is equal to the self-impedance of the shielding layer, and that the non-coaxial mutual impedance between each phase core and the shielding layer of other phases in a three-core armored power cable in a distribution network is equal to the non-coaxial mutual impedance of the shielding layers of each phase, the 7th order unit length impedance matrix is ​​reconstructed to obtain the reconstructed 7th order unit length impedance matrix; the expression for the reconstructed 7th order unit length impedance matrix is ​​as follows:

[0083]

[0084] In this embodiment, analysis using the Carson-Clem formula shows that the mutual impedance between the shielding layers of each phase core of a three-core armored power cable in a distribution network is equal to the self-impedance of the cable's shielding layer. The non-coaxial mutual impedance between each phase core and the shielding layers of the cable is equal to the non-coaxial mutual impedance of each phase shielding layer, i.e. Therefore, the 7th order unit length impedance can be rewritten as:

[0085]

[0086] In one embodiment, step 150 may be specifically implemented as follows: according to the first overall method, the three-phase shielding layer of the three-core armored power cable of the distribution network is taken as a whole to obtain the overall shielding layer of the cable; according to the overall shielding layer of the cable, the mutual impedance between the overall shielding layer of the cable and each phase core of the cable, the mutual impedance between the overall shielding layer of the cable and the armor layer of the cable, and the self-impedance of the overall shielding layer of the cable are obtained; according to the mutual impedance between the overall shielding layer of the cable and each phase core of the cable, the mutual impedance between the overall shielding layer of the cable and the armor layer of the cable, the self-impedance of the overall shielding layer of the cable, the Carson-Clem formula, and the reconstructed 7th order multi-conductor transmission line carrier model, a 5th order multi-conductor transmission line carrier model is constructed.

[0087] In this embodiment, to prevent power cables from getting damp, water-blocking tape is typically wrapped around both the inside and outside of the shielding layer. However, in the actual production of commonly used XLPE three-core armored insulated power cables for power distribution networks, water-blocking tape is not required outside the shielding layer to ensure sufficient contact between the three-phase metallic shielding layers. Therefore, when the shielding layers of the three-core armored power cables in the power distribution network are in contact with each other, the three-phase shielding layers can be considered as a whole when the high-frequency carrier signal is transmitted through the three-core armored power cables. Thus, the carrier model of the three-core armored power cables in the power distribution network can be reduced to a 5th-order multi-conductor transmission line model.

[0088] When analyzing the three-phase shielding layer as a whole, it is easy to determine the mutual impedance between the overall shielding layer of the power cable and the cores of each phase using the overall method. Mutual impedance between the overall cable shield and armor layer The self-impedance of the overall cable shield According to the Carson-Clem formula, the mutual impedance between the overall cable shield and the armor layer is equal to the self-impedance of the armor layer.

[0089] In one embodiment, step 150 can be specifically implemented as follows: according to the Carson-Clem formula, determine that the mutual impedance between the overall shielding layer and the armor layer of the cable is equal to the self-impedance of the armor layer of the cable; based on the mutual impedance between the overall shielding layer and the armor layer of the cable being equal to the self-impedance of the armor layer of the cable, the mutual impedance between the overall shielding layer and each phase core of the cable, the mutual impedance between the overall shielding layer and the armor layer of the cable, the self-impedance of the overall shielding layer of the cable, and the reconstructed 7th order multi-conductor transmission line carrier model, construct a 5th order multi-conductor transmission line carrier model.

[0090] In this embodiment, based on the Carson-Clem formula, since the three-phase shielding layers of the three-core armored power cable in the distribution network are in contact with each other, the mutual impedance between the three-phase cable cores and the corresponding shielding layers (i.e., the self-impedance of each phase shielding layer) and the mutual impedance between the cable cores and the shielding layers of other phases are equal. According to the reconstructed 7th-order unit-length impedance matrix:

[0091] Among them, the reconstructed 7th order unit length impedance matrix The mutual impedance of the three-phase shielding layers of the cable is zero. Then, according to the Carson-Clem formula, the mutual impedance between the overall cable shield and armor layer is equal to the self-impedance of the armor layer. Therefore, the impedance matrix per unit length of the 5th-order multi-conductor transmission line carrier model is expressed as:

[0092] When using the three-phase shielding layer for overall analysis, the admittance matrix per unit length of the 5th-order multi-conductor transmission line carrier model is:

[0093]

[0094] Substituting the unit length impedance matrix and the unit length admittance matrix of the 5th-order multi-conductor transmission line carrier model into its formula... Thus, a fifth-order multiconductor transmission line carrier model is obtained.

[0095] In one embodiment, step 160 can be specifically implemented as follows: constructing a fourth-order multi-conductor transmission line carrier model based on the second overall method, the Carson-Clem formula, and the fifth-order multi-conductor transmission line carrier model.

[0096] When considering the conductive protective layer of the power cable as a whole for equivalent 4th order carrier model analysis, the changes in the equivalent 4th order unit length parameter matrix compared to the 5th order unit length parameter matrix are mainly reflected in: 1) the order of the unit length parameter matrix is ​​reduced to 4th order; 2) the elements related to the conductive protective layer in the unit length impedance matrix of the power cable need to be obtained equivalently.

[0097] According to the Carson-Clem formula, for high-frequency carrier signals, when the real part of the impedance matrix per unit length is ignored, the exponents of each element of the impedance matrix per unit length are proportional to the reciprocal of the geometric distance between conductive layers or the geometric average radius of each conductive layer. Therefore, the parameters related to the conductive shielding layer can be calculated by determining the equivalent position and geometric dimensions of the conductive shielding layer.

[0098] In one embodiment, step 160 may be specifically implemented as follows: according to the second overall method, the conductive protective layer of the cable is treated as a whole to obtain an overall conductive protective layer; based on the overall conductive protective layer, the equivalent radius of the cable's shielding layer and the radius of the cable's armor layer are obtained; based on the equivalent radius of the cable's shielding layer and the radius of the cable's armor layer, the equivalent radius of the cable is obtained; based on the equivalent radius of the cable, the Carson-Clem formula, and the fifth-order multi-conductor transmission line carrier model, a fourth-order multi-conductor transmission line carrier model is constructed.

[0099] When analyzing the conductive protective layer of a power cable as a whole, the equivalent geometric radius can be expressed as:

[0100] d P The equivalent geometric radius of the cable shield and d K Let be the radius of the cable armor layer. The unit length matrix of the equivalent 4th-order carrier model is represented as:

[0101] Wherein, the subscript F represents the conductive protective layer, and the equivalent parameters related to the conductive protective layer are... and All of these are related to its several positions and dimensions, and the size can be calculated according to the Carson-Clem formula.

[0102] When analyzing the conductive protective layer of a power cable as a whole, the equivalent fourth-order unit length admittance is independent of the mutual admittance between the shielding layer and the armor layer of the power cable. Therefore, its fourth-order unit length admittance matrix can be expressed as:

[0103] Substituting Z4 and Y4 into the differential equation Thus, a fourth-order multi-conductor transmission line carrier model is obtained.

[0104] In one embodiment, step 160 may be specifically implemented as follows: obtaining the equivalent load impedance matrix of the cable extending to the distribution network terminal in the 5th order multi-conductor transmission line carrier model; obtaining the rank of the equivalent load impedance matrix of the cable extending to the distribution network terminal as 4 based on the rank of the equivalent load impedance matrix of the cable extending to the distribution network terminal; performing a linear transformation on the equivalent load impedance matrix of the cable extending to the distribution network terminal as 4 based on the rank of the equivalent load impedance matrix of the cable extending to the distribution network terminal to obtain the transformed equivalent load impedance matrix; and constructing a 4th order multi-conductor transmission line carrier model based on the equivalent load impedance matrix and the 5th order multi-conductor transmission line carrier model.

[0105] With the gradual promotion of power cables in distribution networks, distribution networks using power cables as the transmission medium typically adopt a closed-loop design and open-loop operation. In conventional operation, their network topology presents a radial structure, characterized by multiple cascades and branches, with one ring main unit installed on each distribution branch. This topology offers high power supply reliability and flexibility in power supply switching.

[0106] To ensure the electrical safety of power cables and prevent personal injury and equipment damage caused by insulation faults, the armor layers of power cables are typically grounded at both ends during operation. To avoid electromagnetic noise crosstalk between the inner and outer shielding layers, prevent large leakage currents caused by core insulation damage, and prevent induced overvoltages due to three-phase current imbalance, the shielding layers of power cables are typically grounded at both ends during operation. In summary, considering the structure of the distribution network with ring main units for power flow distribution, the shielding and armoring layers (collectively referred to as conductive protective layers) of the power cables in the distribution network are usually directly connected to the grounding electrode of the ring main unit for grounding.

[0107] Therefore, when a carrier signal is transmitted through a power cable in a distribution network, and the carrier channel model is analyzed using the branch addition method, the power cable extending to the distribution network terminal and connecting to the distribution transformer can be equivalent to an equivalent load.

[0108] Based on the distribution terminal structure, the equivalent load impedance matrix of the power cable extending to the distribution network terminal can be expressed as: Among them, Z t This is the equivalent load impedance matrix of the distribution transformer, which is Z. load The third-order symmetric submatrix, Z0 is the grounding resistance of the global cabinet.

[0109] According to the definition of the rank of a linear algebraic matrix, Z load Irreversible (R(Z)) load When using the bottom-up modeling method with branch addition (=4), the coefficient matrix of the corresponding non-homogeneous linear equation system is non-invertible, requiring simplification and introducing errors into the analysis results. Based on the property that linear transformations do not change the rank of a matrix, Z can be transformed using linear transformations.load Perform the transformation to obtain:

[0110]

[0111] Therefore, when analyzing the impedance matrix of the terminal load of the distribution network, its fourth-order submatrix can be used. Its matrix is ​​invertible and requires no simplification. Based on the above processing, it can be considered that in the actual operation of the power distribution network, both ends of the conductive protective layer of the power cable are directly connected to the ground through the ring network cabinet. When the carrier signal is transmitted through the power cable, it can be considered that the conductive protective layer of the power cable is the whole for analysis, that is, the carrier channel model can be equivalent to a fourth-order model.

[0112] Figure 3 This is a schematic diagram of the structure of a reduction device for a three-core armored power cable carrier model in a power distribution network, provided in an exemplary embodiment of this application. Figure 3 As shown, the reduction device 20 for the carrier model of a three-core armored power cable in a distribution network includes: a 7th-order acquisition module 201, used to acquire a 7th-order multi-conductor transmission line carrier model of a three-core armored power cable in a distribution network; an impedance matrix acquisition module 202, used to acquire a 7th-order unit-length impedance matrix in the 7th-order multi-conductor transmission line carrier model; a reconstruction module 203, used to reconstruct the 7th-order unit-length impedance matrix according to the Carson-Clem formula to obtain a reconstructed 7th-order unit-length impedance matrix; a construction module 204, used to construct a 7th-order multi-conductor transmission line carrier model according to the reconstructed 7th-order unit-length impedance matrix to obtain a reconstructed 7th-order multi-conductor transmission line carrier model; a 5th-order construction module 205, used to construct a 5th-order multi-conductor transmission line carrier model according to the first overall method, the Carson-Clem formula, and the reconstructed 7th-order multi-conductor transmission line carrier model; and a 4th-order construction module 206, used to construct a 4th-order multi-conductor transmission line carrier model according to the 5th-order multi-conductor transmission line carrier model.

[0113] This application provides a device for reducing the order of a carrier wave model of a three-core armored power cable in a distribution network. The device includes: a 7th-order acquisition module to acquire a 7th-order multi-conductor transmission line carrier wave model of the three-core armored power cable; an impedance matrix acquisition module to acquire the 7th-order unit-length impedance matrix from the 7th-order multi-conductor transmission line carrier wave model; a reconstruction module to reconstruct the 7th-order unit-length impedance matrix according to the Carson-Clem formula; a construction module to construct a 7th-order multi-conductor transmission line carrier wave model based on the reconstructed 7th-order unit-length impedance matrix; a 5th-order construction module to construct a 5th-order multi-conductor transmission line carrier wave model based on the first global method, the Carson-Clem formula, and the reconstructed 7th-order multi-conductor transmission line carrier wave model; and a 4th-order construction module to construct a 4th-order multi-conductor transmission line carrier wave model based on the 5th-order multi-conductor transmission line carrier wave model. By reducing the order of the 7th-order multi-conductor transmission line carrier wave model twice, i.e., reducing the 7th-order multi-conductor transmission line carrier wave model to 4th order, the complexity of the carrier wave model is significantly reduced, the computational load is reduced, and the analysis speed is improved.

[0114] Figure 4 This is a schematic diagram of the structure of a reduction device for a three-core armored power cable carrier model in a power distribution network, provided in another exemplary embodiment of this application. Figure 4 As shown, the 7th-order acquisition module 201 may include: a 7th-order acquisition subunit 2011, used to acquire the 7th-order multi-conductor transmission line carrier model of a three-core armored power cable in a distribution network; wherein, the differential equation of the 7th-order multi-conductor transmission line carrier model is:

[0115] in, U is the 7th order voltage column vector of the cable, I is the 7th order current column vector of the cable, Z7 is the 7th order impedance matrix per unit length of the cable, Y7 is the 7th order admittance matrix per unit length of the cable, R7 is the 7th order resistance matrix per unit length, L7 is the 7th order inductance matrix per unit length, G7 is the 7th order conductance matrix per unit length, C7 is the 7th order capacitance matrix per unit length, and ω is the angular frequency of the carrier signal.

[0116] In one embodiment, such as Figure 4 As shown, the impedance matrix acquisition module 202 may include: a length impedance matrix acquisition subunit 2021, used to acquire the 7th-order unit length impedance matrix in the 7th-order multi-conductor transmission line carrier model; wherein, the expression for the 7th-order unit length impedance matrix is:

[0117] In this context, the subscript X represents the cable core, the subscript P represents the cable shield, the subscript K represents the cable armor, the superscript s represents the self-impedance, m1 represents the coaxial mutual impedance, and m0 represents the non-coaxial mutual impedance.

[0118] In one embodiment, such as Figure 4 As shown, the construction module 204 may include: an overall unit 2041, used to treat the three-phase shielding layer of the cable as a whole according to the first overall method to obtain the overall shielding layer of the cable; an acquisition subunit 2042, used to obtain the mutual impedance between the overall shielding layer of the cable and each phase core of the cable, the mutual impedance between the overall shielding layer of the cable and the armor layer of the cable, and the self-impedance of the overall shielding layer of the cable based on the overall shielding layer of the cable; and a construction subunit 2043, used to construct a 5th-order multi-conductor transmission line carrier model based on the mutual impedance between the overall shielding layer of the cable and each phase core of the cable, the mutual impedance between the overall shielding layer of the cable and the armor layer of the cable, the self-impedance of the overall shielding layer of the cable, the Carson-Clem formula, and the reconstructed 7th-order multi-conductor transmission line carrier model.

[0119] In one embodiment, the subunit 2043 can be specifically configured as follows: According to the Carson-Clem formula, the mutual impedance between each phase core of the cable and its corresponding shielding layer is equal to the self-impedance of the shielding layer; according to the Carson-Clem formula, the non-coaxial mutual impedance between each phase core of the cable and the shielding layers of other phases is equal to the non-coaxial mutual impedance of each phase shielding layer; based on the equality of the mutual impedance between each phase core of the cable and its corresponding shielding layer with the self-impedance of the shielding layer, and the equality of the non-coaxial mutual impedance between each phase core of the cable and the shielding layers of other phases with the non-coaxial mutual impedance of each phase shielding layer, the 7th-order unit length impedance matrix is ​​reconstructed to obtain the reconstructed 7th-order unit length impedance matrix; wherein, the expression of the reconstructed 7th-order unit length impedance matrix is:

[0120]

[0121] In one embodiment, the 5th-order construction module 205 may be specifically configured as follows: according to the first overall method, the three-phase shielding layer of the cable is treated as a whole to obtain the overall shielding layer of the cable; based on the overall shielding layer of the cable, the mutual impedance between the overall shielding layer of the cable and each phase core of the cable, the mutual impedance between the overall shielding layer of the cable and the armor layer of the cable, and the self-impedance of the overall shielding layer of the cable are obtained; based on the mutual impedance between the overall shielding layer of the cable and each phase core of the cable, the mutual impedance between the overall shielding layer of the cable and the armor layer of the cable, the self-impedance of the overall shielding layer of the cable, the Carson-Clem formula, and the reconstructed 7th-order multi-conductor transmission line carrier model, a 5th-order multi-conductor transmission line carrier model is constructed.

[0122] In one embodiment, the 5th-order construction module 205 can be specifically configured as follows: according to the Carson-Clem formula, determine that the mutual impedance between the overall shielding layer and the armor layer of the cable is equal to the self-impedance of the armor layer of the cable; based on the mutual impedance between the overall shielding layer and the armor layer of the cable being equal to the self-impedance of the armor layer of the cable, the mutual impedance between the overall shielding layer and each phase core of the cable, the mutual impedance between the overall shielding layer and the armor layer of the cable, the self-impedance of the overall shielding layer of the cable, and the reconstructed 7th-order multi-conductor transmission line carrier model, construct a 5th-order multi-conductor transmission line carrier model.

[0123] In one embodiment, such as Figure 4 As shown, the 4th-order building module 206 may include a first 4th-order building unit 2061, which is used to build a 4th-order multi-conductor transmission line carrier model according to the second global method, the Carson-Clem formula and the 5th-order multi-conductor transmission line carrier model.

[0124] In one embodiment, the first fourth-order building unit 2061 may be specifically configured as follows: according to the second overall method, the conductive protective layer of the cable is treated as a whole to obtain an overall conductive protective layer; based on the overall conductive protective layer, the equivalent radius of the cable's shielding layer and the radius of the cable's armor layer are obtained; based on the equivalent radius of the cable's shielding layer and the radius of the cable's armor layer, the equivalent radius of the cable is obtained; based on the equivalent radius of the cable, the Carson-Clem formula, and the fifth-order multi-conductor transmission line carrier model, a fourth-order multi-conductor transmission line carrier model is constructed.

[0125] In one embodiment, the 4th-order construction module 206 may include a second 4th-order construction unit 2062, used to obtain the equivalent load impedance matrix of the cable extending to the distribution network terminal in the 5th-order multi-conductor transmission line carrier model; obtain the rank of the equivalent load impedance matrix of the cable extending to the distribution network terminal as 4 based on the rank of the equivalent load impedance matrix of the cable extending to the distribution network terminal; perform a linear transformation on the equivalent load impedance matrix of the cable extending to the distribution network terminal as 4 based on the rank of the equivalent load impedance matrix of the cable extending to the distribution network terminal to obtain the transformed equivalent load impedance matrix; and construct a 4th-order multi-conductor transmission line carrier model based on the equivalent load impedance matrix and the 5th-order multi-conductor transmission line carrier model.

[0126] Figure 5 A block diagram of an electronic device according to an embodiment of this application is illustrated.

[0127] like Figure 5 As shown, the electronic device 10 includes one or more processors 11 and memory 12.

[0128] The processor 11 may be a central processing unit (CPU) or other form of processing unit with data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device 10 to perform desired functions.

[0129] The memory 12 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 11 may execute the program instructions to implement the reduction method of the three-core armored power cable carrier model of the distribution network described in the various embodiments of this application above, and / or other desired functions. Various contents such as input signals, signal components, and noise components may also be stored in the computer-readable storage medium.

[0130] In one example, the electronic device 10 may also include an input device 13 and an output device 14, which are interconnected via a bus system and / or other forms of connection mechanism (not shown).

[0131] When the electronic device is a standalone device, the input device 13 can be a communication network connector for receiving the collected input signals from the first device and the second device.

[0132] In addition, the input device 13 may also include, for example, a keyboard, a mouse, etc.

[0133] The output device 14 can output various information to the outside, including determined distance information, direction information, etc. The output device 14 may include, for example, a display, a speaker, a printer, and a communication network and its connected remote output devices, etc.

[0134] Of course, for the sake of simplicity, Figure 5 Only some of the components of the electronic device 10 relevant to this application are shown in this illustration; components such as buses, input / output interfaces, etc., are omitted. In addition, the electronic device 10 may include any other suitable components depending on the specific application.

[0135] The computer program product can be written in any combination of one or more programming languages ​​to perform the operations of the embodiments of this application. 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.

[0136] 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, for example, include, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatuses, or devices, or any combination thereof. More specific examples of readable storage media (a non-exhaustive list) include: electrical connections having one or more wires, portable disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0137] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application 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 reducing the order of a carrier wave model of a three-core armored power cable in a power distribution network, characterized in that, include: Obtain the 7th order multi-conductor transmission line carrier model of a three-core armored power cable in a power distribution network; obtain the 7th order unit length impedance matrix in the 7th order multi-conductor transmission line carrier model; According to the Carson-Clem formula, the 7th-order unit-length impedance matrix is ​​reconstructed to obtain a reconstructed 7th-order unit-length impedance matrix; based on the reconstructed 7th-order unit-length impedance matrix, a 7th-order multi-conductor transmission line carrier model is constructed to obtain a reconstructed 7th-order multi-conductor transmission line carrier model; based on the first overall method, the Carson-Clem formula, and the reconstructed 7th-order multi-conductor transmission line carrier model, a 5th-order multi-conductor transmission line carrier model is constructed. The first overall method refers to treating the three-phase shielding layer of the cable as a whole to obtain the overall shielding layer of the cable; based on the 5th-order multi-conductor transmission line carrier model, a 4th-order multi-conductor transmission line carrier model is constructed. The construction of a fourth-order multi-conductor transmission line carrier model based on the fifth-order multi-conductor transmission line carrier model includes: Based on the second overall method, the Carson-Clem formula, and the fifth-order multi-conductor transmission line carrier model, the fourth-order multi-conductor transmission line carrier model is constructed. The second overall method refers to treating the conductive protective layer of the cable as a whole to obtain the overall conductive protective layer; or The construction of a fourth-order multi-conductor transmission line carrier model based on the fifth-order multi-conductor transmission line carrier model includes: Obtain the equivalent load impedance matrix of the cable extending to the distribution network terminal in the 5th order multi-conductor transmission line carrier model; Based on the equivalent load impedance matrix of the cable extending to the distribution network terminal, the rank of the equivalent load impedance matrix of the cable extending to the distribution network terminal is obtained as 4. Based on the fact that the rank of the equivalent load impedance matrix of the cable extending to the distribution network terminal is 4, a linear transformation is performed on the equivalent load impedance matrix of the cable extending to the distribution network terminal to obtain the transformed equivalent load impedance matrix. Based on the equivalent load impedance matrix and the 5th-order multi-conductor transmission line carrier model, the 4th-order multi-conductor transmission line carrier model is constructed.

2. The method for reducing the order of a three-core armored power cable carrier model in a distribution network according to claim 1, characterized in that, The method for obtaining the 7th-order multi-conductor transmission line carrier model of a three-core armored power cable in a power distribution network includes: Obtain a 7th-order multi-conductor transmission line carrier model for a three-core armored power cable in a power distribution network; wherein the differential equation of the 7th-order multi-conductor transmission line carrier model is: ,in, U is the 7th order voltage column vector of the cable, and I is the 7th order current column vector of the cable. This is the 7th order unit length impedance matrix of the cable. The 7th order unit length admittance matrix of the cable is given. It is a 7th order unit length resistance matrix. It is a 7th order unit length inductance matrix. It is a 7th-order unit-length conductance matrix. It is a 7th-order unit-length capacitance matrix, and ω is the angular frequency of the carrier signal.

3. The method for reducing the order of a three-core armored power cable carrier model in a distribution network according to claim 2, characterized in that, The process of obtaining the 7th-order unit-length impedance matrix in the 7th-order multi-conductor transmission line carrier model includes: Obtain the 7th-order unit-length impedance matrix in the 7th-order multi-conductor transmission line carrier model; wherein, the expression for the 7th-order unit-length impedance matrix is: In this context, the subscript X represents the cable core, the subscript P represents the cable shielding layer, the subscript K represents the cable armor layer, and the superscript s represents the self-impedance. Represented as coaxial mutual impedance, This indicates non-coaxial mutual impedance.

4. The method for reducing the order of a three-core armored power cable carrier model in a distribution network according to claim 3, characterized in that, The process of reconstructing the 7th-order unit-length impedance matrix according to the Carson-Clem formula to obtain the reconstructed 7th-order unit-length impedance matrix includes: According to the Carson-Clem formula, the mutual impedance between each phase core of the cable and the corresponding shielding layer is equal to the self-impedance of the shielding layer. According to the Carson-Clem formula, the non-coaxial mutual impedance between each phase core of the cable and the shielding layer of other phases is equal to the non-coaxial mutual impedance of each phase shielding layer. Based on the fact that the mutual impedance between each phase core of the cable and the corresponding shielding layer is equal to the self-impedance of the shielding layer, and that the non-coaxial mutual impedance between each phase core of the cable and the shielding layers of other phases is equal to the non-coaxial mutual impedance of the shielding layers of each phase, the 7th-order unit-length impedance matrix is ​​reconstructed to obtain the reconstructed 7th-order unit-length impedance matrix; wherein, the expression of the reconstructed 7th-order unit-length impedance matrix is: 。 5. The method for reducing the order of a three-core armored power cable carrier model in a distribution network according to claim 4, characterized in that, The construction of a fifth-order multi-conductor transmission line carrier model based on the first overall method, the Carson-Clem formula, and the reconstructed seventh-order multi-conductor transmission line carrier model includes: Based on the overall shielding layer of the cable, the mutual impedance between the overall shielding layer of the cable and each phase core of the cable is obtained, the mutual impedance between the overall shielding layer of the cable and the armor layer of the cable is, and the self-impedance of the overall shielding layer of the cable is obtained. Based on the mutual impedance between the overall shielding layer of the cable and the cores of each phase of the cable, the mutual impedance between the overall shielding layer of the cable and the armor layer of the cable, the self-impedance of the overall shielding layer of the cable, the Carson-Clem formula, and the reconstructed 7th-order multi-conductor transmission line carrier model, the 5th-order multi-conductor transmission line carrier model is constructed.

6. The method for reducing the order of a three-core armored power cable carrier model in a distribution network according to claim 5, characterized in that, The construction of the 5th-order multi-conductor transmission line carrier model, based on the mutual impedance between the overall shielding layer and each phase core of the cable, the mutual impedance between the overall shielding layer and the armor layer of the cable, the self-impedance of the overall shielding layer, the Carson-Clem formula, and the reconstructed 7th-order multi-conductor transmission line carrier model, includes: According to the Carson-Clem formula, the mutual impedance between the overall shielding layer and the armor layer of the cable is equal to the self-impedance of the armor layer of the cable. Based on the mutual impedance between the overall shielding layer and the armor layer of the cable being equal to the self-impedance of the armor layer, the mutual impedance between the overall shielding layer and each phase core of the cable, the mutual impedance between the overall shielding layer and the armor layer of the cable, the self-impedance of the overall shielding layer, and the reconstructed 7th-order multi-conductor transmission line carrier model, the 5th-order multi-conductor transmission line carrier model is constructed.

7. The method for reducing the order of a three-core armored power cable carrier model in a distribution network according to claim 1, characterized in that, The construction of the fourth-order multi-conductor transmission line carrier model based on the second overall method, the Carson-Clem formula, and the fifth-order multi-conductor transmission line carrier model includes: Based on the overall conductive protective layer, the equivalent radius of the cable's shielding layer and the radius of the cable's armor layer are obtained; The equivalent radius of the cable is obtained based on the equivalent radius of the cable's shielding layer and the radius of the cable's armor layer. Based on the equivalent radius of the cable, the Carson-Clem formula, and the fifth-order multi-conductor transmission line carrier model, the fourth-order multi-conductor transmission line carrier model is constructed.

8. A device for reducing the order of a three-core armored power cable carrier model in a distribution network, employing the method for reducing the order of a three-core armored power cable carrier model in a distribution network as described in claim 1, characterized in that... include: The system includes: a 7th-order acquisition module for acquiring a 7th-order multi-conductor transmission line carrier model of a three-core armored power cable in a distribution network; an impedance matrix acquisition module for acquiring a 7th-order unit-length impedance matrix in the 7th-order multi-conductor transmission line carrier model; a reconstruction module for reconstructing the 7th-order unit-length impedance matrix according to the Carson-Clem formula to obtain a reconstructed 7th-order unit-length impedance matrix; a construction module for constructing the 7th-order multi-conductor transmission line carrier model based on the reconstructed 7th-order unit-length impedance matrix to obtain a reconstructed 7th-order multi-conductor transmission line carrier model; a 5th-order construction module for constructing a 5th-order multi-conductor transmission line carrier model according to the first overall method, the Carson-Clem formula, and the reconstructed 7th-order multi-conductor transmission line carrier model; and a 4th-order construction module for constructing a 4th-order multi-conductor transmission line carrier model based on the 5th-order multi-conductor transmission line carrier model.

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