Parallel cable current distribution calculation method and system under cross-connection grounding mode

Abstract

The present invention discloses a method and system for calculating the current distribution of parallel cables under a cross-interconnected grounding mode. The present invention takes into account the influence of the transverse electromagnetic coupling between parallel cables and the longitudinal voltage superposition of three-segment cables in the cross-interconnected mode, and constructs an impedance matrix of the parallel cables under the cross-interconnected grounding mode according to the number of cables in the cross-interconnected unit, the cable cross-section, the cable arrangement mode and the cable segment length. The current distribution calculation model is obtained based on the impedance matrix, the cable core current and the sheath circulating current are calculated, and the calculated current is verified based on preset requirements, so as to effectively evaluate the current distribution of the parallel cables under the cross-interconnected grounding mode, and further optimize the cable segment length and the cable arrangement mode, so as to ensure the long-term stable operation of the cable and realize the reliable transmission of electric energy.

Description

Technical Field

[0001] The invention relates to a method and system for calculating current distribution of parallel cables in a cross-connected grounding mode, belonging to the technical field of cable power transmission. Background Art

[0002] At present, relevant institutions at home and abroad have carried out a lot of research on the parallel operation of multiple cables in the same phase, and its accuracy has been verified in engineering examples. However, there is a lack of relevant research and operation experience for the cross-interconnection grounding method that is most commonly used for high-voltage long-distance cables.

[0003] Parallel cables under the cross-interconnected grounding method (referred to as "cross-interconnected parallel cables") are affected by the coupling of multiple cable core currents and metal sheath circulating currents. Multiple high-voltage cables in parallel with the same phase have complex transverse electromagnetic and longitudinal superposition dual coupling relationships. The existing equivalent calculation model of multiple parallel cables cannot effectively evaluate the current distribution problem of parallel cables under the cross-interconnected grounding method. Summary of the invention

[0004] The present invention provides a method and system for calculating current distribution of parallel cables in a cross-connected grounding mode, which solves the problems disclosed in the background technology.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for calculating current distribution of parallel cables under a cross-connected grounding mode is characterized by comprising:

[0007] According to the number of cables, cable cross-sections, cable arrangement and cable segment length in the cross-connection unit, an impedance matrix of parallel cables under the cross-connection grounding mode is constructed;

[0008] According to the impedance matrix, a current distribution calculation model is obtained;

[0009] Calculate the cable core current and sheath circulating current according to the current distribution calculation model;

[0010] In response to the cable core current meeting the preset current requirement and the sheath induced voltage obtained according to the sheath circulating current meeting the preset voltage requirement, the current cable core current and the sheath circulating current are the calculation results of the parallel cable current distribution under the cross-connected grounding mode.

[0011] There are three cross-connection units. The impedance matrix of the parallel cables in the cross-connection grounding mode is:

[0012] Y 6n×6n =A·(l1·Z 6n×6n +l2·P·Z′ 6n×6n ·Q+l3·P 2 ·Z″6n×6n Q 2 )-(R1+R e +R2)·B

[0013] Among them, Y 6n×6n is the impedance matrix, n is the number of parallel cables in the cross-connection unit, l1, l2, and l3 are the lengths of the cable segments in the three cross-connection units, and Z 6n×6n , Z′ 6n×6n , Z″ 6n×6n are the impedance matrices of the three cables in the cross-connection unit, R1 and R2 are the grounding resistances at both ends of the cable, R e is the large earth leakage resistance;

[0014] are the voltage and current transformation matrices of the cross-connected cables, respectively.

[0015] is the identity matrix, is a zero matrix, is a fully unimodular matrix, is the voltage elimination matrix of the same phase, is the sheath induced voltage elimination matrix.

[0016] The current distribution calculation model is:

[0017]

[0018] Among them, C 3×3 , D 3×(6n-3) , G (6n-3)×3 and H (6n-3)×(6n-3) Y 6n×6n The sub-matrix of

[0019] J 3×(6n-3) To eliminate I A1 ,I B1 ,I C1 Change matrix of impact items

[0020] I Ai ,I Bi ,I Ci They are the A-phase load current, B-phase load current and C-phase load current of the core line loop of the i-th cable line, i=2~n;

[0021] I Asj ,I Bsj ,I Csj They are the A-phase current, B-phase current and C-phase current of the sheath loop of the j-th cable line, j=1~n;

[0022] I A =I A1 +…+I Aj …+I An ,I B =I B1 +…+I Bj …+I Bn ,I C =I C1 +…+I Cj …+I Cn It is the A, B and C phase load current of the parallel cables under the cross-connected grounding method.

[0023] The calculation formula for cable core current and sheath circulating current is:

[0024] Cable core current I Ai ,I Bi ,I Ci and sheath circulation I Asj ,I Bsj ,I Csj The calculation formula is:

[0025]

[0026] Cable core current I A1 ,I B1 ,I C1 The calculation formula is:

[0027]

[0028] In response to the cable core current not meeting the preset current requirement, adjusting the cable arrangement, or increasing the number of cables and the cable cross-section, and recalculating the current distribution;

[0029] In response to the sheath induced voltage obtained according to the sheath circulating current not meeting the preset voltage requirement, the cable section length is reduced and the current distribution calculation is performed again.

[0030] The preset current requirement is:

[0031] The maximum non-uniform coefficient a is less than the threshold value, and max(I A max ,I B max ,I C max ) is less than the maximum allowable current of each cable;

[0032] in,

[0033] I A max =max(I A1 ,…,I An )

[0034] IB max =max(I B1 ,…,I Bn )

[0035] I C max =max(I C1 ,…,I Cn )

[0036] I A min =min(I A1 ,…,I An )

[0037] I B min =min(I B1 ,…,I Bn )

[0038] I C min =min(I C1 ,…,I Cn )

[0039] I Aj ,I Bj ,I Cj They are the A-phase load current, B-phase load current and C-phase load current of the core line loop of the j-th cable line, j=2~n;

[0040] I A max ,I A min I A1 ,…,I An The maximum and minimum values ​​in I B max ,I B min I B1 ,…,I Bn The maximum and minimum values ​​in I C max ,I C min I C1 ,…,I Cn The maximum and minimum values ​​in .

[0041] The preset voltage requirement is: the sheath induced voltage exceeds the limit.

[0042] The parallel cable current distribution calculation system under the cross-connection grounding method includes:

[0043] Impedance matrix construction module: Constructs the impedance matrix of parallel cables under the cross-connection grounding mode according to the number of cables, cable cross-sections, cable arrangement and cable segment length in the cross-connection unit;

[0044] Calculation model acquisition module: obtains the current distribution calculation model according to the impedance matrix;

[0045] Current calculation module: calculates the cable core current and sheath circulating current according to the current distribution calculation model;

[0046] Verification module: In response to the cable core current meeting the preset current requirement and the sheath induced voltage obtained according to the sheath circulating current meeting the preset voltage requirement, the current cable core current and the sheath circulating current are the parallel cable current distribution calculation results under the cross-connected grounding method.

[0047] A computer-readable storage medium storing one or more programs, wherein the one or more programs include instructions, which, when executed by a computing device, enable the computing device to perform a method for calculating current distribution of parallel cables under a cross-connected grounding mode.

[0048] A computing device includes one or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and are configured to be executed by the one or more processors, and the one or more programs include instructions for executing a method for calculating current distribution of parallel cables under a cross-connected grounding method.

[0049] The beneficial effects achieved by the present invention are as follows: the present invention takes into account the influence of the transverse electromagnetic coupling between parallel cables and the longitudinal voltage superposition of three cable sections in the cross-connection, and constructs an impedance matrix of parallel cables under the cross-connection grounding mode according to the number of cables in the cross-connection unit, the cable cross-section, the cable arrangement mode and the cable section length. The current distribution calculation model is obtained based on the impedance matrix, the cable core current and the sheath circulating current are calculated, and the calculated current is verified based on the preset requirements, so as to effectively evaluate the current distribution of parallel cables under the cross-connection grounding mode, and further optimize the cable section length and the cable arrangement mode, so as to ensure the long-term stable operation of the cable and realize the reliable transmission of electric energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is a flow chart of the method of the present invention;

[0051] Figure 2 is a detailed flow chart of the method of the present invention;

[0052] Figure 3 This is the parallel cable structure diagram under the cross-connection grounding method. DETAILED DESCRIPTION

[0053] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0054] like Figure 1 As shown, the method for calculating the current distribution of parallel cables under the cross-connection grounding method includes the following steps:

[0055] Step 1, constructing an impedance matrix of parallel cables under a cross-connection grounding mode according to the number of cables, cable cross-sections, cable arrangement mode and cable segment lengths in the cross-connection unit;

[0056] Step 2, obtaining a current distribution calculation model according to the impedance matrix;

[0057] Step 3, calculating the cable core current and sheath circulating current according to the current distribution calculation model;

[0058] Step 4, in response to the cable core current meeting the preset current requirement and the sheath induced voltage obtained according to the sheath circulating current meeting the preset voltage requirement, the current cable core current and the sheath circulating current are the calculation results of the parallel cable current distribution under the cross-connected grounding method, and the current number of cables, cable cross-section, cable arrangement method and cable segment length are the optimal cable distribution structure.

[0059] The above method takes into account the influence of the transverse electromagnetic coupling of the three-phase cable in the cross-interconnected unit and the longitudinal voltage superposition of the three-segment cable. According to the number of cables, cable cross-section, cable arrangement and cable segment length in the cross-interconnected unit, an impedance matrix of the parallel cables under the cross-interconnected grounding method is constructed. Based on the impedance matrix, a current distribution calculation model is obtained, the cable core current and sheath circulating current are calculated, and the calculated current is verified based on preset requirements. The current distribution of the parallel cables under the cross-interconnected grounding method is effectively evaluated, and the cable segment length and cable arrangement method can be further optimized to ensure the long-term stable operation of the cable and realize the reliable transmission of electric energy.

[0060] like Figure 2 Different cross-connected units can be superimposed in different arrangements and segment lengths. Therefore, it is necessary to first obtain the number of cables, cable cross-sections, cable arrangements and cable segment lengths in the current (i.e., initial) cross-connected unit, so as to obtain the core AC resistance, sheath AC resistance, core wire geometric average distance, sheath geometric average distance and cable spacing of each cable.

[0061] According to the parameters obtained above, the impedance matrix of the cross-connected n-cable parallel system in one unit can be established, with a total of 6n loops. The voltage drop expression of the cable line in these 6n loops can be:

[0062]

[0063] Among them, ΔU Aj , ΔU Bj , ΔU Cj is the three-phase voltage drop of the core line loop of the j-th cable line, j = 1~n, ΔU Asj , ΔU Bsj , ΔU Csjis the three-phase voltage drop of the sheath loop of the j-th cable line, I Aj ,I Bj ,I Cj are the A-phase load current, B-phase load current and C-phase load current of the core line loop of the j-th cable line, respectively, I Asj ,I Bsj ,I Csj are the A-phase current, B-phase current and C-phase current of the sheath loop of the j-th cable line, respectively, and Z 6n×6n is the impedance matrix, and l is the length of the cable segment.

[0064] Using existing technology, the self-impedance per unit length of the cable core (in Ω / km) is:

[0065]

[0066] The self-impedance per unit length of cable sheath (in Ω / km) is:

[0067]

[0068] The mutual impedance of the core and sheath of the same cable (in Ω / km) is:

[0069]

[0070] The mutual impedance between the core wires and sheaths of different cables (in Ω / km) is:

[0071]

[0072] Among them, r c is the AC resistance per unit length of the core, r s is the AC resistance per unit length of the sheath, r e is the earth equivalent unit resistance, r e =π 2 f×10 -4 , f is the AC operating frequency, D e is the equivalent depth of the earth equivalent loop, ρ e is the soil resistivity, D c is the geometric mean distance of the core wire, D s is the geometric mean distance of the sheath, D i′j′ Refers to the distance between each cable.

[0073] When the parallel cables are divided into different grounding loops to form cross-connected grounding, in order to reduce the sheath induced voltage, Figure 3 For example, the cross-connection is generally divided into three sections, that is, there are three cross-connection units, and the induced voltage of each loop sheath can be obtained using the method of one-point grounding.

[0074] make are the voltage and current transformation matrices of the cross-connected cables, respectively.

[0075] Then the opening voltage of the cross-connection section is:

[0076]

[0077] Eliminate ΔU Asj , ΔU Bsj , ΔU Csj , subtract the phase voltage of the first circuit from the phase voltage of the other circuits, and get:

[0078] is the identity matrix, is a zero matrix, is a fully unimodular matrix, is the voltage elimination matrix of the same phase, is the sheath induced voltage elimination matrix;

[0079] The impedance matrix is ​​obtained as follows:

[0080] Y 6n×6n =A·(l1·Z 6n×6n +l2·P·Z′ 6n×6n ·Q+l3·P 2 ·Z″ 6n×6n Q 2 )-(R1+R e +R2)·B

[0081] Among them, Y 6n×6n is an impedance matrix, which consists of self-impedance and mutual impedance. n is the number of parallel cables in the cross-connection unit. l1, l2, and l3 are the lengths of the three cable segments in the cross-connection unit. Z 6n×6n , Z′ 6n×6n , Z″ 6n×6n are the impedance matrices of the three cables in the cross-connection unit, R1 and R2 are the grounding resistances at both ends of the cable, R e It is the large earth leakage resistance.

[0082] At the same time, considering that the potential difference at both ends of the core wires of the same-phase parallel cables is equal, the calculation model under the cross-connection grounding method can be obtained as follows:

[0083]

[0084] Assume that during normal operation, the load current of phases A, B, and C through the parallel cables in the cross-connected grounding mode is I Ai ,I Bi ,I Ci According to Kirchhoff's law:

[0085] I A =I A1 +…+I Aj …+I An

[0086] I B =I B1 +…+I Bj …+I Bn

[0087] I C =I C1 +…+I Cj …+I Cn

[0088] The above 6n equations and the three equations of three-phase load current can be used to solve the 6n variables of current and the three variables of voltage, that is, to obtain the core current and sheath current phasors of each phase of each cable line.

[0089] To facilitate programming and solving, the impedance matrix can be simplified to establish a current distribution calculation model:

[0090] Based on the impedance matrix, let C 3×3 , D 3×(6n-3) , G (6n-3)×3 and H (6n-3)×(6n-3) Y 6n×6n The sub-matrix of

[0091] Combined with the three-phase load current, the A1 , ΔU B1 , ΔU C1 ,I A1 ,I B1 ,I C1 Impact of C 3×3 , D 3×(6n-3) , G (6n-3)×3 Related items;

[0092] make As elimination I A1 ,I B1 ,I C1 Change matrix of influencing items;

[0093] After simplification, the current distribution calculation model can be obtained as follows:

[0094]

[0095] Among them, I Ai ,I Bi ,I CiThey are respectively the A-phase load current, B-phase load current and C-phase load current of the core wire loop of the i-th cable line, and i=2~n.

[0096] Using the above current distribution calculation model, the cable core current and sheath circulating current can be calculated as follows:

[0097] Cable core current I Ai ,I Bi ,I Ci and sheath circulation I Asj ,I Bsj ,I Csj The calculation formula is:

[0098]

[0099] Cable core current I A1 ,I B1 ,I C1 The calculation formula is:

[0100]

[0101] The preset current requirements are defined as follows: the maximum uneven coefficient a (characterizing the impact of 3n cables in parallel arranged in different ways on the load current distribution) is less than the threshold value, and max(I A max ,I B max ,I C max ) is less than the maximum allowable current of each cable; the preset voltage requirement is: the sheath induced voltage exceeds the limit, which is generally 300V;

[0102] in,

[0103] I A max =max(I A1 ,…,I An )

[0104] I B max =max(I B1 ,…,I Bn )

[0105] I C max =max(I C1 ,…,I Cn )

[0106] I A min =min(I A1 ,…,I An )

[0107] I B min =min(I B1 ,…,I Bn )

[0108] I C min =min(I C1 ,…,I Cn )

[0109] I Aj ,I Bj ,I Cj They are the A-phase load current, B-phase load current and C-phase load current of the core line loop of the j-th cable line, j=2~n;

[0110] I A max ,I A min I A1 ,…,I An The maximum and minimum values ​​in I B max ,I B min I B1 ,…,I Bn The maximum and minimum values ​​in I C max ,I C min I C1 ,…,I Cn The maximum and minimum values ​​in .

[0111] According to the cable core current, obtain I A max ,I A min ,I B max ,I B min ,I C max ,I C min , calculate the maximum non-uniformity coefficient If it is determined that the cable core current does not meet the preset current requirements, the cable arrangement is adjusted, or the number of cables and the cable cross-section are increased, and the current distribution calculation is re-performed. If it is determined that the cable core current meets the preset current requirements, the sheath induced voltage is further calculated.

[0112] According to the sheath circulating current and the opening voltage equation of the cross-connection section, the sheath induced voltage U is calculated. Asj , U Bsj , U Csj If it is determined that the sheath induced voltage does not meet the preset voltage requirements, reduce the cable segment lengths l1, l2, and l3, and recalculate the current distribution. If it is determined that the sheath induced voltage meets the preset voltage requirements, the current cable core current and sheath circulating current are the calculation results of the parallel cable current distribution under the cross-connected grounding method, and the current number of cables, cable cross-section, cable arrangement method, and cable segment length are the optimal cable distribution structure.

[0113] The above method comprehensively considers the load current, cross-connected unit core voltage drop and metal sheath circulating current, and cable core current distribution under the cross-connected grounding mode, which can effectively evaluate the core current and metal sheath circulating current distribution, ensure the long-term stable operation of the cable, and realize the reliable transmission of electric energy.

[0114] Based on the same technical solution, the present invention also discloses a software system of the above method, a parallel cable current distribution calculation system under a cross-connected grounding mode, comprising:

[0115] Impedance matrix construction module: Constructs the impedance matrix of parallel cables under the cross-connection grounding mode according to the number of cables, cable cross-sections, cable arrangement and cable segment lengths in the cross-connection unit.

[0116] Calculation model acquisition module: obtains the current distribution calculation model according to the impedance matrix.

[0117] Current calculation module: Calculate the cable core current and sheath circulating current based on the current distribution calculation model.

[0118] Verification module: In response to the cable core current meeting the preset current requirement and the sheath induced voltage obtained according to the sheath circulating current meeting the preset voltage requirement, the current cable core current and the sheath circulating current are the parallel cable current distribution calculation results under the cross-connected grounding method.

[0119] The data processing flow and method of each module in the above software system are consistent and will not be repeated here.

[0120] Based on the same technical solution, the present invention also discloses a computer-readable storage medium storing one or more programs, wherein the one or more programs include instructions, which, when executed by a computing device, enable the computing device to perform a method for calculating the current distribution of parallel cables under a cross-connected grounding method.

[0121] Based on the same technical solution, the present invention also discloses a computing device, including one or more processors, one or more memories and one or more programs, wherein the one or more programs are stored in the one or more memories and are configured to be executed by the one or more processors, and the one or more programs include instructions for executing a method for calculating the current distribution of parallel cables under a cross-connected grounding method.

[0122] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0123] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0124] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0125] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0126] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A method for calculating the current distribution of parallel cables under a cross-connected grounding mode, characterized in that: include: According to the number of cables, cable cross-sections, cable arrangement and cable segment length in the cross-connection unit, the impedance matrix of the parallel cables under the cross-connection grounding mode is constructed; there are three cross-connection units, and the impedance matrix of the parallel cables under the cross-connection grounding mode is: Y 6n×6n =A·(l1·Z 6n×6n +l2·P·Z6′ n×6n ·Q+l3·P 2 ·Z6″ n×6n Q 2 )-(R1+R e +R2)·B;Y 6n×6n is the impedance matrix, n is the number of parallel cables in the cross-connection unit, l1, l2, l3 are the lengths of the three cable segments in the cross-connection unit, Z 6n×6n 、Z6′ n×6n 、Z6″ n×6n are the impedance matrices of the three cables in the cross-connection unit, R1 and R2 are the grounding resistances at both ends of the cable, R e is the earth leakage resistance, They are the voltage and current transformation matrices of the cross-connected cables, is the identity matrix, is a zero matrix, is a fully unimodular matrix, is the voltage elimination matrix of the same phase, is the sheath induced voltage elimination matrix; According to the impedance matrix, a current distribution calculation model is obtained; Calculate the cable core current and sheath circulating current according to the current distribution calculation model; In response to the cable core current meeting the preset current requirement and the sheath induced voltage obtained according to the sheath circulating current meeting the preset voltage requirement, the current cable core current and the sheath circulating current are the calculation results of the parallel cable current distribution under the cross-connected grounding mode.

2. The method for calculating the current distribution of parallel cables in a cross-connected grounding mode according to claim 1, characterized in that: The current distribution calculation model is: Among them, C 3×3 , D 3×(6n-3) , G (6n-3)×3 and H (6n-3)×(6n-3) Y 6n×6n The sub-matrix of J 3×(6n-3) To eliminate I A1 ,I B1 ,I C1 Change matrix of impact items I Ai ,I Bi ,I Ci They are the A-phase load current, B-phase load current and C-phase load current of the core line loop of the i-th cable line, i=2~n; I Asj ,I Bsj ,I Csj They are the A-phase current, B-phase current and C-phase current of the sheath loop of the j-th cable line, j=1~n; I A =I A1 +…+I Aj …+I An 、I B =I B1 +…+I Bj …+I Bn 、I C =I C1 +…+I Cj …+I Cn for A, B and C phase load currents of parallel cables in cross-connected grounding mode.

3. The method for calculating the current distribution of parallel cables in a cross-connected grounding mode according to claim 2 is characterized in that: The calculation formula for cable core current and sheath circulating current is: Cable core current I Ai ,I Bi ,I Ci and sheath circulation I Asj ,I Bsj ,I Csj The calculation formula is: Cable core current I A1 ,I B1 ,I C1 The calculation formula is:

4. The method for calculating the current distribution of parallel cables in a cross-connected grounding mode according to claim 1, characterized in that: In response to the cable core current not meeting the preset current requirement, adjusting the cable arrangement, or increasing the number of cables and the cable cross-section, and recalculating the current distribution; In response to the sheath induced voltage obtained according to the sheath circulating current not meeting the preset voltage requirement, the cable section length is reduced and the current distribution calculation is performed again.

5. The method for calculating the current distribution of parallel cables in a cross-connected grounding mode according to claim 1 or 4, characterized in that: The preset current requirement is: The maximum non-uniform coefficient a is less than the threshold value, and max(I Amax ,I Bmax ,I Cmax ) is less than the maximum allowable current of each cable; in, I Amax =max(I A1 ,…,I An ) I Bmax =max(I B1 ,…,I Bn ) I Cmax =max(I C1 ,…,I Cn ) IN Amin =min(I A1 ,…,IN An ) IN Bmin =min(I B1 ,…,IN Bn ) IN Cmin =min(I C1 ,…,IN Cn ) I Aj ,I Bj ,I Cj They are the A-phase load current, B-phase load current and C-phase load current of the core line loop of the j-th cable line, j=2~n; I Amax ,I Amin I A1 ,…,I An The maximum and minimum values ​​in I Bmax ,I Bmin I B1 ,…,I Bn The maximum and minimum values ​​in I Cmax ,I Cmin I C1 ,…,I Cn The maximum and minimum values ​​in .

6. The method for calculating the current distribution of parallel cables in a cross-connected grounding mode according to claim 1 or 4, characterized in that: The preset voltage requirement is: the sheath induced voltage exceeds the limit.

7. A parallel cable current distribution calculation system under a cross-connected grounding mode, characterized in that: include: Impedance matrix construction module: According to the number of cables, cable cross-section, cable arrangement and cable segment length in the cross-connection unit, the impedance matrix of the parallel cables under the cross-connection grounding mode is constructed; among them, there are three cross-connection units, and the impedance matrix of the parallel cables under the cross-connection grounding mode is: Y 6n×6n =A·(l1·Z 6n×6n +l2·P·Z′ 6n×6n ·Q+l3·P 2 ·Z″ 6n×6n Q 2 )-(R1+R e +R2)·B;Y 6n×6n is the impedance matrix, n is the number of parallel cables in the cross-connection unit, l1, l2, l3 are the lengths of the three cable segments in the cross-connection unit, Z 6n×6n , Z′ 6n×6n , Z″ 6n×6n are the impedance matrices of the three cables in the cross-connection unit, R1 and R2 are the grounding resistances at both ends of the cable, R e is the earth leakage resistance, They are the voltage and current transformation matrices of the cross-connected cables, is the identity matrix, is a zero matrix, is a fully unimodular matrix, is the voltage elimination matrix of the same phase, is the sheath induced voltage elimination matrix; Calculation model acquisition module: obtains the current distribution calculation model according to the impedance matrix; Current calculation module: calculates the cable core current and sheath circulating current according to the current distribution calculation model; Verification module: In response to the cable core current meeting the preset current requirement and the sheath induced voltage obtained according to the sheath circulating current meeting the preset voltage requirement, the current cable core current and the sheath circulating current are the parallel cable current distribution calculation results under the cross-connected grounding method.

8. A computer-readable storage medium storing one or more programs, characterized in that: The one or more programs include instructions which, when executed by a computing device, cause the computing device to perform any one of the methods according to claims 1 to 6.

9. A computing device, characterized in that include: One or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and are configured to be executed by the one or more processors, and the one or more programs include instructions for executing any of the methods according to claims 1 to 6.

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