Cable electrical parameter calculation method, system and device considering influence of backflow cable and storage medium

Abstract

The invention discloses a cable electrical parameter calculation method, system and device considering the influence of a backflow cable and a storage medium. The cable electrical parameter calculation method adopted by the invention comprises the following steps: obtaining structure parameters and material parameters of a cable and a backflow cable; calculating a series impedance matrix including the cable and the backflow cable according to the structure parameters and the material parameters of the cable and the backflow cable; obtaining a voltage drop equation according to the series impedance matrix; and in combination with the installation condition of double-end grounding of the on-site backflow cable, a voltage drop equation is simplified, and cable electrical parameters including positive-sequence resistance, positive-sequence reactance, zero-sequence resistance and zero-sequence reactance are obtained. According to the method, the current coupling influence of the backflow cable and each phase cable is considered, accurate calculation of the electrical parameters of the cable with the backflow cable is realized, and the universality is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of power transmission and distribution of electric power systems, and in particular to a method, system, device and storage medium for calculating electrical parameters of cables taking into account the influence of return cables. Background Art

[0002] As urban electricity consumption continues to increase, higher requirements are placed on the power transmission capacity of the power grid, and cable lines with return cables are increasingly in operation. The parameters of the on-site cable lines are affected by their laying methods. The cable parameters under different laying methods vary significantly, especially the zero-sequence parameters. However, during the on-site infrastructure line parameter measurement test, due to the tight construction period, there is a situation where the return cable is not laid underground. Therefore, it is necessary to make a theoretical judgment on the on-site measured cable parameters. The power frequency sequence parameters of the cable line are an important basis for the design, operation and relay protection of the power system, and directly affect the calculation of the protection setting value of the dispatching operation. Protection misoperation events caused by incorrect line parameter results obtained from the cable parameter measurement test during the infrastructure stage often occur. Therefore, it is of great significance to study the cable parameter calculation method suitable for return cables.

[0003] At present, the calculation method of single-circuit cable line parameters has become relatively mature. Lin Guihui et al. studied the calculation of parallel two-circuit cable sequence parameters when the metal sheath is grounded at two points and at one point in "Power System Protection and Control" in "Electrical Parameters and Unbalance Analysis of 220kV Multi-circuit Cable Lines Based on Carson Theory and EMTP"; Xu Zheng and Qian Jie compared the "Different Calculation Methods and Comparison of Cable Electrical Parameters" in "High Voltage Technology" and the cable electrical parameters calculated by the Carson-Clem formula, "Power System Modeling and Fault Analysis", and the power_cableparam function in MATLAB, indicating that the Carson-Clem formula is the best in terms of accuracy and versatility.

[0004] Xu Zheng et al. studied the cable parameters under the submarine cable sheath and armor grounding methods in the "Calculation of Electrical Parameters in Harmonic Frequency Bands" in "Automation of Electric Power Systems", and considered the cable electrical parameter characteristics during harmonic analysis; Zhang Junqiang et al. compared the optimized layout of the 330kV cable return cable in the "Research on Cross-Interconnected Grounding Methods of Long-Distance 330kV Cable Sheaths and Optimal Layout of Return Cables" in "High Voltage Electrical Appliances", and found that the optimized layout of the 330kV cable return cable has an inhibitory effect on the cable sheath induced voltage during faults and the circulating current during steady-state operation.

[0005] In general, the increasingly widespread application of cable lines and the continuous installation of relay protection instruments have put forward higher requirements for the accurate calculation of cable parameters. However, the current calculation of cable parameters does not take into account the laying of return cables. Summary of the invention

[0006] In view of the above problems in the prior art, the present invention provides a cable electrical parameter calculation method which effectively considers the influence of the return cable, so that the calculation is accurate and has strong applicability.

[0007] To this end, the present invention adopts the following technical solution.

[0008] In a first aspect, the present invention provides a method for calculating electrical parameters of a cable taking into account the influence of a return cable, comprising:

[0009] Obtain the structural parameters and material parameters of the cable and return cable;

[0010] According to the structural parameters and material parameters of the cable and the return cable, the series impedance matrix including the cable and the return cable is calculated;

[0011] According to the series impedance matrix, the voltage drop equation is obtained;

[0012] Combined with the installation condition of double-end grounding of the return cable on site, the voltage drop equation is simplified to obtain the cable electrical parameters, which include positive-sequence resistance, positive-sequence reactance, zero-sequence resistance and zero-sequence reactance.

[0013] Further, the cable comprises a single-phase core, an inner insulating layer, a metal sheath and an outer insulating layer arranged from inside to outside;

[0014] The structural parameters of the cable include the outer diameter of the single-phase core, the outer diameter of the inner insulation layer, the outer diameter of the metal sheath and the outer diameter of the outer insulation layer;

[0015] The material parameters of the cable include single-phase core resistivity, relative dielectric constant of inner insulation layer, resistivity of metal sheath and relative dielectric constant of outer insulation layer;

[0016] The return cable comprises a return cable core and an insulation layer arranged from inside to outside;

[0017] The structural parameters of the return cable include the outer diameter of the return cable core and the outer diameter of the insulation layer;

[0018] The material parameters of the return cable include the return cable core resistivity and the relative dielectric constant of the insulation layer.

[0019] Furthermore, the calculation step of the series impedance matrix includes:

[0020] Calculate the single-phase core DC resistance R at a given temperature dc1 , Metal sheath DC resistance R dc2 and the return cable core DC resistance R dc3 ;

[0021] Calculate the intermediate variable z1 of the single-phase core, the intermediate variable z2 of the metal sheath and the intermediate variable z3 of the return cable core;

[0022] Calculate the skin effect coefficient k of the single-phase line core based on z1, z2 and z3 s1 , Metal sheath skin effect coefficient k s2 , Skin effect coefficient k of return cable core s3 ;

[0023] Calculate the proximity effect coefficient k of the single-phase line core p1 , Metal sheath proximity effect coefficient k p2 and the proximity effect coefficient k of the return cable core p3 ;

[0024] According to R dc1 , k s1 and k p1 Calculate the single-phase line core AC resistance R ac1 According to R dc2 , k s2 and k p2 Calculate the metal sheath AC resistance R ac2 According to R dc3 , k s3 and k p3 Calculate the return cable core AC resistance R ac3 ;

[0025] According to R ac1 , R ac2 and R ac3 Calculate the self-impedance Z of the "single-phase core-earth" loop cc , the self-impedance Z of the "return cable core-earth" loop hh , when the return cable core and the single-phase core are in different phases, the mutual impedance Z between the "return cable core-earth" loop and the "single-phase core-earth" loop ch ;

[0026] According to the self-impedance Z of the "single-phase core-earth" loop cc , the self-impedance Z of the "return cable core-earth" loop hh , when the return cable core and the single-phase core are in different phases, the mutual impedance Z between the "return cable core-earth" loop and the "single-phase core-earth" loop ch , the series impedance matrix Z is constructed according to the following formula;

[0027]

[0028] Where Z is the series impedance matrix; Z cAcA Represents the self-impedance of the A phase core; Z cAcB Represents the mutual impedance between the A phase core and the B phase core; Z cAcC Represents the mutual impedance between the A phase core and the C phase core; Z cAh Represents the mutual impedance between the A phase core and the return cable core; Z cBcARepresents the mutual impedance between the B phase core and the A phase core; Z cBcB Represents the self-impedance of the B phase core; Z cBcC Represents the mutual impedance between the B-phase core and the C-phase core; Z cBh Represents the mutual impedance between the B phase core and the return cable core; Z cCcA Represents the mutual impedance between the C phase core and the A phase core; Z cCcB Represents the mutual impedance between the C phase core and the B phase core; Z cCcC Represents the self-impedance of the C phase core; Z cCh Represents the mutual impedance between the C phase core and the return cable core.

[0029] Furthermore, the single-phase core DC resistance R dc1 The calculation formula is as follows:

[0030]

[0031] Where ρ is the core resistivity; A is the nominal cross-sectional area of ​​the core; T is the core temperature; α 20 is the temperature coefficient of resistance; T0 = 20°C;

[0032] Metal sheath DC resistance R dc2 and the return cable core DC resistance R dc3 The calculation formula is the same as R dc1 The metal sheath is considered as the wire core during calculation.

[0033] According to the single-phase core DC resistance R dc1 Calculate the single-phase line core AC resistance R ac1 :

[0034] R ac1 =R dc1 (1+k s1 +k p1 ),

[0035] Among them, k s1 is the skin effect coefficient of the single-phase line core; k p1 is the single-phase line core proximity effect coefficient;

[0036] Metal sheath AC resistance R ac2 and the return cable core AC resistance R ac3 The calculation formula is the same as R ac1 The metal sheath is considered as the wire core during calculation.

[0037] The single-phase line core intermediate variable z1 is calculated by the following formula:

[0038]

[0039] Where, f is the current frequency; a zIt is a constant that characterizes the skin effect of different types of wire cores;

[0040] The skin effect coefficient k of the single-phase core is calculated by the following formula s1 :

[0041]

[0042] For single-core cables, the single-phase core proximity effect coefficient k p1 =0; For three-core cables, the single-phase core proximity effect coefficient k is calculated by the following formula p1 :

[0043]

[0044] Among them, d c is the diameter of the wire core; S ij is the interaxial distance between core i and core j; a p is a constant that characterizes the proximity effect.

[0045] Metal sheath intermediate variable z2, metal sheath skin effect coefficient k s2 and metal sheath proximity effect coefficient k p2 The calculation formulas are respectively the same as z1 and k s1 , k p1 same.

[0046] The intermediate variable z3 of the return cable core and the skin effect coefficient k of the return cable core s3 and the proximity effect coefficient k of the return cable core p3 The calculation formulas are respectively the same as z1 and k s1 , k p1 same.

[0047] Furthermore, the self-impedance Z of the “single-phase core-earth” loop cc , calculated by the following formula:

[0048]

[0049] In the formula, j is an imaginary unit;

[0050] The loop self-impedance Z of "return cable core-earth" is calculated by the following formula hh :

[0051]

[0052] The mutual impedance Z between the "return cable core-earth" loop and the "single-phase core-earth" loop when the return cable core and the single-phase core are in different phases is calculated by the following formula ch :

[0053]

[0054] The F(r) is calculated by the following formula oc ,r ic ) and F(r oh ,r ih ):

[0055]

[0056] Among them, r c is the AC resistance of the single-phase core per unit length; r h is the AC resistance per unit length of the return cable core; r e is the earth equivalent resistance per unit length, r e =π 2 f10 -4 , f is the current frequency; D e is the virtual core equivalent depth when the earth is used as the loop, ρ e Represents the earth resistivity; r ic 、r oc are the inner and outer radii of the single-phase core respectively. At this time, the inner diameter of the single-phase core r ic Take 0; r ih 、r oh are the inner and outer radii of the return cable core respectively. At this time, the inner diameter of the return cable core is r ih Take 0; D is the distance between the single-phase core of each phase and the return cable core; ln is the natural logarithmic function.

[0057] Furthermore, according to the series impedance matrix, the voltage drop equation is obtained as follows:

[0058]

[0059] Where U cA Indicates the voltage across the A phase core of a unit length cable; U cB Indicates the voltage across the B phase core of the cable per unit length; U cC Indicates the voltage across the C phase core of the cable per unit length; U h Indicates the voltage at both ends of the return cable; I cA Indicates the current flowing through the metal sheath of phase A of the cable; I cB Indicates the current flowing through the cable B phase metal sheath; I cC Indicates the current flowing through the metal sheath of phase C of the cable; I h Indicates the current flowing through the return cable;

[0060] Combined with the on-site installation conditions, since both ends of the return cable are directly grounded, the grounding resistance at both ends is ignored, so U h =0 is substituted into the voltage drop equation, and its matrix block form is as follows:

[0061] Expand to get the following equation:

[0062] U c =Z cc I c +Z ch I h ,

[0063]

[0064] Eliminate I h After that, the simplified voltage drop equation is:

[0065]

[0066] Where U c Indicates the voltage across the single-phase core of a three-core cable; I c Indicates the current flowing through the three-core cable; Z ch Represents the mutual impedance of the return cable and the three-core cable.

[0067] Furthermore, the sequence impedance matrix (Z c ) 120 :

[0068]

[0069] in, a=e j120° ,

[0070] Sequence impedance matrix (Z c ) 120 The main diagonal element Z 11 The real and imaginary parts are the positive sequence resistance and reactance, and the sequence impedance matrix (Z c ) 120 The main diagonal element Z 33 The real and imaginary parts are the zero-sequence resistance and zero-sequence reactance.

[0071] In a second aspect, the present invention provides a cable electrical parameter calculation system taking into account the influence of the return cable, comprising:

[0072] Parameter acquisition unit: used to obtain the structural parameters and material parameters of the cable and return cable;

[0073] Series impedance matrix calculation unit: used to calculate the series impedance matrix including the cable and the return cable according to the structural parameters and material parameters of the cable and the return cable;

[0074] Voltage drop equation acquisition unit: obtains the voltage drop equation according to the series impedance matrix;

[0075] Cable electrical parameter acquisition unit: Combined with the installation condition of double-end grounding of the return cable on site, the voltage drop equation is simplified to obtain the cable electrical parameters, including positive-sequence resistance, positive-sequence reactance, zero-sequence resistance and zero-sequence reactance.

[0076] In a third aspect, the present invention provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the cable electrical parameter calculation method when executing the computer program.

[0077] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the cable electrical parameter calculation method.

[0078] Based on the above technical solution, the present invention has the following beneficial technical effects:

[0079] 1. For cables with return cables, the present invention realizes accurate calculation of electrical parameters of cables with return cables based on the voltage drop equation, which can provide a certain reference for future engineering design.

[0080] 2. The present invention has strong versatility and takes into account the current coupling effect of the return cable and each phase cable. It is not only suitable for the parameter calculation of single-return return cables, but also suitable for the parameter calculation of multi-return return cables. It has no special requirements on the arrangement of the cable body and the return cable, and is suitable for engineering practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 It is a schematic diagram of the cable loop system with return cable;

[0082] Figure 2a It is a schematic diagram of the structural cross section of the cable;

[0083] Figure 2b It is a schematic diagram of the structural cross section of the return cable;

[0084] Figure 3 The diagram is a schematic diagram of the arrangement of cables and return cables arranged in a straight line;

[0085] Figure 4 The diagram is a schematic diagram of the arrangement of cables and return cables in a "pin" shape;

[0086] Figure 5a It is a schematic diagram of the corresponding positive sequence resistance of the cables and return cables arranged in a straight line;

[0087] Figure 5b It is a schematic diagram of the corresponding positive sequence reactance of the "one"-arranged cable and the return cable;

[0088] Figure 5cIt is a schematic diagram of the corresponding positive sequence impedance of the cables and return cables arranged in a straight line;

[0089] Figure 5d It is a schematic diagram of the corresponding zero-sequence resistance of the cables and return cables arranged in a straight line;

[0090] Figure 5e It is a schematic diagram of the corresponding zero-sequence reactance of the "one"-arranged cable and the return cable;

[0091] Figure 5f It is a schematic diagram of the corresponding zero-sequence impedance of the cables and return cables arranged in a straight line;

[0092] Figure 6a It is a schematic diagram of the corresponding positive sequence resistance of the cable and return cable arranged in a "pin" shape;

[0093] Figure 6b It is a schematic diagram of the corresponding positive sequence reactance of the "pin"-arranged cable and the return cable;

[0094] Figure 6c It is a schematic diagram of the corresponding positive sequence impedance of the cable and return cable arranged in a "pin" shape;

[0095] Figure 6d It is a schematic diagram of the corresponding zero-sequence resistance of the cable and return cable arranged in a "pin" shape;

[0096] Figure 6e It is a schematic diagram of the corresponding zero-sequence reactance of the "pin"-arranged cable and the return cable;

[0097] Figure 6f It is a schematic diagram of the corresponding zero-sequence impedance of the cable and return cable arranged in a "pin" shape;

[0098] Figure 7 A flow chart of a method for calculating electrical parameters of a cable taking into account the influence of a return cable according to the present invention;

[0099] Figure 8 The structure diagram of the cable electrical parameter calculation system considering the influence of the return cable of the present invention;

[0100] Fig. 9 A schematic diagram of a logical structure of a computer device provided in Embodiment 4 of the present invention;

[0101] Figure 1 Middle,U cA Indicates the voltage across the A phase core of a unit length cable; U sA Indicates the voltage across the metal sheath of phase A of the cable per unit length; U cB Indicates the voltage across the B phase core of the cable per unit length; U sB Indicates the voltage across the metal sheath of phase B of the cable per unit length; U cC Indicates the voltage across the C phase core of the cable per unit length; UsC It indicates the voltage across the C-phase metal sheath of the cable per unit length; I cA Indicates the current flowing through the metal sheath of phase A of the cable; I sA Indicates the current flowing through the cable A phase core; I cB Indicates the current flowing through the cable B phase metal sheath; I sB Indicates the current flowing through the cable B phase core; I cC Indicates the current flowing through the metal sheath of phase C of the cable; I sC Indicates the current flowing through the C phase core of the cable; I h Indicates the current flowing through the return cable; U h Indicates the voltage across the return cable. DETAILED DESCRIPTION

[0102] In order to facilitate the understanding of the present invention, the present invention is described in more detail below in conjunction with the accompanying drawings and specific embodiments. Preferred embodiments of the present invention are provided in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0103] It should be noted that, unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0104] Example 1

[0105] This embodiment provides a method for calculating the electrical parameters of a cable taking into account the influence of a return cable. Figure 7 As shown, the steps are as follows:

[0106] 1) Obtain the structural parameters and material parameters of the cable and return cable;

[0107] 2) Calculate the series impedance matrix including the cable and the return cable according to the structural parameters and material parameters of the cable and the return cable;

[0108] 3) Obtain the voltage drop equation based on the series impedance matrix;

[0109] 4) Combined with the installation conditions of double-end grounding of the return cable on site, the voltage drop equation is simplified to obtain the cable electrical parameters, including positive-sequence resistance, positive-sequence reactance, zero-sequence resistance and zero-sequence reactance.

[0110] The cable includes a single-phase core, an inner insulating layer, a metal sheath and an outer insulating layer arranged from the inside to the outside; the structural parameters of the cable include the outer diameter of the single-phase core, the outer diameter of the inner insulating layer, the outer diameter of the metal sheath and the outer diameter of the outer insulating layer; the material parameters of the cable include the resistivity of the single-phase core at 90°C, the relative dielectric constant of the inner insulating layer, the resistivity of the metal sheath at 70°C and the relative dielectric constant of the outer insulating layer.

[0111] The return cable includes a return cable core and an insulation layer arranged from inside to outside; the structural parameters of the return cable include the outer diameter of the return cable core and the outer diameter of the insulation layer; the material parameters of the return cable include the resistivity of the return cable core at 90°C and the relative dielectric constant of the insulation layer.

[0112] The calculation steps of the series impedance matrix include:

[0113] Calculate the single-phase core DC resistance R at a given temperature dc1 , Metal sheath DC resistance R dc2 and the return cable core DC resistance R dc3 ;

[0114] Calculate the single-phase line core AC resistance R at a given temperature ac1 , Metal sheath AC resistance R ac2 and the return cable core AC resistance R ac3 ;

[0115] Calculate the intermediate variable z1 of the single-phase line core and the skin effect coefficient k of the single-phase line core s1 and single-phase line core proximity effect coefficient k p1 ;

[0116] Calculate the metal sheath intermediate variable z2 and the metal sheath skin effect coefficient k s2 and metal sheath proximity effect coefficient k p2 ;

[0117] Calculate the intermediate variable z3 of the return cable core and the skin effect coefficient k of the return cable core s3 and the proximity effect coefficient k of the return cable core p3 ;

[0118] Calculate the self-impedance Z of the "single-phase core-earth" loop cc , the self-impedance Z of the "return cable core-earth" loop hh , when the return cable core and the single-phase core are in different phases, the mutual impedance Z between the "return cable core-earth" loop and the "single-phase core-earth" loop ch .

[0119] Specifically, the single-phase core DC resistance R dc1 The calculation formula is as follows:

[0120]

[0121] Where ρ is the core resistivity; A is the nominal cross-sectional area of ​​the core; T is the core temperature; α 20 is the temperature coefficient of resistance; T0 = 20°C;

[0122] Metal sheath DC resistance R dc2 and the return cable core DC resistance R dc3 The calculation formula is the same as R dc1 The metal sheath is considered as the wire core during calculation.

[0123] According to the single-phase core DC resistance R dc1 Calculate the single-phase line core AC resistance R ac1 :

[0124] R ac1 =R dc1 (1+k s1 +k p1 ),

[0125] Among them, k s1 is the skin effect coefficient of the single-phase line core; k p1 is the single-phase line core proximity effect coefficient;

[0126] Metal sheath AC resistance R ac2 and the return cable core AC resistance R ac3 The calculation formula is the same as R ac1 The metal sheath is considered as the wire core during calculation.

[0127] The single-phase line core intermediate variable z1 is calculated by the following formula:

[0128]

[0129] Where, f is the current frequency; a z It is a constant that characterizes the skin effect of different types of wire cores; when the wire core is a copper core stranded / sector conductor, a z =1, when the core is a bow-shaped / split conductor a z =0.43.

[0130] The skin effect coefficient k of the single-phase core is calculated by the following formula s1 :

[0131]

[0132] For single-core cables, the single-phase core proximity effect coefficient k p1 =0; For three-core cables, the single-phase core proximity effect coefficient k is calculated by the following formula p1 :

[0133]

[0134] Among them, d c is the diameter of the wire core; S ij is the interaxial distance between core i and core j; a p is a constant that characterizes the proximity effect; for a stranded copper / aluminum conductor a p =0.8, for split conductor a p =0.37.

[0135] Metal sheath intermediate variable z2, metal sheath skin effect coefficient k s2 and metal sheath proximity effect coefficient k p2 The calculation formulas are respectively the same as z1 and k s1 , k p1 same.

[0136] The intermediate variable z3 of the return cable core and the skin effect coefficient k of the return cable core s3 and the proximity effect coefficient k of the return cable core p3 The calculation formulas are respectively the same as z1 and k s1 , k p1 same.

[0137] The elements of the series impedance matrix Z are described below.

[0138] The self-impedance Z of the "single-phase core-earth" loop cc (Ω / km), calculated by the following formula:

[0139]

[0140] The self-impedance Z of the "return cable core-earth" loop is calculated by the following formula hh (Ω / km):

[0141]

[0142] The mutual impedance Z between the "return cable core-earth" loop and the "single-phase core-earth" loop when the return cable core and the single-phase core are in different phases is calculated by the following formula ch (Ω / km):

[0143]

[0144] The F(r) is calculated by the following formula oc ,r ic ) and F(r oh ,r ih ):

[0145]

[0146] Among them, r c is the AC resistance of the single-phase core per unit length; r h is the AC resistance per unit length of the return cable core; r e is the earth equivalent resistance per unit length, r e =π 2 f10 -4 , f is the current frequency; D e is the virtual core equivalent depth when the earth is used as the loop, ρ e Represents the earth resistivity; r ic 、r oc are the inner and outer radii of the single-phase core respectively. At this time, the inner diameter of the single-phase core r ic Take 0; r ih 、r oh are the inner and outer radii of the return cable core respectively. At this time, the inner diameter of the return cable core is r ih Take 0; D is the distance between the single-phase core of each phase and the return cable core; ln is the natural logarithmic function.

[0147] Specifically, the cable voltage drop equation is written as follows:

[0148]

[0149] Where U cA Indicates the voltage across the A phase core of a unit length cable; U cB Indicates the voltage across the B phase core of the cable per unit length; U cC Indicates the voltage across the C phase core of the cable per unit length; U h Indicates the voltage at both ends of the return cable; I cA Indicates the current flowing through the metal sheath of phase A of the cable; I cB Indicates the current flowing through the cable B phase metal sheath; I cC Indicates the current flowing through the metal sheath of phase C of the cable; I h Represents the current flowing through the return cable; Z cAcA Represents the self-impedance of the A phase core; Z cAcB Represents the mutual impedance between the A phase core and the B phase core; Z cAcC Represents the mutual impedance between the A phase core and the C phase core; Z cAh Represents the mutual impedance between the A phase core and the return cable core; Z cBcA Represents the mutual impedance between the B phase core and the A phase core; Z cBcB Represents the self-impedance of the B phase core; Z cBcC Represents the mutual impedance between the B-phase core and the C-phase core; Z cBh Represents the mutual impedance between the B phase core and the return cable core; Z cCcA Represents the mutual impedance between the C phase core and the A phase core; Z cCcBRepresents the mutual impedance between the C phase core and the B phase core; Z cCcC Represents the self-impedance of the C phase core; Z cCh Represents the mutual impedance between the C phase core and the return cable core; Z hcA Represents the mutual impedance between the return cable core and the A phase core; Z hcB Represents the mutual impedance between the return cable core and the B phase core; Z hcC It represents the mutual impedance between the return cable core and the C phase core;

[0150] Combined with the on-site installation conditions, the return cable is directly grounded at both ends, and the grounding resistance at both ends is ignored. h =0 and substitute it into the voltage drop equation:

[0151] U c =Z cc I c +Z ch I h ,

[0152]

[0153] Eliminate I h After that, the simplified voltage drop equation is:

[0154]

[0155] Where U c Indicates the voltage across the single-phase core of a three-core cable; I c Indicates the current flowing through the three-core cable; Z ch Represents the mutual impedance of the return cable and the three-core cable.

[0156] Furthermore, the impedance matrix Z is obtained by the following formula: cABC and sequence impedance matrix (Z c ) 120 :

[0157]

[0158] (Z c ) 120 =H -1 Z cABC H,

[0159] in, °

[0160] a=e j120 ,

[0161] Sequence impedance matrix (Z c ) 120 The main diagonal element Z 11The real and imaginary parts are the positive sequence resistance and reactance, and the sequence impedance matrix (Z c ) 120 The main diagonal element Z 33 The real and imaginary parts are the zero-sequence resistance and zero-sequence reactance.

[0162] The above cable electrical parameter calculation method is used in the following applications.

[0163] Application: Cable loop system with return cable, see Figure 1 The cable is ABC three-phase single-core cable, model is YJLW-127 / 220kV-1×2500mm 2 ; The return cable is a single-core cable, model is YJV-6.0 / 10kV-1×400mm 2 The structural cross-section of the cable and return cable is shown in Figure 2. The structural parameters and material parameters of the cable and return cable are shown in Table 1. Resistance temperature coefficient α 20 The typical values ​​of the cable core resistivity at 20°C are shown in Table 2. The arrangement of the “one” arrangement cable and return cable is shown in Figure 3 The arrangement of the cables and return cables is shown in Figure 4 .

[0164] Table 1

[0165]

[0166] Table 2 Typical values ​​of resistance temperature coefficient and resistivity

[0167] Material <![CDATA[Temperature coefficient of resistance α 20 / ℃ -1 > Resistivity ρ / (Ω / m) copper <![CDATA[3.93×10 -3 ]]> <![CDATA[1.7241×10 -8 ]]> aluminum <![CDATA[4.03×10 -3 ]]> <![CDATA[2.8264×10 -8 ]]> lead <![CDATA[4×10 -3 ]]> <![CDATA[21.4×10 -8 ]]> bronze <![CDATA[3×10 -3 ]]> <![CDATA[3.5×10 -8 ]]> iron <![CDATA[4.5×10 -3 ]]> <![CDATA[13.8×10 -8 ]]> Stainless steel 0 <![CDATA[70×10 -8 ]]>

[0168] Cable core ρ=1.8e -8 Ω / m; A=0.00345237m 2 ; T = 20 ° C; get:

[0169] Cable core R dc1 =0.0052138Ω;

[0170] Take f = 50Hz, a z =1, we get z1=4.9093856; k s1 =1.0049225; k p1 =1;

[0171] Cable core R ac1 =0.015667Ω.

[0172] Cable metal sheath ρ=2.65e -8 Ω / m; A=0.016856m 2 ; T = 20 ° C; get:

[0173] Cable Metal Sheath R dc2 =0.001572Ω;

[0174] Take f = 50Hz, a z =1, we get z2=8.94055667; k s2 =2.431957; k p2 =0.02078;

[0175] Cable core R ac2 =0.005428Ω.

[0176] Return cable core ρ=1.8e -8 Ω / m; A=0.00039973m 2 ; T = 20 ° C; get:

[0177] Return cable core R dc3 =0.04503025Ω;

[0178] Take f = 50Hz, a z =1, we get z3=1.6705; k s3 =0.039286; k p3 =1;

[0179] Return cable core R ac3 =0.09183Ω.

[0180] Cable core c =0.015667Ω; r e =0.049348Ω; AB spacing 0.5m, BC spacing 0.5m, AC spacing 1m, A phase and return cable spacing 1.15m, B phase and return cable spacing 0.65m, C phase and return cable spacing 0.15m; get:

[0181] Z cAcA =Z cBcB =Z cCcC =0.065015+0.6595i;

[0182] Z cAcB =Z cBcA =0.049348+0.473247i;

[0183] Z cAcC =Z cCcA =0.049348+0.429695i;

[0184] Z cAh =Z hcA =0.049348+0.4209138i;

[0185] Z cBcC =Z cCcB =0.049348+0.47325i;

[0186] Z cBh =Z hcB =0.049348+0.45676i;

[0187] Z cCh =Z hcC =0.049348+0.548895i;

[0188] Z hh =0.14118+0.72719i.

[0189] therefore

[0190] Z=[0.065015+0.6595i, 0.049348+0.473247i, 0.049348+0.429695i, 0.049348+0.4209138i;

[0191] 0.049348+0.473247i, 0.065015+0.6595i, 0.049348+0.47325i, 0.049348+0.45676i;

[0192] 0.049348+0.429695i, 0.049348+0.47325i, 0.065015+0.6595i, 0.049348+0.548895i;

[0193] 0.049348+0.4209138i, 0.049348+0.45676i, 0.049348+0.548895i, 0.14118+0.72719i]

[0194] Combined with U h =0, simplifying to get:

[0195] Z cABC =[0.05492+0.4172i 0.0408+0.2105i 0.04474+0.1144i;

[0196] 0.04079+0.21055i 0.05832+0.3746i 0.04746+0.13146i

[0197] 0.04474+0.11444i 0.04746+0.13146i 0.07011+0.2495i]

[0198] because

[0199] a=-0.50+0.866i;

[0200] H = [1, 1, 1;

[0201] -0.50-0.866i, -0.50+0.866i, 1;

[0202] -0.50+0.866i, -0.50-0.866i, 1]

[0203] so

[0204] (Z c ) 120 =[0.0168+0.1949i, -0.01934+0.01549i, -0.06853+0.04086i;

[0205] 0.0194+0.01324i, 0.01679+0.1949i, 0.0592+0.0500i;

[0206] 0.0592+0.04995i, -0.06853+0.04086i, 0.1500+0.6514i]

[0207] Sequence impedance matrix (Z c ) 120 The main diagonal element Z 11 The real and imaginary parts are the positive sequence resistance and positive sequence reactance, that is, the positive sequence resistance and positive sequence reactance are 0.0168 and 0.1949 respectively; the sequence impedance matrix (Z c ) 120 The main diagonal element Z 33 The real and imaginary parts are the zero-sequence resistance and zero-sequence reactance, that is, the positive-sequence resistance and positive-sequence reactance at this time are 0.1500 and 0.6514 respectively.

[0208] For the "one" arrangement, since the three phases ABC are horizontally symmetrical, the B phase cable core is selected as the origin of the horizontal coordinate, and the ABC three phase cable core is 1m above the ground. Combined with the common tunnel conditions in engineering projects, the return cable x coordinate is within 0~2m, and the corresponding positive and zero sequence parameters of the "one" arrangement cable and the return cable are shown in Figure 5.

[0209] As shown in Figure 5, for the "one"-shaped cable, the characteristic point x = 0.5m is the C-phase cable core. Between 0-0.5m, the positive-sequence parameter decreases first and then increases, and the minimum positive-sequence resistance is 0.01606Ω / km (x = 0.23m), and the zero-sequence parameter increases first and then decreases, and the maximum zero-sequence impedance is 0.6024Ω / km (x = 0.29m); between 0.5m and 2.0m, the positive and zero-sequence resistances decrease, and the positive and zero-sequence reactance and impedance increase. Considering the actual spatial dimensions of the cable and the return cable, when the return cable is close to the C-phase cable (x = 0.6m), the positive-sequence resistance is 0.01725Ω / km and the zero-sequence impedance is 0.6272Ω / km.

[0210] For the "pin" arrangement, there is also horizontal symmetry. The midpoint of phases A and C is selected as the origin of the horizontal coordinate, and the cable cores of phases A and C are 1m above the ground. Combined with the common tunnel conditions in engineering projects, the x-coordinate of the return cable is within 0 to 0.3m. The corresponding positive and zero sequence parameters of the "pin" arrangement cable and the return cable are shown in Figure 6.

[0211] As shown in Figure 6, for the "pin" arrangement of the cable, the characteristic point x = 0.08m is the C-phase cable core. Constrained by the actual spatial size of the cable, the return cable x ≥ 0.1m. At this time, the cable positive sequence resistance is negatively correlated with the distance between the return cable and the C-phase core, and the zero sequence impedance is positively correlated with the distance between the return cable and the C-phase core. Therefore, the greater the distance between the return cable and the C-phase core, the better. When the return cable is close to the C-phase cable (x = 0.1m), the positive sequence resistance is 0.01726Ω / km and the zero sequence impedance is 0.4063Ω / km; when the return cable is far away from the C-phase cable (x = 0.3m), the positive sequence resistance is 0.01575Ω / km and the zero sequence impedance is 0.7250Ω / km.

[0212] Example 2

[0213] This embodiment provides a cable electrical parameter calculation system taking into account the influence of the return cable. Figure 8 As shown, it includes:

[0214] Parameter acquisition unit: used to obtain the structural parameters and material parameters of the cable and return cable;

[0215] Series impedance matrix calculation unit: used to calculate the series impedance matrix including the cable and the return cable according to the structural parameters and material parameters of the cable and the return cable;

[0216] Voltage drop equation acquisition unit: obtains the voltage drop equation according to the series impedance matrix;

[0217] Cable electrical parameter acquisition unit: Combined with the installation condition of double-end grounding of the return cable on site, the voltage drop equation is simplified to obtain the cable electrical parameters, including positive-sequence resistance, positive-sequence reactance, zero-sequence resistance and zero-sequence reactance.

[0218] It should be noted that each unit in the above-mentioned cable electrical parameter calculation system considering the influence of the return cable can be fully or partially implemented by software, hardware and their combination. The above-mentioned units can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above-mentioned modules. For the specific definition of a cable electrical parameter calculation system considering the influence of the return cable, please refer to the definition of a cable electrical parameter calculation method considering the influence of the return cable above. The two have the same functions and effects, which will not be repeated here.

[0219] Example 3

[0220] This embodiment provides a computer device, comprising: at least one processor; and a memory connected to the at least one processor in communication. The memory stores a computer program executable by the at least one processor, and when the at least one processor executes the computer device, the computer program is used to cause the computer device to execute the method according to Embodiment 1 of the present invention.

[0221] Example 4

[0222] This embodiment provides a non-transitory computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor of a computer, is used to cause the computer to execute the method according to Embodiment 1 of the present invention.

[0223] refer to Fig. 9 The structural block diagram of the electronic device 400 that can be used as the server or client of the present invention will now be described, which is an example of a hardware device that can be applied to various aspects of the present invention. The electronic device is intended to represent various forms of digital electronic computer equipment, such as laptop computers, desktop computers, workbenches, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices and other similar computing devices. The components shown herein, their connections and relationships, and their functions are only examples, and are not intended to limit the implementation of the present invention described herein and / or required.

[0224] like Fig. 9As shown, the electronic device 400 includes a computing unit 401, which can perform various appropriate actions and processes according to a computer program stored in a read-only memory (ROM) 402 or a computer program loaded from a storage unit 408 into a random access memory (RAM) 403. In the RAM 403, various programs and data required for the operation of the electronic device 400 can also be stored. The computing unit 401, the ROM 402, and the RAM 403 are connected to each other via a bus 404. An input / output (I / O) interface 405 is also connected to the bus 404.

[0225] A plurality of components in the electronic device 400 are connected to the I / O interface 405, including: an input unit 406, an output unit 407, a storage unit 408, and a communication unit 409. The input unit 406 may be any type of device capable of inputting information to the electronic device 400, and the input unit 406 may receive input digital or character information, and generate key signal inputs related to user settings and / or function control of the electronic device. The output unit 407 may be any type of device capable of presenting information, and may include, but is not limited to, a display, a speaker, a video / audio output terminal, a vibrator, and / or a printer. The storage unit 408 may include, but is not limited to, a disk, an optical disk. The communication unit 409 allows the electronic device 400 to exchange information / data with other devices via a computer network such as the Internet and / or various telecommunication networks, and may include, but is not limited to, a modem, a network card, an infrared communication device, a wireless communication transceiver, and / or a chipset, such as a Bluetooth™ device, a WiFi device, a WiMax device, a cellular communication device, and / or the like.

[0226] The computing unit 401 may be a variety of general and / or special processing components with processing and computing capabilities. Some examples of the computing unit 401 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various dedicated artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, digital signal processors (DSPs), and any appropriate processors, controllers, microcontrollers, etc. The computing unit 401 performs the various methods and processes described above. For example, in some embodiments, the aforementioned cable electrical parameter calculation method may be implemented as a computer software program, which is tangibly included in a machine-readable medium, such as a storage unit 408. In some embodiments, part or all of the computer program may be loaded and / or installed on the electronic device 400 via the ROM 402 and / or the communication unit 409. In some embodiments, the computing unit 401 may be configured to perform the aforementioned cable electrical parameter calculation method by any other appropriate means (e.g., by means of firmware).

[0227] The program code for implementing the method of the present invention can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer or other programmable data processing device, so that the program code, when executed by the processor or controller, enables the functions / operations specified in the flow chart and / or block diagram to be implemented. The program code can be executed entirely on the machine, partially on the machine, partially on the machine as a stand-alone software package and partially on a remote machine, or entirely on a remote machine or server.

[0228] In the context of the present invention, a machine-readable medium may be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, device, or equipment. A machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or equipment, or any suitable combination of the foregoing. A more specific example of a machine-readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0229] As used herein, the terms "machine-readable medium" and "computer-readable medium" refer to any computer program product, apparatus, and / or device (e.g., disk, optical disk, memory, programmable logic device (PLD)) for providing machine instructions and / or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term "machine-readable signal" refers to any signal for providing machine instructions and / or data to a programmable processor.

[0230] To provide interaction with a user, the systems and techniques described herein can be implemented on a computer having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and pointing device (e.g., a mouse or trackball) through which the user can provide input to the computer. Other types of devices can also be used to provide interaction with the user; for example, the feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including acoustic input, voice input, or tactile input).

[0231] The systems and techniques described herein may be implemented in a computing system that includes back-end components (e.g., as a data server), or a computing system that includes middleware components (e.g., an application server), or a computing system that includes front-end components (e.g., a user computer with a graphical user interface or a web browser through which a user can interact with implementations of the systems and techniques described herein), or a computing system that includes any combination of such back-end components, middleware components, or front-end components. The components of the system may be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: a local area network (LAN), a wide area network (WAN), and the Internet.

[0232] A computer system may include clients and servers. Clients and servers are generally remote from each other and usually interact through a communication network. The relationship of client and server is generated by computer programs running on respective computers and having a client-server relationship to each other.

[0233] The above description of the embodiments is to facilitate the understanding and application of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made to the present invention by those skilled in the art based on the disclosure of the present invention should be within the scope of protection of the present invention.

Claims

1. The cable electrical parameter calculation method considering the influence of the return cable is characterized by: include: Obtain the structural parameters and material parameters of the cable and return cable; According to the structural parameters and material parameters of the cable and the return cable, the series impedance matrix including the cable and the return cable is calculated; According to the series impedance matrix, the voltage drop equation is obtained; Combined with the installation condition of double-end grounding of the return cable on site, the voltage drop equation is simplified to obtain the cable electrical parameters, which include positive-sequence resistance, positive-sequence reactance, zero-sequence resistance and zero-sequence reactance.

2. The cable electrical parameter calculation method according to claim 1, characterized in that: The cable comprises a single-phase core, an inner insulating layer, a metal sheath and an outer insulating layer arranged from inside to outside; The structural parameters of the cable include the outer diameter of the single-phase core, the outer diameter of the inner insulation layer, the outer diameter of the metal sheath and the outer diameter of the outer insulation layer; The material parameters of the cable include single-phase core resistivity, relative dielectric constant of inner insulation layer, resistivity of metal sheath and relative dielectric constant of outer insulation layer; The return cable comprises a return cable core and an insulation layer arranged from inside to outside; The structural parameters of the return cable include the outer diameter of the return cable core and the outer diameter of the insulation layer; The material parameters of the return cable include the return cable core resistivity and the relative dielectric constant of the insulation layer.

3. The cable electrical parameter calculation method according to claim 2, characterized in that: The calculation steps of the series impedance matrix include: Calculate the single-phase core DC resistance R at a given temperature dc1 , Metal sheath DC resistance R dc2 and the return cable core DC resistance R dc3 ; Calculate the intermediate variable z1 of the single-phase core, the intermediate variable z2 of the metal sheath and the intermediate variable z3 of the return cable core; Calculate the skin effect coefficient k of the single-phase line core based on z1, z2 and z3 s1 , Metal sheath skin effect coefficient k s2 , Skin effect coefficient k of return cable core s3 ; Calculate the proximity effect coefficient k of the single-phase line core p1 , Metal sheath proximity effect coefficient k p2 and the proximity effect coefficient k of the return cable core p3 ; According to R dc1 , k s1 and k p1 Calculate the single-phase line core AC resistance R ac1 According to R dc2 , k s2 and k p2 Calculate the metal sheath AC resistance R ac2 According to R dc3 , k s3 and k p3 Calculate the return cable core AC resistance R ac3 ; According to R ac1 , R ac2 and R ac3 Calculate the self-impedance Z of the "single-phase core-earth" loop cc , the self-impedance Z of the "return cable core-earth" loop hh , when the return cable core and the single-phase core are in different phases, the mutual impedance Z between the "return cable core-earth" loop and the "single-phase core-earth" loop ch ; According to the self-impedance Z of the "single-phase core-earth" loop cc , the self-impedance Z of the "return cable core-earth" loop hh , when the return cable core and the single-phase core are in different phases, the mutual impedance Z between the "return cable core-earth" loop and the "single-phase core-earth" loop ch , the series impedance matrix Z is constructed according to the following formula; Where Z is the series impedance matrix; Z cAcA Represents the self-impedance of the A phase core; Z cAcB Represents the mutual impedance between the A phase core and the B phase core; Z cAcC Represents the mutual impedance between the A phase core and the C phase core; Z cAh Represents the mutual impedance between the A phase core and the return cable core; Z cBcA Represents the mutual impedance between the B phase core and the A phase core; Z cBcB Represents the self-impedance of the B phase core; Z cBcC Represents the mutual impedance between the B-phase core and the C-phase core; Z cBh Represents the mutual impedance between the B phase core and the return cable core; Z cCcA Represents the mutual impedance between the C phase core and the A phase core; Z cCcB Represents the mutual impedance between the C phase core and the B phase core; Z cCcC Represents the self-impedance of the C phase core; Z cCh Represents the mutual impedance between the C phase core and the return cable core.

4. The cable electrical parameter calculation method according to claim 3, characterized in that: The single-phase core DC resistance R dc1 The calculation formula is as follows: Where ρ is the core resistivity; A is the nominal cross-sectional area of ​​the core; T is the core temperature; α 20 is the temperature coefficient of resistance; T0 = 20°C; According to the single-phase core DC resistance R dc1 Calculate the single-phase line core AC resistance R ac1 : R ac1 =R dc1 (1+k s1 +k p1 ), Among them, k s1 is the skin effect coefficient of the single-phase line core; k p1 is the single-phase line core proximity effect coefficient; The single-phase line core intermediate variable z1 is calculated by the following formula: Where, f is the current frequency; a z It is a constant that characterizes the skin effect of different types of wire cores; The skin effect coefficient k of the single-phase core is calculated by the following formula s1 : For single-core cables, the single-phase core proximity effect coefficient k p1 =0; For three-core cables, the single-phase core proximity effect coefficient k is calculated by the following formula p1 : Among them, d c is the diameter of the wire core; S ij is the interaxial distance between core i and core j; a p is a constant that characterizes the proximity effect.

5. The cable electrical parameter calculation method according to claim 3, characterized in that: The self-impedance Z of the "single-phase core-earth" loop cc , calculated by the following formula: In the formula, j is an imaginary unit; The self-impedance Z of the "return cable core-earth" loop is calculated by the following formula hh : The mutual impedance Z between the "return cable core-earth" loop and the "single-phase core-earth" loop when the return cable core and the single-phase core are in different phases is calculated by the following formula: ch : The F(r) is calculated by the following formula oc ,r ic ) and F(r oh ,r ih ): Among them, r c is the AC resistance of the single-phase core per unit length; r h is the AC resistance per unit length of the return cable core; r e is the earth equivalent resistance per unit length, r e =π 2 f10 -4 , f is the current frequency; D e is the virtual core equivalent depth when the earth is used as the loop, ρ e Represents the earth resistivity; r ic 、r oc are the inner and outer radii of the single-phase core respectively. At this time, the inner diameter of the single-phase core r ic Take 0; r ih 、r oh are the inner and outer radii of the return cable core respectively. At this time, the inner diameter of the return cable core is r ih Take 0; D is the distance between the single-phase core of each phase and the return cable core; ln is the natural logarithmic function.

6. The cable electrical parameter calculation method according to claim 5, characterized in that: According to the series impedance matrix, the voltage drop equation is obtained as follows: Where U cA Indicates the voltage across the A phase core of a unit length cable; U cB Indicates the voltage across the B phase core of the cable per unit length; U cC Indicates the voltage across the C phase core of the cable per unit length; U h Indicates the voltage at both ends of the return cable; I cA Indicates the current flowing through the metal sheath of phase A of the cable; I cB Indicates the current flowing through the cable B phase metal sheath; I cC Indicates the current flowing through the metal sheath of phase C of the cable; I h Indicates the current flowing through the return cable; Combined with the on-site installation conditions, since both ends of the return cable are directly grounded, the grounding resistance at both ends is ignored, so U h =0 is substituted into the voltage drop equation, and its matrix block form is as follows: Expand to get the following equation: U c =Z cc I c +Z ch I h , Eliminate I h After that, the simplified voltage drop equation is: Where U c Indicates the voltage across the single-phase core of a three-core cable; I c Indicates the current flowing through the three-core cable; Z ch Represents the mutual impedance of the return cable and the three-core cable.

7. The cable electrical parameter calculation method according to claim 6, characterized in that: The sequence impedance matrix (Z c ) 120 : in, a=e j120° ; Sequence impedance matrix (Z c ) 120 The main diagonal element Z 11 The real and imaginary parts are the positive sequence resistance and reactance, and the sequence impedance matrix (Z c ) 120 The main diagonal element Z 33 The real and imaginary parts are the zero-sequence resistance and zero-sequence reactance.

8. The cable electrical parameter calculation system considering the influence of return cable is characterized by: include: Parameter acquisition unit: used to obtain the structural parameters and material parameters of the cable and return cable; Series impedance matrix calculation unit: used to calculate the series impedance matrix including the cable and the return cable according to the structural parameters and material parameters of the cable and the return cable; Voltage drop equation acquisition unit: obtains the voltage drop equation according to the series impedance matrix; Cable electrical parameter acquisition unit: Combined with the installation condition of double-end grounding of the return cable on site, the voltage drop equation is simplified to obtain the cable electrical parameters, including positive-sequence resistance, positive-sequence reactance, zero-sequence resistance and zero-sequence reactance.

9. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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