CN102927949B - Based on the powerline ice-covering Forecasting Methodology of multi-element physical quantity mathematical model - Google Patents

Abstract

Based on a powerline ice-covering Forecasting Methodology for multi-element physical quantity mathematical model, comprise the steps: that (1) obtains humiture and the wind-force meteorologic parameter of current time; (2) judge whether current each weather data meets icing condition respectively, temperature-8 ~ 0 DEG C, more than humidity 90%RH, wind speed 2 ~ 7m/s, if satisfy condition, forward to (3), otherwise enter the sampling period next time, namely gets back to (1); (3) data value obtained by tension pick-up and initial value are compared, if illustrate that wire has icing, forward step (4) to, otherwise turn back to (1); (4) obtain current environment atmospheric pressure value by ground based terminal, calculate ice covering thickness b; (5) by ice covering thickness, the parameters such as humiture calculate any time t _ithe comprehensive ratio of wire carries; (6) pass through comprehensively than carrying the axial stress σ obtaining span end points place _x, make σ _x=σ _max, calculate break off remnant time t, send early warning by terminal.The present invention realizes effective monitoring, accuracy is good.

Description

Based on the powerline ice-covering Forecasting Methodology of multi-element physical quantity mathematical model

Technical field

The present invention relates to one, by multi-element physical quantity (wind-force, temperature, humidity, raindrop, air pressure etc.), modeling is affected on ice coating of power line, thus send the realization of the powerline ice-covering Forecasting Methodology of early warning.

Background technology

Within 2008, south China meets with snow disaster, the general icing of transmission line of electricity, transmission line of electricity is caused to rupture under serious conditions, because Utilities Electric Co. cannot judge that circuit where icing is serious, and will when rupture, therefore the preventive measure such as deicing cannot be implemented in time, thus effectively can not avoid the phenomenons such as broken string, the tower of circuit, this is the ubiquitous problem of present powerline systems.

Powerline ice-covering is one of most important disaster of electric system, go deep into the research in this field, first reason and the formation mechenism of defeated powerline ice-covering will be understood fully, applicable line ice coating forecast model to be provided for typical meteorological condition simultaneously, accurately judge the ice covering thickness of circuit and concrete icing position, for the design of transmission line of electricity anti-ice calamity provides important parameter.

Based on the mathematical model that multi-element physical quantity affects icing, by the analysis to line of electric force stressing influence, consider the climatic factor that nature is common, comprise air themperature, humidity, wind direction and wind velocity, Liquid water content, drop diameter etc., affect the factor of icing in conjunction with wire itself simultaneously, as conductor structure and material surface performance etc., the effective prediction to powerline ice-covering situation can be realized, make the ice covering thickness predicted closer to truth.

Summary of the invention

Cannot monitor in time to solve current power line icing situation, so that effectively cannot avoid the situations such as broken string, tower, the present invention devises and carries out mathematical modeling thus the mathematical model of effective prediction powerline ice-covering situation based on multi-element physical quantity to electric power line ice-covering thickness, provides a kind of and realizes the powerline ice-covering Forecasting Methodology based on multi-element physical quantity mathematical model that effective monitoring, accuracy well, effectively avoid broken string and the phenomenon of falling tower.

The technical solution adopted for the present invention to solve the technical problems is:

Based on a powerline ice-covering Forecasting Methodology for multi-element physical quantity mathematical model, described Forecasting Methodology comprises the steps:

(1) Temperature Humidity Sensor, wind sensor is adopted to obtain humiture and the wind-force meteorologic parameter of current time;

(2) judge whether current each weather data meets icing condition respectively, that is: temperature-8 ~ 0 ° of C, more than humidity 90%RH, wind speed 2 ~ 7m/s, if satisfy condition, forward to (3), otherwise enter the sampling period next time, namely turns back to (1);

(3) data value obtained by tension pick-up and initial value are compared, if illustrate that wire has icing, forward step (4) to, otherwise turn back to (1);

(4) obtain current environment atmospheric pressure value by ground based terminal, calculate ice covering thickness b, computing formula is as follows:

$b={\∫}_0^{t_i}f(t,T,V,p)\mathrm{dt}---\left(13\right)$

Unit ice covering thickness Δ r is expressed as:

$\mathrm{\Δr}=\frac{t\sqrt{{\left(\mathrm{VW}\right)}^2+{\left(P{\mathrm{\ρ}}_0\right)}^2}}{{\mathrm{\ρ}}_i\mathrm{\π}}---\left(7\right)$

Wherein, the V Liquid water content (g/m that to be wind speed (m/s), W be in air ³), t is rain time (s); P is rainfall intensity (mm/h), ρ ₀the density (g/cm of water ³), t is rain time (s);

W=aP ^b, wherein a, b are constants, and rainfall intensity P and humidity are changed, P meets following relation:

$P=\frac{1}{\mathrm{\ρg}}{\∫}_0^{p_{z_0}}\mathrm{qdp}---\left(8\right)$

Wherein, q is specific humidity, and p is air pressure (MPa), ρ is aqueous water density (g/cm ³), g is acceleration of gravity (m/s ²), for surface pressure (MPa);

Specific humidity q is according to vapour pressure e(hPa) to calculate, it with the pass of vapour pressure is:

$q=\frac{\mathrm{\ϵe}}{p-(1-\mathrm{\ϵ})e}---\left(9\right)$

In formula, μ _v, μ _dbe respectively the average molar mass of steam and dry air;

The humidity value adopting humidity sensor to obtain is a relative humidity, and its expression formula is:

$f=\frac{e}{E}\×100\%---\left(10\right)$

Wherein, E is the saturation vapour pressure (hPa) under same temperature; ;

In conjunction with formula (7)-(10), obtain the expression formula of unit ice covering thickness Δ r about time t, temperature T, wind speed V and air pressure p:

Δr=f(t,T,V,p) （11）；

Formula (11) is converted into differential form, and both sides integration can obtain formula (13);

(5) any time t is calculated by ice covering thickness and humiture _ithe comprehensive ratio of wire carries g ₅, computing formula is:

$g_5=\sqrt{{g_3}^2+{g_4}^2}---\left(20\right)$

Wherein, g ₄for level is than carrying, g ₃for vertically than carry;

$g_3=g_1+g_2=\frac{\mathrm{gq}}{A}+\frac{\mathrm{g\ρ\πb}(2r_0+b)\×{10}^{-3}}{A}---\left(17\right)$

Wherein, g ₁for wire is than carrying, g ₂for icing is than carrying, g is acceleration of gravity, and q is unit linear mass (kg/m), and ρ is the density (g/cm of icing ³), r ₀for the radius (mm) of wire, A is wire sectional area (mm ²);

$g_4=0.6128K_z\mathrm{\αC}(2r_0+2b)\frac{V^2}{A}$

$=1.2256K_z\mathrm{\αC}(r_0+b)\frac{V^2}{A}---\left(19\right)$

Wherein, K _zbe height variation coefficient of wind pressure, α is uneven factor of wind speed, and C is wind load configure coefficient; (6) pass through comprehensively than carrying a g ₅obtain the axial stress σ at line of electric force span end points place _x, make σ _x=σ _max, calculate break off remnant time t, and send early warning signal.

Technical conceive of the present invention is: the meteorologic parameters such as the humiture of employing Temperature Humidity Sensor, wind sensor acquisition current time and wind-force, then the icing situation of current time circuit is gone out by calculated with mathematical model, dope the icing situation of any time further, show that the ratio that the line of electric force of any time bears carries (comprise level than carry, carry from anharmonic ratio and ice anharmonic ratio is carried), and then calculate the axial stress of arbitrary point on this moment circuit; The maximum value that meets with stresses of line of electric force simultaneously provided according to power department, compares, when prediction meet with stresses value and line of electric force maximum meet with stresses value close to time, expression line of electric force is by rupturing; Calculate from the break off remnant time, send early warning, remind relevant department to carry out deicing and combat a natural disaster work.

Because the present invention adopts wireless sensor node network and background monitoring center to match, and in conjunction with the form of early warning mechanism, the monitoring problem of transmission line of electricity can be solved well, remove complicated processes and the maintenance times of hand inspection from, both cost was reduced, turn improve the reliability of monitoring, be a kind of system being conducive to monitoring ultra-high-tension power transmission line in real time and report to the police simultaneously.

In the present invention simultaneously, each sensor node (comprising tension pick-up, Temperature Humidity Sensor and wind sensor) merges, carry out unified power supply management, and node adopts Miniature wind-driven generator to power, fundamentally solve high-tension electricity and change the problems such as battery difficulty.

Beneficial effect of the present invention is: realization is effectively monitored, accuracy well, effectively avoids breaking and falling tower.

Accompanying drawing explanation

Fig. 1 is wire stressing conditions schematic diagram of the present invention.

Fig. 2 is unit length inside conductor icing situation schematic diagram of the present invention.

Than the schematic vector diagram of carrying when Fig. 3 is wire icing of the present invention.

Its any point predicted stresses value and the maximum value trend graph that meets with stresses when Fig. 4 is wire icing of the present invention.

Fig. 5 is wire icing prediction algorithm process flow diagram of the present invention.

Embodiment

Below in conjunction with accompanying drawing, the invention will be further described.

With reference to Fig. 1 ~ Fig. 5, a kind of powerline ice-covering Forecasting Methodology based on multi-element physical quantity mathematical model, comprises the steps:

(1) adopt Temperature Humidity Sensor, wind sensor to obtain the meteorologic parameters such as the humiture of current time and wind-force, these parameters are analyzed;

(2) judge whether current each weather data meets icing condition, is mainly respectively: temperature-8 ~ 0 ° of C, more than humidity 90%RH, wind speed 2 ~ 7m/s, if satisfy condition, forward to (3), otherwise enter the sampling period next time, namely gets back to (1);

(3) data value obtained by tension pick-up and initial value are compared, if illustrate that wire has icing, forward step (4) to, otherwise turn back to (1);

(4) obtain current environment atmospheric pressure value by ground based terminal, calculate ice covering thickness b;

(5) by ice covering thickness, the parameters such as humiture calculate any time t _ithe comprehensive ratio of wire carries g;

(6) pass through comprehensively than carrying the axial stress σ obtaining span end points place _x, make σ _x=σ _max, calculate break off remnant time t, send early warning by terminal, notice relevant department carries out deicing and combats a natural disaster work.

Because the impact of the meteorologic factor such as humiture, wind-force on wire is less, the sampling period that we set icing monitoring is 10 minutes.In a sampling period, ice covering thickness change is not very greatly, and we do not need to upgrade wire fracture excess time at every turn.After each image data, just calculate ice covering thickness, if with front once poor be not very large, then no longer down to calculate, but the predicted time before maintaining, just recalculate until ice covering thickness exists significant change.

With reference to Fig. 1: described line of electric force stressing conditions, calculate by factors such as Tensity size that trolley wire acts on and electric wire material, sectional area and the loads that bears and obtain.In order to characterize and compare the stressing conditions of electric wire, usually carry out the Mechanics Calculation of electric wire with the value on unit section.The tension force that unit section acts on can be called stress (σ), unit is N/mm ²or MPa; The load that electric wire unit length, unit section bear is called than carrying (g), unit N/mm ²m or MPa/m represents.In icing situation, the vertical ratio of electric wire carries (g _v) comprise wire and carry (g from anharmonic ratio _v1) and an icing ratio year (g _v2):

$g_v=g_{v1}+g_{v2}=\frac{q{g}_n}{A}+\frac{0.9\mathrm{\π}{g}_{n}b(b+D)\×{10}^{-3}}{A}---\left(1\right)$

Wherein, q is electric wire linear mass (kg/m); g _nfor acceleration of gravity (N/kg); A is the long-pending (mm of wire cross-sectional ²); B is ice covering thickness (mm); D is wire external diameter (mm).Electric wire level is than carrying (g _h) be:

$g_h=\frac{(D+2b)W_o\mathrm{\α}{\mathrm{\μ}}_{\mathrm{sc}}{\mathrm{\μ}}_z{\mathrm{\μ}}_{\mathrm{\θ}}\×{10}^{-3}}{A}---\left(2\right)$

Wherein, W _ofor benchmark blast standard value; α is wind evil attacking lung; μ _scfor electric wire Shape Coefficient; μ _zfor height variation coefficient of wind pressure; μ _θfor the variation factor of blast box haul.When having ice to have wind, the comprehensive ratio of electric wire carries g and is: the axial stress σ of electric wire any point C _x(N/mm ²) and this to the relational expression between the minimum point discrepancy in elevation be:

σ _x=σ ₀+g(y-y ₀) （3）

Wherein, σ ₀for the horizontal stress of electric wire lowest part, y and y ₀be respectively the ordinate value (m) at electric wire C point and O point place.From above formula, on the point that electric wire relative height is higher in same shelves, its axial stress is larger.Therefore, we must be contained in the higher place of line of electric force relative position when installation tension sensor.

With reference to Fig. 2: in theory, in unit area, water yield horizontal direction dropped on line of electric force is: w _h=VWt, wherein the V Liquid water content (g/m that to be wind speed (m/s), W be in air ³), t is rain time (s); Water yield vertical direction dropped on line of electric force is: w _v=P ρ ₀t, wherein P is rainfall intensity (mm/h), ρ ₀the density (g/cm of water ³), t is rain time (s).The total precipitation then in line of electric force unit area is:

$w=\mathrm{\γ\β}\sqrt{{w_v}^2+{w_h}^2}=\mathrm{\γ\βt}\sqrt{{\left(\mathrm{VW}\right)}^2+{\left(P{\mathrm{\ρ}}_0\right)}^2}---\left(4\right)$

Wherein γ is collision coefficient (0< γ≤1), and β is the freezing fraction (0< β≤1) that rainfall becomes icing.Consider in actual environment, the temperature forming icing is lower, and the reasons such as rain speed is less, we get γ=1 and β=1.

As shown in Figure 2, the cross section of line of electric force is circle, and we suppose that ice evenly overlays on line of electric force surface.If the radius of moment i line of electric force (containing ice) is r _i, can be obtained by mass conservation theorem:

$2r_i\&CenterDot;\mathrm{\&gamma;\&beta;t}\sqrt{{\left(\mathrm{VW}\right)}^2+{\left(P{\mathrm{\&rho;}}_0\right)}^2}={\mathrm{\&rho;}}_i({{\mathrm{\&pi;r}}_{i+1}}^2-{{\mathrm{\&pi;r}}_i}^2)---\left(5\right)$

Wherein ρ _ithe density of this place's icing.Above formula abbreviation is obtained

$2r_{i}t\sqrt{{\left(\mathrm{VW}\right)}^2+{\left(P{\mathrm{\&rho;}}_0\right)}^2}={\mathrm{\&rho;}}_i\mathrm{\&pi;}(r_{i+1}+r_i)(r_{i+1}-r_i)$

$\&ap;2r_i{\mathrm{\&rho;}}_i\&CenterDot;\mathrm{\&Delta;r}---\left(6\right)$

Further displacement abbreviation can obtain ice covering thickness

$\mathrm{\&Delta;r}=\frac{t\sqrt{{\left(\mathrm{VW}\right)}^2+{\left(P{\mathrm{\&rho;}}_0\right)}^2}}{{\mathrm{\&rho;}}_i\mathrm{\&pi;}}---\left(7\right)$

By BEST(1949) model obtains the relation of Liquid water content and rainfall intensity, W=aP ^b, wherein a, b are constants.Rainfall intensity P and humidity change by below.

In certain hour, P meets following relation:

$P=\frac{1}{\mathrm{\&rho;g}}{\&Integral;}_0^{p_{z_0}}\mathrm{qdp}---\left(8\right)$

Wherein, q is specific humidity, and p is air pressure (MPa), ρ is aqueous water density (g/cm ³), g is acceleration of gravity (m/s ²), for surface pressure (MPa).

In actual applications, specific humidity is usually according to vapour pressure e(hPa) to calculate, it with the pass of vapour pressure is:

$q=\frac{\mathrm{\&epsiv;e}}{p-(1-\mathrm{\&epsiv;})e}---\left(9\right)$

In formula, μ _v, μ _dbe respectively the average molar mass of steam and dry air.Obtain ε=0.622 as calculated.

The humidity value adopting humidity sensor to obtain in the present invention is a relative humidity, and its expression formula is:

$f=\frac{e}{E}\&times;100\%---\left(10\right)$

Wherein E is the saturation vapour pressure (hPa) under same temperature, obtains by tabling look-up.

In conjunction with formula (7)-(10), finally obtain the expression formula of ice covering thickness Δ r about time t, temperature T, wind speed V and air pressure p:

Δr=f(t,T,V,p) （11）

Be converted into differential form

dr=f(t,T,V,p)dt （12）

Both sides integration, can obtain t _ithe ice covering thickness in moment

$b={\&Integral;}_0^{t_i}f(t,T,V,p)\mathrm{dt}---\left(13\right)$

With reference to Fig. 3: the ratio of wire carries computation process.

1. wire carries g from anharmonic ratio ₁(N/ (mmm ²))

Carrying from anharmonic ratio is that the ratio that overhead line conductor own wt causes carries, and is calculated as follows:

$g_1=\frac{\mathrm{gq}}{A}---\left(14\right)$

Wherein g is acceleration of gravity, and q is unit linear mass (kg/m), A is wire sectional area (mm ²).

2. the ice anharmonic ratio of wire carries g ₂(N/ (mmm ²))

Wire that icing quality on wire causes is than carrying (N/ (the mmm that is called that ice anharmonic ratio is carried ²)), use symbol g ₂represent, get the ice coating wire analysis that 1m is long, at this moment the volume V of icing cylinder is

V=π(r ₀+b) ²-πr ₀ ²=πb(2r ₀+b)×10 ^-6（15）

Then ice anharmonic ratio is carried and is

$g_2=\frac{\mathrm{g\&rho;V}}{A\&times;1}=\frac{\mathrm{g\&rho;\&pi;b}(2r_0+b)\&times;{10}^{-3}}{A}---\left(16\right)$

To sum up, when having wind to have ice, wire is vertical always than year being

$g_3=g_1+g_2=\frac{\mathrm{gq}}{A}+\frac{\mathrm{g\&rho;\&pi;b}(2r_0+b)\&times;{10}^{-3}}{A}---\left(17\right)$

3. the level of wire is than carrying g ₄(N/ (mmm ²))

It is that the wire ratio that Action of Wind pressure suffered by guide line causes carries that the level ratio of wire carries, because general wind action direction is in surface level, therefore wind pressure ratio is carried the level ratio being called wire and carries.The formation of blast is the pressure that air flowing kinetic energy produces in wire adverse wind face.

At temperature 15 ° of C, when pressure is 0.101325MPa, the density of dry air is 1.2255kg/m ³, then 1m ³the kinetic energy (being also velocity head) of air is

$q=\frac{1}{2}m{V}^2=0.6128V^2---\left(18\right)$

Wherein V is wind speed (m/s), and q is velocity head, and m is 1m ³the quality of air.

Velocity head i.e. aerodynamic energy act on " theoretic wind pressure " on unit area windward side.During icing, the facing the wind diameter of wire is 2r ₀+ 2b, by formula (18) wind pressure ratio is carried and is

$g_4=0.6128K_z\mathrm{\&alpha;C}(2r_0+2b)\frac{V^2}{A}\&times;{10}^{-3}$

$=1.2256K_z\mathrm{\&alpha;C}(r_0+b)\frac{V^2}{A}\&times;{10}^{-3}---\left(19\right)$

Wherein K _zbe height variation coefficient of wind pressure, α is uneven factor of wind speed, and C is wind load configure coefficient (during icing, C=1.2).

4. the comprehensive ratio of wire carries g ₅(N/ (mmm ²))

The comprehensive ratio of wire carries, and is that the level of guide line is than carrying and the vertical vector than carrying.Its expression formula is

$g_5=\sqrt{{g_3}^2+{g_4}^2}---\left(20\right)$

With reference to Fig. 4: As time goes on, ice covering thickness increases gradually, and the comprehensive ratio of wire carries and increases gradually, and the axial tension stress of its any point also increases thereupon, overall in rising trend.The maximal value that meets with stresses of wire remains unchanged, and is worth for σ _max.When the axial stress curve of wire rises gradually, and σ _maxwhen intersecting, illustrate that now wire has reached the maximal value that wire can bear due to axial stress that wire deadweight adds icing impact, wire will rupture.And t _iexactly from icing monitoring to wire fracture excess time, and t ₀it is the moment that system sends early warning.

Claims (1)

1. based on a powerline ice-covering Forecasting Methodology for multi-element physical quantity mathematical model, it is characterized in that: described Forecasting Methodology comprises the steps:

(1) Temperature Humidity Sensor, wind sensor is adopted to obtain humiture and the wind-force meteorologic parameter of current time;

(2) judge whether current each weather data meets icing condition respectively, that is: temperature-8 ~ 0 DEG C, more than humidity 90%RH, wind speed 2 ~ 7m/s, if satisfy condition, forward to (3), otherwise enter the sampling period next time, namely turn back to (1);

(3) data value obtained by tension pick-up and initial value are compared, if illustrate that wire has icing, forward step (4) to, otherwise turn back to (1);

(4) obtain current environment atmospheric pressure value by ground based terminal, calculate ice covering thickness r, computing formula is as follows:

$r={\&Integral;}_0^{t_i}f(t,T,V,p)\mathrm{dt}---\left(13\right)$

Unit ice covering thickness Δ r is expressed as:

$\mathrm{\&Delta;r}=\frac{t\sqrt{{\left(\mathrm{VW}\right)}^2+{\left({\mathrm{P\&rho;}}_0\right)}^2}}{{\mathrm{\&rho;}}_i\mathrm{\&pi;}}---\left(7\right)$

Wherein, V is wind speed, and the unit Liquid water content that to be m/s, W be in air, unit is g/m ³, P is rainfall intensity, and unit is mm/h, ρ ₀be the density of water, unit is g/cm ³, ρ _ibe the density of this place's icing, unit is g/cm ³, t is rain time, and unit is s; Need constituent parts to be converted into SI units when concrete operation, so the unit of result of calculation Δ r is m;

W=aP ^b, wherein a, b are constants, and rainfall intensity P and humidity are changed, P meets following relation:

$P=\frac{1}{{\mathrm{\&rho;}}_{0}g}{\&Integral;}_0^{p_{z_0}}\mathrm{qdp}---\left(8\right)$

Wherein, q is specific humidity, and p is air pressure, and unit is MPa, ρ ₀be the density of water, unit is g/cm ³, g is acceleration of gravity, and unit is m/s ², for surface pressure, unit is MPa;

Specific humidity q is according to vapour pressure e, and unit is that hPa calculates, and it with the pass of vapour pressure is:

$q=\frac{\mathrm{\&epsiv;e}}{p-(1-\mathrm{\&epsiv;})e}---\left(9\right)$

In formula, μ _v, μ _dbe respectively the average molar mass of steam and dry air;

The humidity value adopting humidity sensor to obtain is a relative humidity, and its expression formula is:

$f=\frac{e}{E}\&times;100\%---\left(10\right)$

Wherein, E is the saturation vapour pressure under same temperature, and unit is hPa;

In conjunction with formula (7)-(10), obtain the expression formula of unit ice covering thickness Δ r about time t, temperature T, wind speed V and air pressure p:

Δr＝f(t,T,V,p) (11)

Formula (11) is converted into differential form, and both sides integration can obtain formula (13);

(5) any time t is calculated by ice covering thickness and humiture _ithe comprehensive ratio of wire carries g ₅, computing formula is:

$g_5=\sqrt{{g_3}^2+{g_4}^2}---\left(20\right)$

Wherein, g ₄for level is than carrying, g ₃for vertically than carry;

$g_3=g_1+g_2=\frac{\mathrm{gw}}{A}+\frac{{\mathrm{g\&rho;}}_i\mathrm{\&pi;b}({2r}_0+b)\&times;{10}^{-3}}{A}---\left(17\right)$

Wherein, g ₁for wire is than carrying, g ₂for icing is than carrying, g is acceleration of gravity, and w is the linear mass before wire icing, and unit is kg/m, ρ _ibe the density of this place's icing, unit is g/cm ³, r ₀for the radius of wire, unit is mm, A is wire sectional area, and unit is mm ²;

$\begin{array}{c}{g}_4=0.6128K_z\mathrm{\&alpha;C}({2r}_0+2b)\frac{V_2}{A}\&times;{10}^{-3}\\ =1.2256K_z\mathrm{\&alpha;C}(r_0+b)\frac{V^2}{A}\&times;{10}^{-3}\end{array}---\left(19\right)$

Wherein, K _zbe height variation coefficient of wind pressure, α is uneven factor of wind speed, and C is wind load configure coefficient;

(6) pass through comprehensively than carrying a g ₅obtain the axial stress σ at line of electric force span end points place _x, make σ _x=σ _max, calculate break off remnant time t, and send early warning signal.