CN102735487A - Detection method for reliability of 500kV four-circuit transmission towers on same tower - Google Patents

Abstract

The invention discloses a detection method for reliability of 500kV four-circuit transmission towers on the same tower, which comprises the following steps: taking a maximum value of a wind load as a variable load and taking a sum of dead loads of power transmission towers and a ground lead as a permanent load; calculating a ratio of a wind resultant force of tower bodies of the power transmission towers to a wind load of the ground lead, action points of various related loads and important factors of an iron tower root opening and closing structure, thereby obtaining the ratio of a variable load effect to a permanent load effect of the power transmission tower components; adopting a first-order secondary moment method for taking a non-normal basic random variable as an equivalent for performing normalizing treatment and converting the non-normal basic random variable into an equivalent normal random variable; and calculating a reliability index and a failure probability of the 500kV four-circuit transmission towers on the same tower. According to the detection method provided by the invention, the safe reliability of line engineering and the correctness of engineering construction are effectively and accurately demonstrated; the calculation for the reliability index and the failure probability of the 500kV four-circuit transmission towers on the same tower is very accurate; and the technical problem of the prior art is excellently solved.

Description

500kV is with the detection method of four times electric transmission pole tower fiduciary levels of tower

Technical field

The present invention relates to the transmission line structure field, particularly relate to the detection method of a kind of 500kV with four times electric transmission pole tower fiduciary levels of tower.

Background technology

Most important with many back transmission lines of tower reliability index and failure probability to the security of transmission line of electricity, at present, be applied to the detection of four times electric transmission pole towers of tower and research seldom with tower many times electric transmission pole towers, especially 500kV for Reliability Theory.And for 500kV with tower four loop line roads; Its engineering itself just has major and immediate significance to society; Therefore, just seem extremely urgent for the reliability assessment of line project, for the electric power enterprise owner, for the vast social common people; How to prove the safety reliability of line project, just it becomes problem demanding prompt solution to prove the correctness of engineering construction.In the face of such realistic problem, for reliability index and the CALCULATION OF FAILURE PROBABILITY of 500kV, just become inevitable problem with tower four feedback electric pole towers, also be key one ring of Engineering Reliability demonstration, and do not have as yet to this way to solve the problem at present.

Summary of the invention

Based on this,, be necessary to propose the detection method of a kind of 500kV with four times electric transmission pole tower fiduciary levels of tower to the problems referred to above.

Technical scheme of the present invention is: a kind of 500kV may further comprise the steps with the detection method of four times electric transmission pole tower fiduciary levels of tower:

The maximal value of getting wind load is a variable load, and getting electric transmission pole tower and lead wire and earth wire deadweight sum is permanent load;

Calculate electric transmission pole tower body of the tower wind and open and coefficient for importance of structure with the ratio of lead wire and earth wire wind load, various relevant load point, iron tower root with joint efforts, draw the ratio of electric transmission pole tower member variable load effect and permanent load effect;

The utilization FOSM carries out normalize to the abnormal basic random variables as equivalent and handles, and is converted into equivalent normal random variable, calculates reliability index and the failure probability of 500kV with four times electric transmission pole towers of tower.

The 500kV that the present technique scheme proposes is with the computation model of the detection method of the fiduciary level of tower four circuit pole tower; Be similar to and think that the maximal value of big wind load is variable load; Permanent load is then got shaft tower and lead wire and earth wire deadweight sum, with reference to the body of the tower wind of this tower ratio with the lead wire and earth wire wind load of making a concerted effort, the application point of various relevant loads; The iron tower root is opened; Information such as coefficient for importance of structure draw the ratio of shaft tower member variable load and permanent load effect, and then use FOSM to calculate reliability index and the failure probability of 500kV with tower four circuit pole tower.

Among embodiment, further comprising the steps of therein:

Outside variable load and permanent load parameter are simulated, press the power function of the electric transmission pole tower structural elements of existing rules design, the structure function function that draws member is: g (R, S _G, S _Q)=R-S _G-S _Q

Draw the statistical parameter of basic random variables in conjunction with " Unified standard for design of building structures ", specific as follows:

K _R=1.14, V _R=0.12, the R obeys logarithm normal distribution,

K _G=1.06, V _G=0.07, S _GNormal Distribution,

K _Q=1.00, V _Q=0.193, S _QObey extreme value I type and distribute,

In the formula: K _R=μ _R/ R _K, $K_{S_G}={\mathrm{\μ}}_{S_T}/S_{\mathrm{GK}},$ $K_Q={\mathrm{\μ}}_{S_Q}/S_{\mathrm{QK}},$

V _R=σ _R/μ _R， $V_G={\mathrm{\σ}}_{S_G}/{\mathrm{\μ}}_{S_G},$ $V_Q={\mathrm{\σ}}_{S_G}/{\mathrm{\μ}}_{S_G},$

μ _R,

Be respectively R, S _G, S _QAverage,

σ _R,

Be respectively R, S _G, S _QMean square deviation;

Drawn by above formula, the parameter relevant with fiduciary level comprises the ratio of variable load effect and permanent load effect, ratio, coefficient for importance of structure, minimal design wind speed and the wind load reoccurrence period that lines wind load effect accounts for the wind load gross effect.

Among embodiment, further comprising the steps of therein:

With the data point of worst each stochastic variable of structure as structural design checking computations point;

Setting checking computations point coordinate

are located the abnormal variable and are equated have with the distribution function value and the distribution density function value of its equivalent normal variate:

$F_{X_I}\left(x_i^{*}\right)=\mathrm{\Φ}\left\{\frac{x_i^{*}-{{\mathrm{\μ}}^{\′}}_{X_i}}{{{\mathrm{\σ}}^{\′}}_{X_i}}\right\}---(3-1)$

In the formula

Ф () representes standardized normal distribution density function and distribution function respectively,

Represent the abnormal variable X respectively _iDistribution density function and distribution function,

Represent equivalent normal variate X ' _iAverage, variance, below on be designated as *'s

All represent the value of variable at design computation point place.Try to achieve equivalent normal variate X ' by formula (3-1), (3-2) _iAverage, mean square deviation be:

In the formula: Ф ^-1The inverse function of () expression Standard Normal Distribution.

Among embodiment, further comprising the steps of therein:

A. supposition

Get

To shaft tower member function function: x ₁=R, x ₂=S _G, x ₃=S _Q

B. to the abnormal variable X _i, according to Ask equivalent normal variate by formula (3-3), (3-4) And use Substitute

If drag R is a lognormal distribution in the shaft tower member function function, employing formula (3-3), (3-4) get average, the mean square deviation of its equivalent normal variate:

σ′ _R=r ^*σ _lnR （4-1）

μ′ _R=r ^*(1-lnr ^*+μ _lnR) （4-2）

Wherein: ${\mathrm{\σ}}_{\mathrm{Ln}R}=\sqrt{\mathrm{Ln}[1+{\left(\frac{{\mathrm{\σ}}_R}{{\mathrm{\μ}}_R}\right)}^2]},$

${\mathrm{\μ}}_{\ln R}=\ln \frac{{\mathrm{\μ}}_R}{\sqrt{1+{\left(\frac{{\mathrm{\σ}}_R}{{\mathrm{\μ}}_R}\right)}^2}}$

Variable load effect S in the shaft tower member function function _QObey extreme value I type and distribute, be respectively at design computation point its distribution function of place and probability density function value:

$F_{S_Q}=\left(S_Q^{*}\right)=\exp \{-\exp [-a(S_Q^{*}-k)\left]\right\}---(4-3)$

$f_{S_Q}\left(S_Q^{*}\right)=\mathrm{aexp}\{-a(S_Q^{*}-k)-\exp [-a(S_Q^{*}-k)\left]\right\}---(4-4)$

Wherein: $a=\frac{1.2825}{{\mathrm{\σ}}_{S_Q}},$ $k={\mathrm{\μ}}_{S_Q}-\frac{0.5772}{a}$

Formula (4-3), (4-4) substitution formula (3-3), (3-4) can be got

C. ask the direction cosine of ultimate limit state face each coordinate in the standard normal coordinate system, computing formula is following:

${\cos \mathrm{\θ}}_{X_i}=\frac{{-\frac{\∂g}{{\∂X}_i}|}_{P^{*}}{\mathrm{\σ}}_{X_i}}{{\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\left(\frac{\∂g}{{\∂X}_i}\right){|}_{P^{*}}{{\mathrm{\σ}}_{X_i})}^2\right]}^{1/2}};$

In the formula, P ^*Be the design computation point;

D. try to achieve reliability index β by limit state equation:

$\mathrm{\β}=\frac{{\mathrm{\μ}}_g}{{\mathrm{\σ}}_g}\frac{g(x_1^{*},\·\·\·,x_n^{*})+{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\frac{\∂g}{{\∂X}_i}|}_{P^{*}}({\mathrm{\μ}}_{X_i}-x_i^{*})}{{\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\left(\frac{\∂g}{{\∂X}_i}\right){|}_{P^{*}}{{\mathrm{\σ}}_{X_i})}^2\right]}^{1/2}};$

E. the checking computations point that utilizes the β tried to achieve and direction cosine to look for novelty

$x_i^{*}={\mathrm{\μ}}_{X_i}+{\mathrm{\σ}}_{X_i}\mathrm{\β}\cos {\mathrm{\θ}}_{X_i};$

F. with new

repeating step b～e, the difference of the β value that twice is calculated up to front and back is less than permissible error.

Among embodiment, among the step f, the numerical value of setting permissible error is 0.01 therein, and promptly the difference of β value is less than 0.01.

The invention has the beneficial effects as follows: can effectively accurately prove the safety reliability of line project and prove the correctness of engineering construction; Feed back the reliability index and the CALCULATION OF FAILURE PROBABILITY of electric pole tower with tower four for 500kV; Very accurate, solved of the prior art one big technical barrier well.

Embodiment

Be elaborated in the face of embodiments of the invention down.

Embodiment:

A kind of 500kV is with the detection method of four times electric transmission pole tower fiduciary levels of tower, and at first, the maximal value of getting wind load is a variable load, and getting electric transmission pole tower and lead wire and earth wire deadweight sum is permanent load.Secondly, calculate electric transmission pole tower body of the tower wind and open and coefficient for importance of structure with the ratio of lead wire and earth wire wind load, various relevant load point, iron tower root with joint efforts, draw the ratio of electric transmission pole tower member variable load effect and permanent load effect.Once more, the utilization FOSM carries out normalize to the abnormal basic random variables as equivalent and handles, and is converted into equivalent normal random variable, calculates reliability index and the failure probability of 500kV with four times electric transmission pole towers of tower.

Specifically may further comprise the steps:

Step 1, by the power function of the electric transmission pole tower structural elements of existing rules design, the structure function function that draws member is: g (R, S _G, S _Q)=R-S _G-S _Q

By the power function of the tower structure member of existing rules design, be by the ultimate limit states Design Expression formula of partial safety factor method member:

γ ₀(γ _GS _GK+γ _QS _QK)≤R _K/γ _R （1-1）

In the formula: γ ₀---coefficient for importance of structure;

γ _G, γ _Q, γ _R---be respectively permanent load, variable load and member partial safety factor for resistance, tower structure is taken as 1.2,1.4,1.113 respectively;

S _GK, S _QK, R _K---permanent load effect standard value, variable load effect standard value and member drag standard value.

Get by formula (1-1),

R _K=γ ₀·γ _R(γ _GS _GK+γ _QS _QK) （1-2）

The structure function function of member is:

g(R,S _G,S _Q)=R-S _G-S _Q （1-3）

Step 2 draws the statistical parameter of basic random variables in conjunction with " Unified standard for design of building structures ", and is specific as follows:

K _R=1.14, V _R=0.12, the R obeys logarithm normal distribution,

K _G=1.06, V _G=0.07, S _GNormal Distribution,

K _Q=1.00, V _Q=0.193, S _QObey extreme value I type and distribute,

In the formula: K _R=μ _R/ R _K, $K_{S_G}={\mathrm{\μ}}_{S_T}/S_{\mathrm{GK}},$ $K_Q={\mathrm{\μ}}_{S_Q}/S_{\mathrm{QK}},$

V _R=σ _R/μ _R， $V_Q={\mathrm{\σ}}_{S_G}/{\mathrm{\μ}}_{S_G},$ $V_Q={\mathrm{\σ}}_{S_G}/{\mathrm{\μ}}_{S_G},$

μ _R,

Be respectively R, S _G, S _QAverage,

σ _R, Be respectively R, S _G, S _QMean square deviation.

Step 3, with the data point of worst each stochastic variable of structure as structural design checking computations point.To the data point of worst each stochastic variable of structure, be called structural design checking computations point.In the structural limits state equation each basic random variables at design computation point place value, the structural failure probability is maximum.The structural failure probability is main relevant at the tail area of design computation point with each basic random variables distribution density function.It is constant to guarantee that the abnormal basic random variables converts the structural failure probability of calculating after the normal random variable into, need to guarantee after the conversion each basic random variables the tail area of design computation point punishment cloth density function with change before equate.Produce equivalent normalize switch condition thus.

Step 4; Setting checking computations point coordinate are located the abnormal variable and are equated have with the distribution function value and the distribution density function value of its equivalent normal variate:

$F_{X_I}\left(x_i^{*}\right)=\mathrm{\Φ}\left\{\frac{x_i^{*}-{{\mathrm{\μ}}^{\′}}_{X_i}}{{{\mathrm{\σ}}^{\′}}_{X_i}}\right\}---(3-1)$

In the formula

Ф () representes standardized normal distribution density function and distribution function respectively,

Represent the abnormal variable X respectively _iDistribution density function and distribution function,

Represent equivalent normal variate X ' _iAverage, variance, below on be designated as *'s

All represent the value of variable at design computation point place.Try to achieve equivalent normal variate X ' by formula (3-1), (3-2) _iAverage, mean square deviation be:

In the formula: Ф ^-1The inverse function of () expression Standard Normal Distribution.

Step 5 is supposed

Get

To shaft tower member function function: x ₁=R, x ₂=S _G, x ₃=S _Q

Step 6 is to the abnormal variable X _i, according to

Ask equivalent normal variate by formula (3-3), (3-4)

And use

Substitute

If drag R is a lognormal distribution in the shaft tower member function function, employing formula (3-3), (3-4) get average, the mean square deviation of its equivalent normal variate:

σ′ _R=r ^*σ _lnR （4-1）

μ′ _R=r ^*(1-lnr ^*+μ _lnR) （4-2）

Wherein: ${\mathrm{\σ}}_{\mathrm{Ln}R}=\sqrt{\mathrm{Ln}[1+{\left(\frac{{\mathrm{\σ}}_R}{{\mathrm{\μ}}_R}\right)}^2]},$

${\mathrm{\μ}}_{\ln R}=\ln \frac{{\mathrm{\μ}}_R}{\sqrt{1+{\left(\frac{{\mathrm{\σ}}_R}{{\mathrm{\μ}}_R}\right)}^2}}$

Variable load effect S in the shaft tower member function function _QObey extreme value I type and distribute, be respectively at design computation point its distribution function of place and probability density function value:

$F_{S_Q}=\left(S_Q^{*}\right)=\exp \{-\exp [-a(S_Q^{*}-k)\left]\right\}---(4-3)$

$f_{S_Q}\left(S_Q^{*}\right)=\mathrm{aexp}\{-a(S_Q^{*}-k)-\exp [-a(S_Q^{*}-k)\left]\right\}---(4-4)$

Wherein: $a=\frac{1.2825}{{\mathrm{\σ}}_{S_Q}},$ $k={\mathrm{\μ}}_{S_Q}-\frac{0.5772}{a}$

Formula (4-3), (4-4) substitution formula (3-3), (3-4) can be got

Step 7 is asked the direction cosine of ultimate limit state face each coordinate in the standard normal coordinate system, and computing formula is following:

${\cos \mathrm{\θ}}_{X_i}=\frac{{-\frac{\∂g}{{\∂X}_i}|}_{P^{*}}{\mathrm{\σ}}_{X_i}}{{\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\left(\frac{\∂g}{{\∂X}_i}\right){|}_{P^{*}}{{\mathrm{\σ}}_{X_i})}^2\right]}^{1/2}}$

In the formula, P ^*Be the design computation point;

Step 8, try to achieve reliability index β by limit state equation:

$\mathrm{\β}=\frac{{\mathrm{\μ}}_g}{{\mathrm{\σ}}_g}\frac{g(x_1^{*},\·\·\·,x_n^{*})+{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\frac{\∂g}{{\∂X}_i}|}_{P^{*}}({\mathrm{\μ}}_{X_i}-x_i^{*})}{{\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\left(\frac{\∂g}{{\∂X}_i}\right){|}_{P^{*}}{{\mathrm{\σ}}_{X_i})}^2\right]}^{1/2}}$

Step 9, the checking computations point

that β that utilization has been tried to achieve and direction cosine are looked for novelty

$x_i^{*}={\mathrm{\μ}}_{X_i}+{\mathrm{\σ}}_{X_i}\mathrm{\β}\cos {\mathrm{\θ}}_{X_i};$

Step 10; To step 9, the difference of the β value that twice is calculated up to front and back is less than permissible error with new

repeating step six.The numerical value of setting permissible error is 0.01, and promptly the difference of β value is less than 0.01.

The 500kV that the present invention proposes is with the computation model of the detection method of the fiduciary level of tower four circuit pole tower; Be similar to and think that the maximal value of big wind load is variable load; Permanent load is then got shaft tower and lead wire and earth wire deadweight sum, with reference to the body of the tower wind of this tower ratio with the lead wire and earth wire wind load of making a concerted effort, the application point of various relevant loads; The iron tower root is opened; Information such as coefficient for importance of structure draw the ratio of shaft tower member variable load and permanent load effect, and then use FOSM to calculate reliability index and the failure probability of 500kV with tower four circuit pole tower.

The above embodiment has only expressed embodiment of the present invention, and it describes comparatively concrete and detailed, but can not therefore be interpreted as the restriction to claim of the present invention.Should be pointed out that for the person of ordinary skill of the art under the prerequisite that does not break away from the present invention's design, can also make some distortion and improvement, these all belong to protection scope of the present invention.

Claims (5)

1. a 500kV is characterized in that with the detection method of four times electric transmission pole tower fiduciary levels of tower, may further comprise the steps:

The maximal value of getting wind load is a variable load, and getting electric transmission pole tower and lead wire and earth wire deadweight sum is permanent load;

Calculate electric transmission pole tower body of the tower wind and open and coefficient for importance of structure with the ratio of lead wire and earth wire wind load, various relevant load point, iron tower root with joint efforts, draw the ratio of electric transmission pole tower member variable load effect and permanent load effect;

The utilization FOSM carries out normalize to the abnormal basic random variables as equivalent and handles, and is converted into equivalent normal random variable, calculates reliability index and the failure probability of 500kV with four times electric transmission pole towers of tower.

2. 500kV according to claim 1 is characterized in that with the detection method of four times electric transmission pole tower fiduciary levels of tower, and is further comprising the steps of:

Outside variable load and permanent load parameter are simulated, press the power function of the electric transmission pole tower structural elements of existing rules design, the structure function function that draws member is: g (R, S _G, S _Q)=R-S _G-S _Q

Draw the statistical parameter of basic random variables in conjunction with " Unified standard for design of building structures ", specific as follows:

K _R=1.14, V _R=0.12, the R obeys logarithm normal distribution,

K _G=1.06, V _G=0.07, S _GNormal Distribution,

K _Q=1.00, V _Q=0.193, S _QObey extreme value I type and distribute,

In the formula: K _R=μ _R/ R _K, $K_{S_G}={\mathrm{\μ}}_{S_T}/S_{\mathrm{GK}},$ $K_Q={\mathrm{\μ}}_{S_Q}/S_{\mathrm{QK}},$

V _R=σ _R/μ _R， $V_Q={\mathrm{\σ}}_{S_G}/{\mathrm{\μ}}_{S_G},$ $V_Q={\mathrm{\σ}}_{S_G}/{\mathrm{\μ}}_{S_G},$

μ _R, Be respectively R, S _G, S _QAverage,

σ _R,

Be respectively R, S _G, S _QMean square deviation;

Drawn by above formula, the parameter relevant with fiduciary level comprises the ratio of variable load effect and permanent load effect, ratio, coefficient for importance of structure, minimal design wind speed and the wind load reoccurrence period that lines wind load effect accounts for the wind load gross effect.

3. 500kV according to claim 1 and 2 is characterized in that with the detection method of four times electric transmission pole tower fiduciary levels of tower, and is further comprising the steps of:

With the data point of worst each stochastic variable of structure as structural design checking computations point;

Setting checking computations point coordinate

are located the abnormal variable and are equated have with the distribution function value and the distribution density function value of its equivalent normal variate:

$F_{X_I}\left(x_i^{*}\right)=\mathrm{\Φ}\left\{\frac{x_i^{*}-{{\mathrm{\μ}}^{\′}}_{X_i}}{{{\mathrm{\σ}}^{\′}}_{X_i}}\right\}---(3-1)$

In the formula Ф () representes standardized normal distribution density function and distribution function respectively, Represent the abnormal variable X respectively _iDistribution density function and distribution function,

Represent equivalent normal variate X ' _iAverage, variance, below on be designated as *'s

All represent the value of variable at design computation point place.Try to achieve equivalent normal variate X ' by formula (3-1), (3-2) _iAverage, mean square deviation be:

In the formula: Ф ^-1The inverse function of () expression Standard Normal Distribution.

4. 500kV according to claim 3 is characterized in that with the detection method of four times electric transmission pole tower fiduciary levels of tower, and is further comprising the steps of:

A. supposition

Get

To shaft tower member function function: x ₁=R, x ₂=S _G, x ₃=S _Q

B. to the abnormal variable X _i, according to

Ask equivalent normal variate by formula (3-3), (3-4) And use

Substitute

If drag R is a lognormal distribution in the shaft tower member function function, employing formula (3-3), (3-4) get average, the mean square deviation of its equivalent normal variate:

σ′ _R=r ^*σ _lnR （4-1）

μ′ _R=r ^*(1-lnr ^*+μ _lnR) （4-2）

Wherein: ${\mathrm{\σ}}_{\mathrm{Ln}R}=\sqrt{\mathrm{Ln}[1+{\left(\frac{{\mathrm{\σ}}_R}{{\mathrm{\μ}}_R}\right)}^2]},$

${\mathrm{\μ}}_{\ln R}=\ln \frac{{\mathrm{\μ}}_R}{\sqrt{1+{\left(\frac{{\mathrm{\σ}}_R}{{\mathrm{\μ}}_R}\right)}^2}}$

Variable load effect S in the shaft tower member function function _QObey extreme value I type and distribute, be respectively at design computation point its distribution function of place and probability density function value:

$f_{S_Q}\left(S_Q^{*}\right)=\exp \{-\exp [-a(S_Q^{*}-k)\left]\right\}---(4-3)$

$f_{S_Q}\left(S_Q^{*}\right)=\mathrm{aexp}\{-a(S_Q^{*}-k)-\exp [-a(S_Q^{*}-k)\left]\right\}---(4-4)$

Wherein: $a=\frac{1.2825}{{\mathrm{\σ}}_{S_Q}},$ $k={\mathrm{\μ}}_{S_Q}-\frac{0.5772}{a}$

Formula (4-3), (4-4) substitution formula (3-3), (3-4) can be got

C. ask the direction cosine of ultimate limit state face each coordinate in the standard normal coordinate system, computing formula is following:

${\cos \mathrm{\θ}}_{X_i}=\frac{{-\frac{\∂g}{{\∂X}_i}|}_{P^{*}}{\mathrm{\σ}}_{X_i}}{{\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\left(\frac{\∂g}{{\∂X}_i}\right){|}_{P^{*}}{{\mathrm{\σ}}_{X_i})}^2\right]}^{1/2}};$

In the formula, P ^*Be the design computation point;

D. try to achieve reliability index β by limit state equation:

$\mathrm{\β}=\frac{{\mathrm{\μ}}_g}{{\mathrm{\σ}}_g}\frac{g(x_1^{*},\·\·\·,x_n^{*})+{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\frac{\∂g}{{\∂X}_i}|}_{P^{*}}({\mathrm{\μ}}_{X_i}-x_i^{*})}{{\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\left(\frac{\∂g}{{\∂X}_i}\right){|}_{P^{*}}{{\mathrm{\σ}}_{X_i})}^2\right]}^{1/2}};$

E. the checking computations point

that utilizes the β tried to achieve and direction cosine to look for novelty

$x_i^{*}={\mathrm{\μ}}_{X_i}+{\mathrm{\σ}}_{X_i}\mathrm{\β}\cos {\mathrm{\θ}}_{X_i};$

F. with new

repeating step b～e, the difference of the β value that twice is calculated up to front and back is less than permissible error.

5. 500kV according to claim 4 is characterized in that with the detection method of four times electric transmission pole tower fiduciary levels of tower among the step f, the numerical value of setting permissible error is 0.01, and promptly the difference of β value is less than 0.01.