CN104517241A - Risk evaluation method based on power transmission line full-working-condition information - Google Patents

Abstract

The invention discloses a risk evaluation method based on power transmission line full-working-condition information. The risk evaluation method includes building a power transmission line risk evaluation model for a part; determining a mode for modifying power transmission line risk by factors like running period of the part, running environment of line and power grid state; utilizing a statistical method to quantify risk state quantity to be risk degree, and acquiring a risk value of the part through a membership model acquired by defect and fault data; sequentially modifying period coefficient, running environment coefficient and power grid state coefficient to acquire an overall risk value of the power transmission line, and performing aided decision making on the line according to evaluation result. Full-working-condition information like historical fault defect information, online monitoring and manual patrolling data, equipment ledger, line working environment data and power grid running state is taken into consideration comprehensively, so that the risk evaluation method is comprehensive and has guiding significance in operation and maintenance decision making of the power transmission line.

Description

A kind of methods of risk assessment based on transmission line of electricity full working scope information

Technical field

The present invention relates to a kind of methods of risk assessment based on transmission line of electricity full working scope information.

Background technology

The continuous expansion of electric system scale and growing with each passing day of importance, make society have higher requirement to the reliability service of electric system.Work about electric power person not only will solve produced problem, more needs to understand the possibility of equipment generation problem and the order of severity of problem by risk assessment.Moreover, the data of risk assessment are usually dispatched for the O&M of electrical network, can play directive function to the operation monitoring, overhaul management, fault handling, on-the-spot tour etc. of electric power enterprise.

Simultaneously, residing for overhead transmission line, circumstance complication is changeable, running status is serious by the impact of sleet, thunder and lightning, disaster etc., be necessary to assess the operation risk of transmission line of electricity, the transmission line of electricity that Timeliness coverage risk is larger, provides technical support for power grid enterprises formulate equipment emphasis management and control strategy.The service work pattern of current electric grid enterprise is still based on periodic scheduled overhaul, and along with increasing of grid equipment quantity, maintenance workload also increases greatly, and the problem of maintenance strength deficiency is also more and more outstanding, and work quality is difficult to ensure.Utilizing risk evaluation result to utilize maintenance strength efficiently, complete the service work needed most with the order of optimum, is the key point addressed this problem.

Risk assessment is all a complexity and work consuming time in all industries, because assessment result is doped with a large amount of subjective factors, makes the mathematical model precision of assessment on the low side, and poor compatibility.In power industry, have the subject matter that transmission line of electricity carries out risk assessment at present: 1. evaluation method is simple, and parameter is fixed, and result cogency is limited.2. data acquisition difficulty is large, and information is incomplete, and assessment is comprehensive not, and assessment result truly can not reflect the risk situation of equipment.3. state estimation and risk assessment disconnect, and power grid enterprises have only carried out state estimation link mostly, and follow-up maintenance, risk assessment work are no longer paid close attention to.4. the low and incomplete Risk Assessment Report of precision cannot reflect the real risk of equipment, and assessment result often affects limited on maintenance decision, therefore cannot provide powerful support for the formulation of maintenance decision.

The risk of transmission line of electricity is mainly derived from three aspects, and one is outside environmental elements, such as sleet, air etc. to the burn into of transmission line of electricity component wind-inducedly greatly to lead () skew of line, artificially steal destruction of transmission line of electricity etc.; Two is self deterioration factors, mainly the metal fatigue, the crackle that produce along with the increase of the time limit that puts into operation of transmission line part, wire strand breakage, the phenomenons such as affiliated facility functional failure; Three is transmission line of electricity emergency case along the line, comprises the unexpected power failure, fault etc. of the disasteies such as thunderbolt, mountain fire and electrical network.As can be seen here, the circumstance complication residing for transmission line of electricity, carrying out risk assessment to it needs to consider many-sided factor.

Summary of the invention

The present invention, according to the own characteristic of transmission line of electricity and ruuning situation, proposes a kind of methods of risk assessment based on transmission line of electricity full working scope information.First transmission line of electricity is subdivided into some parts by the present invention, for different parts, finds the state parameter reflecting their ruuning situation, the history of these state parameters and current data are obtained the risk of tower position section by statistical analysis technique.Then, according to the running status of the operation time limit of parts, the operation period zone field of circuit and electrical network, risk is revised.Finally, according to the value-at-risk of each section of transmission line of electricity obtained before and the risk modified value that obtained by transmission line of electricity full working scope information, obtain the overall risk value being evaluated transmission line of electricity, and provide aid decision making to the O&M maintenance of transmission line of electricity thus.

The full working scope information spinner related in the present invention will comprise the following aspects.Historical data: fault, defect statistics information over the years; Real-time status data: on-line monitoring, manual patrol and off-line testing result; Equipment account: unit type, put into operation the time limit etc.; Line work environmental data: run period, geographical location information and electrical network self-operating state.

Methods of risk assessment based on transmission line of electricity full working scope information of the present invention, comprises the following steps:

Step S1, sets up the general frame of transmission line of electricity risk assessment, sets up risk evaluation model for each parts of transmission line of electricity, the quantification of asserted state amount and degree of membership acquiring method;

Step S2, establishment equipment runs the time limit, running environment and operation of power networks state to the computing method of transmission line of electricity value-at-risk correction and evaluation criterion, the parameters such as the running environment time coefficient of the main definitions aging coefficient of parts, transmission line of electricity and geographic position coefficient;

Step S3, is obtained the overall risk value of transmission line of electricity, and carries out aid decision making according to risk evaluation result to transmission line of electricity O&M through a series of correction by the value-at-risk of each parts.

In above-mentioned transmission line of electricity methods of risk assessment, described step S1 comprises:

1) general frame of transmission line of electricity risk assessment is set up

According to transmission line of electricity composition and the requirement of risk assessment, based on transmission line of electricity is divided, shaft tower, lead () line, insulator, gold utensil, earthing device, affiliated facility and channel environment 8 parts, corresponding to each parts, according to code and accident defect record etc., choose the risk status that several risk status parameters carry out comprehensive characterization parts, the risk status parameter of each parts is as shown in table 1.

The risk status parameter of each parts of table 1

According to the comprehensive principle of risk assessment, comprehensively all correlative factors, set up transmission line of electricity risk assessment general frame as shown in Figure 1.

The present invention is from the risk status parameter of parts, and the state parameter obtained by the method such as on-line monitoring, manual patrol evaluates the risk obtaining quantity of state by quantifying.Meanwhile, by the historic state of parts, comprise data based on failure message, defect information etc. and carry out modeling, obtain degree of membership model.Then, the risk of all risk status parameters of parts is inputted this model, namely obtain the value-at-risk of corresponding component, and the value-at-risk of whole transmission line of electricity is obtained by probability sum formula by the risk of all parts.After obtaining preliminary transmission line of electricity value-at-risk, need to substitute into corresponding time limit coefficient, running environment coefficient and operation of power networks coefficient of regime and carry out further computing.

2) quantification and the degree of membership acquiring method of risk status amount is established

1. the quantification of risk status amount

In the risk assessment of transmission line of electricity, some quantity of state directly cannot be monitored by instrument and equipment, and obtain concrete monitor value.Therefore, quantity of state is divided into direct observer state amount and general state amount two class, is quantized by different modes.

(1) quantification of direct observer state amount

For by the quantity of state of directly observation, can only giving a mark according to table 2, thus obtain the risk quantized value of these quantity of states.

The quantification of the direct observer state amount of table 2

Quantity of state monitoring situation	Completely normal	Slight abnormality	General exception	Severely subnormal	Complete deterioration
						Risk quantized value	0	0.2	0.5	0.8	1

Table 3 gives to lead () line is the risk quantization table of the direct observer state amount of example.

Risk quantization table (leading () line of the direct observer state amount of table 3)

Suppose have n name personnel to give a series of quantized value q according to the experience of oneself and relevant regulations to some quantity of states ₁, q ₂..., q _n, then risk quantized value Q is determined by following formula.

$Q=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{q}_i$

(2) quantification of general state amount

For by observing the quantity of state carrying out quantizing, a kind of quantity of state risk quantization method of Corpus--based Method being proposed below.

First, add up the number of times of each quantity of state in operating data over the years and correspondence, obtain as the state quantity data distribution situation in Fig. 2 by matching, transverse axis represents the monitor value ω of certain quantity of state, and the longitudinal axis represents the number of times ψ that this monitor value occurs.What be in normal condition in "as if" statistics data accounts for a%, then the cut off value of overall data a% is designated as normal limit, represents with μ.In the statistics of the various quantity of state of transmission line of electricity, having at least the data of 90%-95% to belong to normal condition, in order to avoid failing to judge, getting a%=90%.

When quantity of state is considerably beyond normal limit, and when making parts close to 100% fault, remember that the value of now quantity of state is fault limit value, represent with ξ, the risk of corresponding states amount is 100%.

The certain multiple of the demand value or warning value of getting quantity of state is as fault limit value, and note demand value is ξ _z, warning value is ξ _j, obtain normal limit μ as shown in table 4 and fault limit value ξ, it should be noted that, what discuss at present is the quantity of state that the value of failure state amount can increase, and is called positive status amount.

The normal limit of table 4 positive status amount and fault limit value

If the monitor value of quantity of state is x, then the risk of its correspondence is determined by following formula.

$Q\left(x\right)=\left\{\begin{array}{cc}0& x\&le;\mathrm{\&mu;}\\ {\left(\frac{x-\mathrm{\&mu;}}{\mathrm{\&xi;}-\mathrm{\&mu;}}\right)}^k& \mathrm{\&mu;}<x<\mathrm{\&xi;}\\ 1& x\&GreaterEqual;\mathrm{\&xi;}\end{array}\right.$

Wherein, k is Trend index and gets k>1.

The determination bearing the normal limit of quantity of state (quantity of state that during fault, its value reduces) and deviation sexual state amount (during fault, its value is to the quantity of state of both sides deviation), fault limit value and risk is as shown in table 5.

The quantification of the negative quantity of state of table 5 and deviation sexual state amount

2. the asking for of quantity of state degree of membership

On the basis of known state amount risk, also need to determine that each quantity of state affects size to parts value-at-risk, be referred to as degree of membership, represent with α.

Suppose to add up fault in nearly n of certain parts of transmission line of electricity in a certain region and great, urgent defect, obtain all quantity of state QSs relevant in fault and defect to these parts ₁, QS ₂..., QS _n, and the occurrence number t that these quantity of states are corresponding ₁, t ₂..., t _n.So, the degree of membership α of i-th quantity of state of these parts _idetermined by following formula.Leading () line, its degree of membership occurrence is as table 6.

${\mathrm{\&alpha;}}_i=\frac{t_i}{\underset{k=1}{\overset{n}{\mathrm{\&Sigma;}}}{t}_k}$

Table 6 quantity of state degree of membership (leading () line)

Sequence number	Quantity of state	Degree of membership
			13	Lead () line exist burn into break stock, damage and flashover burn	0.589
14	Lead () line waves	0.037
			15	Lead () line icing	0.034
16	Lead () bank hang down	0.023
			17	Lead () line windage yaw	0.037
18	Lead () suspension of line foreign matter	0.044
			19	Lead () line slippage in wire clamp	0.034
20	Lead () line ice-shedding	0.027
			21	All kinds of connecting pipe, repair sleeve have flexural deformation phenomenon	0.008
22	Wire jumper breaks stock, distortion, distortion, burn, damage	0.104

23	OPGW cable line breaks stock	0.036
			24	Wire jumper windage yaw	0.027

So, certain parts i-th quantity of state QS _isingle quantity of state value-at-risk r _ibe shown below.

r _i＝Q _i×α _i

If single quantity of state value-at-risk of all quantity of states is respectively r ₁, r ₂..., r _n, then the value-at-risk R of these parts is determined by following formula.

$R=\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{r}_i$

In above-mentioned transmission line of electricity methods of risk assessment, described step S2 comprises:

The equipment that establishes runs the time limit, running environment and operation of power networks state to the computing method of transmission line of electricity value-at-risk correction.

1) time limit coefficient of calculating unit

First introduce this parameter of ageing index of parts, its computing formula is:

${\mathrm{AG}}_t={\mathrm{AG}}_0\&times;e^{B(T-T_0)}\&times;f_{\mathrm{mod}}$

Wherein AG _tfor being asked for the ageing index in time, AG ₀for the initial aged index of equipment, generally getting 0.5, B is aging constant, and T is the time needing to ask for ageing index, T ₀for the putting equipment in service time, f _modfor correction factor.

According to the expected life n that device fabrication manufacturer is given, (f under common running environment _mod=1), the ageing index of equipment can become 5.5 when finally stopping transport from incipient 0.5.The aging constant of equipment thus:

$B=\frac{\ln (5.5/0.5)}{n}=\frac{\ln 11}{n}\&ap;\frac{2.40}{n}$

Under most rugged surroundings, the ageing equipment index of expected life one's last year is 10, and now corresponding correction factor is 10/5.5 ≈ 1.82, then according to concrete running environment, and f _modspan be [1,1.82].

After parts put into operation, the time limit coefficient of t is obtained by following formula.

FY _t＝0.05AG _t+1

For basis, shaft tower, earthing device, its time limit coefficient obtains according to main element.For leading () line, insulator, gold utensil, affiliated facility, the mean value of each equipment time limit coefficient in line taking road.For channel environment, do not need the time limit coefficient considering it.

2) the running environment coefficient of computational scheme

In conjunction with operating experience and transmission line of electricity own characteristic, choose thunderbolt, mountain fire, icing, typhoon, bird pest and outside destroy these six to the maximum environmental factor of transmission line of electricity venture influence.Then running environment coefficient T P is obtained by following formula.

$\mathrm{TP}=\underset{i=1}{\overset{6}{\mathrm{\&Pi;}}}{\mathrm{tp}}_i$

Wherein, during i=1 ~ 6, tp _irepresent the one-sided running environment coefficient of these six kinds of factors of thunderbolt, mountain fire, icing, typhoon, bird pest and outside destroy respectively.

Two factors are relevant with one-sided running environment coefficient, and one is time section, corresponding time coefficient t, and two is geographic position section, corresponding geographical position parameter p.So one-sided running environment coefficient is obtained by following formula.

Wherein, t _iand p _irepresent time coefficient and the geographic position coefficient of i-th kind of single running environment respectively.

1. the asking for of time coefficient

For southern running environment, add up according to accident defect over the years, determine special time section, as shown in table 7.

The special time section of table 7 running environment

Special running environment	Take place frequently time section	Special running environment	Take place frequently time section
				Thunderbolt	3 ~ September	Typhoon	6 ~ October
Mountain fire	September ~ January next year	Bird pest	9 ~ November
				Icing	November ~ February next year	Outside destroy	9 ~ November

For icing, according to the statistics icing fault rate of icing Frequent Troubles time over the years, namely the time coefficient of icing is in time in the normal distribution N (μ shown in following formula ₁, δ ₁ ²).Obtain time coefficient normal distribution as shown in Figure 3 thus.

$t\left(x\right)=\frac{1}{\sqrt{2\mathrm{\&pi;}}{\mathrm{\&delta;}}_1}{e}^{-\frac{{\left({x-\mathrm{\&mu;}}_1\right)}^2}{2{{\mathrm{\&delta;}}_1}^2}}+K_1$

Wherein x is evaluation time (in units of the moon), μ ₁for the average of t, δ ₁ ²for the variance of t, K ₁for normal distribution off-set value.

For other five kinds of special running environment, according to the analytical approach of icing, obtaining take time as the distribution function of variable.On the summit of distribution function, get t _i=1.2, in the special time section of fault, the value of time coefficient obtains according to the value of distribution function, outside section, gets t _i=1.

2. the asking for of geographic position coefficient

The value of geographic position coefficient p is drawn by the statistical study of trouble spot density in Frequent Troubles region.For icing, according to the statistics in the geographic position of fault over the years in icing Frequent Troubles region, obtain Fig. 4, with icing Frequent Troubles regional center for density center, draw icing trouble spot density function φ, φ is normal distyribution function, is designated as φ ~ N (μ ₂, δ ₂ ²).

For other five kinds of special running environment, according to the analytical approach of icing, the distribution function that to obtain with decentering point distance be variable.On the summit of distribution function, get p _i=1.2, in the section of fault, the value of geographic position coefficient obtains according to the value of distribution function, outside section, gets p _i=1.

3) electric network state coefficient is calculated

The influential running status of transmission line of electricity risk tool is comprised to trend is out-of-limit, these three kinds of situations of voltage out-of-limit, Voltage Instability.

The corresponding relation of the out-of-limit situation of trend and electric network state coefficient S as shown in Figure 5.

When duty factor is less than 0.8, get S=1; When duty factor is greater than 1.3, get S=1.2; When duty factor is between 0.8 to 1.3, linear between electric network state coefficient S and duty factor.

The corresponding relation of voltage out-of-limit situation and electric network state coefficient S as shown in Figure 6.

When voltage ratio be less than 0.85, be greater than 1.15 time, get S=1.2; When voltage ratio is between 0.95 to 1.05, get S=1; When voltage ratio is between 0.85 to 0.95,1.05 to 1.15, linear between electric network state coefficient S and voltage ratio.

The corresponding relation of Voltage Instability situation and electric network state coefficient S as shown in Figure 7.

When load margin is greater than 10%, get S=1; When load margin is less than 0, get S=1.2; When load margin is between 0 to 10%, linear between electric network state coefficient S and load margin.

In above-mentioned transmission line of electricity methods of risk assessment, described step S3 comprises:

According to value-at-risk and a series of correction index of each parts obtained in step S1 and S2, obtain the value-at-risk of transmission line of electricity entirety, and according to risk evaluation result, aid decision making is carried out to transmission line of electricity.

1) computing electric power line overall risk value

The value-at-risk of parts needs the correction through parts time limit coefficient FY (being called for short F), transmission line of electricity overall risk value needs the correction through running environment coefficient T P (being called for short T) and electric network state coefficient S, so revised transmission line of electricity overall risk value is expressed from the next.

$\stackrel{\&OverBar;}{R}=(1-\underset{i=1}{\overset{8}{\mathrm{\&Pi;}}}(1-\frac{R_i{F}_i}{1.5}))\&CenterDot;T\&CenterDot;S$

Wherein, R _iand F _irepresent value-at-risk and the time limit coefficient of i-th parts respectively.

2) based on the aid decision making of circuit risk

The value-at-risk of transmission line of electricity is defined as zone of acceptability section between [0,0.1], between [0.1,0.5], is defined as low-risk section, between [0.5,1], be defined as excessive risk section.For the transmission line of electricity of zone of acceptability section, without the need for special maintenance measure, maintain normal service arrangement.For the transmission line of electricity of low-risk section, the maintenance to this section of transmission line of electricity should be strengthened, and give more sustained attention the change of its value-at-risk, for the transmission line of electricity of excessive risk section, with good conditionsily should to overhaul the section that may go wrong at once, the equipment that can not continue to run should be stopped transport in time and be changed.

For shaft tower, table 8 indicates and needs at the circuit of low-risk and excessive risk section the maintenance measure that carries out.

Table 8 risk maintenance measure (for shaft tower)

Accompanying drawing explanation

Fig. 1 is transmission line of electricity risk assessment general frame

Fig. 2 is the monitor value of certain quantity of state and the matching of occurrence number

Fig. 3 is the Annual distribution of icing probability of malfunction

Fig. 4 is the geographic position statistics of fault over the years in icing Frequent Troubles region

Fig. 5 is the out-of-limit corresponding relation with electric network state coefficient of trend

Fig. 6 is voltage out-of-limit and electric network state coefficient corresponding relation

Fig. 7 is Voltage Instability and electric network state coefficient corresponding relation

Embodiment

The present invention will be further described according to drawings and embodiments below, but should not limit the scope of the invention with this.

The risk assessment processes of methods of risk assessment according to the present invention to this transmission line of electricity is as follows:

1. the value-at-risk of calculating unit

According to full working scope Information Risk appraisal procedure of the present invention, risk assessment is carried out to the 500kV transmission line of electricity osmanthus naze line of south electric network subordinate, according to its tour record in July, 2013 and online monitoring data, the defect of this section of circuit in patrolling and examining is as shown in table 9.

The defective data of table 9 circuit and the risk of correspondence and degree of membership

Leading () line, question blank 3 (the risk quantization table of direct observer state amount) is known, the risk of defect " 195# right aerial earth wire wire clamp is to small size side skew 10cm " is 0.5, and the risk of defect " disconnected 4 strands of 230# optical fiber drainage thread " is 0.8.Meanwhile, question blank 6 (quantity of state degree of membership) can obtain, and the degree of membership of quantity of state " lead wire and earth wire is slippage in wire clamp " is 0.034, and the degree of membership of quantity of state " OPGW cable line break stock " is 0.036.Can obtain thus, lead () the parts value-at-risk of line is 0.5 × 0.034+0.8 × 0.036 ≈ 0.046 before correction.

By same mode, risk corresponding to each defect can be obtained and degree of membership as shown in table 9, obtain the value-at-risk of each parts before correction further: shaft tower is 0.035, lead () line is 0.046, insulator is 0.028, gold utensil is 0.005, channel environment is 0.083.Owing to not there is defect record in other 3 kinds of parts, therefore their value-at-risk is 0.

2. ask for time limit coefficient, running environment coefficient and electric network state coefficient

First the time limit coefficient of calculating unit, for shaft tower, the time of putting into operation of the 500kV steel tower of this section of circuit is 1997, and design period is 50 years, can obtain aging constant B=0.048, get f _mod=1, obtain ageing index AG _t=1.078, so the time limit coefficient FY obtaining shaft tower _t=1.0539.Time limit coefficient and the revised parts value-at-risk of miscellaneous part are as shown in table 10, wherein, channel environment are not considered to its time limit coefficient.

The time limit coefficient of table 10 parts and the value-at-risk of correction front and back

Parts	Value-at-risk before revising	Time limit coefficient	Value-at-risk after revising
				Shaft tower	0.035	1.054	0.025
Lead () line	0.046	1.091	0.033
				Insulator	0.028	1.175	0.022
Gold utensil	0.005	1.152	0.004
				Channel environment	0.083	/	0.083

Following consideration running environment coefficient is to the correction of transmission line of electricity value-at-risk.Osmanthus naze line is subject to the impact of thunderbolt and typhoon two kinds of special running environment in July, for thunderbolt, and corresponding time coefficient t=1.12, geographic position coefficient p=1.07, therefore, the running environment coefficient of thunderbolt is 1.198, and the running environment coefficient that can obtain typhoon is equally 1.035.

Due to electrical network no exceptions within this period, therefore, electric network state coefficient S=1, namely the value-at-risk of running status on transmission line of electricity of electrical network does not affect.

3. ask for transmission line of electricity overall risk value

By the data in table 10 can this section of transmission line of electricity in the value-at-risk before running environment coefficient and the correction of electric network state coefficient after being substituted into by correction factor, the overall risk value obtaining transmission line of electricity is 0.196.

According to the definition to value-at-risk, now circuit is in low-risk section, should strengthen the maintenance to this section of transmission line of electricity, and gives more sustained attention the change of its value-at-risk, and takes appropriate measures according to table 8 pair transmission line of electricity.

Claims (4)

1. based on a methods of risk assessment for transmission line of electricity full working scope information, it is characterized in that, said method comprising the steps of:

Step S1, sets up transmission line of electricity risk assessment general frame, sets up risk evaluation model for each parts of transmission line of electricity, the quantification of asserted state amount with ask for degree of membership;

Step S2, equipment of establishing runs the time limit, running environment and operation of power networks state to the computing method of transmission line of electricity value-at-risk correction and evaluation criterion, the aging coefficient of definition component, the running environment time coefficient of transmission line of electricity and geographic position coefficient;

Step S3, is obtained the overall risk value of transmission line of electricity, and carries out aid decision making according to risk evaluation result to transmission line of electricity O&M through a series of correction by the value-at-risk of each parts.

2. transmission line of electricity methods of risk assessment according to claim 1, is characterized in that, described step S1 specifically:

1. set up the transmission line of electricity risk assessment general frame of sub-unit, this transmission line of electricity risk assessment general frame period, section and operation of power networks status information residing for the value-at-risk of these 8 parts of basis, shaft tower, lead wire and earth wire, insulator, gold utensil, earthing device, affiliated facility and channel environment and transmission line of electricity are formed;

2. the risk evaluation model of each parts is set up

The risk evaluation model of described each parts is made up of the operation time limit of some quantity of states of parts, historical failure, defect statistics data and parts;

3. the risk of each quantity of state is quantized, specifically:

Described quantity of state is divided into direct observer state amount and general state amount two kinds:

A) the risk quantized value Q of direct observer state amount, formula is as follows:

$Q=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{q}_i$

In formula: q ₁, q ₂..., q _nfor some quantity of states have n name personnel to give a series of quantized value according to the experience of oneself and relevant regulations;

B) the risk quantized value of general state amount, first determines the normal limit μ of quantity of state, then by the demand value of quantity of state or the certain multiple of the warning value fault limit value ξ as quantity of state;

For positive status amount, the quantity of state that namely during fault, its value increases, if the monitor value of quantity of state is x, then the risk of its correspondence is determined by following formula:

$Q\left(x\right)=\left\{\begin{array}{cc}0& x\&le;\mathrm{\&mu;}\\ {\left(\frac{x-\mathrm{\&mu;}}{\mathrm{\&xi;}-\mathrm{\&mu;}}\right)}^k& \mathrm{\&xi;}<x<\mathrm{\&xi;}\\ 1& x\&GreaterEqual;\mathrm{\&xi;}\end{array}\right.$

For negative quantity of state and deviation sexual state amount, the determination of risk is determined by lower two formulas respectively:

$Q\left(x\right)=\left\{\begin{array}{cc}1& x\&le;\mathrm{\&xi;}\\ {\left(\frac{\mathrm{\&mu;}-x}{\mathrm{\&mu;}-\mathrm{\&xi;}}\right)}^k& \mathrm{\&xi;}<x<\mathrm{\&mu;}\\ 0& x\&GreaterEqual;\mathrm{\&mu;}\end{array}\right.$

$Q\left(x\right)=\left\{\begin{array}{cc}1& x<{\mathrm{\&xi;}}_1\\ {\left(\frac{{\mathrm{\&mu;}}_1-x}{{\mathrm{\&mu;}}_1-{\mathrm{\&xi;}}_1}\right)}^k& {\mathrm{\&xi;}}_1<x<{\mathrm{\&mu;}}_1\\ 0& {\mathrm{\&mu;}}_1\&le;x\&le;{\mathrm{\&mu;}}_2\\ {\left(\frac{x-{\mathrm{\&mu;}}_2}{{\mathrm{\&xi;}}_2-{\mathrm{\&mu;}}_2}\right)}^k& {\mathrm{\&mu;}}_2<x<{\mathrm{\&xi;}}_2\\ 1& x\&GreaterEqual;{\mathrm{\&xi;}}_2\end{array}\right.$

Wherein, μ ₁and μ ₂two normal limit up and down of deviation sexual state amount, ξ ₁and ξ ₂be two fault limit values up and down of deviation sexual state amount, k is the fault trend index of quantity of state and gets k>1;

4. the degree of membership of each quantity of state is asked for:

When fault in nearly l of certain parts of transmission line of electricity in a certain region and great, urgent defect are added up, obtain all quantity of state QSs relevant in fault and defect to these parts ₁, QS ₂..., QS _m, and the occurrence number t that these quantity of states are corresponding ₁, t ₂..., t _m, so, the degree of membership α of i-th quantity of state of these parts _idetermined by following formula:

${\mathrm{\&alpha;}}_i=\frac{t_i}{\underset{k=1}{\overset{m}{\mathrm{\&Sigma;}}}{t}_k}$

5. calculation risk value, formula is as follows:

$R=\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{r}_i$

In formula: r ₁, r ₂..., r _i..., r _nfor single quantity of state value-at-risk of all quantity of states, r _i=Q _i× α _ibe i-th quantity of state QS _isingle quantity of state value-at-risk.

3. transmission line of electricity methods of risk assessment according to claim 1, is characterized in that described step S2 specifically comprises:

1. establish the acquiring method based on the time limit coefficient running the time limit, running environment and equipment expected life to each parts of transmission line of electricity, formula is as follows:

FY _t＝0.05AG _t+1

In formula: FY _tfor the time limit coefficient of t after putting into operation, AG _tfor being asked for the ageing index in time.Ageing index is obtained by following formula:

${\mathrm{AG}}_t={\mathrm{AG}}_0\&times;e^{B(T-T_0)}\&times;f_{\mathrm{mod}}$

In formula: AG ₀for the initial aged index of equipment, generally getting 0.5, B is aging constant, n _gfor equipment expected life, T is the time needing to ask for ageing index, T ₀for the putting equipment in service time, f _modfor correction factor, span is [1,1.82], determines according to concrete running environment;

2. the running environment coefficient of computational scheme, formula is as follows:

In formula: t _ibe the time coefficient of i-th kind of single running environment, p _iit is the geographic position coefficient of i-th kind of single running environment;

3. electric network state coefficient S is calculated.

4. transmission line of electricity methods of risk assessment according to claim 1, is characterized in that described step S3 specifically comprises:

1. the overall risk value of computing electric power line, formula is as follows:

$\stackrel{\&OverBar;}{R}=(1-\underset{i=1}{\overset{8}{\mathrm{\&Pi;}}}(1-\frac{R_i{F}_i}{1.5}))\&CenterDot;T\&CenterDot;S$

In formula: R _ibe the value-at-risk of i-th parts, F _ibe the time limit coefficient of i-th parts, S is electric network state coefficient, and T is running environment coefficient;

2. by the value-at-risk of transmission line of electricity [0, 0.1] zone of acceptability section is defined as between, [0.1, 0.5] low-risk section is defined as between, [0.5, 1] excessive risk section is defined as between, for the transmission line of electricity of zone of acceptability section, without the need for special maintenance measure, maintain normal service arrangement, for the transmission line of electricity of low-risk section, the maintenance to this section of transmission line of electricity should be strengthened, and give more sustained attention the change of its value-at-risk, for the transmission line of electricity of excessive risk section, should overhaul to this section of transmission line of electricity at once, the equipment that can not continue to run should be stopped transport in time and be changed.