Wire deicing judgment method under different damage time sequences and simulation analysis system

Abstract

The invention discloses a lead deicing judgment method under different damage time sequences. The lead deicing judgment method comprises the following steps: S1, presetting a lead deicing judgment criterion based on transverse cohesion damage control; s2, presetting a wire deicing judgment criterion based on transverse bonding failure control; s3, presetting a wire deicing judgment criterion based on longitudinal fracture failure control; s4, calculating a damage time sequence of ice coating of the lower part of the lead according to different preset lead deicing judgment criteria; s5, calculating a damage time sequence of partial ice coating on the wire according to different preset wire deicing judgment criteria; and S6, inputting preset different conductor deicing judgment criteria and calculation time sequence data into a simulation analysis system for dynamic evolution for transmission conductor deicing judgment. According to the method, reference can be provided for real reproduction of the wire deicing process, and the local deicing position and the deicing rate can be predicted more accurately, so that design waste and potential safety hazards caused by wrong prediction are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of ice melting and de-icing of power transmission lines, and in particular to a method for determining de-icing of a conductor under different damage time sequences and a simulation analysis system. Background Art

[0002] The key issue in the study of the dynamic response of transmission line conductor shedding ice jump is to determine the reasonable shedding ice form of the line, which is not only directly related to the conductor tension value and shedding ice jump trajectory, but also the premise for conducting numerical simulation and artificial simulation tests of shedding ice dynamic behavior. Traditionally, the shedding ice form recommended by the "Design Manual of High Voltage Transmission Lines for Electric Power Engineering" and the "Technical Code for Design of Overhead Transmission Lines with Heavy Ice" is mainly adopted in the design of transmission lines, that is, only the middle stage of the continuous stage conductor is shedding ice, and the shedding ice rate should be determined according to actual operating experience; when there is a lack of shedding ice rate data, the shedding ice rate for the medium ice zone and heavy ice zone transmission lines of 110~220kV shall be not less than 50% and 60% of the design ice weight respectively, and for 330kV and above lines, the shedding ice rate shall be not less than 70% and 80% of the design ice weight respectively.

[0003] In addition to the above-mentioned artificially assumed deicing forms, in recent years, some researchers have carried out numerical simulations of the dynamic process of conductor deicing based on the criteria for judging the shedding of ice. There are three main criteria for judging deicing, namely the stress criterion, the strain criterion and the acceleration criterion: (1) The stress criterion takes into account the axial stress and bending stress of the ice on the conductor. When any point in the ice unit reaches the maximum allowable plastic stress, the deicing is judged to have occurred. Therefore, the stress criterion can more accurately predict the changes in the tension and mid-span displacement of the conductor during the deicing process, but it will overestimate the deicing rate of the line; (2) The strain criterion believes that when the strain of the ice exceeds the maximum allowable plastic stress, the deicing rate will increase. When the conductor is subjected to plastic strain, the ice falls off the conductor. Therefore, the line de-icing rate can be predicted more accurately. However, it still cannot explain the phenomenon that the ice on the conductor is separated into many fragments instead of falling off directly under the impact load. (3) The acceleration criterion divides the conductor de-icing process into two stages. The first stage is the transverse wave generated by the initial impact, which causes the ice unit to break into independent ice fragments. This stage can be judged by the stress criterion or the strain criterion. The second stage is when the inertia force of the ice fragments can simultaneously overcome the bonding force between the ice and the conductor and the cohesive force of the ice itself during the conductor vibration process, and the ice is judged to have fallen off.

[0004] In fact, there are still many deficiencies in the existing technology for judging the deicing form and deicing rate of conductors. On the one hand, the recommended deicing form of only intermediate deicing lacks scientific basis, which will cause adverse deicing dynamic response and may cause great waste in design. On the other hand, only the value recommendation of the conductor deicing rate is provided, but the specific location of local deicing is not clear, which brings certain difficulties to engineering applications. At the same time, the conductor deicing jump height is very sensitive to the location of local deicing. In addition, a small number of numerical simulations of the dynamic process of conductor deicing based on deicing judgment criteria can avoid the problem of artificial assumptions of deicing forms that are out of touch with reality to a certain extent. However, the existing icing failure criteria are not entirely reasonable. They are divorced from the actual damage mechanism of conductor icing and it is difficult to effectively achieve the true reproduction of the deicing process.

[0005] To this end, the present application specifically proposes a conductor deicing determination method and a simulation analysis system under different damage time sequences to solve the above technical problems. Summary of the invention

[0006] Based on the technical problems raised above, the main purpose of the present invention is to provide a method and simulation analysis system for determining conductor deicing under different damage sequences of transverse bonding failure, transverse cohesive failure and longitudinal fracture failure of ice coating, which can correspond to the occurrence sequence of each damage and its corresponding determination conditions when the ice coating on the conductor falls off, introduce the proposed determination criteria into the multi-stage conductor deicing numerical simulation, simulate the dynamic deicing process along the span under the action of external impact load, and summarize the induced deicing probability of the conductor by utilizing the influence of the changes in key parameters such as the initial excitation size, excitation position, and bonding strength on the dynamic deicing process in combination with a large number of numerical simulation results, so as to facilitate further analysis of the weak positions of the conductor deicing, and further propose specific local deicing forms of the conductor in combination with the existing line design.

[0007] The present invention adopts the following technical solutions to solve the above technical problems:

[0008] A method for determining conductor deicing under different damage time sequences, comprising:

[0009] S1. Preset the wire deicing judgment criteria based on lateral cohesive failure control;

[0010] S2. Preset the wire deicing judgment criteria based on lateral bonding failure control;

[0011] S3. Preset the wire deicing judgment criteria based on longitudinal fracture damage control;

[0012] S4. Calculate the destruction time sequence of ice covering the lower part of the conductor according to different preset conductor deicing judgment criteria;

[0013] S5. Calculate the destruction time sequence of ice covering on the conductor according to different preset conductor deicing judgment criteria;

[0014] S6. The preset different conductor deicing judgment criteria and calculation time series data are input into the simulation analysis system for dynamic evolution and used for transmission conductor deicing judgment.

[0015] Preferably, the method for presetting the wire deicing judgment criterion based on lateral cohesive failure control in step S1 includes:

[0016] S11. Select the wrapped ice-covered conductor, and set the deadweight of the ice on the upper and lower parts of the conductor to and The inertial forces of the upper and lower ice covering are set as and The cohesion between the upper and lower ice cover 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 can be obtained as follows:

[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 line connecting the suspension points. The load per unit horizontal projection length of the conductor is set to p / cosβ, where β is the height difference angle of the suspension points at both ends of the conductor. Then:

[0019]

[0020] Where: ice is the density of 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 AB segment of the ice-covered fracture surface; τ cohesive is the cohesive strength of the ice; L e is the length of the independent ice-covered segment; S t and S b are the cross-sectional areas of ice covering the upper and lower parts, respectively; and They are the inertial acceleration of the upper and lower parts of the wrapped ice-covered conductor under the critical state of lateral cohesive failure;

[0021] S13. The geometric relationship of the force on the wrapped ice-covered section can be obtained:

[0022]

[0023] Where: D t is the outer diameter of the circular cross section where the ice-covered conductor is located; e is the eccentricity between the center O2 of the ice-covered conductor and the center C of the bare conductor;

[0024] S14. Combining the above formulas, the deicing criterion for wrapped ice-covered conductors controlled by lateral cohesive failure can be obtained as follows:

[0025]

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

[0027] Preferably, the preset method of the wire deicing judgment criterion based on the lateral bonding failure control in step S2 includes:

[0028] S21. Determine whether the ice-covered conductor is a wrapping type. If so, set the bonding force between the ice unit and the conductor contact surface to F. adhesive At this time, according to the vertical force balance, the critical condition for the transverse bonding failure of the wrapped ice on the conductor can be obtained as in:

[0029]

[0030] Where: τ adhesive is the bonding strength between the conductor and the ice unit contact surface; and They are the inertial acceleration of the upper and lower parts of the wrapped ice-covered conductor under the critical state of lateral bonding failure;

[0031] Then, the deicing criterion for the wrapped ice-covered conductor controlled by transverse bonding failure can be obtained as follows:

[0032]

[0033] Where: 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-covered conductor is a non-wrapped ice-covered conductor, the criterion for conductor deicing controlled by transverse bonding failure is:

[0035]

[0036] Where: a critical is the critical acceleration of ice shedding on the conductor; and They are the inertial acceleration under the critical state of lateral bonding failure of ice when only the upper and lower parts of the non-wrapped ice-covered conductor are covered with ice.

[0037] Preferably, the preset method of the wire deicing judgment criterion based on longitudinal fracture damage control in step S3 includes:

[0038] S31. Determine whether the ice-covered conductor is of the wrapped type. If so, the deicing criterion for the wrapped type ice-covered conductor controlled by longitudinal fracture damage can be expressed as:

[0039]

[0040] Where: and are the inertial accelerations of the non-wrapped ice-covered conductor when only the upper and lower parts are covered with ice and the ice-covered conductor is in a critical state of longitudinal fracture, q ice H is the deadweight of ice-covered conductor per unit length; ice is the initial horizontal tension of the ice-covered conductor;

[0041] S32. If the ice-covered conductor is non-wrapped ice, the criteria for judging the de-icing of the conductor under longitudinal fracture damage control are:

[0042]

[0043] Where: and are the inertial accelerations of the non-wrapped ice-covered conductor when only the upper and lower parts are covered with ice and the ice-covered conductor is in a critical state of longitudinal fracture, q ice H is the deadweight of ice-covered conductor per unit length; ice is the initial horizontal tension of the ice-covered conductor.

[0044] Preferably, the specific calculation method for calculating the damage time sequence of ice covering the lower part of the conductor in step S4 includes:

[0045] S41. For the ice on the lower part of the wrapped ice-covered conductor, the lateral bonding failure is compared. Cohesive failure and longitudinal fracture failure The critical acceleration can be used to obtain the sequence of the occurrence of damage;

[0046] S42. For non-wrapped iced conductors with only the lower part covered with ice, the ice on the conductor will separate from the conductor after the transverse bonding failure and longitudinal fracture failure occur. At this time, only the transverse bonding failure is required. Longitudinal fracture failure By comparing the critical accelerations, the sequence of the destruction can be obtained.

[0047] Preferably, the specific comparison method for obtaining the sequence of occurrence of destruction by comparison in step S41 includes:

[0048] (1) When satisfied At this time, the order of ice damage under the conductor is longitudinal fracture damage, transverse bonding damage, and transverse cohesive damage. The criterion for shedding is: Simplify We can get:

[0049]

[0050] (2) When satisfied When the ice damage of the lower part of the conductor is in the order of longitudinal fracture damage, transverse cohesive damage, and transverse bonding damage, the criterion for the fall-off is Simplify We can get:

[0051]

[0052] (3) When satisfied When the ice damage of the lower part of the conductor is in the order of transverse cohesive damage, longitudinal fracture damage, and transverse bonding damage, the criterion for the fall-off is Simplify We can get:

[0053]

[0054] (4) When satisfied When the ice damage of the lower part of the conductor is in the order of transverse cohesive damage, transverse adhesive damage, and longitudinal fracture damage, the criterion for the fall-off is Simplify We can get:

[0055]

[0056] (5) When satisfied When the ice damage of the lower part of the conductor is in the order of transverse bonding damage, longitudinal fracture damage, and transverse cohesive damage, the criterion for the fall-off is Simplify We can get:

[0057]

[0058] (6) When satisfied When the ice damage of the lower part of the conductor occurs, the order of damage is transverse bonding damage, transverse cohesive damage, and longitudinal fracture damage. At this time, the criterion for judging the fall-off is Simplify We can get:

[0059]

[0060] Preferably, the specific comparison method for obtaining the sequence of occurrence of destruction by comparison in step S42 includes:

[0061] (1) When satisfied When the conductor is damaged by ice, the order of damage is transverse bonding damage and longitudinal fracture damage. At this time, the criterion for the fall-off is Simplify We can get:

[0062]

[0063] (2) When satisfied When the non-wrapped ice damage of the conductor occurs, the sequence is longitudinal fracture damage and transverse bonding damage. At this time, the criterion for the fall-off is Simplify We can get:

[0064]

[0065] Preferably, the specific calculation method for calculating the damage time sequence of the partial ice covering on the conductor in step S5 includes:

[0066] S51. Critical acceleration for lateral cohesive failure of the upper part of the wrapped ice-covered conductor Critical acceleration of transverse bond failure and the critical acceleration of longitudinal fracture failure Satisfies the following relationship:

[0067]

[0068] Therefore, for the upper part of the wrapped ice-covered conductor, the longitudinal fracture failure usually occurs first, and the occurrence sequence of the transverse bonding and cohesive failure needs to be compared. and Size relationship

[0069] S52. When satisfied When , it is simplified to The upper part of the ice first undergoes longitudinal fracture failure, followed by transverse cohesive failure, and finally the conductor is peeled off after transverse bonding failure. The criterion for shedding is:

[0070] S53. When satisfied When , it is simplified to At this time, the upper part of the ice first breaks longitudinally, then breaks transversely, and finally breaks away from the conductor after transverse cohesive failure. The criterion for shedding is:

[0071] S54 For non-wrapped ice-covered conductors with only the upper part covered with ice, due to different parameter conditions Therefore, the upper part of the ice first breaks longitudinally, and then breaks away from the conductor after transverse bonding failure. The criterion for shedding is:

[0072] A simulation analysis system is applied to any of the above-mentioned wire deicing determination methods under different damage time sequences, comprising:

[0073] A refined finite element model of ice-covered transmission lines established based on ANSYS finite element simulation technology is used to simulate wrap-type icing and non-wrapped icing;

[0074] The model uses a three-dimensional rod unit LI NK10 to simulate the ice-covered conductor unit, the model uses a LINK8 unit to simulate the insulator string, the model uses a three-dimensional beam unit BEAM188 to simulate icing, the conductor unit and the icing unit share nodes during the modeling process, and the model uses a Rayleigh damping model to simulate the structural damping of the line.

[0075] Preferably, the specific steps of introducing the derived deicing judgment criterion into the conductor deicing dynamic simulation analysis to perform deicing judgment on the transmission conductor include:

[0076] L1. Establish a finite element model of ice-covered transmission line in ANSYS, apply initial excitation at node i at the initial time, use the unconditionally stable Newmark method to solve the conductor dynamic equation at any time t, and use the Newton-Raphson method to iteratively obtain the transient acceleration value a of any ice unit j jt ;

[0077] L2. In the simulation analysis, when the transient acceleration value of any ice unit j exceeds the critical acceleration value, that is, When the ice unit is determined to be detached, the unit load, mass, damping and strain of the ice unit are set to 0. The stiffness matrix of the ice unit is multiplied by a very small factor using the EKI LL command in ANSYS, and the value of the factor is set to 1.0E-6 using the EST IF command, thereby killing the ice unit and no longer including it in the solution of the model.

[0078] L3. After completing the judgment on ice unit j, the remaining ice units are judged in turn whether they have fallen off, until all N ice units at time t are judged, and the system matrix is ​​updated synchronously.

[0079] L4. Enter the next time step solution, the time step of the iterative solution is Δt, and obtain the transient acceleration value a of the residual ice unit j on the wire at time t+Δt j,t+Δt , by comparing a j,t+Δt With critical acceleration value a criticalThe size of the residual ice unit on the conductor is used to further determine the shedding situation and update the system matrix in time.

[0080] L5. When the solution time of the simulation analysis has not reached the set total time T, continue to enter the solution of 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.

[0081] The present invention provides a wire deicing determination method and simulation analysis system under different damage time sequences. Compared with the prior art, the present invention has the following beneficial effects:

[0082] 1. The present invention is based on the conductor ice damage mechanism. By setting a conductor deicing judgment method under different occurrence sequences of transverse bonding failure, transverse cohesive failure and longitudinal fracture failure of ice, it can be used as the occurrence sequence of each failure and its corresponding judgment condition when the ice on the conductor falls off. It not only provides a reference for the true reproduction of the conductor deicing process, but also can more accurately predict the location and deicing rate of local deicing, thereby reducing design waste and safety hazards caused by erroneous predictions.

[0083] 2. The present invention introduces the proposed judgment criteria into the simulation system to perform multi-level conductor deicing numerical simulation, which can further simulate the dynamic deicing process along the span under the action of external impact loads, and further obtain the influence of changes in key parameters such as initial excitation size, excitation position, and bonding strength on the deicing dynamic process. It is convenient to summarize and analyze the weak positions of conductor deicing through a large number of numerical simulation results, avoid the deviations that may be caused by artificial assumptions, make the numerical simulation of the deicing dynamic process closer to the actual situation, improve the reliability and practicality of the simulation results, and help engineering design to optimize the line structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

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

[0086] Figure 2 It is a schematic diagram of the wire wrapping type ice-covering damage and shedding of the present invention;

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

[0088] Figure 4 It is a force diagram of the wrapped ice-covered section under the critical state of transverse cohesive failure of the present invention;

[0089] Figure 5 It is a force diagram of the non-wrapped ice-covered conductor of the present invention;

[0090] Figure 6 It is a force diagram of the wrapped ice-covered cross section under the critical state of transverse bonding failure of the present invention;

[0091] Figure 7 It is a schematic diagram of the force of the ice-covered micro-element cross section under the critical state of longitudinal fracture failure of the present invention;

[0092] Figure 8 It is a schematic diagram of a finite element simulation model of an ice-covered power transmission line of the present invention;

[0093] Fig. 9 A schematic diagram of a conductor ice coating simulation of the system of the present invention;

[0094] Fig.10 The figure is a schematic diagram of the flow chart of the power transmission line deicing determination of the system of the present invention. DETAILED DESCRIPTION

[0095] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0096] In addition, the meaning of "and / or" appearing in the full text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, in the embodiments of the present invention, "multiple" refers to more than two. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the protection scope required by the present invention.

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

[0098] In the prior art: Figure 2 As shown in the figure, the necessary conditions for the upper and lower parts of the ice-covered conductor to break and fall off are transverse bonding failure between the ice and the conductor contact surface, transverse cohesive failure between the upper and lower parts of the conductor, and longitudinal fracture failure along the span of the ice. Figure 3As shown in the figure, the necessary conditions for non-wrapping type ice damage and shedding are transverse bonding damage between the contact surface of the ice and the conductor and longitudinal fracture damage along the span of the ice. Although the conductor ice will be damaged and detached from the conductor in a very short time during the de-icing process, there will be an obvious sequence of occurrence between the various damages. Different sequences directly affect the judgment of the ice shedding on the conductor and the dynamic process of line de-icing.

[0099] When the conductor ice coating suffers longitudinal fracture damage and transverse bonding damage, regardless of the order of occurrence of the two preceding damages, the transverse cohesive damage of the upper and lower parts of the conductor ice coating will play a major controlling role in the determination of conductor de-icing. At this time, if the inertial acceleration of the ice coating can reach the critical acceleration that overcomes the cohesive force of the upper and lower parts, it can be determined that the ice coating has fallen off. Similarly, when the conductor ice coating suffers longitudinal fracture damage and transverse cohesive damage first, the transverse bonding damage will play a major controlling role in the determination of conductor de-icing; when the conductor ice coating suffers transverse bonding damage and transverse cohesive damage first, the longitudinal fracture damage will play a major controlling role in the determination of conductor de-icing.

[0100] Based on the above principles, Figure 1 The present invention provides a method for determining whether a conductor has iced off under different damage time sequences, comprising:

[0101] S1. Preset the wire deicing judgment criteria based on lateral cohesive failure control;

[0102] For wrapped ice-covered conductors, when the lateral pulling off of the ice on the upper and lower parts of the conductor is more difficult than the lateral peeling and longitudinal fracture of the ice, the ice on the conductor will first suffer longitudinal fracture failure and lateral bonding failure. At this time, lateral cohesive failure plays a major controlling role in the judgment of conductor de-icing.

[0103] refer to Figure 4 , the preset method of the conductor deicing judgment criterion based on lateral cohesive failure control includes:

[0104] S11. Select the wrapped ice-covered conductor, and set the deadweight of the ice on the upper and lower parts of the conductor to and The inertial forces of the upper and lower ice covering are set as and The cohesion between the upper and lower ice cover 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 can be obtained as follows:

[0105]

[0106] 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 line connecting the suspension points. The load per unit horizontal projection length of the conductor is set to p / cosβ, where β is the height difference angle of the suspension points at both ends of the conductor. Then:

[0107]

[0108] Where: ice is the density of 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 AB segment of the ice-covered fracture surface; τ cohesive is the cohesive strength of the ice; L e is the length of the independent ice-covered segment; S t and S b are the cross-sectional areas of ice covering the upper and lower parts, respectively; and They are the inertial acceleration of the upper and lower parts of the wrapped ice-covered conductor under the critical state of lateral cohesive failure;

[0109] S13. The geometric relationship of the force on the wrapped ice-covered section can be obtained:

[0110]

[0111] Where: D t is the outer diameter of the circular cross section where the ice-covered conductor is located; e is the eccentricity between the center O2 of the ice-covered conductor and the center C of the bare conductor;

[0112] S14. Combining the above formulas, the deicing criterion for wrapped ice-covered conductors controlled by lateral cohesive failure can be obtained as follows:

[0113]

[0114] Where: a critical is the critical acceleration of ice shedding on the conductor; a v is the acceleration of ice on the wire.

[0115] In addition, it should be noted that Figure 5 As shown, for non-wrapped ice-coated conductors, since only the upper part or the lower part of the conductor is covered with ice, the ice shedding does not require lateral cohesive failure to occur.

[0116] S2. Preset the wire deicing judgment criteria based on lateral bonding failure control;

[0117] For wrapped ice-coated conductors, when the transverse peeling between the ice coating and the contact surface of the conductor becomes more difficult than the longitudinal fracture of the ice coating and the transverse pulling off of the ice coating on the upper and lower parts of the conductor, the transverse bonding failure of the ice coating plays a major controlling role in the judgment of conductor de-icing.

[0118] Therefore, reference Figure 6 , the preset method of the conductor deicing judgment criterion based on the lateral bonding failure control includes:

[0119] S21. Determine whether the ice-covered conductor is a wrapping type. If so, set the bonding force between the ice unit and the conductor contact surface to F. adhesive At this time, according to the vertical force balance, the critical condition for the transverse bonding failure of the wrapped ice on the conductor can be obtained as in:

[0120]

[0121] Where: τ adhesive is the bonding strength between the conductor and the ice unit contact surface; and They are the inertial acceleration of the upper and lower parts of the wrapped ice-covered conductor under the critical state of lateral bonding failure;

[0122] Then, the deicing criterion for the wrapped ice-covered conductor controlled by transverse bonding failure can be obtained as follows:

[0123]

[0124] Where: a critical is the critical acceleration of ice shedding on the conductor; a v is the acceleration of ice on the conductor;

[0125] It is worth noting that the above-mentioned conductor deicing judgment criteria are not only applicable to eccentrically iced conductors, but also to uniform circular ice coverage. When the eccentricity e≠0, it corresponds to the eccentric ice coverage of the conductor, and when e=0, it corresponds to uniform circular ice coverage.

[0126] S22. If the ice-covered conductor is a non-wrapped ice-covered conductor, the criterion for conductor deicing controlled by transverse bonding failure is:

[0127]

[0128] Where: a critical is the critical acceleration of ice shedding on the conductor; and They are the inertial acceleration under the critical state of lateral bonding failure of ice when only the upper and lower parts of the non-wrapped ice-covered conductor are covered with ice.

[0129] S3. Preset the wire deicing judgment criteria based on longitudinal fracture damage control;

[0130] For wrapped ice-covered conductors, when the longitudinal fracture of the conductor ice is the most difficult to occur, the ice will first cause transverse bonding failure and transverse cohesive failure. At this time, the longitudinal fracture of the ice plays a major controlling role in the determination of conductor deicing.

[0131] Therefore, reference Figure 7 As shown, the preset method of the conductor deicing judgment criterion based on longitudinal fracture damage control includes:

[0132] S31. Determine whether the ice-covered conductor is of the wrapped type. If so, the deicing criterion for the wrapped type ice-covered conductor controlled by longitudinal fracture damage can be expressed as:

[0133]

[0134] Where: and are the inertial accelerations of the non-wrapped ice-covered conductor when only the upper and lower parts are covered with ice and the ice-covered conductor is in a critical state of longitudinal fracture, q ice H is the deadweight of ice-covered conductor per unit length; ice is the initial horizontal tension of the ice-covered conductor;

[0135] It is worth noting that the criterion for conductor deicing controlled by longitudinal fracture damage has nothing to do with the length of the ice-covered microelement, so the criterion is applicable to ice-covered segments of different lengths. In addition, the criterion is not only applicable to eccentrically iced conductors, but also to uniform circular ice-covered conductors. When the eccentricity e≠0, it corresponds to the eccentric ice-covered conductor, and when e=0, it corresponds to uniform circular ice-covered conductors.

[0136] S32. If the ice-covered conductor is non-wrapped ice, the criteria for judging the de-icing of the conductor under longitudinal fracture damage control are:

[0137]

[0138] Where: and are the inertial accelerations of the non-wrapped ice-covered conductor when only the upper and lower parts are covered with ice and the ice-covered conductor is in a critical state of longitudinal fracture, q ice H is the deadweight of ice-covered conductor per unit length; ice is the initial horizontal tension of the ice-covered conductor.

[0139] S4. Calculate the destruction time sequence of ice covering the lower part of the conductor according to different preset conductor deicing judgment criteria;

[0140] The damage sequence of conductor wrapping ice is divided into upper and lower parts. For the lower part of the wrapped ice conductor, the damage sequence can be obtained by comparing the critical accelerations of transverse bonding failure, cohesive failure and longitudinal fracture failure. The larger the critical acceleration required, the more difficult the ice damage is.

[0141] Therefore, the specific calculation method for calculating the damage time sequence of ice covering the lower part of the conductor includes:

[0142] S41. For the ice on the lower part of the wrapped ice-covered conductor, the lateral bonding failure is compared. Cohesive failure and longitudinal fracture failure The critical acceleration can be used to obtain the sequence of the occurrence of damage;

[0143] At this time, the specific comparison methods for obtaining the sequence of damage occurrence by comparison include:

[0144] (1) When satisfied At this time, the order of ice damage under the conductor is longitudinal fracture damage, transverse bonding damage, and transverse cohesive damage. The criterion for shedding is: Simplify We can get:

[0145]

[0146] (2) When satisfied When the ice damage of the lower part of the conductor is in the order of longitudinal fracture damage, transverse cohesive damage, and transverse bonding damage, the criterion for the fall-off is Simplify We can get:

[0147]

[0148] (3) When satisfied When the ice damage of the lower part of the conductor is in the order of transverse cohesive damage, longitudinal fracture damage, and transverse bonding damage, the criterion for the fall-off is Simplify We can get:

[0149]

[0150] (4) When satisfied When the ice damage of the lower part of the conductor is in the order of transverse cohesive damage, transverse adhesive damage, and longitudinal fracture damage, the criterion for the fall-off is Simplify We can get:

[0151]

[0152] (5) When satisfied When the ice damage of the lower part of the conductor is in the order of transverse bonding damage, longitudinal fracture damage, and transverse cohesive damage, the criterion for the fall-off is Simplify We can get:

[0153]

[0154] (6) When satisfied When the ice damage of the lower part of the conductor occurs, the order of damage is transverse bonding damage, transverse cohesive damage, and longitudinal fracture damage. At this time, the criterion for judging the fall-off is Simplify We can get:

[0155]

[0156] S42. For non-wrapped iced conductors with only the lower part covered with ice, the ice on the conductor will separate from the conductor after the transverse bonding failure and longitudinal fracture failure occur. At this time, only the transverse bonding failure is required. Longitudinal fracture failure By comparing the critical acceleration of the load, the sequence of the destruction can be obtained.

[0157] At this time, the specific comparison methods for obtaining the sequence of damage occurrence by comparison include:

[0158] (1) When satisfied When the conductor is damaged by ice, the order of damage is transverse bonding damage and longitudinal fracture damage. At this time, the criterion for the fall-off is Simplify We can get:

[0159]

[0160] (2) When satisfied When the non-wrapped ice damage of the conductor occurs, the sequence is longitudinal fracture damage and transverse bonding damage. At this time, the criterion for the fall-off is Simplify We can get:

[0161]

[0162] S5. Calculate the destruction time sequence of ice covering on the conductor according to different preset conductor deicing judgment criteria;

[0163] The specific calculation method for calculating the damage time sequence of partial ice coverage on the conductor includes:

[0164] S51. Critical acceleration for lateral cohesive failure of the upper part of the wrapped ice-covered conductor Critical acceleration of transverse bond failure and the critical acceleration of longitudinal fracture failure Satisfies the following relationship:

[0165]

[0166] Therefore, for the upper part of the wrapped ice-covered conductor, the longitudinal fracture failure usually occurs first, and the occurrence sequence of the transverse bonding and cohesive failure needs to be compared. and Size relationship

[0167] S52. When satisfied When , it is simplified to The upper part of the ice first undergoes longitudinal fracture failure, followed by transverse cohesive failure, and finally the conductor is peeled off after transverse bonding failure. The criterion for shedding is:

[0168] S53. When satisfied When , it is simplified to At this time, the upper part of the ice first breaks longitudinally, then breaks transversely, and finally breaks away from the conductor after transverse cohesive failure. The criterion for shedding is:

[0169] S54 For non-wrapped ice-covered conductors with only the upper part covered with ice, due to different parameter conditions Therefore, the upper part of the ice first breaks longitudinally, and then breaks away from the conductor after transverse bonding failure. The criterion for shedding is:

[0170] S6. The preset different conductor deicing judgment criteria and calculation time series data are input into the simulation analysis system for dynamic evolution and used for transmission conductor deicing judgment.

[0171] Based on the above embodiment, a second embodiment is proposed. Figure 8 , Fig. 9 and Fig.10 .

[0172] Based on the above first embodiment, refer to Figure 8 and Fig. 9 The present invention also provides a simulation analysis system, which is applied to the conductor deicing determination method under different damage time sequences proposed in the first embodiment, and the system includes:

[0173] A refined finite element model of a 500kV four-speed four-split iced transmission line established based on ANSYS finite element simulation technology is used to simulate wrapping and non-wrapping icing;

[0174] The conductor-insulator string-icing finite element model of a 500kV four-speed four-split iced transmission line was established based on the real conductor icing shape with only the lower part covered with ice using ANSYS finite element simulation technology. It is only used to simulate non-wrapped icing.

[0175] The three-dimensional rod unit LI NK10 is used in the model to simulate the iced conductor unit, the LI NK8 unit is used in the model to simulate the insulator string, and the three-dimensional beam unit BEAM188 is used in the model to simulate icing. During the modeling process, the conductor unit and the icing unit share a total of 136 nodes. The Rayleigh damping model is used in the model to simulate the structural damping of the line.

[0176] It should be noted that the transmission line includes transmission towers, conductors, ground wires, hardware, insulator strings, spacers, etc., among which the conductor is one of the important components of the transmission line. The conductor-insulator string-icing finite element model established above is a specific implementation model proposed for the refined finite element model of iced transmission lines for non-wrapped icing.

[0177] Furthermore, it should be noted that the number of shared nodes here is divided according to the specific parameter values ​​of the actual ice-covered transmission line (for example, 500kV four-speed four-split). For other transmission lines of different lengths, the number of nodes should be divided according to the actual ice-covered transmission line. The main division principle is to divide a node every 10 meters on the transmission line, which can ensure the accuracy of de-icing simulation while taking into account the efficiency of simulation, and avoid inefficient simulation caused by too close node distance.

[0178] At this time, the physical parameter values ​​involved in the equivalent single conductor are shown in the following table:

[0179]

[0180] The physical parameters of ice-covered conductors are shown in the following table:

[0181]

[0182] Therefore, in the process of realizing the finite element method of conductor ice shedding, the specific implementation steps include:

[0183] Apply an impact load F with a magnitude ranging from 100 to 500N and a vertical downward direction at the conductor node i. initial To simulate the initial excitation of the external environment on the ice-covered conductor.

[0184] Taking into account the randomness of the initial excitation position on the line, the interval of the impact load on the conductor is set to about 50m, 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 is shown in Figure 2. Figure 8 .

[0185] The bonding strength at the contact surface with the ice unit is τ adhesive The data are commonly used in the prior art. The ice type in the test is artificial ice. The ice on the aluminum substrate is peeled off by centrifugal method. The bond strength values ​​obtained in the test are discrete in a large range. The bond strength τ under some typical working conditions adhesive Considering that the bonding strength between ice and conductor in actual situation is smaller than the bonding strength between artificial ice and substrate under laboratory conditions, the bonding strength τ in the deicing criterion is adhesive The value range is set to 0.9~1.2kPa.

[0186] Also, due to the cohesive strength τ of the wire ice coating in the prior art cohesive It is rarely tested. Therefore, for rime-type ice, it is generally believed that the bonding strength between it and the conductor is τ adhesive will be greater than the cohesive strength τ of the ice cohesive Therefore, in this embodiment, only the lower part of the non-wrapped ice-covered conductor is ice-covered, and the relevant physical parameters meet the judgment conditions of the damage occurrence order mentioned in the above method (i.e. ), therefore, the ice first breaks longitudinally into several small ice segments, and then the small ice segments peel off from the conductor contact surface transversely. The criterion for judging ice shedding is:

[0187] At this time, in order to simulate the situation where the external initial excitation induces the ice shedding on the conductor, the derived ice shedding judgment criterion is introduced into the conductor ice shedding dynamic simulation analysis. Fig.10 At this time, the specific steps for determining whether the transmission line is de-iced include:

[0188] L1. Establish a finite element model of ice-covered transmission line in ANSYS, apply initial excitation at node i at the initial time, use the unconditionally stable Newmark method to solve the conductor dynamic equation at any time t, and use the Newton-Raphson method to iteratively obtain the transient acceleration value a of any ice unit j jt ;

[0189] L2. In the simulation analysis, when the transient acceleration value of any ice unit j exceeds the critical acceleration value, that is, When the ice unit is determined to be detached, the unit load, mass, damping and strain of the ice unit are set to 0. The stiffness matrix of the ice unit is multiplied by a very small factor using the EKI LL command in ANSYS, and the value of the factor is set to 1.0E-6 using the EST IF command, thereby killing the ice unit and no longer including it in the solution of the model.

[0190] L3. After completing the judgment on ice unit j, the remaining ice units are judged in turn whether they have fallen off, until all N ice units at time t are judged, and the system matrix is ​​updated synchronously.

[0191] L4. Enter the next time step solution, the time step of the iterative solution is Δt, and obtain the transient acceleration value a of the residual ice unit j on the wire at time t+Δt j,t+Δt , by comparing a j,t+Δt With critical acceleration value a critical The size of the residual ice unit on the conductor is used to further determine the shedding situation and update the system matrix in time.

[0192] L5. When the solution time of the simulation analysis has not reached the set total time T, continue to enter the solution of 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for determining wire deicing under different damage sequences, characterized in that: include: S1. Preset the wire deicing judgment criteria based on lateral cohesive failure control; S2. Preset the wire deicing judgment criteria based on lateral bonding failure control; S3. Preset the wire deicing judgment criteria based on longitudinal fracture damage control; S4. Calculate the destruction time sequence of ice covering the lower part of the conductor according to different preset conductor deicing judgment criteria; S5. Calculate the destruction time sequence of ice covering on the conductor according to different preset conductor deicing judgment criteria; S6. The preset different conductor deicing judgment criteria and calculation time series data are input into the simulation analysis system for dynamic evolution and used for transmission conductor deicing judgment.

2. The method for determining wire deicing under different damage time sequences according to claim 1, characterized in that: The preset method of the wire deicing judgment criterion based on lateral cohesive failure control in step S1 includes: S11. Select the wrapped ice-covered conductor, and set the deadweight of the ice on the upper and lower parts of the conductor to and The inertial forces of the upper and lower ice covering are set as and The cohesion between the upper and lower ice cover 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 can be obtained as follows: 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 line connecting the suspension points. The load per unit horizontal projection length of the conductor is set to p / cosβ, where β is the height difference angle of the suspension points at both ends of the conductor. Then: Where: ice is the density of 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 AB segment of the ice-covered fracture surface; τ cohesive is the cohesive strength of the ice; L e is the length of the independent ice-covered segment; S t and S b are the cross-sectional areas of ice covering the upper and lower parts, respectively; and They are the inertial acceleration of the upper and lower parts of the wrapped ice-covered conductor under the critical state of lateral cohesive failure; S13. The geometric relationship of the force on the wrapped ice-covered section can be obtained: Where: D t is the outer diameter of the circular cross section where the ice-covered conductor is located; e is the eccentricity between the center O2 of the ice-covered conductor and the center C of the bare conductor; S14. Combining the above formulas, the deicing criterion for wrapped ice-covered conductors controlled by lateral cohesive failure can be obtained as follows: Where: a critical is the critical acceleration of ice shedding on the conductor; a v is the acceleration of ice on the wire.

3. The method for determining wire deicing under different damage time sequences according to claim 1, characterized in that: The preset method of the wire deicing judgment criterion based on the lateral bonding failure control in the step S2 includes: S21. Determine whether the ice-covered conductor is a wrapping type. If so, set the bonding force between the ice unit and the conductor contact surface to F. adhesive At this time, according to the vertical force balance, the critical condition for the transverse bonding failure of the wrapped ice on the conductor can be obtained as in: Where: τ adhesive is the bonding strength between the conductor and the ice unit contact surface; and They are the inertial acceleration of the upper and lower parts of the wrapped ice-covered conductor under the critical state of lateral bonding failure; Then, the deicing criterion for the wrapped ice-covered conductor controlled by transverse bonding failure can be obtained as follows: Where: a critical is the critical acceleration of ice shedding on the conductor; a v is the acceleration of ice on the conductor; S22. If the ice-covered conductor is a non-wrapped ice-covered conductor, the criterion for conductor deicing controlled by transverse bonding failure is: Where: a critical is the critical acceleration of ice shedding on the conductor; and They are the inertial acceleration under the critical state of lateral bonding failure of ice when only the upper and lower parts of the non-wrapped ice-covered conductor are covered with ice.

4. The method for determining wire deicing under different damage time sequences according to claim 1, characterized in that: The preset method of the wire deicing judgment criterion based on the longitudinal fracture damage control in step S3 includes: S31. Determine whether the ice-covered conductor is of the wrapped type. If so, the deicing criterion for the wrapped type ice-covered conductor controlled by longitudinal fracture damage can be expressed as: Where: and are the inertial accelerations of the non-wrapped ice-covered conductor when only the upper and lower parts are covered with ice and the ice-covered conductor is in a critical state of longitudinal fracture, q ice H is the deadweight of ice-covered conductor per unit length; ice is the initial horizontal tension of the ice-covered conductor; S32. If the ice-covered conductor is non-wrapped ice, the criteria for judging the de-icing of the conductor under longitudinal fracture damage control are: Where: and are the inertial accelerations of the non-wrapped ice-covered conductor when only the upper and lower parts are covered with ice and the ice-covered conductor is in a critical state of longitudinal fracture, q ice H is the deadweight of ice-covered conductor per unit length; ice is the initial horizontal tension of the ice-covered conductor.

5. The method for determining wire deicing under different damage time sequences according to claim 1, characterized in that: The specific calculation method for calculating the damage time sequence of ice covering the lower part of the conductor in step S4 includes: S41. For the ice on the lower part of the wrapped ice-covered conductor, the lateral bonding failure is compared. Cohesive failure and longitudinal fracture failure The critical acceleration can be used to obtain the sequence of the occurrence of damage; S42. For non-wrapped iced conductors with only the lower part covered with ice, the ice on the conductor will separate from the conductor after the transverse bonding failure and longitudinal fracture failure occur. At this time, only the transverse bonding failure is required. Longitudinal fracture failure By comparing the critical accelerations, the sequence of the destruction can be obtained.

6. The wire deicing determination method and simulation analysis system under different damage time sequences according to claim 5, characterized in that: The specific comparison method for obtaining the sequence of occurrence of destruction by comparison in step S41 includes: (1) When satisfied At this time, the order of ice damage under the conductor is longitudinal fracture damage, transverse bonding damage, and transverse cohesive damage. The criterion for shedding is: Simplify We can get: (2) When satisfied When the ice damage of the lower part of the conductor is in the order of longitudinal fracture damage, transverse cohesive damage, and transverse bonding damage, the criterion for the fall-off is Simplify We can get: (3) When satisfied When the ice damage of the lower part of the conductor is in the order of transverse cohesive damage, longitudinal fracture damage, and transverse bonding damage, the criterion for the fall-off is Simplify We can get: (4) When satisfied When the ice damage of the lower part of the conductor is in the order of transverse cohesive damage, transverse adhesive damage, and longitudinal fracture damage, the criterion for the fall-off is Simplify We can get: (5) When satisfied When the ice damage of the lower part of the conductor is in the order of transverse bonding damage, longitudinal fracture damage, and transverse cohesive damage, the criterion for the fall-off is Simplify We can get: (6) When satisfied When the ice damage of the lower part of the conductor occurs, the order of damage is transverse bonding damage, transverse cohesive damage, and longitudinal fracture damage. At this time, the criterion for judging the fall-off is Simplify We can get:

7. The conductor deicing determination method and simulation analysis system under different damage time sequences according to claim 5, characterized in that: The specific comparison method for obtaining the sequence of occurrence of the destruction by comparison in step S42 includes: (1) When satisfied When the conductor is damaged by ice, the order of damage is transverse bonding damage and longitudinal fracture damage. At this time, the criterion for the fall-off is Simplify We can get: (2) When satisfied When the non-wrapped ice damage of the conductor occurs, the sequence is longitudinal fracture damage and transverse bonding damage. At this time, the criterion for the fall-off is Simplify We can get:

8. The method for determining wire deicing under different damage time sequences according to claim 1, characterized in that: The specific calculation method for calculating the damage time sequence of the partial ice covering on the conductor in step S5 includes: S51. Critical acceleration for lateral cohesive failure of the upper part of the wrapped ice-covered conductor Critical acceleration of transverse bond failure and the critical acceleration of longitudinal fracture failure Satisfies the following relationship: Therefore, for the upper part of the wrapped ice-covered conductor, the longitudinal fracture failure usually occurs first, and the occurrence sequence of the transverse bonding and cohesive failure needs to be compared. and Size relationship S52. When satisfied When , it is simplified to The upper part of the ice first undergoes longitudinal fracture failure, followed by transverse cohesive failure, and finally the conductor is peeled off after transverse bonding failure. The criterion for shedding is: S53. When satisfied When , it is simplified to At this time, the upper part of the ice first breaks longitudinally, then breaks transversely, and finally breaks away from the conductor after transverse cohesive failure. The criterion for shedding is: S54 For non-wrapped ice-covered conductors with only the upper part covered with ice, due to different parameter conditions Therefore, the upper part of the ice first breaks longitudinally, and then breaks away from the conductor after transverse bonding failure. The criterion for shedding is:

9. A simulation analysis system, applied to the method for determining wire deicing under different damage time sequences as described in any one of claims 1 to 8, characterized in that: include: A refined finite element model of ice-covered transmission lines established based on ANSYS finite element simulation technology is used to simulate wrap-type icing and non-wrapped icing; The model uses a three-dimensional rod unit LINK10 to simulate an ice-covered conductor unit, the model uses a LINK8 unit to simulate an insulator string, the model uses a three-dimensional beam unit BEAM188 to simulate icing, the conductor unit and the icing unit share nodes during the modeling process, and the model uses a Rayleigh damping model to simulate the structural damping of the line.

10. The simulation analysis system according to claim 9, characterized in that: The specific steps of introducing the derived deicing judgment criteria into the dynamic simulation analysis of conductor deicing for determining deicing of transmission conductors include: L1. Establish a finite element model of ice-covered transmission line in ANSYS, apply initial excitation at node i at the initial time, use the unconditionally stable Newmark method to solve the conductor dynamic equation at any time t, and use the Newton-Raphson method to iteratively obtain the transient acceleration value a of any ice unit j jt ; L2. In the simulation analysis, when the transient acceleration value of any ice unit j exceeds the critical acceleration value, that is, When the ice unit is determined to be detached, the unit load, mass, damping and strain of the ice unit are set to 0. The stiffness matrix of the ice unit is multiplied by a very small factor using the EKILL command in ANSYS, and the value of the factor is set to 1.0E-6 using the ESTIF command, thereby achieving the effect of killing the ice unit and it will no longer be included in the solution results of the model; L3. After completing the judgment on ice unit j, the remaining ice units are judged in turn whether they have fallen off, until all N ice units at time t are judged, and the system matrix is ​​updated synchronously. L4. Enter the next time step solution, the time step of the iterative solution is Δt, and obtain the transient acceleration value a of the residual ice unit j on the wire at time t+Δt j,t+Δt , by comparing a j,t+Δt With critical acceleration value a critical The size of the residual ice unit on the conductor is used to further determine the shedding situation and update the system matrix in time. L5. When the solution time of the simulation analysis has not reached the set total time T, continue to enter the solution of 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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