CN106684864A - Overhead line dynamic capacity increase method based on BOTDR thermometric technique - Google Patents

Abstract

The invention relates to an overhead line dynamic capacity increase method, in particular to an overhead line dynamic capacity increase method based on the BOTDR thermometric technique. By means of the BOTDR thermometric technique on an OPGW, distributed measurement is conducted on environment temperatures around an overhead line, a wire temperature is derived through the Newton iteration method, and a bottleneck point of the wire real-time temperature is put into a new heat balance equation, so that a real-time current-carrying capacity is calculated. It is proved by calculation that the line current-carrying capacity can be effectively improved by means of the method, and the method plays a theoretical guiding role is played on design optimization of the line current-carrying capacity. In the method, no extra temperature sensing device is needed, the cost of a common DTP device is reduced, maintenance is simple and reliability is high. The method can be widely used in power grids, and the real capacity of a power transmission line is produced.

Description

A kind of overhead transmission line dynamic compatibilization method based on BOTDR thermometrys

Technical field

The present invention relates to a kind of overhead transmission line dynamic compatibilization method, more particularly, to a kind of based on BOTDR thermometrys Overhead transmission line dynamic compatibilization method.

Background technology

Because overhead power transmission conducting wire has resistance, when certain load current is flow through, resistance will " loss " part Electric energy and become heat, wire will necessarily generate heat.And the temperature of transmission pressure can gradually go up with the increase of load current Rise, it is inevitable to burn because producing excessively stream and generating heat when the maximum allowable operating temperature more than wire, chopper may be caused to jump Lock.Therefore we are needed neither affecting safe operation of electric network, and are not changed under conditions of original overhead transmission line structure, to transmission of electricity The hiding transmission of electricity potentiality of circuit carry out depth excavation, scientifically improve the transmission line capability of circuit, high to solve some areas transmission of electricity The unbalanced supply-demand problem at peak.

Typically improve the current-carrying capacity of overhead transmission line using following two methods both at home and abroad at present：Static increase-volume and dynamic State increase-volume.

Static capacity increasing technique needs to be improved existing conductor material, specification and its corollary equipment, to conventional electric power row Industry technical stipulation is updated, and the maximum allowable operating temperature for making overhead transmission line brings up to 80 DEG C from traditional 70 DEG C, so as to About 20% power transmission capacity of pow is improved, but this method needs to consider the restriction of three aspects：(1) existing setting whether is met Meter standard；(2) life-span and the mechanical strength of wire and its corollary equipment can whether be affected；(3) affected by wire temperature rise, wire arc Hanging down also can increase therewith, it is understood that there may be the wire not enough hidden danger of safe distance over the ground so that transmission line safety coefficient is too little.Cause , according to conservative static calculation method, each department unified standard, annual temperature are single, it is impossible to embody to greatest extent built on stilts for this The true ability to transmit electricity of circuit, in vain waste huge power network resources.

And dynamic compatibilization technology then improves computational methods and measuring method, by increasing monitoring device on the line to leading The state and its ambient environmental factors of line carries out accurate on-line checking, does not change original configuration and does not affect operation of power networks Safety, adequately accurately monitors overhead transmission line ambient parameter to calculate the maximum capacity of circuit, and line energizing flow can be improved in theory Amount about 10%~30%.What now Chinese scholars were commonly used is Dynamic Thermal stabilization system (DTR systems) increases entering Mobile state Hold, the real-time environmental conditions (data such as wind speed, sunshine and temperature) that the system is provided according to SCADA, calculate conductor it is real-time most It is big to allow current-carrying value.But its equipment cost is higher, safeguard more difficult, constrain the system the shortcomings of reliability is difficult to ensure that and exist The application of electrical network, its value can not normally be brought into play.

In order to make full use of the ability to transmit electricity of existing overhead transmission line, present aspect to propose a kind of based on BOTDR thermometric skills The online dynamic compatibilization new method of art：Overhead transmission line ambient temperature is carried out point using the BOTDR thermometrys on OPGW Cloth is measured, and by Newton iteration conductor temperature is derived, brings wire real time temperature bottleneck point into new heat balance equation, from And calculate real-time current-carrying capacity.Calculating proves, the method can effectively improve line energizing flow amount, designs excellent to line energizing flow amount Change has theoretical directive function.And the method does not need extra temperature sensing device, the cost of general DTR equipment is reduced, Safeguard relatively simple, reliability is high, can be widely applied in electrical network, has given play to the true capacity of power transmission line.

The content of the invention

The present invention mainly solves the technical problem existing for existing method；There is provided the BOTDR on a kind of utilization OPGW Thermometry carries out distributed measurement to overhead transmission line ambient temperature, and by Newton iteration conductor temperature is derived, will lead Line real time temperature bottleneck point brings new heat balance equation into, so as to the online dynamic compatibilization of the overhead transmission line for calculating real-time current-carrying capacity Method.

What the above-mentioned technical problem of the present invention was mainly addressed by following technical proposals：

A kind of overhead transmission line dynamic compatibilization method based on BOTDR thermometrys, it is characterised in that comprise the following steps：

Step 1, by BOTDR equipment the continuous measurement of ambient temperature is carried out to whole piece transmission line of electricity each point, is transmitted electricity The environment temperature vs. time sequence of circuit each point along the line, specifically includes：

In temp measuring system, BOTDR equipment produces one end of the pulsed light Jing OPGW optical cable and optical fibres of one fixed width to step 1.1 Orientation injects optical-fibre channel；Light pulse is constantly propagated forward inside optical fiber, when by the acoustic wavefield that is mutated when acting on just Brillouin scattering can be produced, wherein the dorsad Brillouin scattering for having the sub-fraction direction of propagation contrary with incident direction can be carried The temperature of optical fiber and strain characteristics return the BOTDR equipment of optical fiber transmitting terminal；

Step 1.2 can obtain whole piece temperature measuring optical cable this moment by the analysis to dorsad Brillouin scattering frequency drift Ambient temperature distribution along the line, that is, measure the ambient temperature of overhead transmission line；

Step 2, by the ambient temperature for measuring conductor temperature is converted into, and records and preserve the temperature at conductor temperature maximum Degree-time serieses, specifically includes：

Step 2.1, this reality that there is certain non-linear relation between the ratio with current in wire and alternating current-direct current resistance Trample conclusion to carry out abbreviation to the equation of heat balance calculating process of the OPGW in the same space position and power transmission line；

Step 2.2, is solved by Newton iteration method to conductor temperature；

Step 3, in the Temperature-time sequence from conductor temperature maximum, chooses continuous four temperature sampling values and brings into Heat balance equation, calculates one group of environment recessiveness capacity coefficient vector, is specifically calculated according to the ambient temperature that step 2 is measured and is led Line temperature, obtains the time dependent sequence of conductor temperature, in the heat balance equation that temperature information is brought into after abbreviation, due to only There are three unknown parameter numbers, therefore continuous sampling just can determine that the coefficient of equation for four times, because each moment estimates uncorrelated, Therefore estimated result is separate, can solve one group of environment recessiveness capacity coefficient vector；

Step 4, calculates the real-time maximum carrying capacity of overhead transmission line, and constantly real-time update, specifically：Work as previous group when known Coefficient vector S_k=[θ_1,k,θ_2,k,θ_3,k]^TWith initial temperature T_k, in a period of time after, maximum carrying capacity can be according under The formula in face is being calculated：

In formula, T_maxSpecify that the wire of power transmission line allows maximum temperature limit value according to China's Electric Design code；Take The temperature change average in continuous four sampling periods.

In a kind of above-mentioned overhead transmission line dynamic compatibilization method based on BOTDR thermometrys, the step 2.1 it is concrete Method is：

Because on overhead transmission line, the equation of heat balance of OPGW and power transmission line in the same space position can be write a Chinese character in simplified form Into as follows：

OPGW：q_co+q_ro-q_so=0

Overhead transmission line：I²R(T_c)-q_cc-q_rc+q_sc=0

In above formula, I is power transmission line current-carrying capacity, R (T_c) it is temperature T_cWhen wire per km AC resistance, q_soAnd q_scRespectively Sunshine for OPGW and wire is absorbed heat, and is unknown quantity；q_roAnd q_rcIt is respectively the heat loss through radiation of OPGW and wire, q_coAnd q_ccPoint It is not the heat loss through convection of OPGW and wire；Expression formula is respectively：

q_ro=16.03D_o×10^-8[(T_o+273)⁴-(T_a+273)⁴]

q_rc=16.03D_c×10^-8[(T_c+273)⁴-(T_a+273)⁴]

q_co=h (t) D_o ^0.75(T_o-T_a)

q_cc=h (t) D_c ^0.75(T_c-T_a)

In above formula, it is believed that OPGW optical cables and overhead transmission line have identical skin-material characteristic (i.e. heat loss through convection coefficient h The ρ of (t)=0.0205_f ^0.5It is identical), wherein ρ_fFor atmospheric density, km/m₃；T_oFor the temperature that OPGW sensor fibres are measured, T_cFor wire Temperature, T_aFor ambient temperature；D_oWith D_cThe diameter of respectively OPGW and wire；Because OPGW and power transmission line are in same naturally empty Between position, the solar radiation that both are subject to is identical, so sunshine heat absorption has lower relation of plane：

Bringing above formula into can obtain：

I²R(T_c)=D_c[(T_c+273)⁴-(T_a+273)⁴]+0.0205ρ_f ^0.5D_c(T_c-T_a)

In above formula, when calculating current carrying capacity of conductor, alternating current-direct current resistance R (T_c) computing it is cumbersome, but due to Morgan Formula is built upon on a large amount of practical basis, and we can be used between current in wire I and the ratio beta of alternating current-direct current resistance is present This of certain non-linear relation puts into practice conclusion to carry out abbreviation to calculating process, and formula is as follows,

β=ζ I^τ

After wire standard section determines, ζ and τ is constant, i.e.,

R(T_c)=β R_d

R_d=R₂₀[1+α(T_c-20)]

Wherein, R_dFor the D.C. resistance of operating temperature lower conductor, R₂₀It is 20 DEG C of D.C. resistance；

Wherein, d be aluminum line diameter, mm；ρ₂₀For the resistivity of aluminum single line, 2.8264 × 10 are taken^-8(20 DEG C), Ω m；N For the total radical of aluminum steel；λ_amFor the average Haul Rate of aluminum steel by each layer aluminum steel mean pitch than calculating；α is temperature coefficient, and aluminum takes 0.00403,1/ DEG C；T_cTemperature DEG C when working for conductor.

In a kind of above-mentioned overhead transmission line dynamic compatibilization method based on BOTDR thermometrys, the step 2.2 it is concrete Method is：Carry out solving conductor temperature T by Newton iteration method_c, order

f(T_c)=D_c[(T_c+273)⁴-(T_a+273)⁴]+h(t)D_c(T_c-T_a)-I²R(T_c)

f'(T_c)=4D_c(T_c+273)³+h(t)D_c-I²R'(T_c)

N=1,2,3 ..., n are iterationses；The conductor temperature of overhead transmission line can be calculated.

In a kind of above-mentioned overhead transmission line dynamic compatibilization method based on BOTDR thermometrys, the concrete side of the step 3 Method is：Conductor temperature is calculated by the ambient temperature for measuring, the time dependent sequence of conductor temperature is obtained：T₁, T₂..., T_k, Temperature information is brought in heat balance equation,

In formula, Δ t is the sampling period；

Due to there was only three unknown parameter numbers, therefore continuous sampling just can determine that the coefficient of equation for four times, due to each Moment estimates uncorrelated, therefore estimated result is separate, can solve one group of environment recessiveness capacity coefficient vector S_k=[θ_1,k, θ_2,k,θ_3,k]^T。

In a kind of above-mentioned overhead transmission line dynamic compatibilization method based on BOTDR thermometrys, the concrete side of the step 4 Method is：

When known as previous system number vector S_kWith initial temperature T_k, in a period of time after, maximum carrying capacity can be with It is calculated according to the formula：

In above formula, specify that the wire of power transmission line allows maximum temperature limit T according to China's Electric Design code_maxTake 70 DEG C；Take the temperature change average in continuous four sampling periods：

Therefore, the invention has the advantages that：Power transmission line ambient temperature is entered using the optical fiber BOTDR technologies based on OPGW The continuous measurement of row, by methods herein the maximum carrying capacity of overhead transmission line is assessed, and is much better than in theory based on traditional most evil Current capacity under bad environment.And the method does not need extra temperature sensing device, reduce general DTR equipment into This, safeguards relatively simple, and reliability is high, can be widely applied in electrical network, has given play to the true capacity of power transmission line.

Description of the drawings

Accompanying drawing 1 is method of the present invention schematic flow sheet.

Accompanying drawing 2 is in the embodiment of the present invention overhead transmission line to be solved with the optical fiber BOTDR technologies based on OPGW to obtain The schematic diagram that the current-carrying value that maximum carrying capacity value is calculated with Morgan compares.

Specific embodiment

Below by embodiment, and accompanying drawing is combined, technical scheme is described in further detail.

Embodiment：

The step of specific embodiment using the present invention is presented herein below, it is as follows：

First, data acquisition is obtaining detected overhead transmission line ambient temperature

1) zone sensors detect incident pulse light using optical time-domain analysis method during Brillouin light, in specific light frequency difference The lower watt level that can respectively obtain incident pulse light and excitation light is set, the Brillouin scattering of OPGW inner fibers is calculated then The gain of light.Further according to gain size distribution can obtain optical fiber Brillouin scattering frequency shift amount, by frequency displacement and temperature it Between linear relationship calculate the profiling temperatures of whole piece optical fiber.

When optical fiber is not strained, the frequency displacement of Brillouin scattering is linear with fiber optic temperature：

The distance between arbitrfary point and pulse light incident side on OPGW optical fiber L can be calculated according to following formula and obtained：

In above formula, c is the light velocity in vacuum, and n is the refractive index of optical fiber, and Δ T is the excitation light that sends of OTDR equipment and connect The time difference of the dorsad Brillouin scattering for receiving.

2nd, ambient temperature is converted into into conductor temperature

Because on overhead transmission line, the equation of heat balance of OPGW and power transmission line in the same space position can be write a Chinese character in simplified form Into as follows：

OPGW：q_co+q_ro-q_so=0

Overhead transmission line：I²R(T_c)-q_cc-q_rc+q_sc=0

In above formula, I is power transmission line current-carrying capacity, R (T_c) it is temperature T_cWhen wire per km AC resistance, q_soAnd q_scRespectively Sunshine for OPGW and wire is absorbed heat, and is unknown quantity；q_roAnd q_rcIt is respectively the heat loss through radiation of OPGW and wire, q_coAnd q_ccPoint It is not the heat loss through convection of OPGW and wire.Expression formula is respectively：

q_ro=16.03D_o×10^-8[(T_o+273)⁴-(T_a+273)⁴]

q_rc=16.03D_c×10^-8[(T_c+273)⁴-(T_a+273)⁴]

In above formula, it is believed that OPGW optical cables and overhead transmission line have identical skin-material characteristic (i.e. heat loss through convection coefficient h The ρ of (t)=0.0205_f ^0.5It is identical), wherein ρ_fFor atmospheric density, km/m³；T_oFor the temperature that OPGW sensor fibres are measured, T_cFor wire Temperature, T_aFor ambient temperature；D_oWith D_cThe diameter of respectively OPGW and wire.Because OPGW and power transmission line are in same naturally empty Between position, the solar radiation that both are subject to is identical, so sunshine heat absorption has lower relation of plane：

Bringing above formula into can obtain：

I²R(T_c)=D_c[(T_c+273)⁴-(T_a+273)⁴]+0.0205ρ_f ^0.5D_c(T_c-T_a)

In above formula, when calculating current carrying capacity of conductor, alternating current-direct current resistance R (T_c) computing it is cumbersome, but due to Morgan Formula is built upon on a large amount of practical basis, and we can be used between current in wire I and the ratio beta of alternating current-direct current resistance is present This of certain non-linear relation puts into practice conclusion to carry out abbreviation to calculating process, and formula is as follows,

β=ζ I^τ

After wire standard section determines, ζ and τ is constant, i.e.,

R(T_c)=β R_d

R_d=R₂₀[1+α(T_c-20)]

Wherein, R_dFor the D.C. resistance of operating temperature lower conductor, R₂₀It is 20 DEG C of D.C. resistance.

Wherein, d be aluminum line diameter, mm；ρ₂₀For the resistivity of aluminum single line, 2.8264 × 10 are taken^-8(20 DEG C), Ω m；N For the total radical of aluminum steel；λ_amFor the average Haul Rate of aluminum steel by each layer aluminum steel mean pitch than calculating；α is temperature coefficient, and aluminum takes 0.00403,1/ DEG C；T_cTemperature when working for conductor, DEG C.

There was only conductor temperature T in above formula_cIt is known variables, is solved by Newton iteration method, makes

f(T_c)=D_c[(T_c+273)⁴-(T_a+273)⁴]+h(t)D_c(T_c-T_a)-I²R(T_c)

f'(T_c)=4D_c(T_c+273)³+h(t)D_c-I²R'(T_c)

N=1,2,3 ..., n are iterationses.The conductor temperature of overhead transmission line can be calculated.

3rd, environment recessiveness capacity coefficient vector is solved：

Conductor temperature is calculated by the ambient temperature for measuring, the time dependent sequence of conductor temperature is obtained：T₁, T₂..., T_k, temperature information is brought in heat balance equation,

In formula, Δ t is the sampling period.

Due to there was only three unknown parameter numbers, therefore continuous sampling just can determine that the coefficient of equation for four times, due to each Moment estimates uncorrelated, therefore estimated result is separate, can solve one group of environment recessiveness capacity coefficient vector S_k=[θ_1,k, θ_2,k,θ_3,k]^T。

4th, the real-time maximum carrying capacity of overhead transmission line is calculated：

When known as previous system number vector S_kWith initial temperature T_k, in a period of time after, maximum carrying capacity can be with It is calculated according to the formula：

In above formula, specify that the wire of power transmission line allows maximum temperature limit T according to China's Electric Design code_maxTake 70 DEG C.Take the temperature change average in continuous four sampling periods：

Specific embodiment described herein is only explanation for example spiritual to the present invention.Technology neck belonging to of the invention The technical staff in domain can be made various modifications to described specific embodiment or supplement or replaced using similar mode Generation, but without departing from the spiritual of the present invention or surmount scope defined in appended claims.

Claims (5)

1. a kind of overhead transmission line dynamic compatibilization method based on BOTDR thermometrys, it is characterised in that comprise the following steps：

Step 1, by BOTDR equipment the continuous measurement of ambient temperature is carried out to whole piece transmission line of electricity each point, obtains transmission line of electricity The environment temperature vs. time sequence of each point along the line, specifically includes：

In temp measuring system, BOTDR equipment produces one end orientation of the pulsed light Jing OPGW optical cable and optical fibres of one fixed width to step 1.1 Inject optical-fibre channel；Light pulse is constantly propagated forward inside optical fiber, when will producing when acting on for the acoustic wavefield by being mutated Raw Brillouin scattering, wherein the dorsad Brillouin scattering for having the sub-fraction direction of propagation contrary with incident direction can carry optical fiber Temperature and strain characteristics return optical fiber transmitting terminal BOTDR equipment；

Step 1.2 can obtain whole piece temperature measuring optical cable this moment along the line by the analysis to dorsad Brillouin scattering frequency drift Ambient temperature distribution, that is, measure the ambient temperature of overhead transmission line；

Step 2, by the ambient temperature for measuring conductor temperature is converted into, record and preserve at conductor temperature maximum temperature-when Between sequence, specifically include：

Step 2.1, this practice knot that there is certain non-linear relation between the ratio with current in wire and alternating current-direct current resistance By carrying out abbreviation to the OPGW and the equation of heat balance calculating process of power transmission line in the same space position；

Step 2.2, is solved by Newton iteration method to conductor temperature；

Step 3, in the Temperature-time sequence from conductor temperature maximum, chooses continuous four temperature sampling values and brings hot putting down into Weighing apparatus formula, calculates one group of environment recessiveness capacity coefficient vector, specifically calculates wire temperature according to the ambient temperature that step 2 is measured Degree, obtains the time dependent sequence of conductor temperature, in the heat balance equation that temperature information is brought into after abbreviation, due to there was only three Individual unknown parameter number, therefore continuous sampling just can determine that the coefficient of equation for four times, because each moment estimates uncorrelated, therefore Estimated result is separate, can solve one group of environment recessiveness capacity coefficient vector；

Step 4, calculates the real-time maximum carrying capacity of overhead transmission line, and constantly real-time update, specifically：When known when previous system number Vectorial S_k=[θ_1,k,θ_2,k,θ_3,k]^TWith initial temperature T_k, in a period of time after, maximum carrying capacity can be according to following Formula is being calculated：

$I_{max}=\sqrt{\frac{\frac{dT}{dt}-{\mathrm{\θ}}_1\·T_{max}-{\mathrm{\θ}}_3}{{\mathrm{\θ}}_2}}$

In formula, T_maxSpecify that the wire of power transmission line allows maximum temperature limit value according to China's Electric Design code；Take continuous Four sampling periods temperature change average.

2. a kind of overhead transmission line dynamic compatibilization method based on BOTDR thermometrys according to claim 1, its feature exists In the concrete grammar of the step 2.1 is：

Because on overhead transmission line, the OPGW in the same space position can write a Chinese character in simplified form into such as with the equation of heat balance of power transmission line Under：

OPGW：q_co+q_ro-q_so=0

Overhead transmission line：I²R(T_c)-q_cc-q_rc+q_sc=0

In above formula, I is power transmission line current-carrying capacity, R (T_c) it is temperature T_cWhen wire per km AC resistance, q_soAnd q_scRespectively The sunshine heat absorption of OPGW and wire, is unknown quantity；q_roAnd q_rcIt is respectively the heat loss through radiation of OPGW and wire, q_coAnd q_ccRespectively It is the heat loss through convection of OPGW and wire；Expression formula is respectively：

q_ro=16.03D_o×10^-8[(T_o+273)⁴-(T_a+273)⁴]

q_rc=16.03D_c×10^-8[(T_c+273)⁴-(T_a+273)⁴]

q_co=h (t) D_o ^0.75(T_o-T_a)

q_cc=h (t) D_c ^0.75(T_c-T_a)

In above formula, it is believed that OPGW optical cables and overhead transmission line have identical skin-material characteristic (i.e. heat loss through convection coefficient h (t)= 0.0205ρ_f ^0.5It is identical), wherein ρ_fFor atmospheric density, km/m³；T_oFor the temperature that OPGW sensor fibres are measured, T_cFor conductor temperature, T_aFor ambient temperature；D_oWith D_cThe diameter of respectively OPGW and wire；Because OPGW and power transmission line are in same place position Put, the solar radiation that both are subject to is identical, so sunshine heat absorption has lower relation of plane：

$\frac{q_{so}}{q_{sc}}=\frac{D_o}{D_c}$

Bringing above formula into can obtain：

I²R(T_c)=D_c[(T_c+273)⁴-(T_a+273)⁴]+0.0205ρ_f ^0.5D_c(T_c-T_a)

In above formula, when calculating current carrying capacity of conductor, alternating current-direct current resistance R (T_c) computing it is cumbersome, but because Morgan equation is Set up on a large amount of practical basis, we can use presence between current in wire I and the ratio beta of alternating current-direct current resistance certain non- This of linear relationship puts into practice conclusion to carry out abbreviation to calculating process, and formula is as follows,

β=ζ I^τ

After wire standard section determines, ζ and τ is constant, i.e.,

R(T_c)=β R_d

R_d=R₂₀[1+α(T_c-20)]

Wherein, R_dFor the D.C. resistance of operating temperature lower conductor, R₂₀It is 20 DEG C of D.C. resistance；

$R_{20}=\frac{4{\mathrm{\ρ}}_{20}{\mathrm{\λ}}_{am}}{{\mathrm{\πd}}^{2}N}$

Wherein, d be aluminum line diameter, mm；ρ₂₀For the resistivity of aluminum single line, 2.8264 × 10 are taken^-8(20 DEG C), Ω m；N is aluminum The total radical of line；λ_amFor the average Haul Rate of aluminum steel by each layer aluminum steel mean pitch than calculating；α is temperature coefficient, and aluminum takes 0.00403, 1/℃；T_cTemperature DEG C when working for conductor.

3. a kind of overhead transmission line dynamic compatibilization method based on BOTDR thermometrys according to claim 1, its feature exists In the concrete grammar of the step 2.2 is：Carry out solving conductor temperature T by Newton iteration method_c, order

f(T_c)=D_c[(T_c+273)⁴-(T_a+273)⁴]+h(t)D_c(T_c-T_a)-I²R(T_c)

f'(T_c)=4D_c(T_c+273)³+h(t)D_c-I²R'(T_c)

$T_{c(n+1)}=T_{c\left(n\right)}-\frac{f\left(T_{c\left(n\right)}\right)}{f^{\′}\left(T_{c\left(n\right)}\right)}$

N=1,2,3 ..., n are iterationses；The conductor temperature of overhead transmission line can be calculated.

4. a kind of overhead transmission line dynamic compatibilization method based on BOTDR thermometrys according to claim 1, its feature exists In the concrete grammar of the step 3 is：Conductor temperature is calculated by the ambient temperature for measuring, conductor temperature anaplasia at any time is obtained The sequence of change：T₁, T₂..., T_k, temperature information is brought in heat balance equation,

$\left[\begin{array}{c}{T}_{k-2}-T_{k-3}\\ T_{k-1}-T_{k-2}\\ T_k-T_{k-1}\end{array}\right]\mathrm{\Δ}t=\left[\begin{array}{ccc}{T}_{k-2}& I_{k-2}^2& 1\\ T_{k-1}& I_{k-1}^2& 1\\ T_k& I_k^2& 1\end{array}\right]S_k$

In formula, Δ t is the sampling period；

Due to there was only three unknown parameter numbers, therefore continuous sampling just can determine that the coefficient of equation for four times, due to each moment Estimate uncorrelated, therefore estimated result is separate, can solve one group of environment recessiveness capacity coefficient vector S_k=[θ_1,k,θ_2,k, θ_3,k]^T。

5. a kind of overhead transmission line dynamic compatibilization method based on BOTDR thermometrys according to claim 1, its feature exists In the concrete grammar of the step 4 is：

When known as previous system number vector S_kWith initial temperature T_k, in a period of time after, maximum carrying capacity can be by It is calculated according to equation below：

$I_{\max }=\frac{\sqrt{\frac{\mathrm{dT}}{\mathrm{dt}}-{\mathrm{\θ}}_1\·T_{\max }-{\mathrm{\θ}}_3}}{{\mathrm{\θ}}_2}$

In above formula, specify that the wire of power transmission line allows maximum temperature limit T according to China's Electric Design code_maxTake 70 DEG C； Take the temperature change average in continuous four sampling periods：

$\frac{(T_{k-2}-T_{k-3})+(T_{k-1}-T_{k-2})+(T_k-T_{k-1})}{3\mathrm{\Δ}t}=\frac{T_k-T_{k-3}}{3\mathrm{\Δ}t}.$