Dynamic capacity increasing method for overhead transmission line based on heat balance equation parameter optimization

Abstract

The invention discloses an overhead transmission line dynamic capacity increasing method based on heat balance equation parameter optimization, and relates to the technical field of overhead transmission line dynamic capacity increasing. The invention aims to solve the problem that an overhead line is not efficiently utilized during electric energy transmission of an existing overhead transmission line. According to the dynamic capacity increasing method for the overhead transmission line based on heat balance equation parameter optimization, the transmission line current-carrying capacity limit calculation model is constructed based on the heat balance equation, the error polynomial is introduced to eliminate the input data error, the current-carrying capacity limit calculation model is finally obtained, and then the overhead line is efficiently utilized.

Description

Technical Field

[0001] The invention belongs to the technical field of dynamic capacity increase of overhead power transmission lines. Background Art

[0002] Due to the increase in the capacity of new energy grid connection and the growth of social electricity demand, the transmission capacity of my country's power grid transmission lines is relatively lagging behind. In order to increase the transmission capacity of transmission lines to meet the growing demand, the technical investment cost of using existing lines and equipment to increase the transmission capacity of transmission lines is lower and easier to implement than building new transmission lines.

[0003] The power transmission capacity index of overhead transmission lines, namely the static thermal rating (STR), has been calculated during the design, but the static rating is a conservative value. The meteorological boundary conditions of overhead wires are usually difficult to reach very severe conditions at the same time. Therefore, the actual temperature of the wire using the static rating is much lower than the maximum operating allowable temperature, thus ignoring the power transmission potential of overhead transmission lines and failing to use overhead lines efficiently. Summary of the invention

[0004] The present invention aims to solve the problem that the existing overhead transmission lines do not efficiently utilize the overhead lines when transmitting electric energy, and provides a method for dynamically increasing the capacity of overhead transmission lines based on thermal balance equation parameter optimization.

[0005] The method for dynamic capacity increase of overhead transmission lines based on thermal balance equation parameter optimization includes:

[0006] Collect the operating temperature T of the overhead transmission line avg and the meteorological data around the line, and calculate the current carrying capacity limit through the current carrying capacity limit calculation model, thereby realizing the dynamic capacity increase of the overhead transmission line, the meteorological data around the line includes: ambient temperature T a , wind speed v w , wind direction φ and solar radiation intensity Q se ;

[0007] The expression of the current carrying capacity limit calculation model is:

[0008]

[0009] Among them, I' is the current carrying capacity limit, q c is the heat dissipated by wire convection, q r1 is the heat dissipated by the conductor, q s1 is the solar radiation heat generated by the conductor, α is the solar radiation absorption rate of the overhead transmission line surface, ε is the thermal radiation coefficient, R(T avg ) is the transmission line at operating temperature T avgThe resistance under w ,φ,T a ,Q se ) is the error polynomial.

[0010] Furthermore, the constraints of the solar radiation absorption rate α and the thermal radiation coefficient ε on the surface of the overhead transmission line are as follows:

[0011] 0.35≤α≤0.95,

[0012] 0.23≤ε≤0.95.

[0013] Furthermore, the error polynomial f(v w ,φ,T a ,Q se ) is:

[0014] f(v w ,φ,T a ,Q se )=δ1·v w 2 +δ2·v w +δ3·T a 2 +δ4·T a +δ5·φ+δ6·Q se +δ7,

[0015] Among them, δ1, δ2, δ3, δ4, δ5, and δ6 are the coefficients of the corresponding terms, and δ7 is a constant term.

[0016] Furthermore, the method for constructing the above-mentioned current carrying capacity limit calculation model includes:

[0017] Based on the thermal balance equation of the overhead transmission line, a difference relationship between the heat generation and the heat dissipation of the overhead transmission line is established, and an error polynomial is introduced into the difference relationship. The operating current when the difference between the heat generation and the heat dissipation of the overhead transmission line is 0 is the current carrying capacity limit.

[0018] Furthermore, the difference between the heat generation and heat dissipation of the overhead transmission line is expressed as follows:

[0019] ΔQ=q c +ε·q r1 -α·q s1 -I 2 R(T avg ),

[0020] Among them, ΔQ is the difference between the heat generated and the heat dissipated by the overhead transmission line, and I is the operating current of the overhead transmission line.

[0021] Furthermore, the operating temperature Tavg Obtained through the temperature measuring device of the overhead transmission line.

[0022] Furthermore, the meteorological data around the above-mentioned line is obtained by installing a micro-meteorological station on the tower.

[0023] The method for dynamic capacity increase of overhead transmission lines based on thermal balance equation parameter optimization described in the present invention constructs a transmission line current carrying capacity limit calculation model based on the thermal balance equation, introduces an error polynomial to eliminate input data errors, and finally obtains a current carrying capacity limit calculation model, thereby efficiently utilizing overhead lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention provides a flow chart of a method for dynamically increasing the capacity of overhead power transmission lines based on heat balance equation parameter optimization. DETAILED DESCRIPTION

[0025] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0026] In the existing technology, the heat balance equation is introduced into the dynamic thermal rating (DTR) technology. The concept of dynamic thermal customization clearly points out how to calculate the current carrying capacity of the line in a real-time changing environment. This technology reveals the time-varying nature of the load capacity of the transmission element. Studies have shown that in most cases the DTR of overhead lines is significantly higher than STR, and the dynamic capacity increase effect is significant. By making full use of meteorological conditions and combining temperature monitoring data, the dynamic capacity increase of the line is determined, which improves the flexibility of power system operation.

[0027] The heat balance equation shows that the transmission capacity of the transmission line is mainly affected by the meteorological conditions of the environment, such as temperature, wind speed, wind direction and solar radiation. For specific transmission lines, the parameters of the transmission line current limit calculation formula will also change with the operation of the line. Therefore, it is necessary to optimize the parameters of the transmission line current limit calculation formula based on historical operation data using optimization algorithms to improve the accuracy of dynamic capacity increase technology.

[0028] Reference Figure 1 Specifically describing this embodiment, the method for dynamically increasing the capacity of overhead transmission lines based on thermal balance equation parameter optimization described in this embodiment includes:

[0029] S110, obtaining the operating temperature T of the steady-state overhead transmission line avg , operating current I, and meteorological data around the line.

[0030] The operating temperature data can be obtained by installing a temperature measuring device; the operating current data can be obtained through the dispatching center; the meteorological data around the overhead transmission line can be obtained by installing a micro-meteorological station on the tower. The meteorological data that needs to be obtained include: ambient temperature T a , wind speed v w , wind direction φ, and solar radiation intensity Q se . The acquired data is matched according to time for easy subsequent use.

[0031] S120. Construct a current carrying capacity limit calculation model based on the thermal balance equation of the overhead transmission line.

[0032] Based on the heat balance equation of the transmission line, the difference relationship between the heat generation and heat dissipation of the line is established and formalized into the following mathematical model:

[0033] ΔQ=q c +ε·q r1 -α·q s1 -I 2 R(T avg ),

[0034] Among them, ΔQ is the difference between the heat generated and the heat dissipated by the overhead transmission line, q c is the heat dissipated by wire convection, q r1 is the heat dissipated by the conductor, q s1 is the heat generated by solar radiation from the conductor, I 2 R(T avg ) is the heat generated by the Joule heating effect of the transmission line. Among them, the heat generated by the overhead transmission line is related to the solar radiation intensity, the solar radiation absorption rate α of the overhead transmission line surface and the current, and the heat dissipation of the overhead transmission line is related to the wind speed, wind direction, ambient temperature, thermal radiation coefficient ε and the operating temperature of the conductor.

[0035] S130, use optimization algorithm to optimize the parameters in the heat balance equation

[0036] The key parameters to be optimized include: parameters that can change with the running time of the conductor, such as the solar radiation absorption rate α and thermal radiation coefficient ε of the conductor surface, the influence coefficient of current and temperature on heat generation, and the influence coefficient of wind speed, solar radiation and other factors on heat dissipation.

[0037] Note that the optimization algorithm here can adopt the commonly used least squares method, genetic algorithm and particle swarm optimization algorithm, etc., and no specific explanation is given.

[0038] S140, introducing an error polynomial to eliminate the error of input data.

[0039] Taking into account the errors in the data, error polynomials are used for correction. For the influence of wind speed and ambient temperature, quadratic functions are used for fitting to more accurately reflect their sensitivity to heat dissipation; for the influence of solar radiation intensity and wind direction, linear functions are used for fitting.

[0040] Error polynomial f(v w ,φ,T a ,Q se ) is as follows:

[0041] f(v w ,φ,T a ,Q se )=δ1·v w 2 +δ2·v w +δ3·T a 2 +δ4·T a +δ5·φ+δ6·Q se +δ7,

[0042] Among them, δ1, δ2, δ3, δ4, δ5, and δ6 are the coefficients of the corresponding terms, and δ7 is a constant term.

[0043] The error polynomial f(v w ,φ,T a ,Q se ) is added to the heat balance equation:

[0044] ΔQ=q c +ε·q r1 -α·q s1 -I 2 R(T avg )+f(v w ,φ,T a ,Q se ).

[0045] S150. List the constraints of the model optimization parameters.

[0046] The parameters obtained through optimization meet certain constraints, among which the solar radiation absorption rate α and thermal radiation coefficient ε of the conductor surface should be within the range of physical significance. The constraints are:

[0047] 0.35≤α≤0.95,

[0048] 0.23≤ε≤0.95,

[0049] This constraint ensures that the optimized model has sufficient accuracy and adaptability.

[0050] S160, current carrying capacity limit calculation model.

[0051] The parameter values ​​obtained by optimization are made to make ΔQ equal to 0, and the calculation model of the current carrying capacity limit I′ applicable to a specific transmission line is established:

[0052]

[0053] Among them, R(T avg ) is the transmission line at operating temperature T avg The resistance below.

[0054] The model can dynamically adjust the maximum carrying capacity of the line based on environmental factors, thereby improving the operating efficiency and safety of the transmission system.

[0055] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. A method for dynamic capacity increase of overhead transmission lines based on thermal balance equation parameter optimization, characterized in that: include: Collect the operating temperature T of the overhead transmission line avg and the meteorological data around the line, and calculate the current carrying capacity limit through the current carrying capacity limit calculation model, thereby realizing the dynamic capacity increase of the overhead transmission line, the meteorological data around the line includes: ambient temperature T a , wind speed v w , wind direction φ and solar radiation intensity Q se ; The expression of the current carrying capacity limit calculation model is: Among them, I' is the current carrying capacity limit, q c is the heat dissipated by wire convection, q r1 is the heat dissipated by the conductor, q s1 is the solar radiation heat generated by the conductor, α is the solar radiation absorption rate of the overhead transmission line surface, ε is the thermal radiation coefficient, R(T avg ) is the transmission line at operating temperature T avg The resistance under w ,φ,T a ,Q se ) is the error polynomial.

2. The method for dynamic capacity increase of overhead power transmission lines based on thermal balance equation parameter optimization according to claim 1, characterized in that: The constraints of the solar radiation absorption rate α and thermal radiation coefficient ε on the surface of the overhead transmission line are: 0.35≤α≤0.95， 0.23≤ε≤0.

95.

3. The method for dynamic capacity increase of overhead power transmission lines based on thermal balance equation parameter optimization according to claim 1, characterized in that: The error polynomial f(v w ,φ,T a ,Q se ) is: f(v w ,φ,T a ,Q se )=δ1·v w 2 +δ2·v w +δ3·T a 2 +δ4·T a +δ5·φ+δ6·Q se +δ7, Among them, δ1, δ2, δ3, δ4, δ5, and δ6 are the coefficients of the corresponding terms, and δ7 is a constant term.

4. The method for dynamic capacity increase of overhead power transmission lines based on thermal balance equation parameter optimization according to claim 1, 2 or 3, characterized in that: The method for constructing the current carrying capacity limit calculation model includes: Based on the thermal balance equation of the overhead transmission line, a difference relationship between the heat generation and the heat dissipation of the overhead transmission line is established, and an error polynomial is introduced into the difference relationship. The operating current when the difference between the heat generation and the heat dissipation of the overhead transmission line is 0 is the current carrying capacity limit.

5. The method for dynamic capacity increase of overhead power transmission lines based on thermal balance equation parameter optimization according to claim 4, characterized in that: The difference between the heat generation and heat dissipation of the overhead transmission line is expressed as: ΔQ=q c +ε·q r1 -α·q s1 -I 2 R(T avg ), Among them, ΔQ is the difference between the heat generated and the heat dissipated by the overhead transmission line, and I is the operating current of the overhead transmission line.

6. The method for dynamic capacity increase of overhead power transmission lines based on thermal balance equation parameter optimization according to claim 1, characterized in that: The operating temperature T avg Obtained through the temperature measuring device of the overhead transmission line.

7. The method for dynamic capacity increase of overhead power transmission lines based on heat balance equation parameter optimization according to claim 6, characterized in that: The meteorological data around the line is obtained by installing a micro-meteorological station on the tower.

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