CN102590594B - Transient state thermal circuit model-based method and device for determining permissible current of overhead conductor - Google Patents

Transient state thermal circuit model-based method and device for determining permissible current of overhead conductor Download PDF

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CN102590594B
CN102590594B CN201210059507.5A CN201210059507A CN102590594B CN 102590594 B CN102590594 B CN 102590594B CN 201210059507 A CN201210059507 A CN 201210059507A CN 102590594 B CN102590594 B CN 102590594B
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resistance
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张鸣
刘刚
阮班义
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South China University of Technology SCUT
Foshan Power Supply Bureau of Guangdong Power Grid Corp
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Foshan Power Supply Bureau of Guangdong Power Grid Corp
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Abstract

The invention discloses a transient state thermal circuit model-based method and device for determining a permissible current of an overhead conductor. The method comprises the steps of: firstly, loading a current to the overhead conductor, measuring the temperature of the conductor and an environment temperature of an environment where the conductor is in in real time; if wanting to know the maximum permissible current at some moment, calculating an AC resistance; by adopting a special formula, sequentially calculating the AC resistance and an environment thermal resistance of a moment to be detected, and the maximum permissible current when the temperature of the conductor reaches 70 DEG C under the outside environment of the moment to be detected; and comparing the current current and the maximum permissible current to carry out corresponding compatibility on the overhead conductor, and providing basis for load transfer, scheduling plan and the like, wherein the formula for calculating the environment thermal resistance and the maximum permissible current is based on a transient state thermal circuit model, the maximum permissible current can be obtained through measuring the temperature of the conductor and the environment temperature of the environment where the conductor is in and through simple calculation, and proved by experiments, result errors are in a permissible range.

Description

Allow definite method and apparatus of electric current based on the aerial condutor of Transient Thermal Circuit model
Technical field
The present invention relates to high voltage overhead technology of transmission of electricity field, particularly a kind of aerial condutor based on Transient Thermal Circuit model allows definite method and apparatus of electric current.
Background technology
While not passing through electric current in wire, its temperature equates with ambient temperature; During by electric current, resistance is heat energy by electric energy conversion, and conductor temperature, higher than environment temperature, is added the impact at convection heat transfer, heat radiation and sunshine etc., in dynamic changing process.In the time that transmission line of electricity based model for load duration increases, will there is overheating fault in circuit, in order to prevent that this phenomenon from occurring, and occurred the concept of maximum allowed current.
The allowable temperature of regulation steel-cored aluminium strand is+70 ℃ (large leap can adopt+90 ℃) in China's " 110-500kV aerial power transmission line designing technique rules ".Therefore, maximum allowed current refer to aerial condutor in other words transmission line of electricity operate in weather environment, conductor temperature reaches+electric current 70 ℃ time.
Understand the maximum allowed current of aerial condutor, be conducive to fully excavate the ability to transmit electricity of existing transmission line of electricity, for the scheduling of traffic department, line maintenance, newly-built layout of roads etc. provide foundation.But the parameter that definite method of existing maximum allowed current need to be measured, the factor of consideration are too many, as wind speed, atmospheric density, diameter of wire, the effective incident angle of sunshine etc., make to measure that input cost is high, computing is complicated, result reliability is not high.
Summary of the invention
The present invention is directed to the problems referred to above, propose a kind of definite method and apparatus of the permission of the aerial condutor based on Transient Thermal Circuit model electric current, to reduce monitoring variable, simplified operation process.
The aerial condutor that the present invention is based on Transient Thermal Circuit model allows definite method of electric current, comprises step:
To aerial condutor loading current I;
Real-Time Monitoring conductor temperature T 1and the wire environment temperature T of specified distance around 2;
Calculate the AC resistance R in moment to be measured c, according to described I, T 1, T 2, R c, adopt following formula to calculate the environment thermal resistance R in moment to be measured x:
R x = T 1 - T 2 I 2 R c - C x dT 1 dt
According to described T 1, T 2, R c, R x, adopt following formula, calculate the maximum allowed current I of aerial condutor under moment external environment to be measured max:
I max = 70 - T 2 R x R c
Preferably, adopt following formula to calculate described AC resistance:
R c＝ζI τR 20[1+α(T 1-20)]
In formula, ζ represents the constant relevant with wire standard section with τ, and α is temperature coefficient, R 20direct current resistance while representing 20 ℃ of conductor temperatures.
Preferably, around described wire, specific range is specially apart from the optional position of conductive line surfaces 30cm.
Preferably, described conductor temperature is conductive line surfaces temperature.
The aerial condutor that the present invention is based on Transient Thermal Circuit model allows the determining device of electric current, comprising:
Current load module, for to aerial condutor loading current I;
Temperature monitoring module, for Real-Time Monitoring conductor temperature T 1and the wire environment temperature T of specified distance around 2;
Environment thermal resistance determination module, for calculating the AC resistance R in moment to be measured c, according to described I, T 1, T 2, R c, adopt following formula to calculate the environment thermal resistance R in moment to be measured x:
R x = T 1 - T 2 I 2 R c - C x dT 1 dt
Maximum allowed current determination module, for according to described T 1, T 2, R c, R x, adopt following formula, calculate the maximum allowed current I of aerial condutor under moment external environment to be measured max:
I max = 70 - T 2 R x R c
Preferably, described environment thermal resistance determination module is also for adopting following formula to calculate described AC resistance:
R c＝ζI τR 20[1+α(T 1-20)]
In formula, ζ represents the constant relevant with wire standard section with τ, and α is temperature coefficient, R 20direct current resistance while representing 20 ℃ of conductor temperatures.
Preferably, around described wire, specific range is specially apart from the optional position of conductive line surfaces 30cm.
Preferably, described conductor temperature is conductive line surfaces temperature.
The aerial condutor that the present invention is based on Transient Thermal Circuit model allows definite method of electric current, first to aerial condutor loading current, the environment temperature of Real-Time Monitoring conductor temperature and wire environment of living in, and calculate the AC resistance in moment to be measured, according to electric current, conductor temperature, environment temperature and AC resistance, adopt specific formula to calculate the environment thermal resistance in moment to be measured, again according to conductor temperature, environment temperature, AC resistance and environment thermal resistance, adopt specific formula to calculate under moment external environment to be measured, conductor temperature reaches 70 maximum allowed currents while spending.The real-time current and the maximum allowed current that contrast the moment to be measured can carry out corresponding increase-volume to moment aerial condutor to be measured, for load transfer, operation plan etc. provide foundation.Wherein, the formula of computing environment thermal resistance and maximum allowed current is based upon on Transient Thermal Circuit model basis, only needs two parameters of measure traverse line temperature and wire environment temperature of living in and through simple calculations, can draw maximum allowed current, empirical tests, the error of result is in allowed band.In addition, the determining device that the present invention is based on the aerial condutor permission electric current of Transient Thermal Circuit model is the device corresponding with above-mentioned definite method, and beneficial effect repeats no more.
Accompanying drawing explanation
Fig. 1 is the physical model schematic diagram of only monitoring conductor temperature;
Fig. 2 is the physical model schematic diagram of monitoring conductor temperature and wire environment temperature of living in;
Fig. 3 is the corresponding Re of Fig. 1 road model schematic diagram;
Fig. 4 is the corresponding Re of Fig. 2 road model schematic diagram;
Fig. 5 is that aerial condutor of the present invention allows electric current to determine model basis-Transient Thermal Circuit model schematic diagram of method;
Fig. 6 is the schematic flow sheet that the present invention is based on definite method of the aerial condutor permission electric current of Transient Thermal Circuit model;
Fig. 7 is the structural representation that the present invention is based on the determining device of the aerial condutor permission electric current of Transient Thermal Circuit model;
Fig. 8 is the experimental device for verifying schematic diagram that the present invention is based on definite method of the aerial condutor permission electric current of Transient Thermal Circuit model;
Fig. 9 is environment temperature in 24h, humidity, wind speed, solar radiation, the measured value of conductor temperature and the calculated value schematic diagram of maximum allowed current.
Embodiment
In order to realize the object of simplified operation, first inventor has built the Transient Thermal Circuit model of aerial condutor, thereby derives the formula of maximum allowed current.Set up and start to explain in detail the present invention from model below.
Comprised and being absorbed heat at the heating of wire self, sunshine by the heat of the known wire absorption of wire thermal balance equation, heat radiation comprises convection heat transfer and heat radiation.By the relation one to one between the temperature difference in voltage, resistance, electric capacity Yu Re road in electric field, thermal resistance, thermal capacitance, can set up take wire as core corresponding hot road model.
In the time only monitoring conductive line surfaces temperature T 1, as shown in Figure 1, the physical model of monitoring conductive line surfaces temperature T 1 and wire environment temperature T2 around as shown in Figure 2 for the physical model of wire.Corresponding to Fig. 1,2 physical model, can be able to Re road model centered by aerial condutor, as shown in Figure 3,4.
In Fig. 3,4, F (t) is the equivalent heat flux of sunshine heat absorption, and this part changed with weather condition, geographic position, time, but in a certain section of time range of wire for a certain particular location, can think constant.T 1, T 2be respectively conductor temperature, wire environment temperature of living in, R xfor wire is to T 2the thermal resistance of monitoring point, C x2for the thermal capacitance of steel core aluminum stranded conductor aluminium, C x1for the thermal capacitance of steel-cored aluminium strand steel core.R n, C nfor environment T 2thermal resistance, thermal capacitance beyond point, Φ c=I 2r cfor wire self-heating amount, R cfor conductor temperature T 1time AC resistance.
From 3,4 contrasts, because Fig. 3 only has a conductive line surfaces temperature T 1, cannot solve R according to model x.Meanwhile, due at certain hour scope inside conductor ambient temperature T 2can think constant, according to measuring T 1, T 22 temperature, Fig. 4 model can solve, so the present invention has selected 2 temperature Re road models of monitoring to study.
Monitoring point T 2the distance of distance of wire should not be too closely or is too far away, is too closely subject to the impact of wire self temperature, too is far not enough to again characterize the environment temperature of wire environment of living in.As a preferred embodiment, get the aerial condutor of unit length and the T at 30cm place, distance of wire surface 2monitoring point is research object.For wire LGJ-240/30, the concentrated thermal capacitance of the airequivalent of selected location is 35 times of wire thermal capacitance, so in the present invention, environment thermal capacitance is negligible.
When the heat absorption of wire and heat radiation, both reach mobile equilibrium, are also that conductor temperature is basicly stable, and now wire thermal capacitance is inoperative.Because absorb heat sunshine on the impact of current-carrying capacity only in 1.2%, so ignore at this.Or consider that F (t) is zero in the time there is no sunshine, now corresponding Transient Thermal Circuit model as shown in Figure 5.
On the basis of model shown in Fig. 5, according to the basic theories of thermal conduction study, can obtain the formula of environment thermal resistance and maximum allowed current:
R x = T 1 - T 2 I 2 R c - C x dT 1 dt - - - ( 1 )
I max = 70 - T 2 R x R c - - - ( 2 )
In formula (2) 70 represents 70 ℃.
There are above-mentioned two formula, can have calculated maximum allowed current.The aerial condutor that the present invention is based on Transient Thermal Circuit model allows definite method of electric current, as shown in Figure 6, carries out according to following steps:
Step 1, to aerial condutor loading current I;
Step 2, Real-Time Monitoring conductor temperature T 1and the wire environment temperature T of specified distance around 2;
Step 3, calculate the AC resistance R in moment to be measured c, according to described I, T 1, T 2, R c, employing formula (1) is calculated the environment thermal resistance R in moment to be measured x;
Step 4, according to described T 1, T 2, R c, R x, employing formula (2), calculates the maximum allowed current I of aerial condutor under moment external environment to be measured max.
The determining device that the present invention is based on the aerial condutor permission electric current of Transient Thermal Circuit model is the device corresponding with said method, as shown in Figure 7, comprising:
Current load module, for to aerial condutor loading current I;
Temperature monitoring module, for Real-Time Monitoring conductor temperature T 1and the wire environment temperature T of specified distance around 2;
Environment thermal resistance determination module, for calculating the AC resistance R in moment to be measured c, according to described I, T 1, T 2, R c, (1) formula of employing is calculated the environment thermal resistance R in moment to be measured x:
Maximum allowed current determination module, for according to described T 1, T 2, R c, R x, adopt (2) formula, calculate the maximum allowed current I of aerial condutor under moment external environment to be measured max.
As shown in Figure 7, the annexation of the each module of this determining device is as follows: environment thermal resistance determination module is connected with current load module, temperature monitoring module, maximum allowed current determination module respectively, and maximum allowed current determination module is connected with temperature monitoring module with current load module respectively again.From the function of each module, current load module, temperature monitoring module, environment thermal resistance determination module and maximum allowed current determination module are corresponding with step 1, step 2, step 3 and the step 4 of above-mentioned definite method respectively.Above-mentioned definite method is that example description is equally applicable to this determining device below.
Due to the computing more complicated of AC resistance, Morgan equation not only Consideration is many, and has larger error.Known according to prior art, alternating current-direct current resistance becomes nonlinear relationship than with electric current, can simplify the calculating of AC resistance, and computation process is suc as formula shown in (3), (4), wherein β=ζ I τ.By calculating this algorithm of known employing and Morgan normalized form result of calculation relative error in 1.4%.After wire standard section is determined, ζ and τ are constants.
R d＝R 20[1+α(T 1-20)] (3)
R C＝βR d (4)
Composite type (3), (4) can obtain formula (5):
R c＝ζI τR 20[1+α(T 1-20)] (5)
In formula, ζ represents the constant relevant with wire standard section with τ, and α is temperature coefficient, R drepresent direct current resistance, R 20direct current resistance while representing 20 ℃ of conductor temperatures.
As a preferred embodiment, described conductor temperature is conductive line surfaces temperature.
In order to verify correctness and the application scenario thereof of aerial condutor Transient Thermal Circuit model, prove the feasibility of aerial condutor increase-volume, design aerial condutor Transient Thermal Circuit modelling verification experiment.Test unit as shown in Figure 8.
Experimental provision is mainly made up of 5 parts: reactive compensation capacitor, pressure regulator, current lifting device, test circuit (model is LGJ-240/30), automatic weather station.At outdoor, indoor conductor temperature and the wire environment temperature monitoring point of being equiped with.Wherein the basic parameter of LGJ-240/30 experiment wire is as shown in table 1, and its rated current is 445A.
Table 1 LJG-240/30 wire basic parameter
Figure BDA0000141458100000071
In experiment, utilize the temperature T 1 of thermocouple monitoring wire aluminium lamination, the temperature of distance of wire 4cm is the residing environment temperature T2 of wire.The every 1min of thermopair gathers a secondary data, by data collecting instrument autostore.The every 1min of automatic weather station gathers a secondary data, can Real-Time Monitoring wind speed, the local weather information such as wind direction, humidity, solar radiation.
According to the hot road of aerial condutor transient Model, in order to investigate wire wire maximum allowed current situation of change in 24h changing environment, the feasibility of checking aerial condutor dynamic compatibilization, wire has loaded steady current 428A, maximum allowed current calculates according to formula (2), and the time interval is 1min.In experiment, the weather information of the temperature of conductor temperature and environment, solar radiation, humidity, wind speed as shown in Figure 9.
As shown in Figure 9, in 24h, air humidity is all in 50% left and right, changes littlely, and variation of ambient temperature is mild.Maximum allowed current was not necessarily greater than and had the permission of solar radiation situation electric current daytime night, and therefore, wire transmission ability and wind speed have great relation, simultaneously wind speed again with sunshine situation relevant.In the model of hot road, only ignore the impact of F (t) on wire quantity of heat production, do not ignore the impact of sunshine on environment.
In 24h experiment, each stage is realized phenomenon and the analysis of causes is as shown in table 2.
In 24h experiment, because environment temperature is lower, be 9 ℃-20 ℃, so increase-volume large percentage, increase-volume space is 10%-50%.
Table 2 24h experimental phenomena and analysis thereof
Figure BDA0000141458100000081
From above data, calculate the method for maximum allowed current by the present invention, can calculate the maximum allowed current of wire any time.Wire increase-volume space difference under varying environment condition, in outdoor experiment, increase-volume ratio is 10%-50%.
Above-described embodiment of the present invention, does not form limiting the scope of the present invention.Any modification of doing within the spirit and principles in the present invention, be equal to and replace and improvement etc., within all should being included in claim protection domain of the present invention.

Claims (6)

1. a definite method that allows electric current based on the aerial condutor of Transient Thermal Circuit model, is characterized in that, comprises step:
To aerial condutor loading current I;
Real-Time Monitoring conductor temperature T 1and the wire environment temperature T of specified distance around 2;
Calculate the AC resistance R in moment to be measured c, according to described I, T 1, T 2, R c, adopt following formula to calculate the environment thermal resistance R in moment to be measured x:
R x = T 1 - T 2 I 2 R c - C x dT 1 dt
C in formula xrepresent wire thermal capacitance;
According to described T 1, T 2, R c, R x, adopt following formula, calculate the maximum allowed current I of aerial condutor under moment external environment to be measured max:
I max = 70 - T 2 R x R c
Adopt following formula to calculate described AC resistance:
R c＝ζI τR 20[1+α(T 1-20)]
In formula, ζ represents the constant relevant with wire standard section with τ, and α is temperature coefficient, R 20direct current resistance while representing 20 ℃ of conductor temperatures.
2. the aerial condutor based on Transient Thermal Circuit model according to claim 1 allows definite method of electric current, it is characterized in that, described wire around specific range is specially apart from the optional position of conductive line surfaces 30cm.
3. the aerial condutor based on Transient Thermal Circuit model according to claim 1 allows definite method of electric current, it is characterized in that, described conductor temperature is conductive line surfaces temperature.
4. a determining device that allows electric current based on the aerial condutor of Transient Thermal Circuit model, is characterized in that, comprising:
Current load module, for to aerial condutor loading current I;
Temperature monitoring module, for Real-Time Monitoring conductor temperature T 1and the wire environment temperature T of specified distance around 2;
Environment thermal resistance determination module, for calculating the AC resistance R in moment to be measured c, according to described I, T 1, T 2, R c, adopt following formula to calculate the environment thermal resistance R in moment to be measured x:
R x = T 1 - T 2 I 2 R c - C x dT 1 dt
C in formula xrepresent wire thermal capacitance;
Maximum allowed current determination module, for according to described T 1, T 2, R c, R x, adopt following formula, calculate the maximum allowed current I of aerial condutor under moment external environment to be measured max:
I max = 70 - T 2 R x R c
Described environment thermal resistance determination module is also for adopting following formula to calculate described AC resistance:
R c＝ζI τR 20[1+α(T 1-20)]
In formula, ζ represents the constant relevant with wire standard section with τ, and α is temperature coefficient, R 20direct current resistance while representing 20 ℃ of conductor temperatures.
5. the aerial condutor based on Transient Thermal Circuit model according to claim 4 allows the determining device of electric current, it is characterized in that, described wire around specific range is specially apart from the optional position of conductive line surfaces 30cm.
6. the aerial condutor based on Transient Thermal Circuit model according to claim 4 allows the determining device of electric current, it is characterized in that, described conductor temperature is conductive line surfaces temperature.
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