A method for selecting conductors for increasing capacity based on spherical fuzzy sets and analytic hierarchy process

Abstract

The present invention relates to the technical field of conductor comparison and selection, and specifically to a method for selecting a capacity-increasing conductor based on spherical fuzzy sets and a hierarchical analysis method. The conductor selection steps are as follows: S1, collecting basic parameters of a 500kV overhead transmission line to be increased and reconstructed as an existing conductor; S2, based on the collected basic parameters of the line, selecting the conductor that meets the requirements of the reconstructed line from the existing capacity-increasing conductor as the candidate conductor for the capacity-increasing and reconstructing project, and calculating the resistance loss, maximum current carrying capacity, vertical and horizontal loads and life cycle cost indicators of the selected capacity-increasing conductor. This application establishes a hierarchical evaluation model based on the three dimensions of electrical performance, mechanical performance and economic efficiency of the conductor, and uses spherical fuzzy numbers to score various indicators in the model, so as to construct a capacity-increasing conductor selection model in a 500kV transmission line capacity-increasing and reconstructing project, realize the comparison of various performances of the selectable capacity-increasing conductors, reduce the subjectivity in the final scheme selection, and improve the applicability.

Description

Technical Field

[0001] The invention belongs to the technical field of conductor selection, and in particular relates to a method for selecting a capacity-increasing conductor based on spherical fuzzy sets and a hierarchy analysis method. Background Art

[0002] Conductor selection mainly involves selecting conductor types, specifications and materials suitable for specific application conditions. The main considerations include conductor specifications, conductor materials, voltage levels, working environment and economy. In actual power system operation, with the increasing penetration of wind power and photovoltaic power, the load in the system is also increasing. Even during peak hours of electricity consumption, the line operation department has to increase the transmission capacity of the transmission line to meet the electricity demand of users. The methods of increasing the transmission capacity of the line are divided into two categories: dynamic capacity increase and replacement of capacity increase conductors. The dynamic capacity increase method is based on the relationship between the meteorological conditions in the area where the transmission line is located and the maximum current carrying capacity allowed to pass during its own operation. The increase in transmission capacity is achieved by increasing the current carrying capacity; the replacement of the capacity-increasing conductor method is to replace the original line conductor with a new type of high-efficiency and heat-resistant capacity-increasing conductor. This type of conductor has a higher maximum allowable operating temperature and current carrying capacity, and has good sag characteristics, which can effectively improve the line transmission capacity. This method can better cope with the growing demand for electricity and ensure the long-term and efficient operation of the transmission line. However, since there are many types and characteristics of capacity-increasing conductors on the market, it is necessary to fully consider the electrical performance, mechanical performance and economy of the capacity-increasing conductor, compare the advantages of various types of conductors from different dimensions, and finally make a better conductor selection plan;

[0003] Conductor selection can be regarded as a multi-objective decision-making problem. A hierarchical evaluation model is established based on the analytic hierarchy process. The basic indicators that can reflect the operating characteristics and application reliability of the capacity-increasing conductor are used as conductor evaluation indicators. By comparing the relative importance of each indicator, a fuzzy judgment matrix is ​​constructed. The weight vector of each indicator is calculated and sorted according to the expert's score. This method can fully consider the electrical, mechanical, and economic indicators that affect the performance of the capacity-increasing conductor, and obtain the order of advantages and disadvantages of multiple capacity-increasing transformation schemes, thereby realizing the optimization of the capacity-increasing conductor. However, in the scoring stage of this method, the scoring experts usually give subjective scores based on their empirical knowledge, which leads to a strong subjectivity in the final scheme. In this regard, we propose a capacity-increasing conductor selection method based on spherical fuzzy sets and analytic hierarchy process. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for selecting a capacity-increasing conductor based on spherical fuzzy sets and a hierarchy analysis method to solve the above technical problems.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for selecting a capacity-increasing conductor based on spherical fuzzy sets and analytic hierarchy process, wherein the conductor selection steps are as follows:

[0006] S1. Collect the basic parameters of the 500kV overhead transmission line to be expanded and renovated as the current conductor;

[0007] S2. Based on the collected basic line parameters, select the existing capacity-increasing conductors that meet the requirements of the modified line as the candidate conductors for the capacity-increasing and modification project, and calculate the resistance loss, maximum current carrying capacity, vertical and horizontal loads and life cycle cost indicators of the selected capacity-increasing conductors;

[0008] S3. A hierarchical evaluation model consisting of a target layer, an indicator layer and a scheme layer is established based on the indicators that reflect the electrical performance, mechanical performance and economic efficiency of the capacity-increasing conductors. Each indicator is scored using spherical fuzzy numbers, thereby constructing a fuzzy judgment matrix and calculating the weight of each indicator. The score of each indicator is calculated and ranked based on the weight, and the capacity-increasing conductor with the highest total score is selected as the optimal choice for the capacity-increasing reconstruction project.

[0009] Preferably, the basic parameters of the conductor used in the transmission line to be expanded and renovated in step S1 include data on the conductor model, cross-section, outer diameter, DC resistance, maximum current carrying capacity and maximum allowable operating temperature.

[0010] Preferably, in step S2, a capacity-increasing conductor having a maximum current carrying capacity, a maximum allowable temperature and a similar cross-section is selected as an alternative conductor for the reconstruction project.

[0011] Preferably, the calculation formula for the resistance loss of the capacity-increasing conductor in step S2 is:

[0012] L R =I 2 ×R×τ×10 3

[0013] Where L R is the resistance loss, in kW·h / km; I is the current carrying capacity, in A; R is the resistance of the capacity-increasing conductor, in Ω; τ is the number of hours of capacity-increasing conductor loss, in h;

[0014] The calculation of the maximum current carrying capacity of the increased capacity conductor is based on the thermal balance equation of the conductor. The calculation formula is:

[0015] I l 2 R ac +Q s =Q c +Q r

[0016] Among them I l The allowable current carrying capacity is in A; Q s is the solar heat gain, in W / m; Q c is convection heat dissipation, unit is W / m; Qr is the radiation heat dissipation, the unit is W / m; R ac is the AC resistance of the wire, in Ω.

[0017] Preferably, the calculation formula for the vertical load of the capacity-increasing conductor in step S2 is:

[0018] W=w×9.80665

[0019] Wherein, W is the vertical load per unit length of the capacity-increasing conductor, in N / m; w is the deadweight per unit length of the capacity-increasing conductor, in kg / m;

[0020] The calculation formula for the horizontal load of the capacity-increasing conductor is:

[0021] W x =α·W0·μ z ·μ sc β c ·d·L p ·B1·sin 2 θ

[0022] Where Wx is the standard value of horizontal wind load perpendicular to the conductor and ground line, in kN; α is the wind pressure unevenness coefficient; W0 is the standard value of the reference wind pressure, in kN / m 2 ;μ z is the wind pressure height variation coefficient; μ sc is the body coefficient of the conductor; β c is the wind load adjustment factor of the 500kV line conductor; d is the outer diameter of the conductor or the calculated outer diameter when covered with ice; L p is the horizontal spacing of the tower, in m; B1 is the wind load increase coefficient when covered with ice; θ is the angle between the wind direction and the conductor or ground wire direction, in degrees.

[0023] Preferably, the calculation formula for the full life cycle cost index in step S2 is:

[0024] LCC=IC+OC+MC+FC+DC

[0025] Among them, LCC is the full life cycle of the conductor; IC is the one-time investment cost of the conductor; OC is the operating loss cost of the conductor; MC is the operating and maintenance cost of the conductor; FC is the fault loss cost of the conductor; and DC is the decommissioning and recovery cost of the conductor.

[0026] Preferably, in step S3, the target layer is the selection of capacity-increasing conductors, and the indicator layer includes electrical performance, mechanical performance and economic efficiency, wherein the electrical performance includes the maximum allowable operating temperature, resistance loss and maximum current carrying capacity, the mechanical performance includes vertical load, horizontal load and sag characteristics, and the economic efficiency includes the full life cycle operating cost, and the solution layer is the selection of capacity-increasing conductors for 500kV overhead transmission lines.

[0027] Preferably, the spherical fuzzy number in step S3 is expressed as:

[0028] A=(μ A ,v A ,π A )

[0029] where μ A ,v A ,π A They are respectively expressed as membership, non-membership and hesitation. The indicators in the hierarchical evaluation model are scored in the form of spherical fuzzy numbers. The consistency is checked through the fuzzy judgment matrix, and the scores and weights are calculated. The schemes are sorted according to the weight values. The larger the weight, the better the scheme.

[0030] Preferably, the consistency check formula is:

[0031]

[0032] Among them, CR is the consistency index. When CR < 0.1, it means that the fuzzy judgment matrix passes the consistency test; CI is the consistency ratio; n is the order of the fuzzy judgment matrix; λ max is the maximum eigenvalue of the fuzzy judgment matrix; RI is the correction factor, which is related to the order n and is obtained by looking up the table.

[0033] Preferably, the weight calculation formula is:

[0034]

[0035] in, is the weight value; a is the value in the fuzzy judgment matrix; i is the number of rows in the fuzzy judgment matrix; j is the number of columns in the fuzzy judgment matrix.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] This application establishes a hierarchical evaluation model based on the three dimensions of electrical performance, mechanical performance and economy of the conductor, and uses spherical fuzzy numbers to score the indicators of various aspects in the model, constructs a capacity-increasing conductor selection model in the 500kV transmission line capacity-increasing and reconstruction project, realizes the comparison of various performances of the selectable capacity-increasing conductors, reduces the subjectivity in the final scheme selection, and improves the applicability of the capacity-increasing conductor scheme. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a flowchart of the wire selection steps in the present invention;

[0039] Figure 2 This is the hierarchical evaluation model diagram of the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The present invention provides a technical solution: a method for selecting a capacity-increasing conductor based on spherical fuzzy sets and a hierarchical analysis method, wherein the conductor selection steps are as follows:

[0042] S1. Collect the basic parameters of the 500kV overhead transmission line to be expanded and renovated as the current conductor;

[0043] S2. Based on the collected basic line parameters, select the existing capacity-increasing conductors that meet the requirements of the modified line as the candidate conductors for the capacity-increasing and modification project, and calculate the resistance loss, maximum current carrying capacity, vertical and horizontal loads and life cycle cost indicators of the selected capacity-increasing conductors;

[0044] S3. A hierarchical evaluation model consisting of a target layer, an indicator layer and a scheme layer is established based on the indicators that reflect the electrical performance, mechanical performance and economic efficiency of the capacity-increasing conductors. Each indicator is scored using spherical fuzzy numbers, thereby constructing a fuzzy judgment matrix and calculating the weight of each indicator. The score of each indicator is calculated and ranked based on the weight, and the capacity-increasing conductor with the highest total score is selected as the optimal choice for the capacity-increasing reconstruction project.

[0045] Furthermore, the basic parameters of the conductors used in the transmission line to be expanded and renovated in step S1 include data on conductor model, cross-section, outer diameter, DC resistance, maximum current carrying capacity and maximum allowable operating temperature.

[0046] Furthermore, in step S2, a capacity-enhanced conductor with a maximum current carrying capacity, a maximum allowable temperature and a similar cross-section is selected as an alternative conductor for the reconstruction project.

[0047] Furthermore, the calculation formula for the resistance loss of the capacity-increasing conductor in step S2 is:

[0048] L R =I 2 ×R×τ×10 3

[0049] Where L R is the resistance loss, in kW·h / km; I is the current carrying capacity, in A; R is the resistance of the capacity-increasing conductor, in Ω; τ is the number of hours of capacity-increasing conductor loss, in h;

[0050] In the case of increasing the capacity of the conductor, consider the effect of increasing the length or cross-sectional area of ​​the conductor on the resistance loss. If the length of the conductor increases while the cross-sectional area and material remain unchanged, the resistance will increase because the resistance is proportional to the length; if the cross-sectional area of ​​the conductor increases while the length and material remain unchanged, the resistance will decrease because the resistance is inversely proportional to the cross-sectional area.

[0051] The magnitude of the resistance loss is proportional to the square of the working current of the transformer. Therefore, when the current is large, the resistance loss will increase greatly. When designing power equipment such as transformers, it is necessary to minimize the resistance loss to improve the efficiency of the equipment.

[0052] The calculation of the maximum current carrying capacity of the increased capacity conductor is based on the thermal balance equation of the conductor. The calculation formula is:

[0053] I l 2 R ac +Q s =Q c +Q r

[0054] Among them I l The allowable current carrying capacity is in A; Q s is the solar heat gain, in W / m; Q c is convection heat dissipation, unit is W / m; Q r is the radiation heat dissipation, the unit is W / m; R ac is the AC resistance of the wire, in Ω;

[0055] The cross-sectional area of ​​the conductor is an important factor affecting the current carrying capacity. Generally speaking, the larger the cross-sectional area of ​​the conductor, the greater its current carrying capacity. The conductor material is also an important factor affecting the current carrying capacity. Different materials have different resistivities and conductivity, so their current carrying capacities are also different. Ambient temperature and heat dissipation conditions will also affect the current carrying capacity of the conductor. When the ambient temperature is high or the heat dissipation conditions are poor, the maximum current carrying capacity of the conductor will decrease.

[0056] Furthermore, the calculation formula for the vertical load of the capacity-increasing conductor in step S2 is:

[0057] W=w×9.80665

[0058] Wherein, W is the vertical load per unit length of the capacity-increasing conductor, in N / m; w is the deadweight per unit length of the capacity-increasing conductor, in kg / m;

[0059] The vertical load of the capacity-enhanced conductor refers to the weight of the conductor and its accessories when the conductor is subjected to vertical force. This load mainly comes from the weight of the conductor itself, the additional weight of environmental factors such as ice and snow, and dynamic loads such as wind pressure.

[0060] The calculation formula for the horizontal load of the capacity-increasing conductor is:

[0061] W x =α·W0·μ z ·μ sc β c ·d·L p ·B1·sin 2 θ

[0062] Where Wx is the standard value of horizontal wind load perpendicular to the conductor and ground line, in kN; α is the wind pressure unevenness coefficient; W0 is the standard value of the reference wind pressure, in kN / m 2 ;μ z is the wind pressure height variation coefficient; μ sc is the body coefficient of the conductor; β c is the wind load adjustment factor of the 500kV line conductor; d is the outer diameter of the conductor or the calculated outer diameter when covered with ice; L p is the horizontal spacing of the tower, in m; B1 is the wind load increase factor when covered with ice; θ is the angle between the wind direction and the conductor or ground wire direction, in degrees;

[0063] The horizontal load of the capacity-enhanced conductor refers to the force or load that the conductor bears in the horizontal direction. These horizontal loads may come from various factors such as the effect of wind, conductor expansion and contraction caused by temperature changes, displacement or vibration of adjacent structures, etc.

[0064] Furthermore, the calculation formula of the life cycle cost index in step S2 is:

[0065] LCC=IC+OC+MC+FC+DC

[0066] Among them, LCC is the full life cycle of the conductor; IC is the one-time investment cost of the conductor; OC is the operating loss cost of the conductor; MC is the operating and maintenance cost of the conductor; FC is the loss cost of the conductor failure; DC is the decommissioning and recovery cost of the conductor;

[0067] The life cycle cost indicator refers to the sum of the discounted values ​​of all costs incurred in owning, operating, maintaining, repairing and disposing of a building, equipment or construction project system over a certain period of time. This indicator evaluates the economic performance of an asset or project from a long-term and comprehensive perspective.

[0068] Furthermore, in step S3, the target layer is the selection of capacity-increasing conductors, and the indicator layer includes electrical performance, mechanical performance and economic efficiency, wherein the electrical performance includes the maximum allowable operating temperature, resistance loss and maximum current carrying capacity, the mechanical performance includes vertical load, horizontal load and sag characteristics, and the economic efficiency includes the full life cycle operating cost. The solution layer is the selection of capacity-increasing conductors for 500kV overhead transmission lines.

[0069] Furthermore, the spherical fuzzy number in step S3 is expressed as:

[0070] A=(μ A ,v A ,π A )

[0071] where μ A ,v A ,π A They are respectively expressed as membership, non-membership and hesitation. The indicators in the hierarchical evaluation model are scored in the form of spherical fuzzy numbers. The consistency is checked through the fuzzy judgment matrix, and the scores and weights are calculated. The schemes are sorted according to the weight values. The larger the weight, the better the scheme.

[0072] Furthermore, the consistency test formula is:

[0073]

[0074] Among them, CR is the consistency index. When CR < 0.1, it means that the fuzzy judgment matrix passes the consistency test; CI is the consistency ratio; n is the order of the fuzzy judgment matrix; λ max is the maximum eigenvalue of the fuzzy judgment matrix; RI is the correction factor, which is related to the order n and is obtained by looking up the table.

[0075] Furthermore, the weight calculation formula is:

[0076]

[0077] in, is the weight value; a is the value in the fuzzy judgment matrix; i is the number of rows in the fuzzy judgment matrix; j is the number of columns in the fuzzy judgment matrix.

[0078] Example 1

[0079] Since the conductors currently on the market only need to meet the requirements of regulations and specifications such as the distance to the ground and the horizontal distance from the building during normal operation to meet the requirements of the ground electric field strength, radio interference level, and corona audible noise, when comparing and selecting the capacity-increasing conductors, the focus is on comparing and analyzing the maximum operating temperature, current carrying capacity, mechanical properties, sag characteristics, and economy of each selected conductor, and finally giving the best solution. The capacity-increasing conductors are compared based on the three main indicators of electrical performance, mechanical performance, and economy. The electrical performance includes the maximum allowable temperature, line loss, and current carrying capacity; the economy is compared from the full life cycle cost of the last selected capacity-increasing solution; the mechanical performance includes vertical load, horizontal load, and sag characteristics. The evaluation model established based on the above indicators is as follows: Figure 2 As shown in the figure, spherical fuzzy numbers are used to score the main indicator layer in the figure, and a fuzzy judgment matrix is ​​constructed:

[0080]

[0081] In the evaluation model, the maximum allowable temperature of the conductor is the main condition for controlling the current carrying capacity of the conductor. The maximum allowable temperature of the conductor is mainly determined by the strength loss of the conductor after long-term operation and the heating of the connecting hardware. The higher the working temperature and the longer the operation time, the greater the strength loss of the conductor. Generally speaking, the allowable temperature of ordinary steel-core aluminum stranded wire and steel-core aluminum alloy stranded wire should be 70℃, and 80℃ when necessary. Steel-core aluminum-clad steel stranded wire and aluminum-clad steel stranded wire can be 80℃. Among other capacity-increasing conductors, the long-term operating temperature of heat-resistant aluminum alloy conductors can reach 150℃, and the long-term operating temperature of super heat-resistant aluminum alloy conductors can reach 210℃. The long-term operating temperature of soft aluminum conductors can reach 150℃~180℃. The influence of conductors on the mechanical load of poles and towers is mainly controlled by longitudinal tension, horizontal force and vertical force. The line design must ensure that the loads of the conductors in these three directions do not exceed the bearing capacity of the poles and towers under various meteorological conditions, so as to ensure the safe and stable operation of the line. The maximum longitudinal tension is determined by the breaking tension of the conductor itself, the safety factor of the design regulations and the meteorological conditions; the maximum horizontal load is determined by the outer diameter of the conductor, the horizontal span of the line and the maximum wind speed; the maximum vertical load is determined by the mass per unit length of the conductor, the vertical span of the line and the thickness of the ice cover.

[0082] This embodiment selects a domestic 500kV overhead transmission line as the object. The original line is a double circuit on the same tower. The original conductor uses 4×LGJ-630 / 45 steel-core aluminum stranded wire. The maximum allowable temperature of the conductor is 70°C, and the corresponding current carrying capacity is 873A.

[0083] According to the commonly used capacity-increasing conductors in the capacity-increasing reconstruction project, the capacity-increasing conductors with larger maximum current carrying capacity and maximum allowable temperature than the existing conductors of the original line and similar cross-section are selected as the alternative conductors for the reconstruction project. In this embodiment, the aluminum-clad steel core aluminum stranded wire with model JL / LB1A-630 / 45, the aluminum-clad steel core heat-resistant aluminum alloy stranded wire with model JNRLH60 / LB1A-630 / 45, and the carbon fiber composite core soft aluminum stranded wire with model JLRX1 / JFB-620 / 60 are selected as the alternative capacity-increasing conductor schemes for the embodiment line, and the indicators of the selected conductors are calculated and analyzed. The spherical fuzzy number is used to score the seven indicators of the sub-indicator layer in the hierarchical evaluation model and the consistency indicators CR are calculated to be: -8.5402×10 -16 , 0.0019, 0.0019, 1.4131×10 -4 , 1.4131×10 -4 , 1.4131×10 -4 , 0.0019; after the consistency test is passed, the corresponding weights of each indicator are calculated respectively, and the ranking results are as follows;

[0084] Table 1 below shows the weights and ranking results of each indicator.

[0085]

[0086] Through the above weight calculation and sorting, it is found that the optimal choice of capacity-increasing conductor in the capacity-increasing and reconstruction project of the 500kV overhead transmission line is the aluminum-clad steel core heat-resistant aluminum alloy stranded wire with model JNRLH60 / LB1A-630 / 45.

[0087] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0088] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for selecting capacity-increasing conductors based on spherical fuzzy sets and analytic hierarchy process, characterized in that: The steps for selecting wires are: S1. Collect the basic parameters of the 500kV overhead transmission line to be expanded and renovated as the current conductor; S2. Based on the collected basic line parameters, select the existing capacity-increasing conductors that meet the requirements of the modified line as the candidate conductors for the capacity-increasing and modification project, and calculate the resistance loss, maximum current carrying capacity, vertical and horizontal loads and life cycle cost indicators of the selected capacity-increasing conductors; S3. A hierarchical evaluation model including the target layer, the indicator layer and the scheme layer is established based on the indicators reflecting the electrical performance, mechanical performance and economic efficiency of the capacity-increasing conductor. Each indicator is scored using spherical fuzzy numbers, thereby constructing a fuzzy judgment matrix and calculating the weight of each indicator. The score of each indicator is calculated and ranked based on the weight, and the capacity-increasing conductor with the highest total score is selected as the optimal choice for the capacity-increasing reconstruction project. Among them, the target layer in step S3 is the selection of capacity-increasing conductors, and the indicator layer includes electrical performance, mechanical performance and economic performance. The electrical performance includes the maximum allowable operating temperature, resistance loss and maximum current carrying capacity, the mechanical performance includes vertical load, horizontal load and sag characteristics, and the economic performance includes the full life cycle operation cost. The solution layer is the selection of capacity-increasing conductors for 500kV overhead transmission lines. Among them, the spherical fuzzy number in step S3 is expressed as: A=(μ A ,v A ,p A ) where μ A ,v A ,π A They are expressed as membership, non-membership and hesitation respectively. The indicators in the hierarchical evaluation model are scored in the form of spherical fuzzy numbers. The consistency is checked through the fuzzy judgment matrix. The scores and weights are calculated and sorted according to the weight values. The larger the weight, the better the solution. The weight calculation formula is: in, is the weight value; a is the value in the fuzzy judgment matrix; i is the number of rows in the fuzzy judgment matrix; j is the number of columns in the fuzzy judgment matrix; n is the order of the fuzzy judgment matrix.

2. The method for selecting a capacity-increasing conductor based on spherical fuzzy sets and analytic hierarchy process according to claim 1 is characterized in that: The basic parameters of the conductors used in the transmission lines to be expanded and renovated in step S1 include data on conductor model, cross-section, outer diameter, DC resistance, maximum current carrying capacity and maximum allowable operating temperature.

3. The method for selecting a capacity-increasing conductor based on spherical fuzzy sets and analytic hierarchy process according to claim 1 is characterized in that: In step S2, a capacity-enhanced conductor with a maximum current carrying capacity, maximum allowable temperature and similar cross-section is selected as an alternative conductor for the reconstruction project.

4. The method for selecting a capacity-increasing conductor based on spherical fuzzy sets and analytic hierarchy process according to claim 1 is characterized in that: The calculation formula for the resistance loss of the increased capacity conductor in step S2 is: L R =I 2 ×R×τ×10 3 Where L R is the resistance loss, in kW·h / km; I is the current carrying capacity, in A; R is the resistance of the capacity-increasing conductor, in Ω; τ is the loss hours of the capacity-increasing conductor, in h; The calculation of the maximum current carrying capacity of the increased capacity conductor is based on the thermal balance equation of the conductor. The calculation formula is: I l 2 R ac +Q s =Q c +Q r Among them I l The allowable current carrying capacity is in A; Q s is the solar heat gain, in W / m; Q c is convection heat dissipation, unit is W / m; Q r is the radiation heat dissipation, the unit is W / m; R ac is the AC resistance of the wire, in Ω.

5. The method for selecting a capacity-increasing conductor based on spherical fuzzy sets and analytic hierarchy process according to claim 1 is characterized in that: The calculation formula for the vertical load of the capacity-increasing conductor in step S2 is: W=w×9.80665 Wherein, W is the vertical load per unit length of the capacity-increasing conductor, in N / m; w is the deadweight per unit length of the capacity-increasing conductor, in kg / m; The calculation formula for the horizontal load of the capacity-increasing conductor is: W x =α·W0·μ z ·m sc ·b c ·d·L p ·B1·sin 2 i Where Wx is the standard value of horizontal wind load perpendicular to the conductor and ground line, in kN; α is the wind pressure unevenness coefficient; W0 is the standard value of the reference wind pressure, in kN / m 2 ;μ z is the wind pressure height variation coefficient; μ sc is the body coefficient of the conductor; β c is the wind load adjustment factor of the 500kV line conductor; d is the outer diameter of the conductor or the calculated outer diameter when covered with ice; L p is the horizontal spacing of the tower, in m; B1 is the wind load increase coefficient when covered with ice; θ is the angle between the wind direction and the conductor or ground wire direction, in degrees.

6. The method for selecting a capacity-increasing conductor based on spherical fuzzy sets and analytic hierarchy process according to claim 1 is characterized in that: The calculation formula for the life cycle cost index in step S2 is: LCC=IC+OC+MC+FC+DC Among them, LCC is the full life cycle of the conductor; IC is the one-time investment cost of the conductor; OC is the operating loss cost of the conductor; MC is the operating and maintenance cost of the conductor; FC is the fault loss cost of the conductor; and DC is the decommissioning and recovery cost of the conductor.

7. The method for selecting a capacity-increasing conductor based on spherical fuzzy sets and analytic hierarchy process according to claim 1 is characterized in that: The consistency test formula is: Among them, CR is the consistency index. When CR < 0.1, it means that the fuzzy judgment matrix passes the consistency test; CI is the consistency ratio; n is the order of the fuzzy judgment matrix; λ max is the maximum eigenvalue of the fuzzy judgment matrix; RI is the correction factor, which is related to the order n and is obtained by looking up the table.

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