CN104167076B

CN104167076B - A kind of icing transmission line of electricity weak link method for early warning

Info

Publication number: CN104167076B
Application number: CN201410399008.XA
Authority: CN
Inventors: 谢云云; 张连花; 金颖; 张明宇; 张令灏
Original assignee: Nanjing University of Science and Technology
Current assignee: Nanjing University of Science and Technology
Priority date: 2014-08-13
Filing date: 2014-08-13
Publication date: 2016-08-31
Anticipated expiration: 2034-08-13
Also published as: CN104167076A

Abstract

The invention discloses an early warning method for weak links of ice-covered transmission lines, which comprises the following steps: 1. Determining weather forecast information, ice-covered information, and transmission line information; The real-time stress value of each gear in the tower section, and calculate the unbalanced force on the tower, 3. Analyze the numerical relationship between the real-time stress value and the ultimate stress value, conduct early warning for wires in different levels, and compare the unbalanced force and limit unbalance of the tower Power, and the tower early warning is carried out in different levels. The invention can realize the intelligent judgment on the wire breakage of the transmission line when the power system is in ice-covered period. Through the comprehensive collection of information, the representative span calculation model and the precise stress calculation model are used to measure the stress values of each gear of the line, so as to accurately judge whether the line is in danger of disconnection, and avoid the indirect, low precision, and energy-consuming traditional judgment methods. Shortcomings of time.

Description

An early warning method for weak links of ice-covered transmission lines

技术领域technical field

本发明属电力系统覆冰灾害安全防御，特别是一种覆冰输电线路薄弱环节预警方法。The invention belongs to the safety defense of icing disasters in power systems, in particular to an early warning method for weak links of icing transmission lines.

背景技术Background technique

由于我国幅员辽阔，地理环境复杂以及气候类型多样化，极端的自然灾害频繁发生，如每年东南沿海地区常发生的台风灾害、在云贵高原和三峡地区的冰灾等。在这些极端天气条件下，输电线路所受荷载会超过其设计承受能力，引起输电线应力会发生显著变化，从而引发电网故障。如在2008年冰雪灾害中，由于长时间的冻雨，输电线路上产生了严重的覆冰，引起导线应力的变化，导致导线应力过大造成输电线路断线倒塔事故。因此，在电网设计、运行和故障后分析中常需要对极端天气条件下的线路进行力学计算。Due to my country's vast territory, complex geographical environment and diverse climate types, extreme natural disasters occur frequently, such as typhoon disasters that often occur in the southeastern coastal areas every year, ice disasters in the Yunnan-Guizhou Plateau and the Three Gorges area, etc. Under these extreme weather conditions, the load on the transmission line will exceed its design capacity, causing significant changes in the stress of the transmission line, which will cause grid failure. For example, in the ice and snow disaster in 2008, due to the long-term freezing rain, serious icing occurred on the transmission line, which caused changes in the stress of the conductors, resulting in excessive stress on the conductors and the accident of the transmission line breaking and the tower falling. Therefore, mechanical calculations for lines under extreme weather conditions are often required in power grid design, operation, and post-fault analysis.

目前，常用来判断覆冰时期输电线路导线断线的方法有两种：一种是通过导线的弧垂值来判定其应力值；另一种是通过专门的覆冰厚度监测装置获取冰厚数据，再根据经验判断导线大致所受的应力是否处于危险范围。上述这两种方法共同的不足之处是，间接获取应力值，缺少精确度；第一种方法需要相关工作人员去现场测量弧垂，不仅耗费人力资源，而且耗时长；第二种方法依赖专家经验，不够自动化，且精确度相对较低。At present, there are two methods commonly used to judge the disconnection of transmission line conductors during the ice-covered period: one is to determine the stress value through the sag value of the conductor; the other is to obtain ice thickness data through a special ice-covered thickness monitoring device , and then judge whether the stress on the conductor is in the dangerous range based on experience. The common disadvantage of the above two methods is that the indirect acquisition of stress values lacks accuracy; the first method requires relevant staff to go to the site to measure the sag, which not only consumes human resources, but also takes a long time; the second method relies on experts Experience, not automatic enough, and relatively low accuracy.

发明内容Contents of the invention

本发明所解决的技术问题在于提供一种覆冰输电线路薄弱环节预警方法。The technical problem solved by the present invention is to provide an early warning method for weak links of ice-covered transmission lines.

实现本发明目的的技术解决方案为：一种覆冰输电线路薄弱环节预警方法，包括如下步骤：The technical solution to realize the object of the present invention is: a method for early warning of weak links of ice-coated transmission lines, comprising the following steps:

步骤1、确定气象信息、覆冰厚度信息和架空线路详细信息，所述气象信息具体包括：实时温度t、最高气温t_max、最低气温t_min、平均气温t_av与覆冰产生的平均气温t_ice；覆冰厚度信息即连续档各档的覆冰厚度b；架空线路详细信息具体包括导线型号、该导线型号对应的弹性系数E、截面积A、外径D、单位长度质量q、各档档距l_i0、各档高差h_i0、各档高差角β_i0、各基直线塔上悬垂串的长度λ_i、垂向荷载G_i、架线时温度t₀、架线气温下各档水平应力σ₀₀；Step 1. Determine meteorological information, ice thickness information and overhead line detailed information. The meteorological information specifically includes: real-time temperature t, maximum air temperature t _max , minimum air temperature t _min , average air temperature t _av , and average air temperature t generated by icing _ice ; the ice thickness information is the ice thickness b of each gear in the continuous gear; the detailed information of the overhead line specifically includes the wire type, the elastic coefficient E corresponding to the wire type, the cross-sectional area A, the outer diameter D, the mass per unit length q, and the Gap l _i0 , height difference h _i0 of each gear, height difference angle β _i0 of each gear, length λ _i of the hanging string on each base line tower, vertical load G _i , temperature t ₀ during stringing, and temperature under stringing temperature The horizontal stress of the gear σ ₀₀ ;

步骤2、根据已知的气象信息，通过代表档距法计算模型确定初始水平应力，再由精确应力计算模型确定耐张塔段内每一档的实时应力值σ_i；具体包括如下几个步骤：Step 2. According to the known meteorological information, the initial horizontal stress is determined through the calculation model of the representative span method, and then the real-time stress value σ _i of each level in the tension tower section is determined by the accurate stress calculation model; specifically, the following steps are included :

步骤2-1、确定输电线路导线的极限应力σ_lim；所用公式为：Step 2-1. Determine the ultimate stress σ _lim of the transmission line conductor; the formula used is:

${σ σ}_{lim lim} = = \frac{{T T}_{b b} \times \times 0.4 0.4}{A A}$

式中，T_b为导线的计算拉断力，A为导线的截面积。In the formula, T _b is the calculated breaking force of the wire, and A is the cross-sectional area of the wire.

步骤2-2、确定代表高差角β_r与代表档距l_r；所用公式分别为：Step 2-2. Determine the representative height difference angle β _r and the representative span l _r ; the formulas used are:

$cos cos {β β}_{r r} = = \frac{{Σ Σ}_{11}^{n no} (({l l}_{i i 00} / / cos cos {β β}_{i i 00}))}{{Σ Σ}_{11}^{n no} (({l l}_{i i 00} / / {cos cos}^{22} {β β}_{i i 00}))}$

式中，β_r待求，为代表高差角，l_i0为第i档档距，β_i0为第i档高差角，i为从1到n的正整数，n为档数；In the formula, β _r is to be found, which represents the height difference angle, l _i0 is the distance of the i-th gear, β _i0 is the height difference angle of the i-th gear, i is a positive integer from 1 to n, and n is the number of gears;

${l l}_{r r} = = \frac{11}{cos cos {β β}_{r r}} \sqrt{\frac{{Σ Σ}_{11}^{n no} {l l}_{i i 00}^{33} cos cos {β β}_{i i 00}}{{Σ Σ}_{11}^{n no} (({l l}_{i i 00} / / cos cos {β β}_{i i 00}))}}$

式中，l_r待求，为代表档距，β_r为代表高差角，l_i0为第i档档距，β_i0为第i档高差角，i为从1到n的正整数，n为档数；In the formula, l _r to be found represents the stand distance, β _r represents the height difference angle, l _i0 is the stand distance of the i-th gear, β _i0 is the height difference angle of the i-th gear, and i is a positive integer from 1 to n, n is the number of files;

步骤2-3、通过代表档距法计算模型，利用架设电线时的气温t₀与输电线路导线的参数，计算最高气温t_max、最低气温t_min、平均气温t_av三种气象条件下各自的应力值，将应力值最接近水平应力设计值σ_i的计算状态所对应的气象条件作为精确应力计算模型的初始气象条件，以及下述步骤2-5中计算的末态气象条件；所述代表档距法计算模型如下：Step 2-3, through the calculation model of the representative span method, using the temperature t ₀ when the power line is erected and the parameters of the transmission line conductor, calculate the maximum temperature t _max , the minimum temperature t _min , and the average temperature t _av under the three meteorological conditions Stress value, the meteorological condition corresponding to the calculation state that the stress value is closest to the horizontal stress design value σ _i is used as the initial meteorological condition of the accurate stress calculation model, and the final meteorological condition calculated in the following steps 2-5; said representative The calculation model of the span method is as follows:

${σ σ}_{0202} - - \frac{E E. {γ γ}_{22}^{22} {l l}_{r r}^{22} {cos cos}^{33} {β β}_{r r}}{24 twenty four {σ σ}_{0202}^{22}} = = {σ σ}_{0101} - - \frac{E E. {γ γ}_{11}^{22} {l l}_{r r}^{22} {cos cos}^{33} {β β}_{r r}}{24 twenty four {σ σ}_{0101}^{22}} - - αE αE (({t t}_{22} - - {t t}_{11})) cos cos {β β}_{r r}$

式中，数字1代表初始气象状态，数字2代表末端气象状态，E为输电线路导线的弹性系数，α为输电线路导线的线膨胀系数,t为温度，σ₀₁为初始态水平应力，σ₀₂为末态水平应力，l_γ为代表档距，β_γ为代表高差角，γ为比载，γ＝q*g/A，其中q为导线单位长度质量，g为重力加速度，A为导线的截面积。In the formula, the number 1 represents the initial meteorological state, the number 2 represents the terminal meteorological state, E is the elastic coefficient of the transmission line conductor, α is the linear expansion coefficient of the transmission line conductor, t is the temperature, σ ₀₁ is the initial state horizontal stress, σ ₀₂ is the final horizontal stress, l _γ represents the span, β _γ represents the height difference angle, γ is the specific load, γ=q*g/A, where q is the mass per unit length of the wire, g is the gravitational acceleration, and A is the wire cross-sectional area.

步骤2-4、再次通过代表档距法计算模型，利用架设电线时的气温t₀、覆冰产生的平均气温t_ice与输电线路导线的参数，确定不同覆冰厚度对应的导线总比载γ_b条件下的应力值，将应力值最接近极限σ_lim的计算状态所对应的气象条件作为下述步骤2-5中的初始气象条件；所述不同覆冰厚度对应的导线总比载γ_b计算公式为：Step 2-4, calculate the model again by the representative span method, use the air temperature t ₀ when the wire is erected, the average air temperature t _ice generated by ice coating, and the parameters of the transmission line wire to determine the total specific load of the wire corresponding to different ice thickness γ The stress value under the condition _b , the meteorological condition corresponding to the calculation state where the stress value is closest to the limit σ _lim is taken as the initial meteorological condition in the following steps 2-5; the total specific load γ _b of the conductors corresponding to the different ice coating thicknesses The calculation formula is:

${γ γ}_{b b} = = \frac{9.81 9.81 q q + + 0.03 0.03 b b ((b b + + D D.))}{A A}$

式中，q为导线的单位质量，D为导线的外径，b覆冰厚度，A为导线的截面积。In the formula, q is the unit mass of the wire, D is the outer diameter of the wire, b is the ice thickness, and A is the cross-sectional area of the wire.

步骤2-5、利用如计算工序中步骤2-3所述的末态气象条件、步骤2-4所述的初始气象条件，并且设极限应力σ_lim为初始应力值，第三次使用代表档距法计算模型，求得初始水平应力值σ₀，并且将它作为精确应力计算模型的初始水平应力；Step 2-5, using the final meteorological conditions described in step 2-3 in the calculation process, the initial meteorological conditions described in step 2-4, and setting the limit stress σ _lim as the initial stress value, the third time using the representative file Calculate the model by the distance method, obtain the initial horizontal stress value σ ₀ , and use it as the initial horizontal stress of the accurate stress calculation model;

步骤2-6、根据所有已知的实时气象条件，运用精确应力计算模型确定耐张塔段内每一档的实时应力值σ_i；所述精确应力计算模型包括以下三个关系模型：Step 2-6, according to all known real-time meteorological conditions, use the accurate stress calculation model to determine the real-time stress value σ _i of each gear in the tension tower section; the accurate stress calculation model includes the following three relationship models:

(1)档距增量Δl_i与水平应力σ_i间的关系模型：(1) The relationship model between the span increment Δl _i and the horizontal stress σ _i :

$\begin{matrix} Δ Δ {l l}_{i i} = = {{[[{((\frac{{γ γ}_{00}}{{σ σ}_{00}}))}^{22} - - {((\frac{{γ γ}_{i i}}{{σ σ}_{i i}}))}^{22}]] \frac{{l l}_{i i 00}^{22} {cos cos}^{22} {β β}_{i i 00}}{24 twenty four} + + ((\frac{{σ σ}_{i i} - - {σ σ}_{00}}{E E. cos cos {β β}_{i i 00}})) + + α α ((t t - - {t t}_{00})) - - \frac{Δ Δ {h h}_{i i}}{22 {l l}_{i i 00}} {cos cos}^{22} {β β}_{i i 00}}} \\ \times \times \frac{{l l}_{i i 00}}{{cos cos}^{22} {β β}_{i i 00} ((11 + + {γ γ}_{i i}^{22} {l l}_{i i 00}^{22} / / 88 {σ σ}_{i i}^{22}))} \end{matrix}$

式中σ_i——待求值，为第i档的水平应力，具体为第i档在气温为t、比载为γ_i下的电线水平应力；i为从1到n的正整数，n为档数；In the formula, σ _i ——value to be evaluated is the horizontal stress of the i-th file, specifically the horizontal stress of the wire at the i-th file at the temperature of t and the specific load of γ _i ; i is a positive integer from 1 to n, and n is the file number;

σ₀——初始水平应力值；σ ₀ ——initial horizontal stress value;

l_i0——第i档档距；l _{i0 ——the} i-th gear distance;

γ₀、γ_i——导线覆冰前比载和导线覆冰后比载，γ₀为q*g/A，γ_i为q*g/A+0.027728(b(b+D)/A)，其中q为导线单位长度质量，g为重力加速度，A为导线的截面积，b为导线覆冰厚度，D为导线外径；γ ₀ , γ _i — specific load before and after icing of the wire, γ ₀ is q*g/A, γ _i is q*g/A+0.027728(b(b+D)/A) , where q is the mass per unit length of the wire, g is the acceleration of gravity, A is the cross-sectional area of the wire, b is the ice thickness of the wire, and D is the outer diameter of the wire;

Δl_i——待求值，第i档档距的l_i0的增量，具体为第i档档距比架线情况悬垂串处于中垂位置时档距的增长量；Δl _i ——to be evaluated, the increment of l _i0 of the i-th gear span, specifically, the increment of the i-th gear span when the suspension string is in the sag position when the i-th gear span is at the neutral position;

Δh_i——待求值，第i档高差h_i0的增量，具体为第i档两端悬垂串偏斜后悬挂点间高差h_i0的变化量，右悬挂点高左悬挂点者h_i0及高差角β_i0为正值；Δh _i ——to be evaluated, the increment of the height difference h _i0 of the i-th gear, specifically the variation of the height difference h _i0 between the suspension points after the suspension strings at both ends of the i-th gear are deflected, and the right suspension point is higher than the left suspension point h _i0 and height difference angle β _i0 are positive values;

t、t₀——分别为实时温度和架线时气温；t, t ₀ ——Respectively, the real-time temperature and the air temperature at the time of wiring;

α——导线温度膨胀系数；α——wire temperature expansion coefficient;

E——导线弹性系数；E——conductor elastic coefficient;

(2)第i档高差增量Δh_i与第i基塔悬挂点偏移δ_i间的关系模型：(2) The relationship model between the height difference increment Δh _i of the i-th gear and the suspension point offset δ _i of the i-th base tower:

$Δ Δ {h h}_{i i} = = \sqrt{{λ λ}^{22} - - {δ δ}_{i i - - 11}^{22}} - - \sqrt{{λ λ}^{22} - - {δ δ}_{i i}^{22}}$

式中Δh_i——待求值，第i档高差h_i0的增量，i为从1到n的正整数，n为档数；In the formula, Δh _i ——to be evaluated, the increment of the i-th gear height difference h _i0 , i is a positive integer from 1 to n, and n is the number of gears;

δ_i、δ_i-1—第i档两端第i-1基塔上悬挂点偏移的水平距离，其中两端耐张塔的δ为0；δ _i , δ _i-1 — the horizontal distance of the suspension point offset on the i-1th base tower at both ends of the i-th gear, where the δ of the tension towers at both ends is 0;

λ——各杆塔上的悬垂绝缘子串长度，其中两端耐张塔上也假定有λ，但δ为0；λ——the length of the suspension insulator string on each tower, where λ is also assumed on the tension towers at both ends, but δ is 0;

(3)第i基塔悬挂点偏移δ_i与水平应力间σ_i的关系模型：(3) The relationship model between the offset δ _i of the suspension point of the i-th base tower and the horizontal stress σ _i :

$\begin{matrix} {σ σ}_{i i + + 11} = = {{((\frac{{G G}_{i i}}{22 A A} + + \frac{{γ γ}_{i i} {l l}_{i i 00}}{22 cos cos {β β}_{i i 00}} + + \frac{{γ γ}_{((i i + + 11))} {l l}_{((i i + + 11)) 00}}{22 cos cos {β β}_{((i i + + 11)) 00}} + + \frac{{σ σ}_{i i} {h h}_{i i 00}}{{l l}_{i i 00}})) + + \frac{{σ σ}_{i i}}{{δ δ}_{i i}} \sqrt{{λ λ}_{i i}^{22} - - {δ δ}_{i i}^{22}}}} \\ \div \div ((\frac{11}{{δ δ}_{i i}} \sqrt{{λ λ}_{i i}^{22} - - {δ δ}_{i i}^{22}} + + \frac{{h h}_{((i i + + 11)) 00}}{{l l}_{((i i + + 11)) 00}})) \end{matrix}$

式中σ_i——待求值，为第i档水平应力，具体为第i档在气温为t、比载为γ_i下的电线水平应力；i为从1到n的正整数，n为档数；In the formula, σ _i ——value to be evaluated is the horizontal stress of the _i -th file, specifically the horizontal stress of the wire at the temperature of t and the specific load of the i-th file; i is a positive integer from 1 to n, and n is file number;

δ_i——δ_i＝δ_i-1+Δl_i；δ _i —— δ _i = δ _i-1 + Δl _i ;

A——导线的截面积；A - the cross-sectional area of the wire;

γ_i——导线覆冰后比载，γ_i为q*g/A+0.03(b(b+D)/A)，其中q为导线单位长度质量，g为重力加速度，A为导线的截面积，b为导线覆冰厚度，D为导线外径；γ _i ——the specific load of the conductor after being covered with ice, γ _i is q*g/A+0.03(b(b+D)/A), where q is the mass per unit length of the conductor, g is the acceleration of gravity, and A is the cross section of the conductor area, b is the thickness of the wire ice coating, D is the outer diameter of the wire;

δ_i——第i档两端基塔上悬挂点偏移的水平距离，其中两端耐张塔的δ为0；δ _i ——horizontal distance of the suspension point offset on the base towers at both ends of the i-th gear, where the δ of the tension towers at both ends is 0;

G_i、λ——各杆塔上的悬垂绝缘子串的垂向荷载及长度，其中两端耐张塔上也假定有λ，但δ为0；G _i , λ—the vertical load and length of the suspension insulator strings on each tower, where λ is also assumed on the tension towers at both ends, but δ is 0;

l_i0——第i档档距；l _{i0 ——the} i-th gear distance;

h_i0、h_(i+1)0——第i档和第i+1档高差，具体为悬垂串均处于中垂位置时，第i基直线塔上电线悬挂点对邻塔第i-1和第i+1基悬挂点间的高差，大号比小号塔高者h本身值为正值，反之为负值，现场测得；h _i0 , h _(i+1)0 ——height difference between the i-th gear and the i+1-th gear, specifically, when the suspension strings are all in the mid-sag position, the wire suspension point on the i-th base line tower is opposite to the i-th tower on the adjacent tower The height difference between 1 and the i+1th base suspension point, if the large tower is higher than the small tower, h itself is a positive value, otherwise it is a negative value, measured on site;

β_i0——第i档高差角。β _{i0 ——the} height difference angle of the i-th gear.

步骤3、由步骤2中确定的每个档距内导线的应力σ_i，确定各杆塔上所受不平衡力ΔF_i；所述杆塔不平衡张力的计算模型为：Step 3. From the stress σ _i of the wires in each span determined in step 2, determine the unbalanced force ΔF _i on each tower; the calculation model of the unbalanced tension of the tower is:

ΔF_i＝(σ_i+1-σ_i)A＝F_i+1-F_i (i＝1,2,…,n-1)ΔF _i =(σ _i+1 -σ _i )A=F _i+1 -F _i (i=1,2,...,n-1)

式中：σ_i+1和σ_i分别为第i+1档和第i档电线的水平应力，i为从1到n-1的正整数，n为档数；In the formula: σ _i+1 and σ _i are the horizontal stresses of the i+1 and i-th gear wires respectively, i is a positive integer from 1 to n-1, and n is the number of gears;

A——为电线的截面积；A——is the cross-sectional area of the wire;

F_i+1和F_i——为第i+1和第i档电线的水平张力；F _i+1 and F _i - the horizontal tension of the i+1 and i-th wires;

ΔF_i——第i基直线杆塔除冰过程中所承受的不平衡张力差；ΔF _i ——the unbalanced tension difference borne by the i-th linear tower during the deicing process;

步骤4、将每个档距内导线应力σ_i与其极限应力σ_lim进行比较，分等级进行导线预警；将每个杆塔上不平衡力ΔF_i与其设计可承受不平衡力ΔF_s进行比较，分等级进行杆塔不平衡力预警；Step 4. Compare the conductor stress σ _i in each span with its limit stress σ _lim , and carry out conductor warning in different levels; compare the unbalanced force ΔF _i on each tower with its designed unbalanced force ΔF _s , and divide Early warning of unbalanced force of the tower;

所述导线预警具体的数值关系与相应的预警等级为：The specific numerical relationship of the wire early warning and the corresponding early warning level are:

当σ_i<50％σ_lim时，不预警；When σ _i <50% σ _lim , no warning;

当50％σ_lim≤σ_i≤70％σ_lim时，输出第i档导线黄色预警；When 50% σ _lim ≤ σ _i ≤ 70% σ _lim , output a yellow warning for the i-th wire;

当70％σ_lim<σ_i<85％σ_lim时，输出第i档导线橙色预警；When 70% σ _lim < σ _i < 85% σ _lim , output the i-th wire orange warning;

当σ_i≥85％σ_lim时，输出第i档导线红色预警。When σ _i ≥ 85% σ _lim , output a red warning for the i-th wire.

所述杆塔不平衡力预警具体的数值关系与相应的预警等级为：The specific numerical relationship and corresponding early warning level of the unbalanced force early warning of the tower are:

当ΔF_i≤0.6ΔFs，不预警；When ΔF _i ≤0.6ΔFs, no warning;

当0.6ΔFs<ΔF_i<0.8ΔFs，输出第i基杆塔黄色预警；When 0.6ΔFs<ΔF _i <0.8ΔFs, output a yellow warning for the i-th base tower;

当0.8ΔFs≤ΔF_i≤0.95ΔFs，输出第i基杆塔橙色预警；When 0.8ΔFs≤ΔF _i ≤0.95ΔFs, output an orange warning for the i-th base tower;

当ΔF_i>0.95ΔFs，输出第i基杆塔红色预警。When ΔF _i >0.95ΔFs, output a red warning for the i-th base tower.

本发明与现有技术相比，其显著优点为：1)直接获取线路应力值，省略中间环节，精度较高且节省现场测量弧垂的人力物力成本；2)运用数学模型计算线路应力值，自动化程度较高。Compared with the prior art, the present invention has the following remarkable advantages: 1) directly obtain the stress value of the line, omit the intermediate link, have high precision and save the manpower and material cost of on-site sag measurement; 2) use the mathematical model to calculate the stress value of the line, High degree of automation.

下面结合附图对本发明作进一步详细描述。The present invention will be described in further detail below in conjunction with the accompanying drawings.

附图说明Description of drawings

图1为本发明的覆冰输电线路薄弱环节预警方法流程图。Fig. 1 is a flow chart of the method for early warning of weak links of ice-coated transmission lines according to the present invention.

具体实施方式detailed description

结合图1，本发明的一种覆冰输电线路薄弱环节预警方法，包括如下步骤：In conjunction with Fig. 1, a kind of ice-covered transmission line weak link early warning method of the present invention comprises the following steps:

步骤1、确定气象信息、覆冰信息、架空线路详细信息，气象信息具体包括：实时温度t、最高气温t_max、最低气温t_min、平均气温t_av与覆冰产生的平均气温t_ice；覆冰厚度信息即连续档各档的覆冰厚度b；架空线路详细信息具体包括导线型号、该导线型号对应的弹性系数E、截面积A、外径D、单位长度质量q、各档档距l_i0、各档高差h_i0、各档高差角β_i0、各基直线塔上悬垂串的长度λ_i、垂向荷载G_i、覆冰时的温度t、架线时温度t₀、架线气温下各档水平应力σ₀₀；其中各基直线塔上悬垂串的长度λ_i查线路设计值获得，垂向荷载G_i由悬垂串型号查表得。实时温度t由现场测量获得，架线时温度t₀、架线气温下各档水平应力σ₀₀通过架线设计值查得；Step 1. Determine the meteorological information, icing information, and detailed information of overhead lines. The meteorological information specifically includes: real-time temperature t, maximum air temperature t _max , minimum air temperature t _min , average air temperature t _av , and average air temperature t _ice generated by icing; The ice thickness information is the ice thickness b of each gear in the continuous gear; the detailed information of the overhead line specifically includes the wire type, the elastic coefficient E corresponding to the wire type, the cross-sectional area A, the outer diameter D, the mass per unit length q, and the distance l of each gear _i0 , the height difference h _i0 of each gear, the height difference angle β _i0 of each gear, the length λ _i of the hanging string on the linear tower of each base, the vertical load G _i , the temperature t when covered with ice, the temperature t ₀ when erecting wires, and the The horizontal stress σ ₀₀ of each gear under the line air temperature; among them, the length λ _i of the suspension string on each base line tower is obtained by checking the design value of the line, and the vertical load G _i is obtained from the table of the suspension string model. The real-time temperature t is obtained by on-site measurement, the temperature t ₀ at the time of stringing, and the horizontal stress σ ₀₀ of each level at the temperature of stringing are obtained from the design value of the stringing;

${σ σ}_{lim lim} = = \frac{{T T}_{b b} \times \times 0.4 0.4}{A A}$

式中，数字1代表初始气象状态，数字2代表末端气象状态，E为输电线路导线的弹性系数，α为输电线路导线的线膨胀系数,t为温度，σ₀₁为初始态水平应力，σ₀₂为末态水平应力，l_γ为代表档距，β_γ为代表高差角，γ为比载，γ＝q*g/A，其中其中q为导线单位长度质量，g为重力加速度，A为导线的截面积。In the formula, the number 1 represents the initial meteorological state, the number 2 represents the terminal meteorological state, E is the elastic coefficient of the transmission line conductor, α is the linear expansion coefficient of the transmission line conductor, t is the temperature, σ ₀₁ is the initial state horizontal stress, σ ₀₂ is the final horizontal stress, l _γ represents the span, β _γ represents the height difference angle, γ is the specific load, γ=q*g/A, where q is the mass per unit length of the wire, g is the gravitational acceleration, and A is The cross-sectional area of the wire.

步骤2-4、再次通过代表档距法计算模型，利用架设电线时的气温t₀、覆冰产生的平均气温t_ice与输电线路导线的参数，计算不同覆冰厚度对应的导线总比载γ_b条件下的应力值，将应力值最接近极限σ_lim的计算状态所对应的气象条件作为下述步骤2-5中的初始气象条件；所述不同覆冰厚度对应的导线总比载γ_b计算公式为：Step 2-4, calculate the model again by the representative span method, use the air temperature t ₀ when the wire is erected, the average air temperature t _ice caused by ice coating, and the parameters of the transmission line wire to calculate the total specific load of the wire corresponding to different ice thickness γ The stress value under the condition _b , the meteorological condition corresponding to the calculation state where the stress value is closest to the limit σ _lim is taken as the initial meteorological condition in the following steps 2-5; the total specific load γ _b of the conductors corresponding to the different ice coating thicknesses The calculation formula is:

式中，q为导线的单位质量，D为导线的外径，b为覆冰厚度，A为导线的截面积。In the formula, q is the unit mass of the wire, D is the outer diameter of the wire, b is the ice thickness, and A is the cross-sectional area of the wire.

步骤2-6、根据所有已知的实时气象条件，运用精确应力计算模型求得耐张塔段内第i档覆冰时水平应力σ_i；所述运用精确应力计算模型求解实时应力值具体包括如下几个步骤：Step 2-6, according to all known real-time meteorological conditions, use the accurate stress calculation model to obtain the horizontal stress σ _i when the i-th file in the tension tower section is covered with ice; the use of the accurate stress calculation model to solve the real-time stress value specifically includes Follow these steps:

(1)列写档距变化与电线应力间的关系模型：(1) List the relationship model between the span change and the wire stress:

$\begin{matrix} Δ l_{i} = {[{(\frac{γ_{0}}{σ_{0}})}^{2} - {(\frac{γ_{i}}{σ_{i}})}^{2}] \frac{l_{i 0}^{2} \cos^{2} β_{i 0}}{24} + (\frac{σ_{i} - σ_{0}}{E \cos β_{i 0}}) + α (t - t_{0}) - \frac{Δ h_{i}}{2 l_{i 0}} \cos^{2} β_{i 0}} \\ \times \frac{l_{i 0}}{\cos^{2} β_{i 0} (1 + γ_{i}^{2} l_{i 0}^{2} / 8 {σ_{i}}^{2})} \end{matrix}$ (式1)式中σ_i——待求值，为第i档水平应力，具体为第i档覆冰时水平应力，具体为第i档在气温为t、比载为γ_i下的电线水平应力，单位为：N/mm²； $\begin{matrix} Δ l_{i} = {[{(\frac{γ_{0}}{σ_{0}})}^{2} - {(\frac{γ_{i}}{σ_{i}})}^{2}] \frac{l_{i 0}^{2} \cos^{2} β_{i 0}}{twenty four} + (\frac{σ_{i} - σ_{0}}{E. \cos β_{i 0}}) + α (t - t_{0}) - \frac{Δ h_{i}}{2 l_{i 0}} \cos^{2} β_{i 0}} \\ \times \frac{l_{i 0}}{\cos^{2} β_{i 0} (1 + γ_{i}^{2} l_{i 0}^{2} / 8 {σ_{i}}^{2})} \end{matrix}$ (Equation 1) where σ _i ——to be evaluated, is the horizontal stress of the i-th gear, specifically the horizontal stress of the i-th gear when covered with ice, specifically the electric wire of the i-th gear under the temperature of t and the specific load of γ _i Horizontal stress, unit: N/mm ² ;

σ₀——初始水平应力值，单位为：N/mm²；σ ₀ ——initial horizontal stress value, unit: N/mm ² ;

l_i0——第i档档距，单位为：m；l _{i0 ——the} i-th gear distance, the unit is: m;

γ₀、γ_i——导线覆冰前比载和导线覆冰后比载，单位为：N/(m·mm²)，γ₀为q*g/A，γ_i为q*g/A+0.03(b(b+D)/A)，其中q为导线单位长度质量，单位为：kg/m，g为重力加速度，A为导线的截面积，单位为：mm²，b为导线覆冰厚度，单位为：mm，D为导线外径，单位为：mm；γ ₀ , γ _i — specific load before and after icing of the wire, unit: N/(m mm ² ), γ ₀ is q*g/A, γ _i is q*g/A +0.03(b(b+D)/A), where q is the mass per unit length of the wire in kg/m, g is the acceleration of gravity, A is the cross-sectional area of the wire in mm ² , b is the wire covering Ice thickness, unit: mm, D is wire outer diameter, unit: mm;

Δl_i——待求值，第i档档距的l_i0的增量，具体为第i档档距比架线情况悬垂串处于中垂位置时档距的增长量，当档距缩短时Δl_i本身为负值，单位为：m；Δl _i ——to be evaluated, the increment of l _i0 of the i-th gear span, specifically, the increment of the i-th gear span when the suspension string is in the sag position when the suspension string is in the sag position, when the gear span is shortened, Δl _i itself is a negative value, the unit is: m;

Δh_i——待求值，第i档高差h_i0的增量，具体为第i档两端悬垂串偏斜后悬挂点间高差h_i0的变化量，右悬挂点高左悬挂点者h_i0及高差角β_i0为正值，单位为：m；Δh _i ——to be evaluated, the increment of the height difference h _i0 of the i-th gear, specifically the variation of the height difference h _i0 between the suspension points after the suspension strings at both ends of the i-th gear are deflected, and the right suspension point is higher than the left suspension point h _i0 and height difference angle β _i0 are positive values, unit: m;

t、t₀——分别为实时温度和架线时气温，单位为：℃；t, t ₀ ——Respectively, the real-time temperature and the air temperature at the time of wiring, the unit is: ℃;

E、α——导线弹性系数，单位为N/mm²；导线温度膨胀系数，单位为1/℃；E, α——The elastic coefficient of the wire, the unit is N/mm ² ; the temperature expansion coefficient of the wire, the unit is 1/℃;

(2)列写第i档高差变化与第i基塔悬挂点偏移间的关系模型：(2) List the relationship model between the height difference change of the i-th gear and the suspension point offset of the i-th base tower:

$Δ h_{i} = (λ - \sqrt{λ^{2} - {δ_{i}}^{2}}) - (λ - \sqrt{λ^{2} - {δ_{i - 1}}^{2}}) = \sqrt{λ^{2} - {δ_{i - 1}}^{2}} - \sqrt{λ^{2} - {δ_{i}}^{2}}$ (式2)式中Δh_i——待求值，第i档高差h_i0的增量，单位为：m； $Δ h_{i} = (λ - \sqrt{λ^{2} - {δ_{i}}^{2}}) - (λ - \sqrt{λ^{2} - {δ_{i - 1}}^{2}}) = \sqrt{λ^{2} - {δ_{i - 1}}^{2}} - \sqrt{λ^{2} - {δ_{i}}^{2}}$ (Formula 2) where Δh _i ——to be evaluated, the increment of the i-th gear height difference h _i0 , the unit is m;

δ_i、δ_i-1——第i档两端第i和第i-1基塔上悬挂点偏移的水平距离，其中两端耐张塔的δ为0，单位为：m；δ _i , δ _i -1 ——horizontal distance of the suspension point offset on the i-th and i-1-th base towers at both ends of the i-th gear, where the δ of the tension towers at both ends is 0, and the unit is m;

λ——各杆塔上的悬垂绝缘子串长度，单位为：m；λ——the length of the suspension insulator string on each tower, unit: m;

(3)列写悬垂串偏斜与电线应力间的关系模型：(3) List the relationship model between the deflection of the hanging string and the stress of the wire:

$\begin{matrix} σ_{i + 1} = {(\frac{G_{i}}{2 A} + \frac{γ_{i} l_{i 0}}{2 \cos β_{i 0}} + \frac{γ_{(i + 1)} l_{(i + 1) 0}}{2 \cos β_{(i + 1) 0}} + \frac{σ_{i} h_{i 0}}{l_{i 0}}) + \frac{σ_{i}}{δ_{i}} \sqrt{{λ_{i}}^{2} - {δ_{i}}^{2}}} \\ \div (\frac{1}{δ_{i}} \sqrt{{λ_{i}}^{2} - {δ_{i}}^{2}} + \frac{h_{(i + 1) 0}}{l_{(i + 1) 0}}) \end{matrix}$ (式3)式中 δ_i＝δ_i-1+Δl_i (式4) $\begin{matrix} σ_{i + 1} = {(\frac{G_{i}}{2 A} + \frac{γ_{i} l_{i 0}}{2 \cos β_{i 0}} + \frac{γ_{(i + 1)} l_{(i + 1) 0}}{2 \cos β_{(i + 1) 0}} + \frac{σ_{i} h_{i 0}}{l_{i 0}}) + \frac{σ_{i}}{δ_{i}} \sqrt{{λ_{i}}^{2} - {δ_{i}}^{2}}} \\ \div (\frac{1}{δ_{i}} \sqrt{{λ_{i}}^{2} - {δ_{i}}^{2}} + \frac{h_{(i + 1) 0}}{l_{(i + 1) 0}}) \end{matrix}$ (Formula 3) where δ _i = δ _i-1 + Δl _i (Formula 4)

h_i0、h_(i+1)0——第i档和第i+1档高差，具体为悬垂串均处于中垂位置时，第i基直线塔上电线悬挂点对邻塔第i-1和第i+1基悬挂点间的高差，大号比小号塔高者h本身值为正值，反之为负值，单位为：m。h _i0 , h _(i+1)0 ——height difference between the i-th gear and the i+1-th gear, specifically, when the suspension strings are all in the mid-sag position, the wire suspension point on the i-th base line tower is opposite to the i-th tower on the adjacent tower The height difference between 1 and the i+1 base suspension point, if the large tower is higher than the small tower, h itself is a positive value, otherwise it is a negative value, and the unit is m.

联立上述3n个方程，求解Δl_i、Δh_i、σ_i0共3n个未知数，即得各档导线水平应力σ_i。Simultaneously combine the above 3n equations to solve the 3n unknowns of Δl _i , Δh _i , and σ _i0 to obtain the horizontal stress σ _i of each gear.

步骤3、由步骤2中确定的每个档距内导线的应力σ_i，确定各杆塔上所受不平衡力ΔF_i；Step 3. From the stress σ _i of the wires in each span determined in step 2, determine the unbalanced force ΔF _i on each tower;

所述杆塔不平衡张力的计算模型为：The calculation model of the unbalanced tension of the tower is:

式中：σ_i+1和σ_i分别为第i+1档和第i档覆冰时水平应力，i为从1到n-1的正整数，n为档数；In the formula: σ _i+1 and σ _i are the horizontal stresses of the i+1th level and the ith level of icing respectively, i is a positive integer from 1 to n-1, and n is the number of levels;

A——为导线的截面积；A——is the cross-sectional area of the wire;

当σ_i<50％σ_lim时，不预警；When σ _i <50% σ _lim , no warning;

当ΔF_i≤0.6ΔFs，不预警；When ΔF _i ≤0.6ΔFs, no warning;

下面结合实施例对本发明做进一步详细的描述：Below in conjunction with embodiment the present invention is described in further detail:

实施例1Example 1

一覆冰场景，由一个耐张段连续的6档组成。实时温度t＝-5℃、最高气温40℃、最低气温-20℃、平均气温15℃，架线时温度t₀＝10℃。各档覆冰厚度值b_i＝[10mm 15mm15mm25mm 20mm 20mm]。输电线路导线型号为LGJ-300/40，该导线对应的弹性系数E＝73000N/mm²、截面积A＝338.99mm²、外径D＝23.94mm、单位长度质量q＝1.133kg/m、温度膨胀系数α＝19.6/℃、对应的极限拉力为92220N，各档档距l_i0＝[350m 400m 450m500m 500m 350m]，各档高差h_i0＝[20m 20m 10m -10m -20m -20m]，各基直线塔上悬垂串的长度λ_i(m)＝5.2m、垂向荷载G_i＝2300N，架线气温下初始水平应力σ₀₀＝51N/mm²。An icing scene consists of 6 consecutive gears in a tension section. The real-time temperature is t=-5°C, the highest temperature is 40°C, the lowest temperature is -20°C, the average temperature is 15°C, and the temperature during stringing is t ₀ =10°C. Icing thickness value b _i =[10mm 15mm 15mm 25mm 20mm 20mm] at each level. The model of the transmission line conductor is LGJ-300/40, the corresponding elastic coefficient E=73000N/mm ² , cross-sectional area A=338.99mm ² , outer diameter D=23.94mm, mass per unit length q=1.133kg/m, temperature The expansion coefficient α＝19.6/℃, the corresponding ultimate tensile force is 92220N, the span of each gear l _i0 =[350m 400m 450m500m 500m 350m], the height difference of each gear h _i0 =[20m 20m 10m -10m -20m -20m], each The length of the hanging string on the base line tower is λ _i (m) = 5.2m, the vertical load G _i = 2300N, and the initial horizontal stress σ ₀₀ = 51N/mm ² at the temperature of the stringing line.

步骤1、确定气象数据、覆冰厚度及架空线路详细信息如上所述。Step 1. Determine the meteorological data, ice thickness and overhead line details as described above.

步骤2、通过代表档距计算模型计算精确应力模型的初始水平应力。Step 2. Calculate the initial horizontal stress of the precise stress model through the representative span calculation model.

步骤2-1、计算输电线路导线的极限应力σ_lim＝108.82N；Step 2-1, calculating the ultimate stress σ _lim of the transmission line conductor = 108.82N;

步骤2-2、计算代表档距l_r＝435.5888m与代表高差角余弦cosβ_r＝0.9991；Step 2-2, calculating the representative span l _r = 435.5888m and the representative height difference angle cosine cosβ _r = 0.9991;

步骤2-3、通过代表档距法计算模型，利用架设电线时的气温t₀与输电线路导线的参数，计算最高气温t_max、最低气温t_min、平均气温t_avn三种气象条件下各自的应力值，将应力值最接近水平应力设计值σ₀₀的计算状态所对应的气象条件作为精确应力计算模型的初始气象条件，以及下述步骤2-5中计算的末态气象条件；Step 2-3, through the calculation model of the representative span method, using the temperature t ₀ when the wire is erected and the parameters of the transmission line conductor, calculate the maximum temperature t _max , the minimum temperature t _min , and the average temperature t _avn under the three meteorological conditions Stress value, the meteorological condition corresponding to the calculation state whose stress value is closest to the horizontal stress design value σ ₀₀ is used as the initial meteorological condition of the accurate stress calculation model, and the final meteorological condition calculated in the following steps 2-5;

得平均气温下的应力值50.74N/mm²最接近水平应力设计值51N/mm²，因此，将平均气温气象条件作为精确应力计算模型的初始气象条件。The stress value of 50.74N/mm ² at the average temperature is the closest to the horizontal stress design value of 51N/mm ² . Therefore, the average temperature and meteorological conditions are taken as the initial meteorological conditions of the accurate stress calculation model.

步骤2-4、再次通过代表档距法计算模型，利用架设电线时的气温t₀、覆冰产生的平均气温t_ice与输电线路导线的参数，计算不同覆冰厚度对应的导线总比载γ_b条件下的应力值，将应力值最接近极限σ_lim的计算状态所对应的气象条件作为下述步骤2-5中的初始气象条件；Step 2-4, calculate the model again by the representative span method, use the air temperature t ₀ when the wire is erected, the average air temperature t _ice caused by ice coating, and the parameters of the transmission line wire to calculate the total specific load of the wire corresponding to different ice thickness γ Stress value under condition _b , the meteorological condition corresponding to the calculation state where the stress value is closest to the limit σ _lim is taken as the initial meteorological condition in the following steps 2-5;

步骤2-5、利用如计算工序中步骤2-3、步骤2-4所述的末态气象条件、初始气象条件，并且设极限应力σ_lim为初始应力值，第三次使用代表档距法计算模型，求得初始水平应力值σ₀＝52.27N/mm²，并且将它作为精确应力计算模型的初始水平应力；Step 2-5, using the final meteorological conditions and initial meteorological conditions as described in steps 2-3 and 2-4 in the calculation process, and setting the limit stress σ _lim as the initial stress value, and using the representative span method for the third time Calculate the model, obtain the initial horizontal stress value σ ₀ =52.27N/mm ² , and use it as the initial horizontal stress of the accurate stress calculation model;

步骤2-6、根据所有已知的实时气象条件，由精确应力计算模型求得耐张塔段内每一档的实时应力值σ_i。Steps 2-6. According to all known real-time meteorological conditions, the real-time stress value σ _i of each gear in the tension tower section is obtained from the precise stress calculation model.

步骤3、运用精确应力计算模型计算每档水平应力；Step 3, use the accurate stress calculation model to calculate each level of horizontal stress;

σ₁＝121.14N/mm²、σ₂＝123.88N/mm²、σ₃＝130.20N/mm²、σ₄＝145.83N/mm²、σ₅＝143.79N/mm²、σ₆＝141.92N/mm²；σ ₁ =121.14N/mm ² , σ ₂ =123.88N/mm ² , σ ₃ =130.20N/mm ² , σ ₄ =145.83N/mm ² , σ ₅ =143.79N/mm ² , σ ₆ =141.92N / ^mm2 ;

确定各杆塔所受不平衡力；Determine the unbalanced force on each tower;

ΔF₁＝925.9N、ΔF₂＝2142.7N、ΔF₃＝5298.1N、ΔF₄＝688.5N、ΔF₅＝634.3N。ΔF ₁ =925.9N, ΔF ₂ =2142.7N, ΔF ₃ =5298.1N, ΔF ₄ =688.5N, ΔF ₅ =634.3N.

步骤4、比较实时应力值与水平极限应力值的关系及杆塔不平衡力与极限不平衡力的关系，本实施例水平极限应力值σ_lim为108.8N，各个直线杆塔设计可承受不平衡力ΔFs＝7377.6N。Step 4. Compare the relationship between the real-time stress value and the horizontal ultimate stress value and the relationship between the unbalanced force of the tower and the ultimate unbalanced force. The horizontal ultimate stress value σ _lim of this embodiment is 108.8N, and the design of each straight tower can withstand the unbalanced force ΔFs =7377.6N.

本实施例中各档水平应力σ_i>σ_lim，输出各档导线红色预警；In this embodiment, each level of horizontal stress σ _i >σ _lim , output a red warning for each level of wire;

本实施例中各杆塔不平衡力分别为：ΔF₁＝12.55％、ΔF₂＝29.04％、ΔF₃＝71.81％、ΔF₄＝9.33％、ΔF₅＝8.6％，其中，第3基直线杆塔0.6ΔFs<ΔF₃<0.8ΔFs，输出第3基直线杆塔黄色预警，其它直线杆塔不预警。The unbalanced force of each tower in this embodiment is respectively: ΔF ₁ =12.55%, ΔF ₂ =29.04%, ΔF ₃ =71.81%, ΔF ₄ =9.33%, ΔF ₅ =8.6%, among them, the third base linear tower is 0.6 ΔFs<ΔF ₃ <0.8ΔFs, output a yellow warning for the third straight tower, and no warning for other straight towers.

Claims

1. A method for early warning of ice-coated transmission line weak links, is characterized in that, comprises the following steps:

Step 1. Determine meteorological information, ice thickness information and overhead line detailed information. The meteorological information specifically includes: real-time temperature t, maximum air temperature t _max , minimum air temperature t _min , average air temperature t _av , and average air temperature t generated by icing _ice ; the ice thickness information is the ice thickness b of each gear in the continuous gear; the detailed information of the overhead line specifically includes the wire type, the elastic coefficient E corresponding to the wire type, the cross-sectional area A, the outer diameter D, the mass per unit length q, and the Gap l _i0 , height difference h _i0 of each gear, height difference angle β _i0 of each gear, length λ _i of hanging insulator strings on each base straight line tension tower, vertical load G _i , temperature t ₀ during stringing, wire Initial horizontal stress σ ₀₀ at air temperature;

Step 2. According to the known meteorological information, the initial horizontal stress is determined by the calculation model of the representative span method, and then the real-time stress value σ _i of each gear in the tension tower section is determined by the accurate stress calculation model;

Step 3. From the stress σ _i of the wires in each span determined in step 2, determine the unbalanced tension ΔF _i on each tension tower; the calculation model of the unbalanced tension ΔF _i is:

△F _i ＝(σ _i+1 -σ _i )A＝F _i+1 -F _i (i=1,2,…,n-1)

In the formula: σ _i+1 and σ _i are the horizontal stresses of the i+1 and i-th wires respectively, and n is the number of tension towers;

A——is the cross-sectional area of the wire;

F _i+1 and F _i ——the horizontal tension of the i+1 and i-th gear wires respectively;

△F _i ——the unbalanced tension difference borne by the i-th linear strain tower during the deicing process;

Step 4. Compare the conductor stress σ _i in each span with its limit stress _σ _lim , and carry out conductor warning in different grades; Pre-warning of unbalanced force of the tension tower.

2. according to claim 1, a kind of ice-covered transmission line weak link early warning method is characterized in that, described step 2 is based on known meteorological information, determines the initial horizontal stress through the calculation model of representative span method, and then by accurate The stress calculation model determines the real-time stress value σ _i of each gear in the tension tower section, which specifically includes the following steps:

Step 2-1. Determine the ultimate stress σ _lim of the transmission line conductor; the formula used is:

In the formula, _Tb is the calculated breaking force of the wire, and A is the cross-sectional area of the wire;

Step 2-2. Determine the representative height difference angle β _r and the representative span l _r ; the formulas used are:

In the formula, β _r is to be found, which represents the height difference angle, l _i0 is the distance of the i-th gear, β _i0 is the height difference angle of the i-th gear, i is a positive integer from 1 to n, and n is the number of gears;

In the formula, l _r to be found represents the stand distance, β _r represents the height difference angle, l _i0 is the stand distance of the i-th gear, β _i0 is the height difference angle of the i-th gear, and i is a positive integer from 1 to n, n is the number of files;

Step 2-3, through the calculation model of the representative span method, using the temperature t ₀ when the power line is erected and the parameters of the transmission line conductor, determine the maximum temperature t _max , the minimum temperature t _min , and the average temperature t _av under the three meteorological conditions Stress value, the meteorological condition corresponding to the calculation state where the stress value is closest to the horizontal stress design value σ ₀₀ is used as the initial meteorological condition of the accurate stress calculation model, and the final meteorological condition calculated in the following steps 2-5; the representative The calculation model of the span method is as follows:

In the formula, the number 1 represents the initial meteorological state, the number 2 represents the terminal meteorological state, t is the temperature, α is the temperature expansion coefficient of the wire, E is the elastic coefficient of the transmission line wire, σ ₀₁ is the initial state horizontal stress, σ ₀₂ is the final state Horizontal stress, l _γ represents the span, β _γ represents the height difference angle, γ is the specific load, γ=q*g/A, where q is the mass per unit length of the wire, g is the acceleration of gravity, and A is the cross-sectional area of the wire ;

Step 2-4, calculate the model again by the representative span method, use the air temperature t ₀ when the wire is erected, the average air temperature t _ice generated by ice coating, and the parameters of the transmission line wire to determine the total specific load of the wire corresponding to different ice thickness γ The stress value under the condition _b , the meteorological condition corresponding to the calculation state where the stress value is closest to the limit σ _lim is taken as the initial meteorological condition in the following steps 2-5; the total specific load γ _b of the conductors corresponding to the different ice coating thicknesses The calculation formula is:

In the formula, q is the unit mass of the wire, D is the outer diameter of the wire, b is the ice thickness, and A is the cross-sectional area of the wire;

Step 2-5, using the final meteorological conditions described in step 2-3, the initial meteorological conditions described in step 2-4, and setting the limit stress σ _lim as the initial stress value, use the representative span method to calculate the model for the third time , get the initial horizontal stress value σ ₀ , and use it as the initial horizontal stress of the accurate stress calculation model;

Step 2-6, according to all known real-time meteorological conditions, use the accurate stress calculation model to obtain the real-time stress value σ _i of each gear in the tension tower section; the accurate stress calculation model includes the following three relational models:

(1) The relationship model between the span increment Δl _i and the horizontal stress σ _i :

In the formula, σ _i ——value to be evaluated is the horizontal stress of the wire at the i-th gear at the temperature of t and the specific load of γ _i ; i is a positive integer from 1 to n, and n is the number of gears;

σ ₀ ——initial horizontal stress value;

l _{i0 ——the} i-th gear distance;

γ ₀ , γ _i — specific load before and after icing of the wire, γ ₀ is q*g/A, γ _i is q*g/A+0.027728(b(b+D)/A) , where q is the mass per unit length of the wire, g is the acceleration of gravity, A is the cross-sectional area of the wire, b is the ice thickness of the wire, and D is the outer diameter of the wire;

△l _i ——to be evaluated, the increment of l _i0 of the i-th gear span, specifically, the increment of the i-th gear span when the hanging insulator string is in the neutral position when the i-th gear span is in the sagging position;

△h _i ——To be evaluated, the increment of the height difference h _i0 of the i-th gear, specifically, the variation of the height difference h _i0 between the suspension points after the suspension insulator strings at both ends of the i-th gear are deflected, the right suspension point is higher than the left suspension Point h _i0 and height difference angle β _i0 are positive values;

t, t ₀ ——Respectively, the real-time temperature and the air temperature at the time of wiring;

α——wire temperature expansion coefficient;

E——conductor elastic coefficient;

(2) The relationship model between the height difference increment Δh _i of the i-th gear and the suspension point offset δ _i of the i-th tension tower:

In the formula, △h _i ——to be evaluated, the increment of the i-th gear height difference h _i0 , i is a positive integer from 1 to n, and n is the number of gears;

δ _i , δ _i-1 — the horizontal distance of the suspension point offset on the i-1th tension tower at both ends of the i-th gear, where the δ of the tension towers at both ends is 0;

λ——the length of the suspension insulator string on each strain tower, where λ is also assumed to be on the strain towers at both ends, but δ is 0;

(3) The relationship model between the suspension point offset δ _i of the i-th tension tower and the horizontal stress σ _i :

In the formula, σ _i - the value to be evaluated is the horizontal stress of the wire at the i-th gear at the temperature of t and the specific load of γ _i ; i is a positive integer from 1 to n, and n is the number of gears;

δ _i —— δ _i = δ _i-1 + △l _i ;

A - the cross-sectional area of the wire;

γ _i ——the specific load of the conductor after being covered with ice, γ _i is q*g/A+0.03(b(b+D)/A), where q is the mass per unit length of the conductor, g is the acceleration of gravity, and A is the cross section of the conductor area, b is the thickness of the wire ice coating, D is the outer diameter of the wire;

δ _i ——horizontal distance of the suspension point offset on the tension towers at both ends of the i-th gear, where the δ of the tension towers at both ends is 0;

G _i , λ——the vertical load and length of the suspension insulator strings on each tension tower, where λ is also assumed on the tension towers at both ends, but δ is 0;

l _{i0 ——the} i-th gear distance;

h _i0 , h _(i+1)0 ——height difference between the i-th gear and the i+1-th gear, specifically, when the suspension insulator strings are all in the mid-sag position, the suspension points of the wires on the i-th base tension tower face the adjacent tension The height difference between the suspension points of the i-1 and i+1 bases of the tower, if the large-scale strain tower is higher than the small-scale strain tower, h itself has a positive value, otherwise it is a negative value, measured on site;

β _{i0 ——the} height difference angle of the i-th gear.

3. according to claim 1, a kind of ice-coated transmission line weak link early warning method is characterized in that, the specific numerical relationship and corresponding early warning level of wire early warning described in step 4 are:

The specific numerical relationship of the wire early warning and the corresponding early warning level are:

When σ _i <50% σ _lim , no warning;

When 50% σ _lim ≤ σ _i ≤ 70% σ _lim , output a yellow warning for the i-th wire;

When 70% σ _lim < σ _i < 85% σ _lim , output the i-th wire orange warning;

When σ _i ≥ 85% σ _lim , output a red warning for the i-th gear wire;

The specific numerical relationship and corresponding early warning level of the unbalanced force warning of the tension tower are:

When ΔF _i ≤0.6ΔFs, no warning;

When 0.6ΔFs<ΔF _i <0.8ΔFs, output a yellow warning for the i-th base tension tower;

When 0.8ΔFs ≤ ΔF _i ≤ 0.95ΔFs, output an orange warning for the i-th base tension tower;

When ΔF _i >0.95ΔFs, output a red warning for the i-th base strain tower.