Calculation method and system for operating overhead line state
By acquiring measurement data and line parameters in real time, and combining a proportional fusion correction mechanism and a sliding window weighted least squares estimation, the average temperature and maximum heat capacity of overhead lines are calculated. This solves the problem of insufficient accuracy in current carrying capacity calculation in existing technologies, and achieves more efficient current carrying capacity utilization and improved economic efficiency.
Patent Information
- Application Number
- CN202511290127.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-10
- Publication Date
- 2026-02-03
AI Technical Summary
Existing technologies lack accuracy in current carrying capacity calculation, cannot fully utilize the hidden capacity of overhead lines, leading to economic losses and increased construction costs. Furthermore, they do not comprehensively consider environmental factors, and traditional temperature prediction methods are susceptible to sensor bias.
By acquiring measurement data and line parameters in real time, the conductor sag is solved using wind speed, conductor tension, tension section parameters, and conductor parameters. Combined with a proportional fusion correction mechanism and sliding window weighted least squares estimation, the average line temperature and maximum heat capacity are calculated, and the operating current is adjusted in real time.
It improves the accuracy and economy of current carrying capacity calculation, releases the hidden capacity of the line, reduces construction costs, and improves the transmission efficiency and economy of overhead lines.
Smart Images
Figure CN121457057A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of overhead line technology, and more specifically to a calculation method and system for the status of operating overhead lines. Background Technology
[0002] Currently, commonly used models for calculating the current carrying capacity of overhead lines include the IEEE Std 738-2017 calculation standard, the GB50545-2023 (Design Code for 110~750KV Overhead Transmission Lines) calculation standard, and the CIGRE calculation standard. The IEEE Std 738-2017 calculation standard is frequently used in North America. This standard assumes that the overhead transmission line is a uniform conductor, and the temperature rise of the overhead line depends on the difference between the heat generated and the heat dissipated. The relationship between the various heat sources in the conductor is expressed using a dynamic heat balance equation: (1)
[0003] In the formula, t represents time; C P q represents the specific heat capacity of the conductor; l The Joule heat generated by an electric current passing through a conductor; q s Absorbs heat from sunlight; q c For convective heat dissipation; q r denoted as , where is the heat dissipation due to thermal radiation; m is the mass per unit length of the conductor; and Tc is the temperature of the conductor. When the rate of temperature change is zero, i.e. When the conductor reaches a static thermal equilibrium state, the total heat dissipated by the conductor is equal to the total heat absorbed.
[0004] In the CIGRE calculation model, similar to the IEEE Std 738-2017 calculation standard, overhead transmission lines are also treated as uniformly transmitting conductors. Unlike other calculation models, the CIGRE model incorporates factors such as the skin effect and electromagnetic heating, and also accounts for hysteresis loss heating and corona loss heating. Its specific expression is as follows: (2)
[0005] In this formula, q l The Joule heat generated by the electric current; q s Heat absorption by sunlight under direct or diffused conditions; q c for
[0006] Convection heat dissipation; q r q represents radiative heat dissipation. i For corona discharge heat generation; q m Electromagnetic heating; q w This is for evaporative heat dissipation. An equivalent relationship between DC and AC heat generation was calculated in the current-based heating calculation.
[0007] In the calculation standard of GB 50545-2023 (Design Code for 110~750KV Overhead Transmission Lines), fewer factors are considered, and most parameters are directly given with relevant calculation formulas. The main expression is the steady-state thermal balance equation: (3)
[0008] In this expression, q l The Joule heat generated by an electric current passing through a conductor; q s Absorbs heat from sunlight; q c For convective heat dissipation; q r For heat radiation dissipation, the relevant calculations stipulated in the national standard are only used within the domestic scope, and are supplemented with relevant coefficients for different regions for correction. The Reynolds number and Nusselt coefficient have been standardized and limited. Supplementary calculations are made for complex environmental conditions. This calculation standard is often carried out in the early stages of overhead line construction in China, calculating the operating conditions under extreme conditions, focusing more on mechanical calculations to ensure both structural safety and energy security, and conducting basic allowable current-carrying capacity design.
[0009] The GB 50545-2023 calculation standard often considers the most severe operating conditions for overhead lines, which significantly limits the current carrying capacity of existing overhead lines and fails to fully release their hidden capacity. Furthermore, due to China's land conditions, putting new overhead lines into operation is difficult, and the investment required for new construction is substantial. Therefore, the unutilized hidden current carrying capacity leads to significant economic losses. Moreover, this calculation standard does not fully consider environmental factors, often resulting in a lack of dynamic overload capacity, which increases construction costs and wastes human, financial, and material resources. In addition, traditional cable temperature prediction methods often directly use single-point temperatures or simple fitting as the average line temperature, which is easily affected by sensor bias and local operating conditions, thus impacting subsequent thermal calculations. Summary of the Invention
[0010] To overcome the shortcomings in the accuracy of current carrying capacity calculation in the prior art, this invention provides a calculation method and system for the operating status of overhead lines. It uses measurement data and line parameters under actual operating conditions to replace the calculation of the maximum allowable current carrying capacity preset under the worst conditions, thereby improving the utilization rate of hidden capacity.
[0011] According to one aspect of the present invention, a method for calculating the status of an operating overhead line is provided, comprising:
[0012] Real-time acquisition of measurement data and line parameters; the measurement data includes ambient temperature, wind speed and direction, conductor tension, solar radiation intensity, and load current; the line parameters include tension section parameters and conductor parameters; conductor sag is calculated using wind speed and direction, conductor tension, tension section parameters, and conductor parameters; the average line temperature is calculated using the conductor sag based on a proportional fusion correction mechanism; the maximum heat capacity of the line is calculated using ambient temperature, solar radiation intensity, load current, and the average line temperature.
[0013] The operating current on the overhead line is adjusted in real time according to the maximum heat capacity of the line.
[0014] Furthermore, based on the proportional fusion correction mechanism, the average line temperature is calculated using the conductor sag, including: using historical experience data to calculate the cubic relationship between the average line temperature and the conductor sag; substituting the conductor sag calculated using measurement data and line parameters into the cubic relationship between the average line temperature and the conductor sag to obtain the predicted average line temperature; and based on the proportional fusion correction mechanism, fusing the predicted average line temperature with the overhead line operating temperature monitored by the temperature sensor according to the fusion weight to obtain the average line temperature.
[0015] Furthermore, based on the proportional fusion correction mechanism, the predicted average line temperature and the overhead line operating temperature monitored by the temperature sensor are proportionally fused to obtain the average line temperature, including: calculating the current residual between the predicted average line temperature and the overhead line operating temperature; adaptively adjusting the fusion weight according to the relationship between the current residual and a preset threshold; and fusing the predicted average line temperature and the overhead line operating temperature according to the fusion weight to obtain the average line temperature.
[0016] Furthermore, the tension section parameters include span and height difference between the towers on both sides; the conductor parameters include conductor type, conductor unit weight, calculated cross-sectional area, conductor outer diameter, expansion coefficient, heat absorption coefficient, heat dissipation coefficient, and unit resistance.
[0017] Furthermore, the conductor sag is solved using wind speed and direction, conductor tension, tension section parameters, and conductor parameters, including: calculating the self-weight load, wind pressure load, and the line height at each point in the vertical plane of the overhead conductor using wind speed and direction, conductor tension, tension section parameters, and conductor parameters; and calculating the conductor sag based on the self-weight load, wind pressure load, and the line height at each point in the vertical plane of the overhead conductor.
[0018] Furthermore, the maximum heat capacity of the line is determined using ambient temperature, solar radiation intensity, load current, and average line temperature. This includes: determining the solar heat absorption energy, radiative heat dissipation energy, and heat transfer coefficient using ambient temperature, solar radiation intensity, load current, and average line temperature; correcting the heat transfer coefficient using sliding window weighted least squares estimation and adaptive exponential smoothing; and calculating the maximum heat capacity of the line based on the solar heat absorption energy, radiative heat dissipation energy, and the corrected heat transfer coefficient.
[0019] Furthermore, the heat transfer coefficient is corrected using sliding window weighted least squares estimation and adaptive exponential smoothing, including: taking multiple sampling points around the current time to form a time window; performing weighted least squares calculation on the proportional relationship within the time window to obtain multi-point heat transfer coefficients; fusing the multi-point heat transfer coefficients and single-point heat transfer coefficients to obtain fused heat transfer coefficients; and weightedly fusing the fused heat transfer coefficients and the target heat transfer coefficients from the previous time to obtain the target heat transfer coefficients at the current time.
[0020] Furthermore, the calculation method also includes: determining whether the overhead line is in an over-limit operating state based on the maximum heat capacity of the line and a preset threshold, and providing an early warning when the overhead line is in an over-limit operating state.
[0021] According to one aspect of the present invention, a calculation system for the status of an operating overhead line is provided, comprising:
[0022] The data acquisition module acquires measurement data and line parameters in real time. The measurement data includes ambient temperature, wind speed and direction, conductor tension, solar radiation intensity, and load current. The line parameters include tension section parameters and conductor parameters. The conductor sag calculation module calculates conductor sag using wind speed and direction, conductor tension, tension section parameters, and conductor parameters. The line average temperature calculation module calculates the line average temperature using the conductor sag based on a proportional fusion correction mechanism. The line maximum heat capacity calculation module calculates the line maximum heat capacity using ambient temperature, solar radiation intensity, load current, and line average temperature.
[0023] According to one aspect of the present invention, a computing device for calculating the status of an operating overhead line is provided, comprising:
[0024] The monitoring and data acquisition subsystem is used to monitor measurement data and line parameters in real time; the control subsystem is used to execute the calculation method for the status of an operating overhead line based on the measurement data and line parameters monitored by the monitoring and data acquisition subsystem.
[0025] The above technical solution collects measurement data and line parameters under actual operating conditions in real time, and calculates conductor sag using wind speed and direction, conductor tension, tension section parameters, and conductor parameters; based on a proportional fusion correction mechanism, it calculates the average line temperature using the conductor sag; and it calculates the maximum heat capacity of the line using ambient temperature, solar radiation intensity, load current, and the average line temperature. In other words, this invention uses measurement data and line parameters under actual operating conditions instead of calculating the maximum allowable current carrying capacity based on the worst-case conditions, which can release the hidden capacity of the line to a greater extent and improve the economic efficiency of the operating line.
[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0027] (1) Based on the perception of the operating status of overhead lines and considering various environmental parameters and laying conditions (i.e. measurement data and line parameters) under actual operating conditions, this invention replaces the calculation of the maximum allowable current carrying capacity preset under the worst conditions, which can release the hidden capacity of the line to a greater extent and improve the economy of the operating line.
[0028] (2) The current carrying capacity limitations of existing technologies are mainly reflected in sag and average line temperature. This invention first uses measurement data and line parameters to solve for conductor sag, then uses conductor sag to solve for average line temperature, and finally uses measurement data, line parameters, and average line temperature to solve for the maximum heat capacity of the line. That is to say, the calculation of the maximum heat capacity of the line in this invention integrates sag and average line temperature, thereby breaking the limitations of current carrying capacity on sag and average line temperature and improving the accuracy of the maximum heat capacity of the line.
[0029] (3) The present invention solves the average temperature of the line based on the proportional fusion correction mechanism of sag and temperature measurement. Within the same tension section, the predicted value generated by the cubic relationship between sag and temperature and the actual measurement of the thermometer are used simultaneously. The fusion weight is adaptively adjusted according to the residual of the two. When the consistency is high, the actual measurement value is used first. When there is a deviation, the proportion of the model prediction is automatically increased to improve the accuracy of the average temperature of the line, thereby indirectly improving the accuracy of the maximum heat capacity of the line.
[0030] (4) In view of the problem that single-point inversion is susceptible to noise amplification, this invention uses existing input quantities to construct a proportional relationship within the most recent time window, and weights each sampling point according to the stability of wind speed and temperature changes to obtain a consistent heat transfer coefficient estimate for the same time period, thereby significantly reducing instantaneous fluctuations and improving numerical stability. Attached Figure Description
[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0032] Figure 1 This is a flowchart illustrating a calculation method for the status of an operating overhead line, provided as an embodiment of the present invention. Detailed Implementation
[0033] It should be noted that:
[0034] The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and accompanying drawings of this invention are intended to cover a non-exclusive inclusion, such as a process, method, system, product, or apparatus that includes a series of steps or units, not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0035] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices. The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be decomposed, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.
[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In addition, the technical features of the various embodiments or individual embodiments provided by the present invention can be arbitrarily combined to form new technical solutions. Such combinations are not bound by the order of steps and / or structural composition patterns, but must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.
[0037] Please refer to Figure 1 This invention provides a method for calculating the status of operating overhead lines, specifically including the following steps:
[0038] Step S1: Acquire measurement data and line parameters in real time.
[0039] In step S1, the present invention includes two parts of data collection: measurement data and line parameters. The measurement data includes ambient temperature, wind speed and direction, conductor tension, solar radiation intensity, and load current. The line parameters include tension section parameters and conductor parameters. The tension section parameters mainly include physical parameters such as span and height difference between the towers on both sides. The conductor parameters mainly include inherent properties of the conductor such as conductor type, conductor unit weight, calculated cross-sectional area, conductor outer diameter, expansion coefficient, heat absorption coefficient, heat dissipation coefficient, and unit resistance.
[0040] In this embodiment, a SCADA (Supervisory Control and Data Acquisition) system is used to measure physical quantities such as current. The SCADA system measures the real-time temperature of the conductor using a wireless temperature sensor; monitors vibration frequency, amplitude, and galloping trajectory through video monitoring and sensors; measures conductor load current and load factor using devices such as current transformers; measures environmental parameters, including wind speed, wind direction, ambient temperature, humidity, rainfall, and light intensity, by setting up a miniature weather station; and obtains real-time stress changes of the overhead line using stress sensors. Based on these real-time measured data, the national standard calculation model can be corrected, further improving the utilization rate of hidden capacity.
[0041] Step S2: Solve for conductor sag using wind speed and direction, conductor tension, tension section parameters, and conductor parameters.
[0042] In step S2, the self-weight load, wind pressure load, and the line height at each point in the vertical plane of the overhead conductor are calculated using wind speed and direction, conductor tension, tension section parameters, and conductor parameters; the conductor sag is calculated based on the self-weight load, wind pressure load, and the line height at each point in the vertical plane of the overhead conductor.
[0043] The following section further explains step S2 using the formula. The calculation of overhead line sag mainly involves the calculation of geometric stress, as shown in the following formula: (4) (5) (6) (7) (8)
[0044] Of the above series of formulas, formula (4) represents the calculation of the self-weight specific load, where, For the self-weight load, q is the weight per unit overhead line, and A is the calculated cross-sectional area of the overhead line. Formula (5) represents the calculation of wind pressure load considering the influence of wind speed, where, The wind pressure load takes into account the effect of wind speed, where V represents wind speed and D represents the diameter of the overhead line. This represents the wind pressure non-uniformity coefficient. This is the conductor shape factor (1.2 for conductor outer diameter less than 17mm, and 1.1 for conductor outer diameter greater than 17mm). This is the wind pressure height variation coefficient. The angle between the wind direction and the conductor axis. Formula (6) represents the comprehensive specific load calculation expression considering both self-weight specific load and wind pressure specific load. The formula (7) represents the expression for calculating the line height at each point in the vertical plane of the overhead line when performing sag calculation using a parabolic model, where y represents the line height at each point in the vertical plane of the overhead line, and x represents the horizontal distance from the lower tower. The magnitude of the horizontal tension on an overhead power line is typically measured using a stress sensor. Let h be the height angle of the two towers, h be the height difference between the two towers, and l be the span (horizontal distance between the two towers). Formula (8) represents the calculated sag value at each point within the span. This represents the calculated sag value at each point within the span.
[0045] Step S3: Based on the proportional fusion correction mechanism, the average temperature of the line is solved using the conductor sag.
[0046] In step S3, since conductor expansion caused by temperature rise leads to sag, sag can also reflect conductor temperature. Therefore, this invention, for calculating the average line temperature, uses a large amount of historical experience data on average line temperature and conductor sag under the same tension section and conductor type to determine the cubic relationship between the average line temperature and conductor sag. The conductor sag obtained in step S2 using measurement data and line parameters is substituted into the cubic relationship between the average line temperature and conductor sag to infer the average conductor temperature (i.e., predict the average line temperature) from the conductor sag in this cubic fitting relationship. Then, based on a proportional fusion correction mechanism, the predicted average line temperature and the overhead line operating temperature measured by the temperature sensor are fused according to fusion weights to obtain the average line temperature. Specifically: the current residual between the predicted average line temperature and the overhead line operating temperature is calculated; the fusion weights are adaptively adjusted according to the relationship between the current residual and a preset threshold; the predicted average line temperature and the overhead line operating temperature are fused according to the fusion weights to obtain the average line temperature. .
[0047] The following will further explain step S3 in conjunction with the formula. First, the real-time horizontal sag is fitted using historical experience data. The predicted average line temperature is as follows: (9)
[0048] In the formula, These are existing calibration coefficients. To predict the average temperature of the line; the wireless temperature sensor reading is recorded as... ,Right now The operating temperature of overhead lines. This is the real-time horizontal sag (i.e., the conductor sag obtained in step S2).
[0049] Define the current residual Set a threshold Weight upper and lower bounds Construct an adaptive scaling factor : (10)
[0050] in, Indicates weight, Indicates the lower bound of the weight. Indicates the upper bound of the weight. This represents the residual for that time (i.e., the deviation between the predicted average temperature of the line and the operating temperature of the overhead line). Indicates the lower bound of the threshold. This represents the upper bound of the threshold, which is used to predict the average temperature of the line. Operating temperature of overhead lines Adjust and blend the proportions: (11)
[0051] in, This represents the average temperature of the line. When the measurement matches the fitted result (i.e., the current residual),... When the temperature is low, there is more trust in the operating temperature of overhead lines. ( Take the smaller value); the deviation increases (i.e., the residual of the current test). When the temperature is relatively high, increase the prediction of the average line temperature. weights ( Take the larger value). Among them, the parameter The adjustment can be easily made based on the on-site data, and no specific restrictions are imposed here.
[0052] Step S4: Calculate the maximum heat capacity of the line using ambient temperature, solar radiation intensity, load current, and average line temperature.
[0053] In step S4, the solar heat absorption energy, radiative heat dissipation energy, and heat transfer coefficient are calculated using ambient temperature, solar radiation intensity, load current, and average line temperature. The heat transfer coefficient is then corrected using sliding window weighted least squares estimation and adaptive exponential smoothing. Finally, the maximum heat capacity of the line is calculated based on the solar heat absorption energy, radiative heat dissipation energy, and the corrected heat transfer coefficient. The correction of the heat transfer coefficient using sliding window weighted least squares estimation and adaptive exponential smoothing includes: constructing a time window from multiple sampling points around the current moment; performing weighted least squares calculation on the proportional relationships within the time window to obtain multi-point heat transfer coefficients; fusing the multi-point heat transfer coefficients and single-point heat transfer coefficients to obtain a fused heat transfer coefficient; and weighting and fusing the fused heat transfer coefficient with the target heat transfer coefficient from the previous moment to obtain the target heat transfer coefficient for the current moment.
[0054] The following will further explain step S4 with reference to the formula. When calculating the maximum heat capacity of the line, it is assumed that the resistance of the overhead line changes linearly with temperature, that is, the resistance of the overhead line satisfies the following formula: (12)
[0055] In equation (9), Indicates the resistance of the overhead line. This represents the unit resistance value of an overhead line at a temperature of 20℃. This represents the average line temperature during operation. The temperature coefficient of the overhead line material is 0.00403 when the conductor material is aluminum. It should be noted that existing current-carrying capacity calculation methods (e.g., the IEEE Std 738-2017 calculation standard and the CIGRE calculation model) treat overhead transmission lines as uniformly transmitting conductors, neglecting the fact that the resistance of overhead transmission lines changes with temperature, leading to reduced accuracy in current-carrying capacity calculations. This invention establishes a formula for calculating the resistance of overhead lines by treating the resistance as linearly changing with temperature, thereby more accurately determining the resistance of overhead lines at their real-time operating temperature and improving the accuracy of current-carrying capacity calculations.
[0056] Furthermore, the calculation of solar heat absorption and radiative heat dissipation is performed according to the formula specified in the national standard, as shown in the following formula: (13) (14)
[0057] In equation (10), This indicates the heat energy absorbed by sunlight. Indicates the heat absorption coefficient. The outer diameter of the overhead line. This represents the intensity of solar radiation. In equation (11), This represents the energy dissipated through radiation. Indicates the heat dissipation coefficient. , These represent the average line temperature and the ambient temperature during operation, respectively. After obtaining the above calculation results, the conductor temperature model (CMT) is selected to solve for the heat transfer coefficient in the line's heat capacity. The calculation formula for the conductor temperature model is: (15)
[0058] In equation (12), I represents the actual current carrying capacity of the line (i.e., load current). This represents the heat transfer coefficient, and the other physical quantities are expressed in the same way as in the previous formula. Solving formula (12) yields the expression for the heat transfer coefficient: (16)
[0059] Furthermore, considering that the single-point estimation results are easily affected by noise, sliding window weighted least squares estimation and adaptive exponential smoothing are used for correction.
[0060] First, let the current time be... Take the nearest A time window is defined as 10 sampling points. (17)
[0061] in, This represents the difference between the average line temperature and the ambient temperature at the k-th sampling time (unit: °C). This represents the average line temperature at the k-th sampling time. This represents the ambient temperature at the k-th sampling time. This represents the net heat generation power per unit length of the conductor at the k-th sampling time. This represents the actual line load at the k-th sampling time. This represents the line resistance at the k-th sampling time. This represents the solar radiation heat absorption power at the k-th sampling time. This represents the radiative heat dissipation power at the k-th sampling time.
[0062] Furthermore, within this time window, the proportional relationship... We obtain a robust estimate by performing a weighted least squares solution: (18)
[0063] in, The heat transfer coefficient for window robust estimation (i.e., multi-point heat transfer coefficient). The weight is the weight at the k-th sampling time. Based solely on existing measurements, and to suppress the effects of rapid fluctuations in wind speed and temperature, the following can be considered: (19)
[0064] in, Let the wind speed be at the k-th sampling time. Let the wind speed be at the (k-1)th sampling time. This represents the average line temperature at the k-th sampling time. This represents the average temperature of the line at the (k-1)th sampling time. To smooth the scale (constant) separately, it can be tuned on-site, and no restrictions are imposed here.
[0065] The corrected formula for calculating the heat transfer coefficient is denoted as: (20)
[0066] in, This is the single-point heat transfer coefficient.
[0067] Furthermore, the previously obtained multi-point heat transfer coefficient With single-point heat transfer coefficient Integrate into the current "observation" estimate (i.e., the fusion heat transfer coefficient, which can be taken as...) (or set a fixed ratio as needed).
[0068] Furthermore, regarding the fusion heat transfer coefficient Perform adaptive exponential smoothing updates: (twenty one)
[0069] in, The final heat transfer coefficient determined at the current moment (i.e., the target heat transfer coefficient at the current moment). The heat transfer coefficient that was finally determined at the previous moment (i.e., the target heat transfer coefficient at the previous moment). To achieve adaptive exponential smoothing, the weights of the current time step and the previous time step are controlled by the step size. Composed solely of existing stock, to avoid when When the denominator effect is very small, it amplifies the noise. Take: (twenty two)
[0070] in, The upper bound of the step size. The lower bound of the step size. The damping coefficient is used to adjust the sensitivity of the step size to a small temperature rise range, and is usually taken as 1. 30%.
[0071] The target heat transfer coefficient at the current moment is mentioned above. This invention ultimately yields the heat transfer coefficient at the actual operating temperature of the overhead line. The heat transfer coefficient of the overhead line at the actual operating temperature Instead of using the heat transfer coefficient at the specified maximum permissible temperature to calculate the maximum heat capacity of the line under dynamic conditions, the maximum permissible current carrying capacity under the current operating conditions can be estimated. The calculation formula is as follows: (twenty three)
[0072] In this calculation formula, Indicates the maximum heat capacity of the line. This indicates the maximum allowable operating temperature during circuit design. This represents the resistance per unit length of an overhead line at the maximum permissible operating temperature.
[0073] Step S5: Adjust the operating current on the overhead line in real time based on the maximum heat capacity of the line.
[0074] In step S5, the line heat capacity is actually the current carrying capacity of the conductor. The maximum heat capacity of the line (i.e., the heat capacity limit) is actually the maximum current carrying capacity of the overhead line, which is the calculated maximum current carrying capacity at the maximum allowable operating temperature of the line. The calculated current carrying capacity is higher than the actual current carrying capacity. The difference between the calculated and actual current carrying capacity is the hidden capacity. It should be noted that, for safety reasons, existing current carrying capacity calculation methods (such as those in the GB 50545-2023 calculation standard) adopt the most conservative approach, that is, they are designed based on the most severe operating conditions of the overhead line. This results in a significant limitation on the operating current carrying capacity of existing overhead lines, with a very small allowable current carrying capacity, which cannot fully release the hidden capacity of the line.
[0075] Because this invention considers various environmental parameters and laying conditions under actual operating conditions, it replaces the calculation of the maximum allowable current carrying capacity based on the worst-case conditions. Furthermore, this invention also considers the impact of the real-time operating temperature of the overhead line on its resistance. In addition, the current carrying capacity is mainly limited by sag and temperature, while the calculation of the maximum heat capacity of the line in this invention integrates sag and average line temperature, thus breaking the limitations of current carrying capacity based on sag and average line temperature, and improving the accuracy of the maximum heat capacity. Therefore, the maximum heat capacity of the line obtained by this invention is much larger than the maximum allowable current carrying capacity obtained using the worst-case conditions, equivalent to allowing more current to pass through the overhead line. In other words, this invention can appropriately increase the operating current of the overhead line based on the maximum heat capacity to improve the utilization rate of the hidden capacity, thereby increasing the transmission efficiency of the overhead line and improving the economy and transport capacity of the relevant overhead lines.
[0076] The following explanation uses measured environmental data and Supervisory Control and Data Acquisition (SCADA) system data from a 500 kV line in Anhui Province, China, as an example. Specifically, the line uses 4-split JL1 / LHA1-465 / 210 aluminum alloy core stranded wire as the overhead line conductor type. Its specific environmental parameters and actual measurement results are shown in Table 1. Then, the measured environmental parameters and line parameters are input into a program (used to execute a calculation method for the operating state of an overhead line according to this invention) to calculate the relevant heat capacity of the overhead line. The calculation results are shown in Table 2. Furthermore, the following assumptions are made: assuming the maximum allowable operating line temperature is 90 ℃, the minimum value obtained when calculating the maximum heat capacity of the line under known operating conditions is used as the maximum allowable current carrying capacity of the overhead line calculated under the worst operating conditions in the initial design stage of the overhead line. This result is compared with the maximum heat capacity of the line obtained under other operating conditions to determine the improvement in the utilization rate of implicit capacity. In Table 2, the hidden capacity is the calculated maximum heat capacity minus the line flow carried by the overhead line during actual operation. The hidden capacity ratio is the proportion of the calculated hidden capacity to the calculated maximum heat capacity. The calculation results show that the hidden capacity ratio is mostly above 70% during line operation, indicating that the utilization rate of the hidden capacity is low. According to the calculation results of this program, the line transport capacity can be appropriately increased, thereby improving the economy and utilization rate of the overhead line while ensuring safety. This method has strong versatility.
[0077] Table 1. Meteorological, load-carrying capacity, and sag data under actual operating conditions. time T a (°C) V / (m-s -1 ) S / (W-m -2 ) <![CDATA[T C (℃)]]> I(A) 8：00 27.4 4.5 76 28.72 152.798 9：00 27.3 4.6 141 28.73 181.141 10：00 26.3 3.1 79 27.65 180.981 11：00 26.7 1.8 160 27.98 198.875 12：00 27.4 2.8 202 29.08 193.172 13：00 27.6 1.8 153 29.38 182.407 14：00 27.2 1.5 65 28.05 176.548 15：00 26.3 1.3 26 27.15 186.840 16：00 26.3 1.5 84 26.89 170.689
[0078] Table 2. Calculation results of maximum heat capacity and implicit capacity under different operating conditions. Current carrying capacity (A) Calculate the maximum heat capacity (A). Hidden capacity (A) Hidden capacity percentage (%) 152.798 567.905 424.107 74.68 181.141 648.497 467.356 72.07 180.981 667.077 486.096 72.87 198.875 751.294 552.419 73.53 193.172 641.133 447.961 69.87 182.407 588.968 406.561 69.03 176.548 810.333 633.785 78.21 186.840 859.097 672.257 78.25 170.689 937.334 766.645 81.79
[0079] In some feasible embodiments, the calculation method further includes: determining whether the overhead line is in an over-limit operating state based on the line's maximum heat capacity and a preset threshold, and providing an early warning when the overhead line is in an over-limit operating state. The early warning can be set according to actual needs and is not limited here.
[0080] Based on the same inventive concept as the foregoing embodiments, this invention also provides a calculation system for the status of operating overhead lines. The calculation system includes a data acquisition module, a conductor sag calculation module, a line average temperature calculation module, a line maximum heat capacity calculation module, and an operating current adjustment module. The data acquisition module is used to acquire measurement data and line parameters in real time. The conductor sag calculation module is used to solve for conductor sag using wind speed and direction, conductor tension, tension section parameters, and conductor parameters. The line average temperature calculation module is used to solve for the line average temperature using conductor sag based on a proportional fusion correction mechanism. The line maximum heat capacity calculation module is used to solve for the line maximum heat capacity using ambient temperature, solar radiation intensity, load current, and line average temperature. The operating current adjustment module is used to adjust the operating current on the overhead line in real time according to the line maximum heat capacity.
[0081] Based on the same inventive concept as the foregoing embodiments, the present invention also provides a computing device for calculating the status of an operating overhead line. The computing device includes a monitoring and data acquisition subsystem and a control subsystem. The monitoring and data acquisition subsystem is used to monitor measurement data and line parameters in real time. The control subsystem is used to execute the aforementioned calculation method for the status of an operating overhead line based on the measurement data and line parameters monitored by the monitoring and data acquisition subsystem.
[0082] In summary, this invention, based on the perception of the overhead line's operating status and considering various environmental parameters and laying conditions (i.e., measurement data and line parameters) under actual operating conditions, replaces the calculation of the maximum allowable current carrying capacity preset under the worst-case conditions. Furthermore, this invention also considers the impact of the overhead line's real-time operating temperature on its resistance. Therefore, the maximum heat capacity of the line obtained by this invention is much larger than the maximum allowable current carrying capacity obtained under the worst-case conditions, equivalent to allowing more current to pass through the overhead line. In other words, this invention can appropriately increase the operating current of the overhead line based on the line's maximum heat capacity to improve the utilization rate of hidden capacity, thereby increasing the transmission efficiency of the overhead line and improving its economy and transport capacity.
[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.
Claims
1. A calculation method for the status of operating overhead lines, characterized in that, include: Real-time acquisition of measurement data and line parameters; the measurement data includes ambient temperature, wind speed and direction, conductor tension, solar radiation intensity and load current, and the line parameters include tension section parameters and conductor parameters; The conductor sag is determined using wind speed and direction, conductor tension, tension section parameters, and conductor parameters. Based on the proportional fusion correction mechanism, the average temperature of the line is solved by using the conductor sag. The maximum heat capacity of the line is determined by using ambient temperature, solar radiation intensity, load current, and average line temperature. The operating current on the overhead line is adjusted in real time according to the maximum heat capacity of the line.
2. The calculation method for the status of an operating overhead line as described in claim 1, characterized in that, Based on the proportional fusion correction mechanism, the average temperature of the line is calculated using the conductor sag, including: The cubic relationship between the average temperature of the line and the conductor sag was determined using historical experience data. The conductor sag calculated using measurement data and line parameters is substituted into the cubic relationship between the average line temperature and the conductor sag to obtain the predicted average line temperature. Based on the aforementioned proportional fusion correction mechanism, the predicted average line temperature and the overhead line operating temperature monitored by the temperature sensor are fused according to the fusion weight to obtain the average line temperature.
3. The calculation method for the status of an operating overhead line as described in claim 2, characterized in that, Based on the aforementioned proportional fusion correction mechanism, the predicted average line temperature is proportionally fused with the overhead line operating temperature monitored by the temperature sensor to obtain the average line temperature, including: Calculate the current residual between the predicted average temperature of the line and the operating temperature of the overhead line; The fusion weights are adaptively adjusted based on the relationship between the current residual and the preset threshold. The predicted average line temperature and the overhead line operating temperature are fused according to the fusion weight to obtain the average line temperature.
4. The calculation method for the status of an operating overhead line as described in claim 1, characterized in that, The tension section parameters include span and height difference between the towers on both sides; the conductor parameters include conductor type, conductor unit weight, calculated cross-sectional area, conductor outer diameter, expansion coefficient, heat absorption coefficient, heat dissipation coefficient, and unit resistance.
5. The calculation method for the status of an operating overhead line as described in claim 4, characterized in that, Solving for conductor sag using the measurement data and the line parameters includes: Calculate the self-weight load, wind pressure load, and the line height at each point in the vertical plane of the overhead conductor using wind speed, conductor tension, tension section parameters, and conductor parameters. The conductor sag is calculated based on the self-weight load, wind pressure load, and the line height at each point in the vertical plane of the overhead conductor.
6. The calculation method for the status of an operating overhead line as described in claim 4, characterized in that, The maximum heat capacity of the line is calculated using the measured data, line parameters, and average line temperature, including: The solar heat absorption energy, radiative heat dissipation energy, and heat transfer coefficient are calculated using ambient temperature, solar radiation intensity, load current, and average line temperature. The heat transfer coefficient is corrected by using sliding window weighted least squares estimation and adaptive exponential smoothing; The maximum heat capacity of the line is calculated based on the solar heat absorption energy, radiative heat dissipation energy, and the corrected heat transfer coefficient.
7. The calculation method for the status of an operating overhead line as described in claim 6, characterized in that, The heat transfer coefficient is corrected using sliding window weighted least squares estimation and adaptive exponential smoothing, including: A time window is formed by taking multiple sampling points around the current moment; Within the time window, a weighted least squares solution is performed on the proportional relationship to obtain the multi-point heat transfer coefficient; The multi-point heat transfer coefficient and the single-point heat transfer coefficient are fused to obtain the fused heat transfer coefficient; The fused heat transfer coefficient and the target heat transfer coefficient of the previous moment are weighted and fused to obtain the target heat transfer coefficient of the current moment.
8. The calculation method for the status of an operating overhead line as described in claim 1, characterized in that, The calculation method further includes: The system determines whether the overhead line is in an over-limit operating state based on the line's maximum heat capacity and a preset threshold, and provides an early warning when the overhead line is in an over-limit operating state.
9. A calculation system for the status of operating overhead lines, characterized in that, include: The data acquisition module acquires measurement data and line parameters in real time; the measurement data includes ambient temperature, wind speed and direction, conductor tension, solar radiation intensity and load current, and the line parameters include tension section parameters and conductor parameters. The conductor sag calculation module uses wind speed and direction, conductor tension, tension section parameters, and conductor parameters to solve for conductor sag. The average line temperature calculation module, based on the proportional fusion correction mechanism, uses the conductor sag to solve for the average line temperature. The module for calculating the maximum heat capacity of a line uses ambient temperature, solar radiation intensity, load current, and average line temperature to solve for the maximum heat capacity of the line. The operating current adjustment module adjusts the operating current on the overhead line in real time according to the maximum heat capacity of the line.
10. A computing device for the operation of overhead power lines, characterized in that, include: The monitoring and data acquisition subsystem is used to monitor measurement data and line parameters in real time. A control subsystem is used to execute a calculation method for the status of an operating overhead line as described in any one of claims 1 to 8, based on the measurement data and line parameters monitored by the monitoring and data acquisition subsystem.