CN102968554B - Tower pole icing disaster risk prediction method based on safety margin - Google Patents

Abstract

The invention provides a tower pole icing disaster risk prediction method based on the safety margin. With the method, finite element numerical value simulation and data regression analysis are combined; a finite element method is adopted to build a 1:1 overhead transmission line tower pole coupling model; the main stressed factor of a line under various static conditions is comprehensively considered; simulation calculation is carried out to various operation working conditions of an icing line model; and on the basis, a simulation result is subjected to regression analysis and data fitting by the concept of the safety margin to obtain the safety margin curve of a power transmission tower line system so as to obtain the safety level of the power transmission tower line system. The method disclosed by the invention belongs to the safety evaluation field of the power transmission tower line system, the icing and tower falling risk of the power transmission tower line system can be solved, the safety margin range of the tower line system is given in real time so as to determine the line icing risk level at present, a basis is given for formulating an icing-proof transformation scheme, the formulation principle of the icing-proof transformation scheme is determined, and the operation reliability of the power transmission tower line system is improved.

Description

Based on the shaft tower icing calamity risk forecast method of margin of safety

Technical field

The invention belongs to Transmission Tower-line system security assessment field, particularly relate to the shaft tower icing calamity risk forecast method based on margin of safety.

Background technology

Icing is one of common phenomenon of nature, and the leading of overhead transmission line, ground wire and covering ice for insulator all will constitute a threat to its safe and stable operation, and the accident of falling tower particularly caused by icing, once generation can cause serious economic loss and social influence.Along with the rapid economic development of China, the requirement of Large scale construction to the security and stability of electric system along with Extra-high-voltage, extra high voltage line is more and more higher, and what prevent a series of disaster accidents caused by icing is that power industry is badly in need of one of subject matter solved.

The icing disaster of China is more serious, and large-area ice damage once repeatedly occurred in China, and the coated by ice of overhead power transmission line accident of falling tower all occurred on the ground such as Central China, southwest, North China, northwest and northeast.2008, an especially big sleet and snow ice weather attacked the many areas of China, and the regional wide-area power outage such as to cause on the south China the Changjiang river, causing extremely serious destruction to electrical network, is an icing hazardous accidents the most serious over 50 years.Sleet and snow ice weather causes overhead transmission line major part icing, and ice covering thickness is not from 30 millimeters to 80 millimeters etc.This time serious icing density cause altogether 500kV ac and dc circuit fall tower 678 base, stop transport 119, the 220kV circuit bar of falling tower 1432 base, stop transport 343,500kV transformer station stops transport 15, and 220kV transformer station stops transport 86.Between ice period, cause large area blackout, make China's electrical network be subject to threat the severeest since the dawn of human civilization, cause many people dead, the billions of unit of direct economic loss, brings huge economic loss to national economy, brings huge inconvenience to people's lives.

Since the 1950's, the serious country such as Russia, Canada, the U.S., Japan, Britain, Finland, Iceland of coated by ice of overhead power transmission line in succession drops into technical force and observes coated by ice of overhead power transmission line and study, explore computing method of ice and wind load etc. after coated by ice of overhead power transmission line mechanism, the formation condition of icing, wire icing, and long-term observation and experimental study are carried out to wire icing.But research is based on icing formation mechenism and corresponding harm mostly; Or statistical study is carried out to weather during disaster, lack and effectively calculate data verification.At present for the deficiency of powerline ice-covering disaster accident Forecasting Methodology, tower structure safety case in overhead transmission line cannot to be reflected under various service condition comprehensively.

Summary of the invention

For the deficiency that prior art exists, the invention provides a kind of shaft tower icing calamity risk forecast method based on margin of safety, the method energy real-time assessment icing calamity source, can also predict the icing disaster accident of shaft tower.

In order to solve the problems of the technologies described above, the present invention adopts following technical scheme:

Based on a shaft tower icing calamity risk forecast method for margin of safety, comprise step:

Step one, builds shaft tower coupling model;

Step 2, obtains wind speed under critical operating mode of shaft tower in shaft tower coupling model and ice covering thickness;

Step 3, carry out regretional analysis, data fitting and optimization to the wind speed of shaft tower under critical operating mode with ice covering thickness and obtain the regressive prediction model y=f (x) relevant with shaft tower margin of safety, wherein, x is the ice covering thickness on shaft tower, and y is wind speed;

Step 4, obtains the actual time safety margin value of shaft tower according to shaft tower regressive prediction model and real-time working condition according to the icing calamity source of margin of safety value assessment shaft tower, wherein, real-time working condition is:

Ice covering thickness is m, and wind speed is a; N is y=f(x) in the x value of y when getting a, t is y=f(x) the x value of middle y when getting 0.

Above-mentioned shaft tower coupling model builds according to the dimension scale of 1:1.

Above-mentioned shaft tower coupling model can adopt Finite Element Method to build, and construction method is specially:

The three-dimensional finite element model of shaft tower is set up according to the electron diagram of shaft tower, and the three-dimensional finite element model of wire, ground wire and insulator is set up according to the actual track of shaft tower and geographical environment, by wire, ground wire and insulator model each shaft tower coupled together and obtain shaft tower coupling model.

In above-mentioned acquisition shaft tower coupling model, the step of the wind speed of shaft tower under critical operating mode and ice covering thickness is specially:

According to a series of operating modes preset, finite element method is adopted to carry out wind and icing CYCLIC LOADING to node each in shaft tower coupling model respectively, obtain the stressing conditions of shaft tower under different operating mode by analysis, and obtain the wind speed of shaft tower under critical operating mode and ice covering thickness according to the stressing conditions of shaft tower.

Above-mentionedly obtain the regressive prediction model y=f (x) relevant with shaft tower margin of safety and be specially:

1) by carrying out regretional analysis to critical point and data fitting sets up shaft tower regressive prediction model, described critical point is wind speed under the critical operating mode of shaft tower and ice covering thickness;

2) Global Optimization Method optimization is adopted to carry out iteration optimization to set up shaft tower regressive prediction model, judge whether the fitting correlation coefficient R of critical point meets the condition of convergence preset, iteration is stopped when R meets the default condition of convergence, namely the shaft tower regressive prediction model y=f(x after being optimized), wherein, x is ice covering thickness, and y is wind speed; If fitting correlation coefficient R cannot restrain in the iterations being setting, then perform step 3);

3) the maximum shaft tower regressive prediction model of fitting correlation coefficient R in setting iterations is taken at as the shaft tower regressive prediction model after optimizing.

Compared with prior art, the present invention has following characteristics and beneficial effect:

1, the present invention is applicable to overhead transmission line, can the margin of safety value of Real-time Obtaining overhead power transmission line pole tower, thus can the icing calamity source of real-time assessment shaft tower, can predict the icing disaster accident of shaft tower, thus take measures to reduce the icing accident of falling tower odds; Also can be formulation shaft tower ice-covering-proof modification scheme and foundation is provided, determine the formulating rules of ice-covering-proof modification scheme, improve the operational reliability of overhead transmission line.

2, the invention process is simple, only needs to know real-time working condition, just can obtain the margin of safety value of shaft tower, thus can assess the icing calamity source of shaft tower.

Accompanying drawing explanation

Fig. 1 is the inventive method process flow diagram;

Fig. 2 is the tower-coupled model schematic of concrete enforcement king-rod, and wherein, figure (a) is many bases shaft tower coupling model schematic diagram, and figure (b) is single shaft tower coupling model schematic diagram;

Fig. 3 is the margin of safety curve of shaft tower;

Fig. 4 is shaft tower margin of safety value schematic diagram under certain operating mode in concrete enforcement.

Embodiment

Finite Element Numerical Simulation combines with data regression by the inventive method, adopt Finite Element Method to press 1:1 dimension scale and build the tower-coupled model of overhead transmission line king-rod, the main stress factor of comprehensive consideration various static condition line, carries out stress simulation to the various operating condition of icing shaft tower coupling model; Propose the concept of margin of safety value on this basis, regretional analysis and data fitting are carried out to stress simulation result, obtain the margin of safety curve of shaft tower, according to the actual time safety margin value of margin of safety curve acquisition shaft tower, and based on the icing risk of margin of safety value real-time judge shaft tower.The process flow diagram of the inventive method is see Fig. 1.

Fig. 2 is the shaft tower coupling model schematic diagram adopting finite element method to build.Shaft tower coupling model comprises the three-dimensional finite element Tower Model built by 1:1 dimension scale, and is connected with the three-dimensional finite element model of insulator by wire, ground wire.The main material type number of Fig. 2 institute representation model king-rod tower is Q345 steel, and auxiliary material model is Q235 steel, and the beam element of simulation shaft tower is BEAM188; Wire type is 4 × LGJ-400/35, and ground wire model is GJ-80.Wire and ground wire are a kind of flexible members, are characterized in bearing moment of flexure and pressure, can only bear pulling force, therefore can process according to single cable structure accurately, adopt LINK10 bar unit analog conducting wire and ground wire; On insulator chain and insulator chain, the size of gold utensil is very little compared to shaft tower, wire, ground wire, impact for the dynamic analysis of tower line structure is less, LINK8 bar unit can be adopted, LINK8 bar unit has the rigidity of Tension and Compression, usually for simulating spread out frame, sagging cable, connecting rod, spring etc.

After establishing the finite element model of shaft tower, wire, ground wire and insulator, be of coupled connections by the unit of each model of composition, Tower Model is built by beam element, for being rigidly connected between each beam element; Insulator model is built by bar unit, for being hinged between each bar unit; Wire is also built by bar unit with ground line model, also for being hinged between each bar unit; Insulator and shaft tower hitch point, insulator and wire place connected mode also for be hinged, realistic ruuning situation.Shaft tower, wire, ground wire and insulator model group after being of coupled connections are combined into shaft tower coupling model.

Preset a series of different operating mode, according to the different operating modes preset, adopt finite element method to carry out circulation wind speed and ice covering thickness to node each in shaft tower coupling model and load stressing conditions to obtain shaft tower under different operating mode, analyze the stressing conditions of shaft tower under different operating mode and obtain the wind speed of shaft tower under critical operating mode and ice covering thickness.Wind speed under critical operating mode and the basis of ice covering thickness continue to increase wind speed and ice covering thickness, and shaft tower can collapse.

The wind speed of the different operating mode of table 1 and ice covering thickness

In this concrete enforcement, first the 18 kinds of operating modes (i.e. wind speed and ice covering thickness) provided according to table 1 carry out wind-force and icing loading to the wire in shaft tower coupling model, ground wire, insulator, Tower Model respectively, loading method see line design handbook, can be specially:

The wind load of (a) lead model and ground line model

Wind acts on the wind load that wire and ground wire produce, the not product of simple blast and electric wire wind area, also to consider the wind relevant with electric pressure with wind speed size carry wind speed height change factor, wind direction and traverse shaft that regulation coefficient and wire and ground wire average height be correlated with to angle, the wind evil attacking lung relevant with wind speed size and lead, the impact of the correlative factor such as the Shape Coefficient of ground wire.

Employing formula (1) carries out horizontal wind loading to each node on wire and ground line model respectively:

W _x=0.625αμ _scβ _c(d+2δ)l _H(K _hv) ²×sin ²θ×10 ^-3=g _Hl _Hβ _csin ²θ（1）

In formula (1),

W _xfor the horizontal wind excitation perpendicular to wire and ground wire axis, unit: N;

α is the wind evil attacking lung of wire and ground wire, and its value is relevant with the wind speed of altitude datum, and concrete value can reference table 2;

μ _scfor the Shape Coefficient of wire and ground wire, with wire with ground wire external diameter, whether icing is relevant, when icing, gets 1.2, concrete value can reference table 3;

β _cthe wind acted on shaft tower for wire and ground wire carries regulation coefficient, its value is relevant with the wind speed of altitude datum, and the larger value of wind speed is larger, changes with wind speed, value in 1.0 ~ 1.3 scopes, table 4 gives the 500kV line wires wind acted on shaft tower and carries regulation coefficient value;

V is stipulated standard height h in circuit _sthe wind speed at place, unit: m/s, this wind speed is the wind speed shown in table 1, is a series of air speed value designed in advance;

K _hfor the wind speed height change factor that wire and ground wire mean height are h place, h _sfor the wind speed altitude datum of wire and ground wire, β is the coefficient relevant with surface roughness, and general land-line β gets 0.16 by category-B; Wide water surface span line overhead β gets 0.12 by category-A;

D is wire and ground wire external diameter, unit: mm;

δ is wire and ground wire surface ice covering thickness, unit: mm;

L _hfor wire and ground wire horizontal span, unit: m;

θ is wind direction and the angle between wire and ground wire axis, unit: deg;

G _hthe wire produced for horizontal wind and ground wire unit wind load; Because be wire and ground wire are separated into unit form carry out numerical evaluation in the application, be therefore adopt unit load to apply to the wind load of wire and ground wire.When electric wire there being icing, g _hfor the g in formula (2) ₁; When on electric wire without icing time, g _hfor the g in formula (3) ₂.

On wire and ground wire during icing, the wire that horizontal wind direction produces and ground wire unit wind load g1 are:

g ₁=0.625αμ _sc(d+2δ)(K _hv) ²×10 ^-3（2）

Time on wire and ground wire without ice, the wire that horizontal wind direction produces and ground wire unit wind load g ₂for:

g ₂=0.625αμ _scd(K _hv) ²×10 ^-3（3）

Wherein, unit wind load g ₁and g ₂unit be N/m.

The value of table 2 electric wire wind evil attacking lung α

The build system μ of table 3 electric wire _sc

The table 4500kV line wires wind acted on shaft tower carries regulation coefficient β c

Because this part carries out the loading of horizontal direction wind to each node on wire and ground line model, the horizontal wind excitation therefore each node loaded is all equal.

Due to ground line position, comparatively wire is high, and ground wire is not charged, also because ground wire than wire thin and easier icing, therefore when loading wire and ground line model, ground wire ice covering thickness value is larger than wire icing thickness.

The wind load of (b) insulator model

Employing formula (4) carries out wind-force loading to insulator string model each in shaft tower coupling model:

$F_J=n_1{n}_2{A}_p{k}_z\frac{v^2}{1.6}---\left(4\right)$

In formula (4),

F _jfor the wind load of insulator chain J, unit: newton;

N ₁for the insulator chain number that insulator chain J place single-phase transmission line is used;

N ₂for the sheet number of insulator on insulator chain J, each gold utensil part calculates as a slice insulator;

A _pfor the wind area of monolithic insulator on insulator chain J, unit: m ², the wind area of each insulator on insulator chain is approximately equalised, is equally all expressed as A so be used as by the area of each insulator in formula (4) _p; In this concrete enforcement, the wind area of bell insulator gets 0.03m ², the wind area of double petticoat insulator gets 0.04m ²;

K _zfor height variation coefficient of wind pressure, k _zvalue relevant with the terrain clearance of insulator, terrain clearance is higher, and value is larger; Table 5 gives the value condition of the height variation coefficient of wind pressure of insulator on 500kV line wires shaft tower;

V is stipulated standard height h in circuit _sthe wind speed at place, unit: m/s, this wind speed is the wind speed shown in table 1, is a series of air speed value designed in advance, unit: m/s.

Table 5 height variation coefficient of wind pressure k _z

The wind load of (c) Tower Model

Employing formula (5) carries out wind-force loading to wind direction to vertical Tower Model node:

$F_t={\mathrm{kk}}_z{k}_T{A}_c\frac{v^2}{1.6}---\left(5\right)$

In formula (5),

F _tfor the wind load of shaft tower, unit: N;

K is that the wind of shaft tower carries Shape Coefficient, generally only gets 1.3;

K _zfor height variation coefficient of wind pressure, k _zthe value height liftoff with shaft tower relevant, terrain clearance is higher, and value is larger; Table 5 gives the value condition of the height variation coefficient of wind pressure of 500kV line wires shaft tower;

K _tfor the Wind Load Adjustment Coefficients of shaft tower, its value is relevant with shaft tower overall height, and value can reference table 6;

A _c---shaft tower rod member shelves wind area, m ².

Table 6 shaft tower Wind Load Adjustment Coefficients k _t

The ice load of (d) Tower Model

Formula (6) is adopted to carry out icing loading to the node i of Tower Model:

$F_i=\frac{1}{2}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}\mathrm{\ρg}\left(\frac{\mathrm{\π}}{4}{h}_z{D}^2\right)l_j---\left(6\right)$

In formula (6):

F _iice load for Tower Model interior joint i:

N is the sum of the shaft tower unit intersecting at node i, and namely shaft tower unit forms the beam element of Tower Model;

ρ is the density of icing, gets ρ=900kg/m ³;

G is acceleration of gravity;

H _zfor icing diameter is with height change factor, thinks that icing diameter is identical everywhere in this concrete enforcement, namely get h _z=1;

D is icing diameter, and its value is the ice covering thickness in table 1;

L _jfor the length of a jth shaft tower unit, j=1,2 ... .n.

The ice load of (e) lead model and ground line model

Formula (7) is adopted to carry out icing loading to each node on lead model and ground line model respectively:

g ₃=πρgδ(d+δ)×10 ^-3（7）

In formula (7),

G ₃for wire and ground wire icing gravity unit load, unit: N/m;

ρ is the density of icing, gets ρ=900kg/m ³;

D is wire and ground wire external diameter, unit: m;

δ is wire and ground wire ice covering thickness, unit: m.

Adopt said method and the operating mode provided according to table 1 to lead model, in line model, insulator model and Tower Model each node carry out CYCLIC LOADING, obtain the physics stressing conditions of each node under different operating mode, and obtain the wind speed of shaft tower under critical operating mode and ice covering thickness according to joints situation analysis.

According to the wind speed under the critical operating mode of shaft tower and these two influence factors of ice covering thickness, set up the regressive prediction model of shaft tower, the structure of this regressive prediction model comprises to be set up regressive prediction model and optimizes regressive prediction model two sub-steps set up.First, the distribution situation according to critical point sets up the shaft tower regressive prediction model tallied with the actual situation, and described critical point is wind speed under the critical operating mode of shaft tower and ice covering thickness.

Then adopt and with the following method set up shaft tower regressive prediction model be optimized:

1) Global Optimization Method is adopted repeatedly to be calculated each set up shaft tower regressive prediction model by iterative computation, and whether the coefficient R calculating the matching of discrete point meets the condition of convergence, shaft tower regressive prediction model y=f(x stop iteration being optimized when R meets the default condition of convergence after), wherein, x is ice covering thickness, and y is wind speed.Set when R is greater than 0.8 in this concrete enforcement and meet the condition of convergence, stop iterative computation.

2) only have when independent variable x and dependent variable y exists certain relation really, the regression equation of foundation is just meaningful.Coefficient R is larger, and the degree of correlation of independent variable and dependent variable is higher, and shaft tower regressive prediction model is more accurate.Therefore, if coefficient R cannot restrain in the iterations of setting, be then taken at the maximum shaft tower regressive prediction model of coefficient R in setting iterations as the shaft tower regressive prediction model after optimizing.

Take x as horizontal ordinate, y draw y=f(x for ordinate) curve, i.e. the margin of safety curve of shaft tower.

Coefficient R is as follows;

$R=\frac{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}(X_i-\stackrel{\‾}{X})(Y_i-\stackrel{\‾}{Y})}{\sqrt{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{(X_i-\stackrel{\‾}{X})}^2}\sqrt{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{(Y_i-\stackrel{\‾}{Y})}^2}}---\left(8\right)$

In formula (8),

X _irepresent independent variable x, for the mean value of independent variable x; Y represents dependent variable y, represent the mean value of dependent variable y; N is the quantity of discrete point.

Ice covering thickness be m, under wind speed is the operating mode of a, the present invention is according to the regressive prediction model y=f(x of shaft tower) define margin of safety value under this operating mode assess shaft tower icing risk according to margin of safety value, margin of safety value is larger, and the security and stability of shaft tower is better, and wherein, n is y=f(x) in the x value of y when getting a, t is y=f(x) the x value of middle y when getting 0.See Fig. 4, if margin of safety curve and x=m, y=a surround region area be q, i.e. the area of black region in Fig. 4, if margin of safety curve and x-axis, y-axis surround region area be Q, the margin of safety value P=q/Q of shaft tower.

The shaft tower regressive prediction model that in Fig. 3 and 4, margin of safety curve is corresponding is y=4.83e ^-0.33x-66.7e ^0.08x+ 96.7e ^0.07x-4.76-2.61x, wherein, x is ice covering thickness, and y is wind speed.Wind speed be 5m/s, under ice covering thickness is the operating mode of 10mm, the margin of safety value of the shaft tower obtained under this operating mode according to the margin of safety curve of Fig. 3 and 4 is 0.848.

Based on a large amount of real data, table 7 gives shaft tower icing calamity source evaluation grade graded index, according to margin of safety value, the icing calamity source of shaft tower is divided into A, B, C, D tetra-grades, the power relatively of each shaft tower margin of safety performance is showed more intuitively.When that is grade is A in P >=0.75, shaft tower margin of safety is the highest, and now tower structure is stablized, and the reduction of shaft tower margin of safety P shows that the stability of shaft tower reduces.This concrete shaft tower margin of safety value implementing to obtain is 0.848, and risk class is A, and now shaft tower icing calamity source is lower, and tower structure has good stability.

Table 7 shaft tower icing calamity source evaluation grade graded index

Claims (2)

1., based on an icing tower wire system safety in operation appraisal procedure for margin of safety, it is characterized in that, comprise step:

Step one, build shaft tower coupling model, described shaft tower coupling model builds according to the dimension scale of 1:1, and shaft tower coupling model adopts Finite Element Method to build, and the step adopting Finite Element Method to build shaft tower coupling model is specially:

The three-dimensional finite element model of shaft tower is set up according to the electron diagram of shaft tower, and the three-dimensional finite element model of wire, ground wire and insulator is set up according to the actual track of shaft tower and geographical environment, by wire, ground wire and insulator model each shaft tower coupled together and obtain shaft tower coupling model;

Step 2, obtains wind speed under critical operating mode of shaft tower in shaft tower coupling model and ice covering thickness;

Step 3, carry out regretional analysis, data fitting and optimization to the wind speed of shaft tower under critical operating mode with ice covering thickness and obtain the regressive prediction model y=f (x) relevant with shaft tower margin of safety, wherein, x is the ice covering thickness on shaft tower, and y is wind speed;

Step 3 comprises following sub-step further:

1) by carrying out regretional analysis to critical point and data fitting sets up shaft tower regressive prediction model, described critical point is wind speed under the critical operating mode of shaft tower and ice covering thickness;

2) Global Optimization Method is adopted to carry out iteration optimization to set up shaft tower regressive prediction model, judge whether the fitting correlation coefficient R of critical point meets the condition of convergence preset, iteration is stopped when R meets the default condition of convergence, namely shaft tower regressive prediction model y=f (x) after being optimized, wherein, x is ice covering thickness, and y is wind speed; If fitting correlation coefficient R cannot restrain in the iterations of setting, then perform step 3);

3) the maximum shaft tower regressive prediction model of fitting correlation coefficient R in setting iterations is taken at as the shaft tower regressive prediction model after optimizing;

Step 4, obtains the actual time safety margin value of shaft tower according to shaft tower regressive prediction model and real-time working condition according to the icing calamity source of margin of safety value assessment shaft tower, wherein, real-time working condition is: ice covering thickness is m, unit: mm, and wind speed is a, unit: m/s; N is x value when y gets a in y=f (x), and t is the x value of y=f (x) middle y when getting 0.

2., as claimed in claim 1 based on the icing tower wire system safety in operation appraisal procedure of margin of safety, it is characterized in that:

In described acquisition shaft tower coupling model, the step of the wind speed of shaft tower under critical operating mode and ice covering thickness is specially:

According to a series of operating modes preset, finite element method is adopted to carry out wind and icing CYCLIC LOADING to node each in shaft tower coupling model respectively, obtain the stressing conditions of shaft tower under different operating mode by analysis, and obtain the wind speed of shaft tower under critical operating mode and ice covering thickness according to the stressing conditions of shaft tower.