A kind of based on the heat dissipating method having groove box cable tunnel thermal field model
Technical field
The present invention relates to field of power transmission, especially relate to a kind of based on there being groove box cable tunnel thermal field model
Heat dissipating method
Background technology
In order to solve increasingly severe powerup issue, plan utilization lays 220kV power cable at the big passage built.
For this section of river-crossing tunnel, current tentative programme is as high tension cable using the cable passage of segmentation in every tunnel
Tunnel, lays 220kV power cable.
The original scheme in tunnel does not consider lay high voltage power cable, so the design of tunnel ventilation heat radiation is also
Do not consider the caloric value of power cable.Power cable generates heat in longtime running, causes cable passage temperature to raise,
The safe operation of the miscellaneous equipment that may affect in tunnel in the same space.It addition, the radiating condition of this cable passage
Different with conventional tunnel, conventional tunnel four faces up and down the most directly contact soil, can dispel the heat.Shanghai is worshipped
In Soviet Union tunnel, cable passage only one side and bottom are soil, and top is highway, and opposite side is that track is handed over
Circulation passage.
Summary of the invention
Defect that the purpose of the present invention is contemplated to overcome above-mentioned prior art to exist and provide effectively, a kind of accurately
Based on the heat dissipating method having groove box cable tunnel thermal field model
The purpose of the present invention can be achieved through the following technical solutions:
A kind of based on there being the heat dissipating method of groove box cable tunnel thermal field model, comprise the following steps:
1) cable tunnel prospecting, obtains the parameter of each ingredient in cable tunnel;
2) mathematical model of cable tunnel thermal field is set up;
3) caloric value of this cable tunnel is calculated according to mathematical model;
4) draft type and the ventilating system of this cable tunnel are designed.
Described thermal resistance is drawn by R=d/KA, and in formula, R is thermal resistance, and d is the thickness of heat conductor, and A is heat conductor
Area of section, K is heat conductivity.
Described step 2) in the Mathematical Models of cable tunnel thermal field include following sub-step:
21) electric cable heating model is set up:
N telegram in reply cable heat radiation power is:
Wherein, P is cable heat radiation power, and I is current-carrying capacity, and A is cable cross-sectional area, and σ is cable resistance rate,
L be cable length, C be cable radiation loss coefficient value 0.9, n is cable backhaul number;
22) cable thermal losses model is set up:
I2[RT1+R(1+λ1)T2+R(1+λ1+λ2)(T3+T4)]+Wd[0.5T1+n(T2+T3+T4)]=θ1-θC
Wherein:
I: current-carrying capacity, θC: ambient temperature, θ1: cable conductor temperature, the conductor exchange under R: operating temperature
Resistance, Wd: insulation dielectric loss, λ1: metal shading loss factor, λ2: metal armouring loss factor, T1:
Insulating barrier thermal resistance between conductor and protective metal shell, T2: inner liner thermal resistance between protective metal shell and armor, T3: cable
Outer jacket thermal resistance, T4: Exterior cable thermal resistance, ambient temperature θCRefer to air themperature, it is assumed that θCIt is constant, leads
Temperature θ1Refer to the maximum permissible temperature of long-term work, be set to 90 DEG C;θ1And θCIt it is all boundary condition.
Described step 22) in, the calculating formula of described conductor AC resistance R is:
R=R ' (1+Ys+Yp)
R '=R0[1+α20(θ-20)]
Wherein:
R ': maximum operating temperature lower conductor D.C. resistance, Ys;Kelvin effect factor, Yp: kindred effect factor,
R0: conductor DC resistance when 20 DEG C, θ: running temperature, α20: the temperature coefficient of copper conductor when 20 DEG C, for
Circular compact conductor Ks=1, dc: conductor diameter, s: the spacing in each conductor axle center.
Described step 22) in, described dielectric loss WdCalculating formula be:
Wherein:
ω=2 π f, U0: voltage-to-ground, ε=2.3, Di: for outer insulation diameter, dc: for inner shield external diameter.
Described step 22) in metal shading loss λ1Calculating formula be:
λ1=λ1′+λ1″
Then have when for rounded projections arranged:
Δ2=0
Wherein:
λ1'=0, λ1" for eddy-current loss, ρ: protective metal shell resistivity, R: protective metal shell resistance, ts: metal protects
Set thickness, D: protective metal shell external diameter, Doc: corrugated aluminium sheath maximum outside diameter, Dit: corrugated aluminium sheath minimum diameter.
Described step 22) in cable internal thermal resistance T1、T2、T3Calculating formula be:
Wherein:
: insulant thermal resistivity, dc: conductor diameter t1: the insulation thickness between conductor and sheath;
This cable does not has a steel armour, therefore T2=0;
Wherein:
t3: oversheath thickness,: nonmetal oversheath thermal resistivity, Doc: corrugated aluminium sheath maximum outside diameter.
Described step 22) in Exterior cable thermal resistance T4Groove box inwall thermal resistance T is arrived including cable5, groove box body heat
Resistance T6, thermal resistance T of groove outer box wall to air7, thermal resistance T of air to cable passage inwall8, tunnel is at the bottom of river
Soil thermal resistance T9, described T5、T6、T7、T8And T9Calculating formula be:
T8_1=1/X1A1
T8_1=1/X2A2
Wherein:
A5: the average area of dissipation of interlayer inside and outside wall, d1: threephase cable equivalent diameter, d2: the equivalence of groove box inwall
Diameter, the convection transfer rate of X: interlayer,: groove box thermal resistivity, A6: groove box area of dissipation, X7_1、
X7_2、X7_3: groove box side, end face, the convection transfer rate of bottom surface, A7_1、A7_2、A7_3: groove box side,
End face, the area of bottom surface, T8_1: thermal resistance T of air to sidewall8_1: the thermal resistance of air to ground, X1、X2:
The convection transfer rate A of sidewall or bottom1、A2: sidewall or the heat exchange area of bottom, λt: soil thermal conductivity,
H: the tunnel degree of depth, dz: the diameter of circular tunnel outer surface, L and W is the height and width of Rectangular Tunnel respectively.
Compared with prior art, the invention have the characteristics that:
1, set up model accurate, analyze cable heating heat dispersal situations in tunnel from actual scene, examine
It is thorough to consider, and modeling is accurately.
2, good cooling effect, by setting up hair-dryer and other auxiliary equipments at tunnel internal, reaches the mark of cooling
Accurate.
Accompanying drawing explanation
Fig. 1 is the method flow diagram of the present invention.
Detailed description of the invention
The present invention is described in detail with specific embodiment below in conjunction with the accompanying drawings.
Embodiment:
A kind of based on there being the heat dissipating method of groove box cable tunnel thermal field model, comprise the following steps:
1) cable tunnel prospecting, obtains the parameter of each ingredient in cable tunnel;
2) mathematical model of cable tunnel thermal field is set up;
3) caloric value of this cable tunnel is calculated according to mathematical model;
4) draft type and the ventilating system of this cable tunnel are designed.
Described thermal resistance is drawn by R=d/KA, and in formula, R is thermal resistance, and d is the thickness of heat conductor, and A is heat conductor
Area of section, K is heat conductivity.
Described step 2) in the Mathematical Models of cable tunnel thermal field include following sub-step:
21) electric cable heating model is set up:
N telegram in reply cable heat radiation power is:
Wherein, P is cable heat radiation power, and I is current-carrying capacity, and A is cable cross-sectional area, and σ is cable resistance rate,
L be cable length, C be cable radiation loss coefficient value 0.9, n is cable backhaul number;
22) cable thermal losses model is set up:
I2[RT1+R(1+λ1)T2+R(1+λ1+λ2)(T3+T4)]+Wd[0.5T1+n(T2+T3+T4)]=θ1-θC
Wherein:
I: current-carrying capacity, θC: ambient temperature, θ1: cable conductor temperature, the conductor exchange under R: operating temperature
Resistance, Wd: insulation dielectric loss, λ1: metal shading loss factor, λ2: metal armouring loss factor, T1:
Insulating barrier thermal resistance between conductor and protective metal shell, T2: inner liner thermal resistance between protective metal shell and armor, T3: cable
Outer jacket thermal resistance, T4: Exterior cable thermal resistance, ambient temperature θCRefer to air themperature, it is assumed that θCIt is constant, leads
Temperature θ1Refer to the maximum permissible temperature of long-term work, be set to 90 DEG C;θ1And θCIt it is all boundary condition.
Described step 22) in, the calculating formula of described conductor AC resistance R is:
R=R ' (1+Ys+Yp)
R '=R0[1+α20(θ-20)]
Wherein:
R ': maximum operating temperature lower conductor D.C. resistance, Ys;Kelvin effect factor, Yp: kindred effect factor,
R0: conductor DC resistance when 20 DEG C, θ: running temperature, α20: the temperature coefficient of copper conductor when 20 DEG C, for
Circular compact conductor Ks=1, dc: conductor diameter, s: the spacing in each conductor axle center.
Described step 22) in, described dielectric loss WdCalculating formula be:
Wherein:
ω=2 π f, U0: voltage-to-ground, ε=2.3, Di: for outer insulation diameter, dc: for inner shield external diameter.
Described step 22) in metal shading loss λ1Calculating formula be:
λ1=λ1′+λ1″
Then have when for rounded projections arranged:
Δ2=0
Wherein:
λ1'=0, λ1" for eddy-current loss, ρ: protective metal shell resistivity, R: protective metal shell resistance, ts: metal protects
Set thickness, D: protective metal shell external diameter, Doc: corrugated aluminium sheath maximum outside diameter, Dit: corrugated aluminium sheath minimum diameter.
Described step 22) in cable internal thermal resistance T1、T2、T3Calculating formula be:
Wherein:
: insulant thermal resistivity, dc: conductor diameter t1: the insulation thickness between conductor and sheath;
This cable does not has a steel armour, therefore T2=0;
Wherein:
t3: oversheath thickness,: nonmetal oversheath thermal resistivity, Doc: corrugated aluminium sheath maximum outside diameter.
The heat exchange that air and the solid such as tunnel wall, cable are carried out belongs to fluid heat transfer free convection process, and fluid is certainly
So heat convection is divided into large space heat transfer free convection and confined space heat transfer free convection two class, and so-called large space is certainly
So heat convection, refers to the heat transfer free convection that at nearly wall, the development of boundary region is not interfered because space limits,
And when space is little to making fluid rising and descending motion of being heated interfere with each other when affecting, the referred to as confined space is natural
Heat convection, such as, for height h, interval d two pieces of parallel perpendicular planomurals between heat convection, when
< when 0.33, the motion of fluid raising and lowering interferes with each other d/h, it is necessary to calculate by confined space heat transfer free convection.
When fluid flows through the wall differed with its temperature, one layer of temperature will be formed at wall adnexa jumpy
Thin layer of fluid, referred to as thermal boundary layer, the flow regime of thermal boundary layer is divided into turbulent flow and laminar flow two kinds, and both flows
Convection transfer rate computational methods under state also differ.Thermal boundary layer is turbulent flow or laminar flow, depends on this temperature
The temperature difference of air physical parameter, fluid and wall under Du, wall size shape, wall degree of roughness etc. are multiple
Factor.
Have the situation of groove box as it is shown in figure 1, described step 22) in Exterior cable thermal resistance T4Groove is arrived including cable
Box inwall thermal resistance T5, groove box body thermal resistance T6, thermal resistance T of groove outer box wall to air7, in air to cable passage
Thermal resistance T of wall8, tunnel is to soil thermal resistance T at the bottom of river9, described T5、T6、T7、T8And T9Calculating formula be:
T8_1=1/X1A1
T8_1=1/X2A2
Wherein:
A5: the average area of dissipation of interlayer inside and outside wall, d1: threephase cable equivalent diameter, d2: the equivalence of groove box inwall
Diameter, the convection transfer rate of X: interlayer,: groove box thermal resistivity, A6: groove box area of dissipation, X7_1、
X7_2、X7_3: groove box side, end face, the convection transfer rate of bottom surface, A7_1、A7_2、A7_3: groove box side,
End face, the area of bottom surface, T8_1: thermal resistance T of air to sidewall8_1: the thermal resistance of air to ground, X1、X2:
The convection transfer rate A of sidewall or bottom1、A2: sidewall or the heat exchange area of bottom, λt: soil thermal conductivity,
H: the tunnel degree of depth, dz: the diameter of circular tunnel outer surface, L and W is the height and width of Rectangular Tunnel respectively.