A method for determining ice shedding of a conductor under different damage time sequences and a simulation analysis system

Abstract

The application discloses a kind of different destruction timing under the method for determining that wire is deiced, comprising: S1. preset based on transverse cohesion destruction control wire deicing determination criterion;S2. preset based on transverse cohesive destruction control wire deicing determination criterion;S3. preset based on longitudinal fracture destruction control wire deicing determination criterion;S4. according to the destruction timing of preset different wire deicing determination criterion calculation wire lower part icing;S5. according to the destruction timing of preset different wire deicing determination criterion calculation wire upper part icing;S6. preset different wire deicing determination criterion and calculation timing data input simulation analysis system dynamic evolution, for transmission wire deicing determination.The application can provide reference for the real reproduction of wire deicing process, and more accurately predict the position of local deicing and deicing rate, so as to reduce the waste of design and security risks caused by false prediction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ice melting and ice shedding of power transmission lines, and particularly relates to a conductor ice shedding determination method and simulation analysis system under different damage time sequences. BACKGROUND

[0002] The key problem in the study of the dynamic response of conductor ice shedding and jumping of a power transmission line is to determine the reasonable ice shedding form of the line, which is directly related to the tension value of the conductor and the ice shedding jumping trajectory, and is also a prerequisite for numerical simulation and artificial simulation test of the dynamic behavior of ice shedding. In the traditional design of power transmission lines, the conductor ice shedding form recommended in the Design Manual for High Voltage Transmission Lines of Electric Power Engineering and the Technical Regulations for Design of Overhead Transmission Lines with Heavy Ice Cover is mainly used, that is, only the middle section of the conductor is ice shedding in the continuous section conductor, and the ice shedding rate should be determined according to the actual operation experience. When there is a lack of ice shedding rate data, the ice shedding rate of not less than 50% and 60% of the design ice weight is taken for the medium ice area and heavy ice area of 110-220kV power transmission lines, respectively, and the ice shedding rate of not less than 70% and 80% of the design ice weight is taken for the lines of 330kV and above.

[0003] In addition to the above artificially assumed ice shedding form, in recent years, some researchers have carried out numerical simulation of the dynamic process of conductor ice shedding based on the ice shedding determination criterion. There are mainly three kinds of ice shedding determination criteria, namely stress criterion, strain criterion and acceleration criterion: (1) The stress criterion considers the axial stress and bending stress of the ice on the conductor. When the maximum allowable plastic stress of any point in the ice element is reached, the ice is determined to fall off, so the stress criterion can accurately predict the changes of tension and mid-span displacement in the conductor ice shedding process, but it will overestimate the ice shedding rate of the line; (2) The strain criterion considers that when the strain of the ice exceeds the maximum allowable plastic strain, the ice falls off from the conductor, so it can more accurately predict the ice shedding rate of the line, but it still cannot explain the phenomenon that the ice on the conductor separates into many fragments under the action of impact load instead of directly falling off; (3) The acceleration criterion divides the conductor ice shedding process into two stages. The first stage is that the transverse wave caused by the initial impact makes the ice element fracture into independent ice fragments, which can be judged by the stress criterion or the strain criterion. The second stage is that when the inertia force of the ice fragments can overcome the bonding force between the ice and the conductor and the cohesive force of the ice itself at the same time, the ice is determined to fall off.

[0004] In reality, existing technologies for judging conductor de-icing patterns and de-icing rates still have many shortcomings. On the one hand, the recommended de-icing pattern of only the intermediate de-icing range lacks scientific basis and may cause unfavorable de-icing dynamic response, potentially leading to significant design waste. On the other hand, only suggestions for conductor de-icing rates are provided, without specifying the exact location of local de-icing, which brings certain difficulties to engineering applications. At the same time, the conductor de-icing jump height is very sensitive to the location of local de-icing. In addition, a few numerical simulations of the conductor de-icing dynamic process based on de-icing judgment criteria can, to some extent, avoid problems such as artificially assumed de-icing patterns deviating from reality. However, existing icing failure criteria are not entirely reasonable, as they deviate from the actual failure mechanism of conductor icing and are difficult to effectively reproduce the true de-icing process.

[0005] Therefore, this application proposes a method for determining conductor de-icing under different failure sequences and a simulation analysis system to solve the above-mentioned technical problems. Summary of the Invention

[0006] Based on the aforementioned technical problems, the main objective of this invention is to provide a method and simulation analysis system for determining conductor de-icing under different failure sequences of icing-induced lateral bonding failure, lateral cohesive failure, and longitudinal fracture failure. This method can correspond to the occurrence sequence of each failure and its corresponding determination conditions when ice falls off the conductor. The proposed determination criteria are introduced into multi-level conductor de-icing numerical simulations, simulating the dynamic de-icing process of icing along the span under external impact loads. By utilizing the influence of key parameters such as initial excitation magnitude, excitation location, and bonding strength on the dynamic de-icing process, and combining a large number of numerical simulation results, the induced de-icing probability of icing on the conductor is summarized, facilitating further analysis of the weak points of conductor ice de-icing. This method can further propose specific local de-icing forms of conductors in conjunction with existing line designs.

[0007] The present invention solves the above-mentioned technical problems by adopting the following technical solutions:

[0008] A method for determining conductor de-icing under different failure sequences includes:

[0009] S1. Preset conductor de-icing judgment criteria based on lateral cohesive failure control;

[0010] S2. Preset conductor de-icing judgment criteria based on lateral adhesion failure control;

[0011] S3. Preset conductor de-icing judgment criteria based on longitudinal fracture damage control;

[0012] S4. Calculate the failure sequence of ice accumulation on the lower part of the conductor according to the preset different conductor de-icing judgment criteria;

[0013] S5. Calculate the failure sequence of ice covering the upper part of the conductor according to the preset different conductor de-icing judgment criteria;

[0014] S6. The preset different conductor de-icing determination criteria and the calculation time series data input simulation analysis system are dynamically evolved for transmission conductor de-icing determination.

[0015] Preferably, the preset method of the conductor de-icing determination criterion based on transverse cohesive failure control in the S1 step comprises:

[0016] S11. A bundled ice-coated conductor is selected, and the self-weights of the upper and lower ice coatings are respectively set as and The inertial forces of the upper and lower ice coatings are respectively set as and The cohesive force between the upper and lower ice coatings is set as F cohesive At this time, according to the vertical force balance, the critical condition for the transverse cohesive failure of the upper bundled ice coating of the conductor can be obtained as:

[0017]

[0018] S12. Since the vertical span ratio of the conductor is very small, it is approximately assumed that the load p per unit length of the conductor is uniformly distributed along the connecting line of the suspension points, and the load on the unit horizontal projection length of the conductor is set as p / cosβ, β is the height difference angle of the suspension points at both ends of the conductor, and then:

[0019]

[0020] In the formula: ρ ice is the density of the ice coating on the conductor; g is the acceleration of gravity; D is the diameter of the bare conductor; L AB is the length of the ice fracture surface AB segment; τ cohesive is the cohesive strength of the ice coating; L e is the length of the independent ice small segment; S t and S b are the cross-sectional areas of the upper and lower ice coatings, respectively; and are the inertial accelerations of the upper and lower ice coatings of the bundled ice-coated conductor in the critical state of transverse cohesive failure, respectively;

[0021] S13. Through the geometric relationship of the stress of the bundled ice-coated section, the following can be obtained:

[0022]

[0023] In the formula: D t is the outer diameter of the circular section of the ice-coated conductor; e is the eccentric distance between the center O2 of the ice-coated conductor and the center C of the bare conductor;

[0024] S14. The formula of the above steps can be integrated to obtain the ice shedding criterion of the wrapped ice conductor controlled by transverse cohesive failure as follows:

[0025]

[0026] wherein a critical is the critical acceleration of ice shedding on the conductor; a v is the acceleration of ice on the conductor.

[0027] Preferably, the preset method of the conductor ice shedding criterion based on transverse cohesive failure control in the S2 step comprises:

[0028] S21. It is judged whether the ice conductor is wrapped or not. If yes, the cohesive force between the ice unit and the conductor contact surface is set as F adhesive At this time, the critical condition of transverse cohesive failure of the wrapped ice on the conductor can be obtained according to the vertical force balance as follows: wherein:

[0029]

[0030] wherein τ adhesive is the cohesive strength between the conductor and the ice unit contact surface; and are the inertial accelerations of the upper and lower parts of the wrapped ice conductor in the critical state of transverse cohesive failure of the ice on the conductor, respectively;

[0031] The ice shedding criterion of the wrapped ice conductor controlled by transverse cohesive failure can be further obtained as follows:

[0032]

[0033] wherein a critical is the critical acceleration of ice shedding on the conductor; a v is the acceleration of ice on the conductor.

[0034] S22. If the ice conductor is a non-wrapped ice conductor, the conductor ice shedding criterion controlled by transverse cohesive failure is as follows:

[0035]

[0036] wherein a critical is the critical acceleration of ice shedding on the conductor; and are the inertial accelerations of the upper and lower parts of the non-wrapped ice conductor in the critical state of transverse cohesive failure of the ice on the conductor, respectively.

[0037] Preferably, the preset method of the conductor ice shedding criterion based on longitudinal fracture failure control in the S3 step comprises:

[0038] S31. If the icing conductor is of the wrapped type, the icing shedding criterion for the longitudinal fracture failure control of the wrapped icing conductor can be expressed as:

[0039]

[0040] wherein: and are the inertial accelerations at the critical state of the longitudinal fracture failure of the icing conductor with only the upper part or the lower part of the icing conductor, respectively, q ice is the unit length weight of the icing conductor; H ice is the initial horizontal tension of the icing conductor.

[0041] S32. If the icing conductor is of the non-wrapped type, the icing shedding criterion for the longitudinal fracture failure control of the conductor can be expressed as:

[0042]

[0043] wherein: and are the inertial accelerations at the critical state of the longitudinal fracture failure of the icing conductor with only the upper part or the lower part of the icing conductor, respectively, q ice is the unit length weight of the icing conductor; H ice is the initial horizontal tension of the icing conductor.

[0044] Preferably, the specific calculation method for calculating the failure time sequence of the icing of the lower part of the conductor in the S4 step comprises:

[0045] S41. For the icing of the lower part of the wrapped icing conductor, the time sequence of the failure can be obtained by comparing the critical accelerations of the transverse cohesive failure cohesive failure and the longitudinal fracture failure .

[0046] S42. For the icing of the lower part of the non-wrapped icing conductor, the icing of the conductor will be separated from the conductor after the transverse cohesive failure and the longitudinal fracture failure, at this time, the time sequence of the failure can be obtained by comparing the critical accelerations of the transverse cohesive failure and the longitudinal fracture failure .

[0047] Preferably, the specific comparison method for obtaining the time sequence of the failure by comparison in the S41 step comprises:

[0048] (1) When the following condition is met: At this time, the sequence of the damage of the lower icing part of the conductor is longitudinal fracture damage, transverse cohesive damage, and transverse cohesion damage, and the shedding criterion is Simplify It can be obtained that:

[0049]

[0050] (2) When At this time, the sequence of the damage of the lower icing part of the conductor is longitudinal fracture damage, transverse cohesive damage, and transverse cohesion damage, and the shedding criterion is Simplify It can be obtained that:

[0051]

[0052] (3) When At this time, the sequence of the damage of the lower icing part of the conductor is transverse cohesion damage, longitudinal fracture damage, and transverse cohesive damage, and the shedding criterion is Simplify It can be obtained that:

[0053]

[0054] (4) When At this time, the sequence of the damage of the lower icing part of the conductor is transverse cohesion damage, transverse cohesive damage, and longitudinal fracture damage, and the shedding criterion is Simplify It can be obtained that:

[0055]

[0056] (5) When At this time, the sequence of the damage of the lower icing part of the conductor is transverse cohesive damage, longitudinal fracture damage, and transverse cohesion damage, and the shedding criterion is Simplify It can be obtained that:

[0057]

[0058] (6) When At this time, the sequence of the damage of the lower icing part of the conductor is transverse cohesive damage, transverse cohesion damage, and longitudinal fracture damage, and the shedding criterion is Simplify It can be obtained that:

[0059]

[0060] Preferably, the specific comparison method for obtaining the sequence of the damage in the S42 step comprises:

[0061] (1) When the following condition is satisfied the sequence of the icing conductor failure is transverse cohesive failure, longitudinal fracture failure, and the conductor shedding criterion is Simplifying we have

[0062]

[0063] (2) When the following condition is satisfied the sequence of the icing conductor failure is longitudinal fracture failure, transverse cohesive failure, and the conductor shedding criterion is Simplifying we have

[0064]

[0065] Preferably, the specific calculation method for calculating the failure sequence of the upper icing of the conductor in the S5 step comprises:

[0066] S51. For the upper icing of the conductor with the wrapped icing, the critical acceleration of the transverse cohesive failure the critical acceleration of the transverse cohesive failure and the critical acceleration of the longitudinal fracture failure satisfy the following relationship:

[0067]

[0068] Therefore, for the upper icing of the conductor with the wrapped icing, the longitudinal fracture failure generally occurs first, and the size relationship between and needs to be compared

[0069] S52. When the following condition is satisfied after simplifying, we have the upper icing first has the longitudinal fracture failure, then has the transverse cohesive failure, and finally is peeled off from the conductor after the transverse cohesive failure, and the conductor shedding criterion is

[0070] S53. When the following condition is satisfied after simplifying, we have at this time, the upper icing first has the longitudinal fracture failure, then has the transverse cohesive failure, and finally is peeled off from the conductor after the transverse cohesive failure, and the conductor shedding criterion is

[0071] S54 For the non-wrapped icing conductor with only the upper icing, since The ice shedding criterion is that the ice element is considered to be shed when the instantaneous acceleration value of the ice element exceeds the critical acceleration value

[0072] An emulation analysis system applied to the ice shedding determination method of the conductor under different damage time sequences, comprising:

[0073] A fine finite element model of the iced transmission line established based on the ANSYS finite element emulation technology, used for simulating the wrapped-type ice and the non-wrapped-type ice;

[0074] The LINK10 three-dimensional rod element is used to simulate the iced conductor element in the model, the LINK8 element is used to simulate the insulator string in the model, the BEAM188 three-dimensional beam element is used to simulate the ice in the model, the conductor element and the ice element share the nodes in the modeling process of the model, and the Rayleigh damping model is used to simulate the structural damping of the line in the model.

[0075] Preferably, the derived ice shedding determination criterion is introduced into the dynamic emulation analysis of the conductor ice shedding to specifically determine the ice shedding of the transmission conductor, and the specific steps include:

[0076] L1. A finite element model of the iced transmission conductor is established in ANSYS, an initial excitation is applied at the node i at the initial moment, the Newmark method is used to solve the dynamic equation of the conductor at any time t, and the Newton-Raphson method is used to iteratively obtain the instantaneous acceleration value a jt of any ice element j;

[0077] L2. When the instantaneous acceleration value of any ice element j exceeds the critical acceleration value, i.e. , the ice element is determined to be shed, the element load, mass, damping and strain of the ice element are set to 0, the stiffness matrix of the ice element is multiplied by a very small factor in ANSYS by using the EKI LL command, and the value of the factor is set to 1.0E-6 by using the EST I F command, so as to kill the ice element and no longer include it in the solution result of the model;

[0078] L3. After the determination of the ice element j is completed, the shedding of the remaining ice elements is determined in turn, until all the N ice elements at the time t are determined, and the system matrix is updated synchronously.

[0079] L4. The solution of the next time step is entered, the time step length of the iterative solution is Δt, the instantaneous acceleration value a j,t+Δt of the residual ice element j on the conductor at the time t+Δt is obtained, and the instantaneous acceleration value a j,t+Δt is compared with the critical acceleration value a criticalThe size of the ice unit is further determined to determine the shedding of the residual ice unit on the conductor, and the system matrix is updated in time.

[0080] L5. When the solution time of the simulation analysis has not reached the set total time T, the solution of the next time step is continued, that is, the process of step L4 is repeated; when T is reached, the numerical calculation is stopped, and the determination process of the simulation analysis is completed.

[0081] The application provides a conductor ice shedding determination method and a simulation analysis system under different damage sequences.

[0082] 1. The application is based on the ice damage mechanism of the conductor, and a conductor ice shedding determination method under different sequences of transverse bonding damage, transverse cohesion damage and longitudinal fracture damage is set, which can be used as the occurrence sequence of each damage and the corresponding determination condition when the ice on the conductor sheds, thereby providing a reference for the real reproduction of the conductor ice shedding process and more accurately predicting the position of the local ice shedding and the ice shedding rate, so that the design waste and safety hazards caused by false prediction are reduced.

[0083] 2. The application can further simulate the dynamic shedding process of the ice along the span under the action of the external impact load by introducing the proposed determination criterion into the simulation system for multi-grade conductor ice shedding numerical simulation, and can further obtain the influence law of the key parameters such as the initial excitation size, excitation position and bonding strength on the ice shedding dynamic process, so as to facilitate the induction and analysis of the weak position of the conductor ice shedding through a large number of numerical simulation results, avoid the deviation caused by artificial assumption, make the numerical simulation of the ice shedding dynamic process more close to the actual situation, improve the reliability and practicability of the simulation results, and help the optimization of the line structure in engineering design. BRIEF DESCRIPTION OF DRAWINGS

[0084] The drawings accompanying the specification of this application are used to provide a further understanding of the application, the illustrative embodiments of the application and the description thereof serve to explain the application, and do not constitute an improper limitation on the application. In the drawings:

[0085] Figure 1 It is a schematic diagram of the overall process of the application;

[0086] Figure 2 It is a schematic diagram of the damage and shedding of the wrapped ice on the conductor of the application;

[0087] Figure 3 It is a schematic diagram of the damage and shedding of the non-wrapped ice on the conductor of the application;

[0088] Figure 4 It is a schematic diagram of the stress of the wrapped ice section under the critical state of transverse cohesion damage of the application;

[0089] Figure 5 Fig. 1 is a schematic diagram of force on the non-wrapped iced conductor of the present application;

[0090] Figure 6 Fig. 2 is a schematic diagram of force on the wrapped iced conductor section in the transverse cohesive failure critical state of the present application;

[0091] Figure 7 Fig. 3 is a schematic diagram of force on the iced micro-element section in the longitudinal fracture failure critical state of the present application;

[0092] Figure 8 Fig. 4 is a schematic diagram of the finite element simulation model of the iced conductor of the present application;

[0093] Figure 9 Fig. 5 is a schematic diagram of the conductor icing simulation of the system of the present application;

[0094] Figure 10 Fig. 6 is a schematic diagram of the de-icing determination flow of the conductor of the system of the present application. DETAILED DESCRIPTION

[0095] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. The embodiments in the present application and the features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0096] In addition, the meaning of "and / or" appearing throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes A solution, or B solution, or A and B solution. In addition, in the embodiments of the present application, "a plurality of" means two or more. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it. When the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist and is not within the scope of protection claimed by the present application.

[0097] In the first embodiment, see Figures 1 to 7 .

[0098] In the prior art: as shown in Figure 2 , the necessary conditions for the upper and lower part of the wrapped iced conductor to fail and fall off are that the transverse cohesive failure occurs between the contact surface of the ice and the conductor, the transverse cohesive failure occurs between the upper and lower part of the ice on the conductor, and the longitudinal fracture failure occurs along the ice span; as shown in Figure 3As shown, the necessary condition for non-wrapped ice to break and fall off is that the transverse cohesive failure occurs between the ice and the conductor contact surface and the longitudinal fracture failure occurs along the ice span, although the conductor ice will break and fall off in a very short time during the ice shedding process, there is a clear time sequence of the occurrence of each failure, and the different time sequence directly affects the determination of ice shedding on the conductor and the dynamic process of line ice shedding.

[0099] When the longitudinal fracture failure and the transverse cohesive failure occur on the conductor ice, regardless of the sequence of the two failures, the transverse cohesive failure of the upper and lower ice on the conductor will play a major control role in the conductor ice shedding determination, at this time, if the inertial acceleration of the ice can reach the critical acceleration to overcome the cohesive force of the upper and lower ice, the ice shedding can be determined, similarly, when the longitudinal fracture failure and the transverse cohesive failure occur on the conductor ice, the transverse cohesive failure will play a major control role in the conductor ice shedding determination; when the transverse cohesive failure and the transverse cohesive failure occur on the conductor ice, the longitudinal fracture failure will play a major control role in the conductor ice shedding determination.

[0100] Based on the above principle, as shown in the present application provides a conductor ice shedding determination method under different failure time sequences, comprising: Figure 1

[0101] S1. presetting a conductor ice shedding determination criterion based on transverse cohesive failure control;

[0102] For wrapped ice conductor, when the transverse tensile failure of the upper and lower ice on the conductor is more difficult than the transverse peeling and longitudinal fracture of the ice, the ice on the conductor will first occur longitudinal fracture failure and transverse cohesive failure, at this time, the transverse cohesive failure plays a major control role in the conductor ice shedding determination.

[0103] Referring to Figure 4 , the preset method of the conductor ice shedding determination criterion based on transverse cohesive failure control comprises:

[0104] S11. selecting a wrapped ice conductor, the self-weight of the upper and lower ice on the conductor is set to and The inertial force of the upper and lower ice is set to and The cohesive force between the upper and lower ice is set to F cohesive At this time, according to the vertical force balance, the critical condition for the transverse cohesive failure of the wrapped ice on the conductor to occur is:

[0105]

[0106] ​S12. Since the vertical span ratio of the conductor is very small, the load p per unit length of the conductor is assumed to be uniformly distributed along the line connecting the suspension points, and the load per unit horizontal projection length of the conductor is set as p / cosβ, β being the height difference angle of the suspension points at both ends of the conductor, so that

[0107]

[0108] where ρ ice is the density of the ice on the conductor, g is the acceleration of gravity, D is the diameter of the bare conductor, L AB is the length of the ice fracture surface AB segment, τ cohesive is the cohesive strength of the ice, L e is the length of the independent ice segment, S t and S b are the cross-sectional areas of the upper and lower ice segments, respectively. and are the inertial accelerations of the upper and lower ice segments of the wrapped ice conductor in the critical state of transverse cohesive failure, respectively.

[0109] S13. The stress geometry of the wrapped ice section can be used to obtain:

[0110]

[0111] where D t is the outer diameter of the circular section of the ice-covered conductor, and e is the eccentricity between the center O2 of the ice-covered conductor and the center C of the bare conductor.

[0112] S14. The ice shedding criterion for the wrapped ice conductor controlled by transverse cohesive failure can be obtained by integrating the above formulas as:

[0113]

[0114] where a critical is the critical acceleration of ice shedding on the conductor, and a v is the acceleration of the ice on the conductor.

[0115] In addition, it should be noted that, as shown in Figure 5 , for non-wrapped ice conductors, since there is only upper or lower ice on the conductor, the ice shedding does not require transverse cohesive failure.

[0116] S2. The conductor ice shedding criterion based on transverse cohesive failure control is preset;

[0117] For wrapped ice conductors, when the transverse peeling between the ice and the conductor contact surface becomes more difficult than the longitudinal fracture of the ice and the transverse tensile fracture of the upper and lower ice on the conductor, the transverse cohesive failure of the ice plays a major controlling role in the conductor ice shedding criterion.

[0118] Therefore, with reference to Figure 6 , the preset method of the conductor icing shedding criterion based on the transverse adhesion failure control comprises:

[0119] S21. Determine whether the icing conductor is a wrapped type. If yes, the adhesion between the icing unit and the conductor contact surface is set as F adhesive At this time, according to the vertical force balance, the critical condition of transverse adhesion failure of the wrapped icing on the conductor can be obtained as wherein:

[0120]

[0121] In the formula: τ adhesive is the adhesion strength between the conductor and the icing unit contact surface; and are the inertial accelerations of the upper and lower parts of the wrapped icing conductor under the critical state of transverse adhesion failure of the icing, respectively;

[0122] Further, the conductor icing shedding criterion based on the transverse adhesion failure control of the wrapped icing can be obtained as:

[0123]

[0124] In the formula: a critical is the critical acceleration of the icing shedding on the conductor; a v is the acceleration of the icing on the conductor;

[0125] It is worth noting that the above conductor icing shedding criterion is not only applicable to the eccentric icing conductor, but also applicable to the uniform circular icing. When the eccentric distance e ≠ 0, it corresponds to the conductor eccentric icing, and when e = 0, it is the uniform circular icing.

[0126] S22. If the icing conductor is a non-wrapped icing conductor, the conductor icing shedding criterion based on the transverse adhesion failure control is:

[0127]

[0128] In the formula: a critical is the critical acceleration of the icing shedding on the conductor; and are the inertial accelerations of the upper and lower parts of the non-wrapped icing conductor under the critical state of transverse adhesion failure of the icing, respectively.

[0129] S3. Preset the conductor icing shedding criterion based on the longitudinal fracture failure control;

[0130] For the covered icing conductor, the transverse cohesive failure and transverse cohesion failure of the icing will occur first when the longitudinal fracture failure of the icing is most difficult to occur. At this time, the longitudinal fracture failure of the icing plays a major control role in the icing shedding determination of the conductor.

[0131] Therefore, referring to Figure 7 , the preset method of the conductor icing shedding determination criterion controlled by the longitudinal fracture failure includes:

[0132] S31. Determine whether the icing conductor is covered, and if so, the conductor icing shedding determination criterion controlled by the longitudinal fracture failure of the covered icing conductor can be expressed as:

[0133]

[0134] In the formula: and are the inertial accelerations of the icing in the critical state of the longitudinal fracture failure of the icing conductor when only the upper part or the lower part of the non-covered icing conductor has icing, q ice is the unit length weight of the icing conductor; H ice is the initial horizontal tension of the icing conductor.

[0135] It is worth noting that the conductor icing shedding determination criterion controlled by the longitudinal fracture failure is irrelevant to the length of the icing element, so the criterion is applicable to icing small sections of different lengths; in addition, the criterion is not only applicable to the eccentric icing conductor, but also applicable to the uniform circular icing, when the eccentric distance e≠0, the corresponding conductor is eccentric icing, and when e=0, it is uniform circular icing.

[0136] S32. If the icing conductor is non-covered icing, the conductor icing shedding determination criterion controlled by the longitudinal fracture failure is:

[0137]

[0138] In the formula: and are the inertial accelerations of the icing in the critical state of the longitudinal fracture failure of the icing conductor when only the upper part or the lower part of the non-covered icing conductor has icing, q ice is the unit length weight of the icing conductor; H ice is the initial horizontal tension of the icing conductor.

[0139] S4. Calculate the failure time sequence of the icing of the lower part of the conductor according to the preset different conductor icing shedding determination criterion.

[0140] The destruction time sequence of the conductor covered by the wrapping type ice is divided into upper and lower two parts of ice. For the lower part of the ice covered by the wrapping type ice conductor, the destruction time sequence can be obtained by comparing the critical acceleration of the transverse cohesive destruction, the cohesive destruction and the longitudinal fracture destruction. The greater the required critical acceleration, the more difficult the ice destruction.

[0141] Therefore, the specific calculation method of calculating the destruction time sequence of the lower part of the ice covered by the conductor includes:

[0142] S41. For the lower part of the ice covered by the wrapping type ice conductor, the destruction time sequence can be obtained by comparing the critical acceleration of the transverse cohesive destruction Cohesive destruction And the longitudinal fracture destruction ;

[0143] At this time, the specific comparison method for obtaining the destruction time sequence by comparison includes:

[0144] (1) When , at this time, the destruction time sequence of the lower part of the ice covered by the conductor is longitudinal fracture destruction, transverse cohesive destruction, transverse cohesive destruction, and the shedding criterion is Simplified can be obtained:

[0145]

[0146] (2) When , the destruction time sequence of the lower part of the ice covered by the conductor is longitudinal fracture destruction, transverse cohesive destruction, transverse cohesive destruction, and the shedding criterion is Simplified can be obtained:

[0147]

[0148] (3) When , the destruction time sequence of the lower part of the ice covered by the conductor is transverse cohesive destruction, longitudinal fracture destruction, and transverse cohesive destruction, and the shedding criterion is Simplified can be obtained:

[0149]

[0150] (4) When , the destruction time sequence of the lower part of the ice covered by the conductor is transverse cohesive destruction, transverse cohesive destruction, and longitudinal fracture destruction, and the shedding criterion is Simplified can be obtained:

[0151]

[0152] (5) When the condition is met, the sequence of the icing damage of the lower part of the conductor is the transverse cohesive damage, the longitudinal fracture damage, and the transverse cohesive damage, and the shedding criterion is Simplifying we can get:

[0153]

[0154] (6) When the condition is met, the sequence of the icing damage of the lower part of the conductor is the transverse cohesive damage, the transverse cohesive damage, and the longitudinal fracture damage, and the shedding criterion is Simplifying we can get:

[0155]

[0156] S42. For the non-wrapped icing conductor with only the lower part of the conductor icing, the conductor icing will fall off the conductor after the transverse cohesive damage and the longitudinal fracture damage, and at this time, only the critical acceleration of the transverse cohesive damage and the longitudinal fracture damage need to be compared, and the sequence of the damage occurrence can be obtained.

[0157] At this time, the specific comparison method for obtaining the sequence of the damage occurrence through comparison includes:

[0158] (1) When the condition is met, the sequence of the icing damage of the conductor is the transverse cohesive damage and the longitudinal fracture damage, and the shedding criterion is Simplifying we can get:

[0159]

[0160] (2) When the condition is met, the sequence of the non-wrapped icing damage of the conductor is the longitudinal fracture damage and the transverse cohesive damage, and the shedding criterion is Simplifying we can get:

[0161]

[0162] S5. The damage sequence of the upper part of the conductor icing is calculated according to the preset different conductor icing shedding criterion.

[0163] The specific calculation method for calculating the damage sequence of the upper part of the conductor icing includes:

[0164] S51. For the upper part of the conductor icing of the wrapped icing conductor, the critical acceleration of the transverse cohesive damage Critical acceleration of transverse bond failure and critical acceleration of longitudinal fracture failure Satisfy the following relationship:

[0165]

[0166] Therefore, for the upper icing of the wrapped icing conductor, the longitudinal fracture failure generally occurs first, and the timing of the occurrence of the transverse bond and cohesion failure needs to be compared and The size relationship

[0167] S52. When is satisfied, after simplification, it is The upper icing first occurs longitudinal fracture failure, followed by transverse cohesion failure, and finally peels off the conductor after the transverse bond failure occurs, and the shedding criterion is

[0168] S53. When is satisfied, after simplification, it is At this time, the upper icing first occurs longitudinal fracture failure, followed by transverse bond failure, and finally peels off the conductor after the transverse cohesion failure occurs, and the shedding criterion is

[0169] S54 For the non-wrapped icing conductor with only upper icing, since is always true under different parameter conditions, the upper icing first occurs longitudinal fracture failure, and then peels off the conductor after the transverse bond failure occurs, and the shedding criterion is

[0170] S6. The preset different conductor icing shedding criteria and the calculation timing data input simulation analysis system are dynamically evolved for the icing shedding determination of the transmission conductor.

[0171] On the basis of the above embodiment, a second embodiment is proposed, which is described in detail in Figure 8 , Figure 9 and Figure 10 .

[0172] Based on the above first embodiment, referring to Figure 8 and Figure 9 , the application further provides a simulation analysis system applied to the conductor icing shedding determination method under different failure timing proposed in the above first embodiment, and the system comprises:

[0173] Based on the ANSYS finite element simulation technology, a refined finite element model of a 500kV four-grade four-split icing transmission line is established, which is used to simulate wrapped icing and non-wrapped icing;

[0174] The 500kV four-grade four-bundle iced transmission conductor wire's conductor-insulator string-ice finite element model is established based on ANSYS finite element simulation technology and only the lower part of the iced true-type conductor wire ice shape, and is only used to simulate non-wrapped type icing;

[0175] In the model, LINK10 is used to simulate the iced conductor wire unit, LINK8 is used to simulate the insulator string, and BEAM188 is used to simulate the ice in the model. In the modeling process, the conductor wire unit and the ice unit share a total of 136 nodes. Rayleigh damping model is used to simulate the structural damping of the line.

[0176] It should be noted that the transmission line includes a transmission tower, a conductor wire, a ground wire, a fitting, an insulator string, a spacer rod, etc., and the conductor wire is one of the important components of the transmission line. The above established conductor-insulator string-ice finite element model is a specific implementation model proposed for non-wrapped type icing for the fine finite element model of the iced transmission line.

[0177] Further, it should be noted that the number of shared nodes is divided according to the actual icing transmission line specific parameter value (for example, 500kV four-grade four-bundle), and for other transmission lines of different lengths, the number of nodes should be divided according to the actual icing transmission line. The main division principle is to divide a node every 10 meters on the transmission line, which can ensure both the simulation accuracy of ice shedding and the simulation efficiency, and avoid inefficient simulation caused by too close node distance.

[0178] The physical parameter values of the equivalent single conductor wire are shown in the following table:

[0179]

[0180] The physical parameter values of the iced conductor wire are shown in the following table:

[0181]

[0182] In the process of realizing the finite element of the conductor wire icing shedding, the specific implementation steps include:

[0183] An impact load F with a size range of 100-500N and a vertical downward direction is applied at the position of the conductor wire node i to simulate the initial excitation of the iced conductor wire by the outside world. initial

[0184] ​Considering the randomness of the initial excitation position on the line, the position interval of the impact load on the conductor is set to about 50 m, that is, it acts on nodes i = 6, 11, 16, 21, 26, 32, 37, 42, 47, 52, 57, 62, 67, 72, 77, 82, 87, 92, 97, 102, 107, 112, 118, 125, 130, 134, respectively. The distribution of node numbers on the line can be referred to Figure 8 .

[0185] The data of the bonding strength τ adhesive at the contact surface with the ice unit here are the commonly used data in the prior art. The type of ice in the test is artificial ice, and the ice on the aluminum matrix is stripped by centrifugal method. The bonding strength value obtained by testing is scattered in a large range, and the bonding strength τ adhesive in some typical working conditions is about 2 kPa. Considering that the bonding strength between the ice and the conductor in the actual situation will be less than the bonding strength between the artificial ice and the substrate under laboratory conditions, the value range of the bonding strength τ adhesive in the ice shedding criterion proposed here is set to 0.9-1.2 kPa.

[0186] Also, the cohesion strength τ cohesive of the conductor ice in the prior art is rarely tested. Therefore, for the glaze type ice, it is generally considered that the bonding strength τ adhesive between the ice and the conductor will be greater than the cohesion strength τ cohesive of the ice, so in this embodiment, only the lower part of the non-wrapped ice conductor with ice meets the judgment condition of the failure occurrence sequence mentioned in the above method (that is, τ ), therefore, the ice first longitudinally breaks and breaks into several small ice segments, and then the ice segments and the conductor contact surface between them are horizontally peeled off and separated from the conductor, and the ice shedding criterion is

[0187] At this time, in order to simulate the situation that the initial excitation of the outside induces the ice on the conductor to fall off, the derived ice shedding criterion is introduced into the dynamic simulation analysis of the ice shedding of the conductor, which can be referred to Figure 10 At this time, the specific steps of the ice shedding criterion of the power transmission conductor include:

[0188] L1. In ANSYS, a finite element model of the ice-covered power transmission conductor is established, an initial excitation is applied at node i at the initial moment, the Newmark method is used to solve the dynamic equation of the conductor at any time t, and the Newton-Raphson method is used to iteratively obtain the transient acceleration value a jt of any ice element j;

[0189] L2. In the simulation analysis, when the transient acceleration value of any ice element j exceeds the critical acceleration value, that is, When the ice element is determined to have detached, its element load, mass, damping, and strain are set to 0. In ANSYS, the stiffness matrix of the ice element is multiplied by a very small factor using the EKI LL command, and the value of the factor is set to 1.0E-6 using the EST IF command, thereby killing the ice element and removing it from the solution results of the model.

[0190] L3. After determining whether ice unit j has fallen off, determine whether the remaining ice units have fallen off in turn, until all N ice units at time t have been determined, and the system matrix is ​​updated synchronously.

[0191] L4. Proceed to the next time step of the solution. The time step for the iterative solution is Δt. Obtain the transient acceleration value a of the residual ice element j on the conductor at time t+Δt. j,t+Δt By comparing a j,t+Δt With the critical acceleration value a critical The magnitude of the ice concentration is used to further determine the extent of ice detachment from the conductor and to update the system matrix in a timely manner.

[0192] L5. If the solution time of the simulation analysis has not yet reached the set total time T, continue to the next time step, that is, repeat the process of step L4; when T is reached, stop the numerical calculation and complete the judgment process of the simulation analysis.

[0193] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining conductor de-icing under different damage sequences, characterized in that, include: S1. Preset conductor de-icing judgment criteria based on lateral cohesive failure control; S2. Preset conductor de-icing judgment criteria based on lateral adhesion failure control; S3. Preset conductor de-icing judgment criteria based on longitudinal fracture damage control; S4. Calculate the failure sequence of ice accumulation on the lower part of the conductor according to the preset different conductor de-icing judgment criteria; S5. Calculate the failure sequence of ice covering the upper part of the conductor according to the preset different conductor de-icing judgment criteria; S6. Preset different conductor de-icing judgment criteria and calculation time sequence data are input into the simulation analysis system for dynamic evolution, which is used for the de-icing judgment of transmission conductors; The specific calculation method for calculating the failure sequence of ice accumulation on the lower part of the conductor in step S4 includes: S41. For the lower part of the wrapped-type icing conductor, lateral adhesion failure is compared. Cohesion destruction and longitudinal fracture failure The critical acceleration can be used to determine the timing of the failure. S42. For non-encased icing conductors with only the lower portion iced, the ice will detach from the conductor after lateral adhesive failure and longitudinal fracture failure. In this case, only lateral adhesive failure is required. Longitudinal fracture failure By comparing the critical accelerations, the sequence of events in which the damage occurred can be obtained; The specific calculation method for calculating the damage sequence of ice accumulation on the upper part of the conductor in step S5 includes: S51. For the upper part of an ice-covered conductor with a wrapped structure, longitudinal fracture occurs first. To determine the timing of transverse bonding and cohesive failure, it is necessary to compare the critical acceleration at which transverse cohesive failure occurs. Critical acceleration for transverse bond failure Size relationship; S52. When satisfied At that time, the upper part of the ice-covered part first underwent longitudinal fracture failure, followed by transverse cohesive failure, and finally the conductor was peeled off after transverse adhesive failure. S53. When satisfied At that time, the upper part of the ice-covered part first experienced longitudinal fracture failure, followed by transverse adhesive failure, and finally broke off from the conductor after transverse cohesive failure. For non-wrapped icing conductors with only the upper part covered by ice, the upper part of the ice first undergoes longitudinal fracture failure, and then detaches from the conductor after transverse bonding failure.

2. The method for determining conductor de-icing under different damage sequences as described in claim 1, characterized in that, The preset method for determining conductor de-icing based on lateral cohesion failure control in step S1 includes: S11. Select a wrapped-type icing conductor, and set the self-weight of the ice covering the upper and lower parts of the conductor as follows: and The inertial forces of the upper and lower parts covered by ice are respectively set as follows: and The cohesion between the upper and lower ice-covered parts is set to F cohesive At this point, based on the vertical force balance, the critical condition for the transverse cohesive failure of the encased ice on the conductor can be obtained as follows: S12. Since the sag-to-span ratio of the conductor is very small, the load per unit length of the conductor is approximately assumed to be... p If the load is uniformly distributed along the line connecting the suspension points, then the load per unit horizontal projected length of the conductor is set as follows: p / cosβ , β Let be the angle of elevation difference between the two suspension points of the conductor, then we have: In the formula: ρ ice The density of the ice covering the conductor; g D is the acceleration due to gravity; D is the diameter of the bare wire. L AB The length of segment AB of the ice-covered fracture surface; τ cohesive The cohesive strength of the ice layer; L e The length of an independent icing segment; and These are the cross-sectional areas of the upper and lower ice coverings, respectively. and These are the inertial accelerations at the critical state of transverse cohesive failure of the upper and lower parts of the wrapped-type icing conductor, respectively. S13. The following can be obtained from the geometric relationship of the forces acting on the encased ice-covered section: In the formula: D t The outer diameter of the circular cross-section where the ice-covered conductor is located; e Center of the ice-covered conductor O 2. Eccentricity between the conductor and the center C of the bare conductor; S14. Combining the above steps and formulas, the criterion for determining the de-icing of wrapped-type icing conductors under transverse cohesive failure control can be obtained as follows: In the formula: a critical The critical acceleration for ice to detach from the conductor; a v This is the acceleration of the conductor covered with ice.

3. The method for determining conductor de-icing under different damage sequences as described in claim 2, characterized in that, The preset method for determining conductor de-icing based on lateral bond failure control in step S2 includes: S21. Determine if the icing conductor is a wrap-around type. If so, set the adhesion force between the ice unit and the conductor contact surface to... F adhesive At this point, based on the vertical force balance, the critical condition for the transverse adhesion failure of the ice-covered conductor can be obtained as follows: ,in: In the formula: τ adhesive The bonding strength between the conductor and the contact surface of the ice unit; and These are the inertial accelerations at the critical state of transverse adhesion failure of the upper and lower parts of the wrapped ice-covered conductor, respectively. Therefore, the criterion for determining the de-icing of wrapped-type icing conductors under lateral bond failure control can be obtained as follows: In the formula: a critical The critical acceleration for ice to detach from the conductor; a v This is the acceleration of the conductor covered with ice; S22. If the icing conductor is a non-wrapped icing conductor, the criterion for determining conductor de-icing under lateral adhesion failure control is: In the formula: a critical The critical acceleration for ice to detach from the conductor; and These are the inertial accelerations at the critical state of lateral adhesion failure of an unwrapped icing conductor when only the upper and lower parts are covered with ice.

4. The method for determining conductor de-icing under different damage sequences as described in claim 3, characterized in that, The preset method for determining conductor de-icing based on longitudinal fracture damage control in step S3 includes: S31. Determine whether the icing conductor is a wrapped type. If so, the criterion for determining the de-icing of a wrapped type icing conductor under longitudinal fracture control can be expressed as follows: In the formula: and These are the inertial accelerations at the critical state of longitudinal fracture failure when only the upper and lower parts of an unwrapped icing conductor are iced. q ice The weight per unit length of the ice-covered conductor; H ice The initial horizontal tension of the ice-covered conductor; S32. If the icing of the conductor is non-encased, the criterion for determining conductor de-icing controlled by longitudinal fracture failure is as follows: In the formula: and These are the inertial accelerations at the critical state of longitudinal fracture failure when only the upper and lower parts of an unwrapped icing conductor are iced. q ice The weight per unit length of the ice-covered conductor; H ice The initial horizontal tension of the icy conductor.

5. The method for determining conductor de-icing under different damage sequences as described in claim 4, characterized in that, The specific comparison method used in step S41 to determine the chronological order of the damage includes: (1) When satisfied At this time, the sequence of ice-induced failure in the lower part of the conductor is longitudinal fracture failure, transverse bonding failure, and transverse cohesive failure. The detachment judgment criterion is as follows: , simplify We can obtain: (2) When satisfied At that time, the sequence of ice-induced failure in the lower part of the conductor was longitudinal fracture failure, transverse cohesive failure, and transverse bonding failure. The detachment criterion at this point was... , simplify We can obtain: (3) When satisfied At that time, the sequence of ice-induced failure in the lower part of the conductor was transverse cohesive failure, longitudinal fracture failure, and transverse bonding failure. The detachment criterion at this point was... , simplify We can obtain: (4) When satisfied At this time, the sequence of ice-induced failure in the lower part of the conductor is: transverse cohesive failure, transverse bonding failure, and longitudinal fracture failure. The criterion for determining detachment at this point is... , simplify We can obtain: (5) When satisfied At that time, the sequence of ice-induced failure in the lower part of the conductor was transverse bonding failure, longitudinal fracture failure, and transverse cohesive failure. The criterion for determining detachment at this point was... , simplify We can obtain: (6) When satisfied At that time, the sequence of ice-induced failure in the lower part of the conductor was transverse bonding failure, transverse cohesive failure, and longitudinal fracture failure. The criterion for determining detachment at this point was... , simplify We can obtain: 。 6. The method for determining conductor de-icing under different damage sequences as described in claim 4, characterized in that, The specific comparison method used in step S42 to obtain the chronological order of the damage includes: (1) When satisfied At that time, the sequence of ice-induced damage to the conductor was transverse adhesion failure followed by longitudinal fracture failure. The criterion for determining detachment at this point was... , simplify We can obtain: (2) When satisfied At this time, the sequence of non-encased icing failure of the conductor is longitudinal fracture failure followed by transverse adhesion failure. The criterion for determining detachment in this case is... , simplify We can obtain: 。 7. The method for determining conductor de-icing under different damage sequences as described in claim 1, characterized in that, The specific comparison methods in step S5 include: S51. For the upper part of an ice-covered conductor with a wrapped shape, the critical acceleration for transverse cohesive failure. Critical acceleration for transverse bond failure Critical acceleration for longitudinal fracture failure The following relationship must be satisfied: The timing of transverse bond failure and cohesive failure needs to be compared. and Size relationship S52. When satisfied When, after simplification, it becomes The upper part of the icing first undergoes longitudinal fracture failure, followed by transverse cohesive failure, and finally, transverse adhesive failure leads to the detachment of the conductor. The detachment criterion is as follows: ; S53. When satisfied When, after simplification, it becomes At this point, the upper part of the icing first undergoes longitudinal fracture failure, followed by transverse adhesive failure, and finally breaks off from the conductor after transverse cohesive failure. The detachment criterion is as follows: ; For S54, the icing effect varies depending on the parameters of the non-wrapped icing conductor with only the upper part covered by ice. The condition is always true; therefore, the upper part of the icing first undergoes longitudinal fracture failure, followed by transverse bonding failure before detaching from the conductor. The detachment criterion is as follows: .

8. A simulation analysis system, applied to the conductor de-icing determination method under different failure sequences as described in any one of claims 1-7, characterized in that, include: A refined finite element model of an icing transmission line, established based on ANSYS finite element simulation technology, is used to simulate enclosed icing and non-enclosed icing. The model uses LINK10 three-dimensional pole elements to simulate icing conductor elements, LINK8 elements to simulate insulator strings, and BEAM188 three-dimensional beam elements to simulate icing. During the modeling process, conductor elements and icing elements share nodes. The model uses a Rayleigh damping model to simulate the structural damping of the line.

9. The simulation analysis system as described in claim 8, characterized in that, The specific steps for applying the derived de-icing judgment criteria to the dynamic simulation analysis of conductor de-icing in transmission line de-icing judgment include: L1. A finite element model of an ice-covered transmission line is established in ANSYS. Initial excitation is applied at node i at the initial moment. The unconditionally stable Newmark method is used to solve the dynamic equation of the conductor at any time t. The Newton-Raphson method is used to iteratively obtain the transient acceleration value of any ice element j. a jt ; L2. In the simulation analysis, when the transient acceleration value of any ice element j exceeds the critical acceleration value, i.e. When the ice element is determined to have detached, its element load, mass, damping, and strain are set to 0. In ANSYS, the EKILL command is used to multiply the stiffness matrix of the ice element by a very small factor. The ESTIF command is used to set the value of the factor to 1.0E-6, thereby killing the ice element and removing it from the solution results of the model. L3. After determining whether ice unit j has fallen off, determine whether the remaining ice units have fallen off, until all N ice units at time t have been determined, and update the system matrix synchronously. L4. Proceed to the next time step of the solution process. The time step for iterative solution is... Δt , obtain t+Δt The transient acceleration value of residual ice element j on the conductor at time t. a j,t+Δt By comparison a j,t+Δt With critical acceleration value a critical The size of the ice crystals is used to further determine the extent of ice detachment from the conductor and to update the system matrix in a timely manner. L5. If the solution time of the simulation analysis has not yet reached the set total time T, continue to the next time step, that is, repeat the process of step L4; when T is reached, stop the numerical calculation and complete the judgment process of the simulation analysis.

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