Ice melting characteristic analysis and optimization control method for overhead insulated conductor

Abstract

The invention discloses an overhead insulated conductor ice melting characteristic analysis and optimization control method, relates to the technical field of anti-icing and deicing of a power transmission line of a power system, and solves the problems that in the prior art, an ice melting mechanism is understood insufficiently, ice melting efficiency is difficult to predict, and ice melting parameter design lacks a theoretical basis. According to the method, an insulated wire total thermal resistance calculation model is constructed, then an ice melting process is divided into two characteristic stages, a comprehensive heat dissipation coefficient model is established based on the two special stages of the ice melting process, and then an ice outer surface temperature explicit calculation formula is deduced according to an ice layer outer surface heat balance equation. And the ice melting current, the ice melting time and the critical ice melting current are calculated. And finally, establishing an ice-melting current optimization control strategy, adjusting the ice-melting current in real time based on the measured environmental parameters, and implementing sectional ice-melting control. In a word, according to the method, the ice melting time and the prediction precision of the needed current are remarkably improved, the deicing energy consumption is reduced, and the method is suitable for different geographical and climate conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system transmission line ice prevention and removal, and particularly relates to an overhead insulated conductor ice melting characteristic analysis and optimization control method. BACKGROUND

[0002] With the intensification of global climate change, extreme weather events have become the norm, among which the icing problem of transmission lines is particularly prominent, seriously threatening the safe and stable operation of power systems. In the complex environment of high pollution and dense vegetation, traditional overhead bare conductors lack effective protection measures and are easily contaminated by pollutants and disturbed by tree barriers, leading to various safety accidents. In order to cope with these challenges, overhead insulated conductors (AIC) have emerged. AICs have natural anti-pollution flashover, anti-tree barrier and anti-icing capabilities due to their outer insulation layer, which can effectively reduce safety accidents in practical applications, and have been widely used in power systems.

[0003] However, although overhead insulated conductors have significant advantages in anti-pollution flashover, anti-tree barrier and anti-icing, the characteristics of their insulation layer materials have brought new problems. The insulation layer of AICs is mostly made of thermoplastic or cross-linked polyethylene, which has low thermal conductivity characteristics that hinder the effective transfer of Joule heat generated after the conductor is energized to the ice layer. This results in a significant decrease in ice melting efficiency under icing conditions, and even in some cases, complete ice melting is not possible, leaving a safety hazard. In addition, previous research has mostly focused on traditional overhead bare conductors, with relatively little research on AICs. This makes it difficult to have sufficient theoretical and practical guidance when facing the icing problem of AICs, further exacerbating the operational risks of power systems under extreme weather conditions. Therefore, in-depth research on the icing characteristics of AICs and their solutions is of great significance to improving the safety and reliability of power systems.

[0004] In view of this, an overhead insulated conductor ice melting characteristic analysis and optimization control method is needed. SUMMARY

[0005] In view of the problems of insufficient understanding of ice melting mechanism, difficulty in predicting ice melting efficiency, and lack of theoretical basis for ice melting parameter design in the prior art, the present application provides an overhead insulated conductor ice melting characteristic analysis and optimization control method, which can establish a complete "metal-insulation layer-ice layer" composite interface heat transfer theoretical model, and through staged modeling and multi-parameter coupling analysis, significantly improves the prediction accuracy of ice melting time and required current, and finally optimizes the ice melting current and time control to reduce the ice removal energy consumption. Moreover, the model takes into account the influence of temperature, wind speed, ice thickness and other environmental factors, and is suitable for different geographical and climatic conditions. The specific technical solutions are as follows: An overhead insulated conductor ice-melting characteristic analysis and optimization control method, comprising the following steps: Based on the four assumptions that each layer of material is uniform and isotropic, the metal conductor is a uniform Joule heat source, the axial and circumferential heat transfer is ignored, and the ice-water phase change during the ice-melting process is a quasi-steady process, an insulation conductor total thermal resistance calculation model is constructed; The ice-melting process is divided into two characteristic stages, namely a temperature rising stage and a phase change ice-melting stage, in the temperature rising stage, the temperature rises from the ambient temperature to the phase change critical temperature of ice; Based on the two special stages of the ice-melting process, a comprehensive heat dissipation coefficient model is established, which at least includes a natural convection heat transfer coefficient and a radiation heat transfer coefficient; According to the ice outer surface heat balance equation, an explicit calculation formula of the ice outer surface temperature is derived, and the ice-melting current, the ice-melting time and the critical ice-melting current are calculated; An ice-melting current optimization control strategy is established, which at least includes temperature compensation of the current and wind speed compensation of the current, and the ice-melting current is adjusted in real time based on the measured environmental parameters, which at least include temperature, wind speed and ice thickness; A segmented ice-melting control is implemented, which at least includes two stages, wherein the first stage is to rise to near 0℃, and the second stage is to maintain phase change ice-melting by stable current.

[0006] Preferably, the insulation conductor total thermal resistance calculation model is represented as follows: In the formula, R c is the radius of the metal conductor; R ins = R c + d ins is the outer radius of the insulation layer, d ins is the insulation layer thickness; R ice = R ins + d ice is the outer radius of the ice layer, d ice is the ice layer thickness; k ins , k ice are the thermal conductivities of the insulation layer and the ice layer, respectively.

[0007] Preferably, the comprehensive heat dissipation coefficient model is represented as follows: In the formula,h c is the natural convection heat transfer coefficient; h r is the radiation heat transfer coefficient.

[0008] Preferably, the natural convection heat transfer coefficient is calculated by the following equation: where, k air is the air thermal conductivity; Nu is the Nusselt number.

[0009] Preferably, the radiation heat transfer coefficient is calculated by the following equation: where, T io is the ice surface temperature; T a is the ambient temperature; σ is the Stefan-Boltzmann constant; ε is the ice emissivity; is the ice surface temperature difference.

[0010] Preferably, the derivation process of the ice surface temperature explicit calculation formula is as follows: The ice surface heat balance equation is constructed as follows: The ice surface temperature explicit calculation formula is derived based on the ice surface heat balance equation as follows: In the ice melting process, T ii = 0℃.

[0011] Preferably, the ice melting current I and the ice melting time t melt are calculated by the following equations, respectively: where, ρ i is the ice density; L m is the ice latent heat of fusion; is the unit length ice volume; I is the wire current; T a is the ice surface temperature; r T is the temperature T aThe formula for calculating the resistance per unit length of the conductor at 20 DEG C is: In the formula, r 20 R is the resistance of the conductor at 20 DEG C, α R is the resistance temperature coefficient; Based on the heat balance principle, the formula for calculating the critical ice-melting current is derived as follows: .

[0012] Preferably, the temperature compensation specifically refers to increasing the current for ice melting when the ambient temperature decreases; and the wind speed compensation specifically refers to increasing the current compensation when the wind speed increases.

[0013] A computer readable storage medium comprises a stored program, wherein the program controls the device where the computer readable storage medium is located to perform the overhead insulated conductor ice-melting characteristic analysis and optimization control method as described above when the program is run.

[0014] A processor is used to run a program, wherein the program performs the overhead insulated conductor ice-melting characteristic analysis and optimization control method as described above when the program is run.

[0015] Compared with the prior art, the present application has the following beneficial effects: Based on the four assumptions that the materials of each layer are uniform and isotropic, the metal conductor is a uniform Joule heat source, the axial and circumferential heat transfer is ignored, and the ice-water phase change in the ice-melting process is a quasi-steady process, the present application constructs a total thermal resistance calculation model of the insulated conductor, then divides the ice-melting process into two characteristic stages, establishes a comprehensive heat dissipation coefficient model based on the two special stages of the ice-melting process, derives an explicit calculation formula of the ice outer surface temperature according to the heat balance equation of the ice outer surface, and calculates the ice-melting current, the ice-melting time and the critical ice-melting current. Finally, an ice-melting current optimization control strategy is established, which at least includes temperature compensation of the current and wind speed compensation of the current, and the ice-melting current is adjusted in real time based on the measured environmental parameters, and the segmented ice-melting control is implemented. In summary, the present application establishes a complete "metal-insulating layer-ice layer" composite interface heat transfer theoretical model, which provides a scientific basis for the ice-melting design of the overhead insulated conductor. And through the stage-by-stage modeling and multi-parameter coupling analysis, the prediction accuracy of the ice-melting time and the required current is significantly improved, the de-icing energy consumption is reduced, and the present application is suitable for different geographical and climatic conditions. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the specific embodiments or the prior art of the present application, the drawings needed to be used in the specific embodiments or the prior art description will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual proportion.

[0017] Figure 1 A simplified cross-sectional schematic diagram of the AIC; Figure 2 A flowchart of ice-melting analysis and optimization control for an overhead insulated conductor. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without any creative effort fall within the scope of the present application.

[0019] It should be understood that, when used in the specification and the appended claims, the terms "comprise" and "include" indicate the presence of the described features, integers, steps, operations, elements, and / or components, but do not exclude one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0020] It should also be understood that the terms used in the present application specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the present application specification and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0021] It should be further understood that the term "and / or" used in the present application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0022] Embodiment 1 In one embodiment of the present application, an overhead insulated conductor ice-melting characteristic analysis and optimization control method is provided, comprising the following steps: Step 1: Establish a multi-layer structure heat transfer mathematical model 1.1 Abstract the overhead insulated ice-covered conductor system as a "metallic conductor-insulating layer-ice layer" concentric cylindrical system; 1.2 Establish a heat transfer model based on the following assumptions: Each layer of material is uniform and isotropic, and the physical property parameters are constants The metal conductor is a uniform joule heat source, and the insulation layer and ice layer have no internal heat source Ignoring axial and circumferential heat transfer, only radial heat conduction is considered During ice melting, the ice-water phase change interface moves slowly, which is considered as a quasi-steady process 1.3 Establish the total thermal resistance calculation model of the insulated conductor: In the formula, R c is the radius of the metal conductor; R ins =R c +d ins is the outer radius of the insulation layer, d ins is the thickness of the insulation layer; R ice =R ins +d ice is the outer radius of the ice layer, d ice is the thickness of the ice layer; k ins , k ice are the thermal conductivities of the insulation layer and the ice layer, respectively.

[0023] Step 2: Build a melting process stage model 2.1 Divide the melting process into two characteristic stages: Warming-up stage (t1): non-phase change warming-up process, temperature rises from ambient temperature to ice phase change critical temperature Phase change ice melting stage (t2): ice layer melting process, dominated by latent heat consumption 2.2 Establish a comprehensive heat dissipation coefficient model: In the formula, h c is the natural convection heat transfer coefficient; h r is the radiation heat transfer coefficient.

[0024] The calculation formula of the natural convection heat transfer coefficient h c is: In the formula, k air is the air thermal conductivity; Nu is the Nusselt number, determined by the Reynolds number Re range: , where v a is the wind speed (m / s), μ is the air movement viscosity (m 2 / s); Pr is the Prandtl number, take Pr=0.707.

[0025] The calculation formula of the radiation heat transfer coefficient h r is: where T io is the ice layer outer surface temperature; T a is the ambient temperature; σ= 5.67 x 10 -8 W / (m²・K 4 ) is the Stefan-Boltzmann constant; ε = 0.95 is the ice emissivity. When , h r = 0 is assumed to deal with low temperature difference.

[0026] Step three: ice layer outer surface temperature calculation 3.1 According to the ice layer outer surface heat balance equation, the ice outer surface temperature explicit calculation formula is derived Ice layer outer surface heat balance equation: where T ii is the ice layer inner surface temperature.

[0027] The ice outer surface temperature explicit calculation formula is derived: During ice melting, T ii = 0℃.

[0028] Step four: ice melting time and critical current calculation 4.1 The ice melting current calculation formula is: 4.2 The ice melting time calculation formula is: where, ρ i is the ice density; L m is the ice melting latent heat; is the unit length of the ice-covered conductor volume I is the conductor current; r T is the conductor unit length resistance when the temperature is the ice surface temperature T a , and its calculation formula is: where, r 20 is the conductor resistance at 20℃, α is the resistance temperature coefficient.

[0029] 4.2 The critical ice melting current calculation formula is: Based on the heat balance principle, the critical ice melting current calculation formula is derived: Embodiment 2 This embodiment is based on Embodiment 1 and further comprises the following steps: Step five: ice melting optimization control 5.1 Establish ice melting current optimization control strategy: Temperature compensation of current: when the ambient temperature is lower, a relatively higher current is used for ice melting; Wind speed compensation of current: when the wind speed is high, the current compensation is increased.

[0030] 5.2 Real-time adjustment of ice melting current based on measured environmental parameters (temperature, wind speed, ice thickness); 5.3 Implement segmented ice melting control: First stage: quickly warm up to near 0℃; Second stage: stable current to maintain phase change ice melting.

[0031] Further data is used for illustration as follows, which is intended to analyze the ice melting of JKLGYJ-240 / 40 insulated conductor. The given parameters are as follows: JKLGYJ-240 / 40 insulated conductor parameters: conductor outer diameter: 20.00 mm; insulation layer thickness: 3.4 mm; insulation layer outer diameter: 28.40 mm; unit length resistance: 0.1181 Ω / km.

[0032] Environmental conditions: ambient temperature: -10℃; wind speed: 10 m / s; ice layer thickness: 15 mm.

[0033] The calculated thermal resistance is: ; The calculated critical ice melting current is: .

[0034] Considering the temperature compensation by multiplying the current by a factor of 1.2 at a low temperature of -10℃, the calculated ice melting time is 0.27 h.

[0035] Embodiment 3 This embodiment provides an overhead insulated conductor ice melting characteristic analysis and optimization control system, comprising: Insulated conductor total thermal resistance calculation model construction module: based on four premise assumptions that each layer of material is uniform and isotropic, the metal conductor is a uniform Joule heat source, the axial and circumferential heat transfer is ignored, and the ice-water phase change during ice melting process is a quasi-steady process, the insulated conductor total thermal resistance calculation model is constructed; The comprehensive heat dissipation coefficient model construction module: the ice melting process is divided into two characteristic stages, namely, a temperature rising stage and a phase change ice melting stage, in the temperature rising stage, the temperature rises from the ambient temperature to the phase change critical temperature of ice; a comprehensive heat dissipation coefficient model is established based on the two special stages of the ice melting process, and the comprehensive heat dissipation coefficient model at least includes a natural convection heat transfer coefficient and a radiation heat transfer coefficient; The ice melting implementation module: according to the ice outer surface heat balance equation, an ice outer surface temperature explicit calculation formula is derived, and the ice melting current, the ice melting time and the critical ice melting current are calculated; an ice melting current optimization control strategy is established, at least including temperature compensation of the current and wind speed compensation of the current, and the ice melting current is adjusted in real time based on the measured environmental parameters, at least including temperature, wind speed and ice thickness; a segmented ice melting control is implemented, at least including two stages, wherein the first stage is to rise to near 0 DEG C, and the second stage is to maintain phase change ice melting by stable current.

[0036] Based on the four premise assumptions that each layer of material is uniform and isotropic, the metal conductor is a uniform Joule heat source, the axial and circumferential heat transfer is ignored, and the ice water phase change is a quasi-steady process during the ice melting process, an insulating wire total thermal resistance calculation model is constructed, then the ice melting process is divided into two characteristic stages, and a comprehensive heat dissipation coefficient model is established based on the two special stages of the ice melting process, then according to the ice outer surface heat balance equation, an ice outer surface temperature explicit calculation formula is derived, and the ice melting current, the ice melting time and the critical ice melting current are calculated. Finally, an ice melting current optimization control strategy is established, at least including temperature compensation of the current and wind speed compensation of the current, and the ice melting current is adjusted in real time based on the measured environmental parameters, and a segmented ice melting control is implemented. In summary, the present application establishes a complete "metal-insulating layer-ice layer" composite interface heat transfer theoretical model, which provides a scientific basis for the ice melting design of the overhead insulated conductor. And through the stage-by-stage modeling and multi-parameter coupling analysis, the prediction accuracy of the ice melting time and the required current is significantly improved, the deicing energy consumption is reduced, and it is suitable for different geographical and climatic conditions.

[0037] Those skilled in the art can appreciate that the units of each example described in combination with the embodiments disclosed herein can be realized in electronic hardware, computer software or a combination of both. In order to clearly illustrate the interchangeability of hardware and software, the components of each example have been described in the above description in general terms. Whether the functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. The skilled person can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0038] In the embodiments of the present application, it should be understood that the division of units is only a logical functional division, and actual implementation can have another division manner, for example, multiple units can be combined as one unit, one unit can be split into multiple units, or some features can be ignored, etc.

[0039] In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0040] When the integrated unit is realized in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application essentially or the part that contributes to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of the present application. The aforementioned storage medium includes: a U disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a mobile hard disk, a magnetic disk or an optical disk, and various program code storage media.

[0041] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the specification of the present application.

Claims

1. A method for analyzing and optimizing the de-icing characteristics of overhead insulated conductors, characterized in that, Includes the following steps: Based on four assumptions—uniform and isotropic materials in each layer, uniform Joule heat source of the metallic conductor, neglect of axial and circumferential heat transfer, and quasi-steady-state phase transition of ice and water during the melting process—a calculation model for the total thermal resistance of the insulated conductor is constructed. The ice melting process is divided into two characteristic stages: the heating stage and the phase change ice melting stage. In the heating stage, the temperature rises from the ambient temperature to the critical phase change temperature of the ice. A comprehensive heat dissipation coefficient model is established based on two special stages of the ice melting process. The comprehensive heat dissipation coefficient model includes at least the natural convection heat transfer coefficient and the radiation heat transfer coefficient. Based on the heat balance equation of the outer surface of ice, the explicit calculation formula for the outer surface temperature of ice is derived, and the melting current, melting time and critical melting current are calculated. Establish an optimized control strategy for de-icing current, including at least temperature compensation and wind speed compensation for the current, and adjust the de-icing current in real time based on measured environmental parameters, including at least temperature, wind speed and ice thickness. A segmented de-icing control is implemented, which includes at least two stages, wherein the first stage heats up to near 0°C and the second stage maintains a stable current to sustain phase change de-icing.

2. The method for analyzing and optimizing the de-icing characteristics of overhead insulated conductors according to claim 1, characterized in that, The calculation model for the total thermal resistance of the insulated conductor is expressed as follows: In the formula, R c The radius of the metallic conductor; R ins = R c + d ins The outer radius of the insulation layer, d ins This refers to the thickness of the insulation layer. R ice = R ins + d ice The outer radius of the ice layer. d ice This refers to the thickness of the ice layer. k ins , k ice These are the thermal conductivity coefficients of the insulating layer and the ice layer, respectively.

3. The method for analyzing and optimizing the de-icing characteristics of overhead insulated conductors according to claim 1, characterized in that, The comprehensive heat dissipation coefficient model is expressed as follows: In the formula, h c The coefficient of heat transfer is the natural convection heat transfer coefficient. h r denoted as the radiative heat transfer coefficient.

4. The method for analyzing and optimizing the de-icing characteristics of overhead insulated conductors according to claim 3, characterized in that, The natural convection heat transfer coefficient is calculated using the following formula: In the formula, k air The thermal conductivity of air; Nu For Nusselt numbers.

5. The method for analyzing and optimizing the de-icing characteristics of overhead insulated conductors according to claim 3, characterized in that, The radiative heat transfer coefficient is calculated using the following formula: In the formula, T io This refers to the temperature of the outer surface of the ice layer. T a The ambient temperature; σ It is the Stefan-Boltzmann constant; ε For ice emissivity; This represents the temperature difference between the inner and outer surfaces of the ice layer.

6. The method for analyzing and optimizing the de-icing characteristics of overhead insulated conductors according to claim 3, characterized in that, The derivation of the explicit formula for calculating the outer surface temperature of ice is as follows: The thermal equilibrium equation for the outer surface of the ice layer is constructed as follows: The explicit formula for calculating the temperature of the outer surface of ice, derived from the heat balance equation of the outer surface of ice, is shown below: During the ice melting process, T ii =0℃.

7. The method for analyzing and optimizing the de-icing characteristics of overhead insulated conductors according to claim 1, characterized in that, De-icing current I and melting time t melt The calculation formulas are as follows: In the formula, ρ i The density of ice; L m The latent heat of melting ice; The volume of ice per unit length; T a r is the surface temperature of the ice. T The temperature is T a The formula for calculating the resistance per unit length of a conductor is: In the formula, r 20 The resistance of the wire at 20℃ α It is the temperature coefficient of resistance; Based on the principle of thermal balance, the formula for calculating the critical melting current is derived as follows: 。 8. The method for analyzing and optimizing the de-icing characteristics of overhead insulated conductors according to claim 1, characterized in that, The temperature compensation specifically involves increasing the current to melt ice when the ambient temperature drops; the wind speed compensation specifically involves increasing the current compensation when the wind speed increases.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored program, wherein, when the program is executed, it controls the device containing the computer-readable storage medium to perform the overhead insulated conductor de-icing characteristic analysis and optimization control method according to any one of claims 1 to 7.

10. A processor, characterized in that, The processor is used to run a program, wherein the program executes the method for analyzing and optimizing the de-icing characteristics of overhead insulated conductors as described in any one of claims 1 to 7.

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