Optimal calculation method and system for ice melting current and optical fiber critical temperature rise of OPGW (Optical Fiber Composite Overhead Ground Wire)

Abstract

The invention discloses an optimal calculation method and system for ice melting current and optical fiber critical temperature rise of an OPGW (Optical Fiber Composite Overhead Ground Wire). The method comprises the following steps: establishing a calculation expression of Joule heat consumption generated by the OPGW in the ice melting process; obtaining a calculation expression of the ice melting current of the OPGW according to an energy conservation equation in the direct-current ice melting process of the OPGW; obtaining the model of a field icing line and the detection parameters of a field online monitoring device, and obtaining the ice melting current value required by the OPGW according to the calculation expression of the ice melting current of the OPGW in combination with the field specified ice melting time; and according to the ice melting current value required by the OPGW, calculating the maximum value of the temperature of the internal optical fiber of the OPGW before ice shedding and the steady-state value of the temperature of the internal optical fiber of the OPGW after ice shedding, and taking the maximum value of the two values as the critical temperature rise value of the internal optical fiber of the OPGW. On the premise of not depending on finite element modeling simulation calculation, on-site icing monitoring and timely fault response of the high-voltage transmission line are effectively supported.

Description

Technical Field

[0001] The present invention belongs to the field of power grid transmission lines and relates to the optimization calculation of OPGW ice melting current and optical fiber critical temperature rise. Specifically, it is a method and system for optimizing the calculation of OPGW ice melting current and optical fiber critical temperature rise that combines online monitoring parameters and adapts to the complex on-site icing environment. Background Art

[0002] As power grid transmission lines gradually develop towards ultra-high voltage, large capacity and long distance, line channels are becoming increasingly dense, and failure events caused by line icing are frequent, affecting power supply reliability.

[0003] At present, in the design of OPGW de-icing schemes, the determination of key parameters such as the required de-icing current, current generator capacity, and maximum optical fiber temperature of the OPGW often requires the use of finite element simulation calculations. This requires a lot of modeling and simulation time and manpower investment, and is inefficient. It is impossible to respond to impending icing faults on site in a timely manner, and the operational reliability of high-voltage transmission lines cannot be guaranteed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the needs of on-site production lines and provide a method and system for optimizing the calculation of OPGW de-icing current and critical temperature rise of optical fiber in combination with on-site parameters. The method obtains the OPGW de-icing current by simplifying the calculation expression of the OPGW de-icing current with respect to Joule heat consumption; calculates the maximum value of the internal optical fiber temperature of the OPGW before de-icing and the steady-state value of the internal optical fiber temperature of the OPGW after de-icing, and takes the maximum value of the former two as the critical temperature rise of the internal optical fiber of the OPGW. Without the need for finite element simulation calculations, the method effectively supports on-site de-icing monitoring and timely fault response of high-voltage transmission lines, and can also provide a reference for the subsequent design of OPGW DC de-icing solutions.

[0005] To this end, the present invention adopts a technical solution as follows: an optimization calculation method for OPGW ice melting current and optical fiber critical temperature rise, which includes: Step a), establishing a calculation expression for the Joules consumed heat generated by the OPGW during the ice melting process; Step b) obtaining an energy conservation equation for the OPGW DC ice melting process based on a calculation expression for Joule heat consumption, and obtaining an expression for the OPGW ice melting current with respect to Joule heat consumption based on the energy conservation equation for the OPGW DC ice melting process; Step c) obtaining the model of the on-site ice-covered line and the detection parameters of the on-site online monitoring device, calculating the ice melting area in the cross section of the ice-covered line, the heat exchange coefficient of the outer surface of the ice layer, the equivalent thermal conduction resistance of the remaining ice layer after the ice layer falls off, and the heat loss of the outer surface of the ice layer. The calculated melting current value required by the OPGW is then calculated based on the melting current calculation expression of the OPGW in combination with the melting time specified on site. Step d), calculating the maximum temperature of the optical fiber inside the OPGW before de-icing and the steady-state temperature of the optical fiber inside the OPGW after de-icing based on the de-icing current required by the OPGW; Step e): according to the maximum value of the temperature of the optical fiber inside the OPGW before de-icing and the steady-state value of the temperature of the optical fiber inside the OPGW after de-icing, the maximum value of the former two is taken as the critical temperature rise value of the optical fiber inside the OPGW.

[0006] The present invention obtains the required de-icing current value of the OPGW based on the on-site de-icing line model and the detection parameters of the on-site online monitoring device, through the expression of the Joule heat consumption generated by the OPGW during the de-icing process and the OPGW de-icing current, combined with the on-site specified de-icing time. The maximum value of the internal optical fiber temperature of the OPGW before de-icing and the steady-state value of the internal optical fiber temperature of the OPGW after de-icing are calculated, and the larger number of the two is taken as the critical temperature rise value of the internal optical fiber of the OPGW, thereby completing the optimization calculation of the OPGW de-icing current and the critical temperature rise of the optical fiber.

[0007] Furthermore, in step a), the Joule heat consumed by the OPGW during the ice melting process includes the heat required to increase the temperature of the melted ice layer, the latent heat absorbed when the ice melts, the heat lost from the outer surface of the ice layer, the heat required to increase the temperature of the unmelted ice layer, and the heat required to increase the temperature of the OPGW. To simplify the calculation, the heat required to increase the temperature of the unmelted ice layer and the heat required to increase the temperature of the OPGW are ignored.

[0008] Furthermore, in step b), the energy conservation equation during the OPGW direct current ice melting process is simplified to: , Where, I is the OPGW ice melting current, in A; r T for T The unit length resistance of OPGW ice melting conductor is / m; T Indicates the temperature of the OPGW ice melting conductor in °C; t is the ice melting time, in units of s ; P c is the heat dissipated per unit length of the outer surface of the ice layer, in J / m; ρ iis the density of the ice layer in kg / m 3 ; L F is the latent heat absorbed when a unit mass of ice melts, in J / kg; S m The area of ​​ice melted in the cross section during the melting time, in m 2 ; C i is the specific heat capacity of the ice layer, in J / (kg·℃); T a is the ambient temperature in °C.

[0009] Furthermore, in step c), the detection parameters of the on-site online monitoring device include ambient temperature, wind speed, and ice thickness. Ambient temperature, wind speed, and ice thickness are the basis for calculating key parameters such as ice melting area and heat exchange coefficient, and directly affect the calculation results of ice melting current and optical fiber temperature rise. Among them, the ambient temperature is used to determine the heat exchange temperature difference between the ice layer and the environment, the wind speed is used to calculate the Reynolds number and then determine the heat exchange coefficient, and the ice thickness is used to calculate the ice melting area.

[0010] Furthermore, in step c), the heat loss on the outer surface of the ice layer is calculated by: calculating the heat loss on the outer surface of the ice layer based on the radius of the OPGW, the ice thickness, the heat exchange coefficient of the outer surface of the ice layer, the outer surface temperature of the ice layer, the ambient temperature and the ice melting time.

[0011] Furthermore, the surface temperature of the ice layer T i The calculation formula is: , Where, h is the surface thermal conductivity, unit is W / (m 2 ℃); R c is the radius of OPGW, in m; d is the ice thickness of OPGW, in m; R T1 is the equivalent thermal conductivity resistance of the remaining ice layer after the ice layer falls off, in m·℃ / W; T a is the ambient temperature in °C.

[0012] Furthermore, the equivalent thermal conductivity of the remaining ice layer after the ice layer falls off is R T1 The calculation formula is: , Where, The area element in the two-dimensional field representing the remaining ice layer after the ice layer falls off;r out It represents the outer radius after the ice layer falls off, in meters; r in Indicates the contact surface radius between the remaining ice layer and the OPGW optical fiber, in meters; is the thermal conductivity of ice in units of W / ( m ·℃).

[0013] Furthermore, in step d), the maximum temperature of the optical fiber inside the OPGW before de-icing is calculated as follows: , Where, T pm is the maximum temperature of the optical fiber inside the OPGW before de-icing, in °C; R T0 is the equivalent thermal conduction resistance of the air gap, in m·℃ / W; R T2 is the equivalent conduction thermal resistance between the optical fiber inside the OPGW and the surface of the OPGW, in m·°C / W; I 0 is the ice melting current value required by OPGW, in A; r T for T The unit length resistance of the OPGW ice melting conductor is Ω / m.

[0014] Furthermore, in step d), the calculation formula for the steady-state value of the optical fiber temperature inside the OPGW after de-icing is: , Where, T pn is the steady-state value of the optical fiber temperature inside the OPGW after de-icing, in °C; r T for T The unit length resistance of the OPGW ice melting conductor is Ω / m; I 0 is the ice melting current value required by OPGW, in A; R T2 is the equivalent conduction thermal resistance between the optical fiber inside the OPGW and the surface of the OPGW, in m·°C / W; R c is the radius of OPGW, in m; T a is the ambient temperature, in °C; h c is the heat exchange coefficient of the OPGW surface, in W / (m 2 ·℃).

[0015] Another technical solution adopted by the present invention is as follows: an optimization calculation system for OPGW ice melting current and optical fiber critical temperature rise, used to implement the above-mentioned optimization calculation method, which includes: Joule consumption heat calculation expression establishment unit: establishes the calculation expression of Joule consumption heat generated by OPGW during ice melting; Ice-melting current calculation expression acquisition unit: obtains the energy conservation equation in the OPGW DC ice-melting process according to the calculation expression of Joule heat consumption, and obtains the calculation expression of the OPGW ice-melting current according to the energy conservation equation in the OPGW DC ice-melting process; Ice-melting current calculation unit: Obtain the on-site ice-covered line model and the detection parameters of the on-site online monitoring device, calculate the ice melting area in the cross section of the ice-covered line, the heat exchange coefficient of the outer surface of the ice layer, the equivalent thermal conduction resistance of the remaining ice layer after the ice layer falls off, and the heat loss of the outer surface of the ice layer. Combined with the ice-melting time specified on site, the required ice-melting current value of the OPGW is obtained according to the calculation expression of the OPGW ice-melting current; Fiber temperature maximum value calculation unit: calculates the maximum fiber temperature inside the OPGW before de-icing based on the ice-melting current value required by the OPGW; Fiber temperature steady-state value calculation unit: calculates the steady-state value of the fiber temperature inside the OPGW after de-icing based on the ice-melting current value required by the OPGW; Optical fiber critical temperature rise value acquisition unit: According to the maximum value of the temperature of the optical fiber inside the OPGW before de-icing and the steady-state value of the temperature of the optical fiber inside the OPGW after de-icing, the maximum value is taken as the critical temperature rise value of the optical fiber inside the OPGW.

[0016] Compared with the existing technology, the present invention does not require finite element simulation modeling for ice-covered lines, and can quickly obtain the OPGW ice-melting current and the critical temperature rise of the optical fiber, thereby improving the calculation efficiency of the OPGW ice-melting current, effectively supporting on-site ice monitoring and timely fault response of high-voltage transmission lines, and also providing a reference for the subsequent design of OPGW DC ice-melting solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 Flowchart of the optimization calculation method of the OPGW ice melting current and the critical temperature rise of the optical fiber according to the present invention; Figure 2Flowchart of the OPGW ice melting current calculation method of the present invention; Figure 3 This is a cross-sectional view of a model A OPGW line on site in a specific embodiment of the present invention; Figure 4 This is a cross-sectional view of a field B-type OPGW line in a specific embodiment of the present invention; Figure 5 Graph showing the calculated results of the temperature rise characteristic curve of the A-type OPGW optical fiber at different ambient temperatures in a specific embodiment of the present invention; Figure 6 Calculation results of the temperature rise characteristic curve of the B-type OPGW optical fiber at different ambient temperatures in a specific embodiment of the present invention; Figure 7 This is a diagram showing the calculation results of the temperature rise characteristic curve of the A-type OPGW optical fiber under different wind speeds in a specific embodiment of the present invention; Figure 8 This is a diagram showing the calculation results of the temperature rise characteristic curve of the B-type OPGW optical fiber under different wind speeds in a specific embodiment of the present invention; Figure 9 Graph showing the calculation results of the maximum steady-state temperature of two types of OPGW optical fibers after complete ice melting at different ambient temperatures in a specific embodiment of the present invention; Figure 10 Graph showing the calculation results of the maximum steady-state temperature of two types of OPGW optical fibers after complete ice melting at different wind speeds in a specific embodiment of the present invention; Figure 11 This is a composition diagram of the optimization calculation system for OPGW ice melting current and optical fiber critical temperature rise of the present invention. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0020] Example 1 This embodiment is an optimization calculation method for OPGW ice melting current and optical fiber critical temperature rise, such as Figure 1 As shown, the steps are as follows: Step a) establishes a calculation expression for the Joule heat consumption generated by the OPGW during the ice melting process.

[0021] The calculation expression of heat dissipation in joules is as follows: , Where, Pc is the heat loss per unit length of the outer surface of the ice layer, in J / m; ρ i is the density of the ice layer in kg / m 3 ; L F is the latent heat absorbed when a unit mass of ice melts, L F =335000J / kg; S m The area of ​​ice melted in the cross section of the ice-covered line during the ice melting time, in m 2 ; C i is the specific heat capacity of the ice layer, in J / (kg·℃); T a is the ambient temperature, in °C; S i is the area of ​​melted ice in the cross section of the ice-covered line after de-icing, m 2 ; T i Indicates the temperature rise of the remaining ice layer after the ice-covered line is de-iced, in °C; ρ c 、C c and S c Represents the density, specific heat capacity and cross-sectional area of ​​each part of the OPGW, in kg / m 3 、J / (kg·℃)、m 2 ; T c Indicates the temperature of the OPGW when the ice falls off, in °C.

[0022] Step b) The energy conservation equation of the OPGW DC ice melting process is obtained according to the calculation expression of the Joule heat consumption, and the calculation expression of the OPGW ice melting current with respect to the Joule heat consumption is obtained from the energy conservation equation of the OPGW DC ice melting process.

[0023] The calculation expression for the Joules of heat consumed by the OPGW during the ice melting process established in step a) follows the law of conservation of energy. The energy conservation equation for the OPGW DC ice melting process is shown in Equation (1).

[0024] (1) Where: I is the ice melting current, in A; r T for T The unit length resistance of the OPGW ice melting conductor is Ω / m; TIndicates the temperature of the OPGW ice melting conductor in °C; t is the ice melting time, in units of s .

[0025] In formula (1), the Joules of heat consumed by the OPGW during the actual ice melting process include the heat required to raise the temperature of the melted ice layer, the latent heat absorbed during ice melting, the heat lost from the outer surface of the ice layer, the heat required to raise the temperature of the unmelted ice layer, and the heat required to raise the temperature of the OPGW. Since the heat absorbed by the unmelted ice layer and the OPGW temperature rise is relatively small, it can be ignored for the convenience of engineering application calculations. Therefore, formula (1) can be simplified to formula (2).

[0026] (2) The meanings of the variables in the formula are consistent with those in formula (1) and will not be repeated here.

[0027] Step c) Obtain the on-site ice-covered line model and detection parameters of the on-site online monitoring device, calculate the ice melting area in the cross section of the ice-covered line, the heat exchange coefficient of the outer surface of the ice layer, the equivalent thermal conduction resistance of the remaining ice layer after the ice layer falls off, and the heat loss of the outer surface of the ice layer. Combined with the on-site specified ice melting time, the required OPGW ice melting current value is obtained according to the calculation expression of the OPGW ice melting current.

[0028] The detection parameters of the on-site online monitoring device include ambient temperature T a , wind speed V a , ice thickness d .

[0029] Specifically, in step c), the ice melting current value required by the OPGW is as follows: Figure 2 As shown, obtain it through the following steps: Step c1) First calculate the ice melting area in the cross section of the ice-covered line S m , heat exchange coefficient of the outer surface of the ice layer h , ice surface temperature T i and the heat loss per unit length of the outer surface of the ice layer P c .

[0030] In step c1), the ice melting area in the cross section of the ice-covered line S m The calculation is: When the ice layer moves downward s = d When the ice layer falls off the OPGW surface, the ice layer melts in the cross section. S mThe calculation formula is: (3) Where, is pi; R c is the radius of OPGW, in m; R s is the radius of the outermost aluminum-clad steel wire of OPGW, in meters; d is the ice thickness of OPGW, in m; n The number of aluminum-clad steel wires in the outermost layer of OPGW.

[0031] In step c1), the heat exchange coefficient of the outer surface of the ice layer is h The calculation formula is: (4) Where, λ a is the thermal conductivity of air, λ a =0.0244W / (m·℃); ε is the ice surface emissivity, ε =0.9; σ is the radiation constant, σ =5.67×10 -8 W / (m 2 ℃ 4 ); T a is the ambient temperature, in °C; B 、 b for the reason G r coefficient of determination; C 、 n for the reason R e coefficient of determination; R e 、 P r 、 G r They are Reynolds number, Prandlt number and Grashof number respectively. R e 、 P r 、 G r The calculation of the three is shown in formula (5).

[0032] (5) Where, V a is the wind speed in the surrounding environment, in m / s; νis the kinematic viscosity of air, ν =1.328×10 -5 m 2 / s; μ is the dynamic viscosity of air, μ =1.72×10 -5 kg / (m·s); C a is the specific heat capacity of air, C a =1005J / (kg·℃); ρ a is the density of air, ρ a =1.293kg / m 3 .

[0033] in, R e Typical value range of: In laminar flow, R e <2×10 5 In the end flow, R e ≥2×10 5 ; Pr Typical value range: In air at room temperature, the default value is Pr is a constant, Pr ≈0.7; G r Typical value range of: In laminar flow, G r <1.41×10 9 In the end flow, G r ≥1.41×10 9 ; B 、 b for the reason G r coefficient of determination; C 、 n for the reason R e The coefficient of determination is shown below.

[0034] In laminar flow, G r <1.41×10 9 hour, B =0.48, b =0.25; in the end flow, that is, G r ≥1.41×10 9 When B = 0.10, b = 0.33; in laminar flow, that is, Re <2×10 5 hour, C =0.664, n =0.5; in the end flow, that is, R e ≥2×10 5 hour, C =0.0296, n =0.8.

[0035] In step c1), the outer surface temperature of the ice layer T i The calculation formula is: (6) Where, h is the surface thermal conductivity, unit is W / (m 2 ℃); R T1 is the equivalent thermal conduction resistance of the remaining ice layer after the ice layer falls off, in m·℃ / W.

[0036] Equivalent thermal conduction resistance of the remaining ice layer after the ice layer falls off R T1 The calculation formula is as follows: (7) Where, The area element in the two-dimensional field representing the remaining ice layer after the ice layer falls off; r out It represents the outer radius after the ice layer falls off, in meters; r in Indicates the contact surface radius between the remaining ice layer and the OPGW optical fiber, in meters; is the thermal conductivity of ice in units of W / ( m ℃); In step c1), the heat loss on the outer surface of the ice layer is calculated by: calculating the heat loss on the outer surface of the ice layer based on the radius of the OPGW, the ice thickness, the heat exchange coefficient of the outer surface of the ice layer, the outer surface temperature of the ice layer, the ambient temperature and the ice melting time.

[0037] Heat loss from the outer surface of the ice P c The calculation formula is: (8) Where, P c is the heat dissipated per unit length of the outer surface of the ice layer, in J / m; R c is the radius of OPGW, in m; dis the ice thickness of OPGW, in m; T i Indicates the outer surface temperature of the ice layer, in °C; T a is the temperature of the surrounding environment, in °C; t is the ice melting time, in seconds.

[0038] Step c2): Substitute equations (3)-(8) into equation (2) to obtain the energy conservation equation, see equation (9).

[0039] (9) The ice melting time and ice melting current are obtained by transforming Equation (9), which are shown in Equation (10) and Equation (11) respectively.

[0040] (10) (11) Step c3) Obtain the ice melting time specified on site t 0, and then substitute into formula (11) to get the ice melting current value required by OPGW I 0, see formula (12).

[0041] (12) Where, I 0 is the ice melting current value required by OPGW, in A; t 0 is the ice melting time specified on site, in seconds.

[0042] In step d), the maximum temperature of the optical fiber inside the OPGW before de-icing and the steady-state temperature of the optical fiber inside the OPGW after de-icing are calculated based on the de-icing current required by the OPGW.

[0043] In step d), the maximum temperature of the optical fiber inside the OPGW before de-icing T pm For the calculation of , see formula (13).

[0044] (13) Where, T pm is the maximum temperature of the optical fiber inside the OPGW before de-icing, in °C; R T0 is the equivalent thermal conduction resistance of the air gap, in m·℃ / W; R T2 is the equivalent conduction thermal resistance between the optical fiber inside the OPGW and the surface of the OPGW, in units of m·℃ / W, R T2It is determined by the model and structure of OPGW (the model includes the structure); I 0 is the ice melting current value required by OPGW, in A; r T for T The unit length resistance of OPGW ice melting conductor at ℃, in Ω / m.

[0045] Equivalent thermal conduction resistance of air gap R T0 The calculation formula is as follows: (14) Where, λ a is the thermal conductivity of air, λ a =0.0244 W / (m·℃); R c is the radius of OPGW, in m; Represents an area element in a two-dimensional field; is the polar coordinate equation of the inner surface of the ice layer at the moment of deicing, which is expressed as formula (15): (15) In step d), the steady-state value of the optical fiber temperature inside the OPGW after de-icing T n For the calculation of , see formula (16).

[0046] (16) Where, T pn is the steady-state value of the optical fiber temperature inside the OPGW after de-icing, in °C; r T for T The unit length resistance of the OPGW ice melting conductor is Ω / m; I 0 is the ice melting current value required by OPGW, in A; R T2 is the equivalent conduction thermal resistance between the optical fiber inside the OPGW and the surface of the OPGW, in units of m·℃ / W, R T2 It is determined by the model and structure of OPGW (the model includes the structure); R c is the radius of OPGW, in m; T a is the ambient temperature, in °C; h c is the heat exchange coefficient of the OPGW surface, in W / (m 2 ·℃).

[0047] Step e): Based on the maximum value of the temperature of the optical fiber inside the OPGW before de-icing and the steady-state value of the temperature of the optical fiber inside the OPGW after de-icing, the maximum value of the former two is taken as the critical temperature rise value of the optical fiber inside the OPGW. T max .

[0048] T max The calculation of is shown in formula (17).

[0049] (17) Where: T max is the critical temperature rise of the optical fiber inside the OPGW, in °C; T pm is the maximum temperature of the optical fiber inside the OPGW before de-icing, in °C; T pn is the steady-state value of the optical fiber temperature inside the OPGW after de-icing, in °C.

[0050] Application Examples Taking two different types of iced OPGW lines on site as an example, the optimization calculation method of the present invention is applied to calculate the OPGW ice melting current and the critical temperature rise of the optical fiber. The specific steps are as follows: 1) Obtain the model of the ice-covered line on site. The model of the A-type OPGW line is OPGW-12B1+2A1a-68, and the cross-sectional diagram is as follows: Figure 3 As shown, the B-type OPGW line model is OPGW-24B1-122, and the cross-sectional view is as follows Figure 4 As shown in the figure, obtain the various detection parameters of the on-site online monitoring device. Among them, the ambient temperature T a =-5℃, wind speed V a =5m / s, ice thickness d =15mm.

[0051] 2) Based on the iced line model and the various detection parameters obtained by the on-site online monitoring device, the Joule heat consumption generated by the OPGW during the ice melting process was calculated. The Joule heat consumption for the Type A OPGW line was 5.24 kWh, and the Joule heat consumption for the Type B OPGW line was 10.53 kWh.

[0052] 3) Based on the Joule heat consumption generated by the OPGW during the ice melting process, the OPGW ice melting current value is calculated. The ice melting current value of the type A OPGW line is 250A, and the ice melting current value of the type B OPGW line is 300A.

[0053] 4) Based on the on-site regulation of 60 minutes of ice melting time, calculate the maximum temperature of the optical fiber inside the OPGW before ice removal. The calculation results of the temperature rise characteristic curves of the two types of OPGW optical fibers under different ambient temperatures are as follows: Figure 5 and Figure 6 As shown in the figure, the calculation results of the temperature rise characteristic curves of two types of OPGW optical fibers under different wind speeds are as follows: Figure 7 and Figure 8 As shown, the maximum optical fiber temperature before de-icing for the A-type OPGW line is 82° C., and the maximum optical fiber temperature before de-icing for the B-type OPGW line is 71° C.

[0054] 5) According to the on-site regulation of 60 minutes of ice melting time, calculate the steady-state value of the optical fiber temperature inside the OPGW after de-icing. The calculation results of the steady-state temperature of the optical fiber of the two models of OPGW after complete ice melting at different ambient temperatures are as follows: Figure 9 As shown in Figure 2, the calculation results of the steady-state temperature of two types of OPGW optical fibers after complete ice melting at different wind speeds are as follows: Figure 10 As shown, the steady-state value of the optical fiber temperature after deicing of the A-type OPGW line is 44°C, and the steady-state value of the optical fiber temperature after deicing of the B-type OPGW line is 53°C.

[0055] 6) Obtain the maximum value of the optical fiber temperature inside the OPGW before de-icing in step d). The maximum value of the optical fiber temperature before de-icing of the A-type OPGW line is 82°C, and the maximum value of the optical fiber temperature before de-icing of the B-type OPGW line is 71°C. Obtain the steady-state value of the optical fiber temperature inside the OPGW after de-icing in step e). The steady-state value of the optical fiber temperature after de-icing of the A-type OPGW line is 44°C, and the steady-state value of the optical fiber temperature after de-icing of the B-type OPGW line is 53°C. Comparing the two values ​​of the A-type OPGW line, the larger value is 82°C, so the critical temperature rise of the optical fiber inside the A-type OPGW is 82°C; comparing the two values ​​of the B-type OPGW line, the larger value is 71°C, so the critical temperature rise of the optical fiber inside the B-type OPGW is 71°C; Example 2 This embodiment provides an optimization calculation system for OPGW ice melting current and optical fiber critical temperature rise, which is used to implement the optimization calculation method described in the first embodiment. Figure 11 As shown, it consists of a Joule heat consumption calculation expression establishment unit, an ice melting current calculation expression acquisition unit, an ice melting current value calculation unit, an optical fiber temperature maximum value calculation unit, an optical fiber temperature steady-state value calculation unit and an optical fiber critical temperature rise value acquisition unit.

[0056] Joule heat consumption calculation expression establishing unit: establishes a calculation expression for the Joule heat consumption generated by the OPGW during ice melting; used to implement step a) in Example 1, which will not be repeated here.

[0057] Ice-melting current calculation expression acquisition unit: obtains the energy conservation equation in the OPGW DC ice-melting process based on the calculation expression of Joule heat consumption, and obtains the calculation expression of the OPGW ice-melting current from the energy conservation equation in the OPGW DC ice-melting process; used to implement step b) in Example 1, which will not be repeated here.

[0058] Ice-melting current value calculation unit: obtains the on-site ice-covered line model and the detection parameters of the on-site online monitoring device, calculates the ice melting area in the cross section of the ice-covered line, the heat exchange coefficient of the outer surface of the ice layer, the equivalent thermal conduction resistance of the remaining ice layer after the ice layer falls off, and the heat loss of the outer surface of the ice layer, and then combines the ice-melting time specified on site and obtains the ice-melting current value required by the OPGW according to the calculation expression of the OPGW ice-melting current; used to implement step c) in Example 1, which will not be repeated here.

[0059] The optical fiber temperature maximum value calculation unit calculates the maximum optical fiber temperature inside the OPGW before de-icing based on the ice-melting current value required by the OPGW. It is used to implement step d) in Example 1 and will not be repeated here.

[0060] The optical fiber temperature steady-state value calculation unit calculates the steady-state value of the optical fiber temperature inside the OPGW after de-icing based on the ice-melting current value required by the OPGW; it is used to implement step d) in Example 1 and will not be repeated here.

[0061] Optical fiber critical temperature rise value acquisition unit: Based on the maximum value of the temperature of the optical fiber inside the OPGW before de-icing and the steady-state value of the temperature of the optical fiber inside the OPGW after de-icing, the maximum value is taken as the critical temperature rise value of the optical fiber inside the OPGW; used to implement step e) in Example 1, which will not be repeated here.

[0062] It should be noted that the various modules in the aforementioned system for optimizing and calculating the OPGW ice-melting current and the critical temperature rise of an optical fiber can be implemented in whole or in part through software, hardware, or a combination thereof. Each of these modules can be embedded in or independent of a processor within a computer device in hardware form, or stored in a computer device memory in software form, allowing the processor to call and execute the corresponding operations of each module. For specific definitions of the system for optimizing and calculating the OPGW ice-melting current and the critical temperature rise of an optical fiber, refer to the aforementioned definition of the method for optimizing and calculating the OPGW ice-melting current and the critical temperature rise of an optical fiber. Both systems have the same functions and effects and are not further elaborated here.

[0063] The above description of the embodiments is intended to facilitate understanding and application of the present invention by those skilled in the art. It is apparent that those skilled in the art can readily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without requiring creative effort. Therefore, the present invention is not limited to the above embodiments. Any improvements or modifications made by those skilled in the art based on the disclosure of the present invention should fall within the scope of protection of the present invention.

Claims

1. An optimization calculation method for OPGW ice melting current and optical fiber critical temperature rise, characterized in that: include: Step a), establishing a calculation expression for the Joules consumed heat generated by the OPGW during the ice melting process; Step b) obtaining an energy conservation equation for the OPGW DC ice melting process based on a calculation expression for Joule heat consumption, and obtaining an expression for the OPGW ice melting current with respect to Joule heat consumption based on the energy conservation equation for the OPGW DC ice melting process; Step c) obtaining the model of the on-site ice-covered line and the detection parameters of the on-site online monitoring device, calculating the ice melting area in the cross section of the ice-covered line, the heat exchange coefficient of the outer surface of the ice layer, the equivalent thermal conduction resistance of the remaining ice layer after the ice layer falls off, and the heat loss of the outer surface of the ice layer. The calculated melting current value required by the OPGW is then calculated based on the melting current calculation expression of the OPGW in combination with the melting time specified on site. Step d), calculating the maximum temperature of the optical fiber inside the OPGW before de-icing and the steady-state temperature of the optical fiber inside the OPGW after de-icing based on the de-icing current required by the OPGW; Step e): according to the maximum value of the temperature of the optical fiber inside the OPGW before de-icing and the steady-state value of the temperature of the optical fiber inside the OPGW after de-icing, the maximum value of the former two is taken as the critical temperature rise value of the optical fiber inside the OPGW.

2. The optimization calculation method of OPGW ice melting current and optical fiber critical temperature rise according to claim 1 is characterized in that: In step a), the Joules of heat consumed by the OPGW during ice melting include the heat required to raise the temperature of the melted ice layer, the latent heat absorbed during ice melting, the heat lost from the outer surface of the ice layer, the heat required to raise the temperature of the unmelted ice layer, and the heat required to raise the temperature of the OPGW. To simplify the calculation, the heat required to raise the temperature of the unmelted ice layer and the heat required to raise the temperature of the OPGW are ignored.

3. The optimization calculation method of OPGW ice melting current and optical fiber critical temperature rise according to claim 2 is characterized in that: In step b), the energy conservation equation during the OPGW DC ice melting process is simplified to: ， Where, I is the OPGW ice melting current, in A; r T for T The unit length resistance of OPGW ice melting conductor is / m; T Indicates the temperature of the OPGW ice melting conductor in °C; t is the ice melting time, in units of s ; P c is the heat dissipated per unit length of the outer surface of the ice layer, in J / m; ρ i is the density of the ice layer in kg / m 3 ; L F is the latent heat absorbed when a unit mass of ice melts, in J / kg; S m The area of ​​ice melted in the cross section during the melting time, in m 2 ; C i is the specific heat capacity of the ice layer, in J / (kg·℃); T a is the ambient temperature in °C.

4. The optimization calculation method of OPGW ice melting current and optical fiber critical temperature rise according to claim 1 is characterized in that: In step c), the detection parameters of the on-site online monitoring device include ambient temperature, wind speed and ice thickness.

5. The optimization calculation method of OPGW ice melting current and optical fiber critical temperature rise according to claim 1 is characterized in that: In step c), the heat loss on the outer surface of the ice layer is calculated by: calculating the heat loss on the outer surface of the ice layer based on the radius of the OPGW, the ice thickness, the heat exchange coefficient of the outer surface of the ice layer, the outer surface temperature of the ice layer, the ambient temperature and the ice melting time.

6. The optimization calculation method of OPGW ice melting current and optical fiber critical temperature rise according to claim 5 is characterized in that: Ice surface temperature T i The calculation formula is: ， Where, h is the surface thermal conductivity, unit is W / (m 2 ℃); R c is the radius of OPGW, in m; d is the ice thickness of OPGW, in m; R T1 is the equivalent thermal conductivity resistance of the remaining ice layer after the ice layer falls off, in m·℃ / W; T a is the ambient temperature in °C.

7. The optimization calculation method of OPGW ice melting current and optical fiber critical temperature rise according to claim 6 is characterized in that: Equivalent thermal conduction resistance of the remaining ice layer after the ice layer falls off R T1 The calculation formula is: ， Where, The area element in the two-dimensional field representing the remaining ice layer after the ice layer falls off; r out It represents the outer radius after the ice layer falls off, in meters; r in Indicates the contact surface radius between the remaining ice layer and the OPGW optical fiber, in meters; is the thermal conductivity of ice, in units of W / ( m ·℃).

8. The optimization calculation method of OPGW ice melting current and optical fiber critical temperature rise according to claim 1 is characterized in that: In step d), the maximum temperature of the optical fiber inside the OPGW before de-icing is calculated as follows: ， Where, T pm is the maximum temperature of the optical fiber inside the OPGW before de-icing, in °C; R T0 is the equivalent thermal conduction resistance of the air gap, in m·℃ / W; R T2 is the equivalent conduction thermal resistance between the optical fiber inside the OPGW and the surface of the OPGW, in m·°C / W; I 0 is the ice melting current value required by OPGW, in A; r T for T The unit length resistance of the OPGW ice melting conductor is Ω / m. T Indicates the temperature of the OPGW ice melting conductor in °C.

9. The optimization calculation method of OPGW ice melting current and optical fiber critical temperature rise according to claim 1, characterized in that: In step d), the calculation formula for the steady-state value of the optical fiber temperature inside the OPGW after de-icing is: ， Where, T pn is the steady-state value of the optical fiber temperature inside the OPGW after de-icing, in °C; r T for T The unit length resistance of the OPGW ice melting conductor is Ω / m; T Indicates the temperature of the OPGW ice melting conductor in °C; I 0 is the ice melting current value required by OPGW, in A; R T2 is the equivalent conduction thermal resistance between the optical fiber inside the OPGW and the surface of the OPGW, in m·°C / W; R c is the radius of OPGW, in m; T a is the ambient temperature, in °C; h c is the heat exchange coefficient of the OPGW surface, in W / (m 2 ·℃).

10. An optimization calculation system for OPGW ice melting current and optical fiber critical temperature rise, used to implement the optimization calculation method according to any one of claims 1 to 9, characterized in that: include: Joule consumption heat calculation expression establishment unit: establishes the calculation expression of Joule consumption heat generated by OPGW during ice melting; Ice-melting current calculation expression acquisition unit: obtains the energy conservation equation in the OPGW DC ice-melting process according to the calculation expression of Joule heat consumption, and obtains the calculation expression of the OPGW ice-melting current according to the energy conservation equation in the OPGW DC ice-melting process; Ice-melting current calculation unit: Obtain the on-site ice-covered line model and the detection parameters of the on-site online monitoring device, calculate the ice melting area in the cross section of the ice-covered line, the heat exchange coefficient of the outer surface of the ice layer, the equivalent thermal conduction resistance of the remaining ice layer after the ice layer falls off, and the heat loss of the outer surface of the ice layer. Combined with the ice-melting time specified on site, the required ice-melting current value of the OPGW is obtained according to the calculation expression of the OPGW ice-melting current; Fiber temperature maximum value calculation unit: calculates the maximum fiber temperature inside the OPGW before de-icing based on the ice-melting current value required by the OPGW; Fiber temperature steady-state value calculation unit: calculates the steady-state value of the fiber temperature inside the OPGW after de-icing based on the ice-melting current value required by the OPGW; Optical fiber critical temperature rise value acquisition unit: According to the maximum value of the temperature of the optical fiber inside the OPGW before de-icing and the steady-state value of the temperature of the optical fiber inside the OPGW after de-icing, the maximum value is taken as the critical temperature rise value of the optical fiber inside the OPGW.

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