CN104181193B - Method for calculating thermal resistance of packing layer in compound optical fiber of three-core submarine cable - Google Patents

Abstract

The invention relates to a method for calculating thermal resistance of a packing layer in a compound optical fiber of a three-core submarine cable, belonging to the field of thermodynamic calculation of parameters of a cable material. The method comprises the following steps: firstly, calculating thermal resistance between the inner diameter part of the packing layer and the outer diameter part of an armor layer; subsequently, calculating the temperature of the outer diameter part of the packing layer according to the temperature of the compound optical fiber, then calculating the temperature of the outer diameter part of the armor layer, and subsequently, calculating thermal resistance between two isothermal surfaces according to a temperature difference between the isothermal surface of the optical fiber and the isothermal surface of the outer diameter part of the armor layer and loss of a submarine cable core; and finally, subtracting the thermal resistance between the isothermal surface of the optical fiber and the isothermal surface of the outer diameter part of the armor layer from the thermal resistance between the inner diameter part of the packing layer and the outer diameter part of the armor layer so as to obtain the thermal resistance of the packing layer in the compound optical fiber. The method is capable of solving the problem that thermal resistance of a packing layer in a compound optical fiber cannot be calculated when the temperature of a conductor is calculated based on the temperature of the optical fiber by a thermal circuit method and when current-carrying capacity is calculated; the method has the advantages of being high in speed, being accurate and being universally suitable for all three-core cables.

Description

Calculation method of thermal resistance of filling layer inside composite optical fiber in three-core submarine cable

technical field

The invention belongs to the field of thermal calculation of cable material parameters, in particular to a calculation method for the thermal resistance of a filling layer inside a composite optical fiber in a three-core submarine cable.

Background technique

With the development of new offshore energy and the increasing demand for electricity in my country, the demand for cross-sea power transmission is becoming increasingly urgent, and the number of submarine cable applications is increasing day by day. Compared with single-core submarine cables, three-core submarine cables can increase transmission capacity while reducing the width of routing corridors, and have the advantage of reducing losses. They are widely used in coastal island power supply and offshore wind farm power transmission. In order to realize the transmission of information, the three-core submarine cable is generally combined with optical fibers to form an optical fiber composite submarine cable.

Conductor temperature is an important factor in determining the life of submarine cables, an important basis for determining the ampacity, and an important parameter for condition monitoring. There have been cases of using distributed optical fiber sensing technology to monitor the skin temperature of three-core land cables and calculate the conductor temperature. For the three-core optical fiber composite submarine cable, due to the harsh laying environment, it is impossible to lay the sensing optical cable on its skin alone, and because the radial structure of the three-core submarine cable is asymmetrical, the thermal resistance when calculating the conductor temperature from the temperature of the composite optical fiber using the thermal path method The calculation is difficult, resulting in few reports on the calculation method of the conductor temperature of the three-core optical fiber composite submarine cable.

In view of the above problems, the present invention proposes a calculation method for the thermal resistance of the filling layer inside the composite optical fiber in the three-core submarine cable, which solves the problem that the thermal resistance of the filling layer inside the composite optical fiber cannot be calculated when calculating the conductor temperature according to the thermal path method and the temperature of the optical fiber. Using the temperature measurement value of the composite optical fiber in the three-core submarine cable provides an effective method for the status monitoring and ampacity calculation of the submarine cable.

Contents of the invention

The object of the present invention is to propose a calculation method for the thermal resistance of the filling layer inside the composite optical fiber in the three-core submarine cable, which is used to solve the problem that the thermal resistance of the filling layer inside the composite optical fiber cannot be calculated when calculating the conductor temperature according to the thermal path method and using the temperature of the optical fiber.

In order to achieve the above object, the technical solution proposed by the present invention is a calculation method for the thermal resistance of the filling layer inside the composite optical fiber in the three-core submarine cable, which is characterized in that the method includes:

Step 1: Calculate the thermal resistance from the inner diameter of the filler layer to the outer diameter of the armor layer, the specific method is as follows:

(1) Assuming that the thermal resistance coefficient between the inner diameter of the filling layer and the outer diameter of the armor layer is the same as the thermal resistance coefficient of the filling layer, calculate the thermal resistance between the inner diameter of the filling layer and the outer diameter of the armor layer

Among them, R is half of the outer diameter of the armor layer, _r1 is the distance from the center of the core to the center of the submarine cable, n=3 is the number of cores, r is the radius of the core, and λ is the thermal conductivity of the filling layer material;

(2) Use the IEC60853 standard to calculate the sum T _s of the thermal resistance from the outer diameter of the filler layer to the outer diameter of the armored layer, which is equal to the sum of the thermal resistances of the cable tie, brass tape, armored underlayment and armored layer;

(3) Assuming that the material between the outer diameter of the filler layer and the outer diameter of the armor layer is the filler layer material, calculate the thermal resistance T _s ”' using the IEC60853 standard;

(4) Calculate the sum of the real thermal resistance between the inner diameter of the filling layer and the outer diameter of the armor layer T _s = T _s '-(T _s ”'-T _s ”);

Step 2: Calculate the temperature at the outer diameter of the filling layer, the specific method is as follows:

Take the extension line from the center of the optical unit to the center of the submarine cable as the y-axis, the intersection of the y-axis and the outer diameter of the filling layer as the origin, and the tangent of the outer diameter of the filling layer at the origin as the x-axis, establish a coordinate system; calculate the outer diameter of the filling layer The temperature at

Among them, t(x, y) is the temperature of the composite fiber, Q is the total loss of the three cores, λ is the thermal resistance coefficient of the filling layer, _y0 is the distance from the center of the submarine cable to the outer diameter of the filling layer, x and y is the horizontal and vertical coordinates of the center of the light unit, and x=0;

Step 3: Calculate the temperature at the outer diameter of the armor layer, the specific method is as follows:

(1) Let X be the ratio of the material thickness between the lead alloy sheath and the armor layer to the outer diameter of the lead alloy sheath. For the lead alloy sheaths that do not touch each other, calculate the geometric factor

(2) The thermal resistance of each layer of material between the outer diameter of the filling layer and the inner diameter of the armoring layer is calculated by the following formula

Among them, ρ _T is thermal resistance coefficient;

(3) Calculate the temperature of the armor layer

t _a =T _s -Q·T _s1

Among them, T _s1 is the sum of the thermal resistance from the outer diameter of the filler layer to the inner diameter of the armor layer;

Step 4: Calculate the thermal resistance between the isothermal surface at the composite fiber and the isothermal surface at the outer diameter of the armor layer as

Among them, Δt is the temperature difference between the isothermal surface at the optical fiber and the isothermal surface at the armor layer;

Step 5: Calculate the thermal resistance of the filling layer inside the composite optical fiber T _f =T _s -T _fa .

The composite optical fiber is single-mode, multi-mode or other types of optical fiber, and the temperature of the composite optical fiber is measured by distributed optical fiber temperature measurement equipment, which is based on optical fiber Raman scattering, optical fiber Brillouin scattering or optical fiber Rayleigh Distributed optical fiber temperature measurement equipment or instrument based on coherent detection principle.

Beneficial effects of the present invention: 1. The present invention provides a calculation method for the thermal resistance of the filling layer within the composite optical fiber in the three-core submarine cable; 2. The method provided by the present invention is applicable to all three-core optical fiber composite submarine cables or land cables; 3. , The method proposed by the invention lays a theoretical foundation for establishing the relationship between the temperature of the composite optical fiber and the conductor and the calculation of the carrying capacity by using the thermal circuit model.

Description of drawings

Figure 1 is a cross-sectional view of a three-core optical fiber composite submarine cable;

Fig. 2 is a schematic diagram of calculating the temperature at the outer diameter of the filling layer by using the temperature of the composite optical fiber.

detailed description

Below in conjunction with accompanying drawing and embodiment the present invention will be further described:

1. Calculate the thermal resistance from the inner diameter of the filling layer to the outer diameter of the armor layer in the three-core submarine cable. Taking the ZS-YJQF41 type 18/30/36kV three-core XLPE insulated optical fiber composite submarine cable as an example, its internal structure is shown in Figure 1. The specific calculation steps are:

(1) Assuming that the thermal resistance coefficient between the inner diameter of the filling layer and the outer diameter of the armor layer is the same as the thermal resistance coefficient of the filling layer, calculate the thermal resistance between the inner diameter of the filling layer and the outer diameter of the armor layer

Among them, R is half of the outer diameter of the armor layer, _r1 is the distance from the center of the core to the center of the submarine cable, n=3 is the number of cores, r is the radius of the core, and λ is the thermal conductivity of the filling layer material.

(2) Use the IEC60853 standard to calculate the sum T _s " of the thermal resistance from the outer diameter of the filler layer to the outer diameter of the armored layer, which is equal to the sum of the thermal resistances of the cable tie, brass tape, armored underlayment and armored layer.

(3) Assuming that the material between the outer diameter of the filler layer and the outer diameter of the armor layer is the filler layer material, the thermal resistance T _s ”' is calculated using the IEC60853 standard.

(4) Calculate the sum of the real thermal resistances between the inner diameter of the filler layer and the outer diameter of the armor layer T _s =T _s '-(T _s ”'-T _s ”).

2. Calculate the temperature at the outer diameter of the filling layer, the specific method is as follows:

As shown in Figure 2, the extension line from the center of the optical unit (i.e. composite optical fiber) to the center of the submarine cable is the y-axis, the intersection of the y-axis and the outer diameter of the filling layer is the origin, and the tangent to the outer diameter of the filling layer at the origin is x axis, establish a coordinate system; calculate the temperature at the outer diameter of the filled layer as

Among them, t(x, y) is the temperature of the composite optical fiber (the temperature can be obtained by using distributed optical fiber temperature measurement equipment), Q is the total loss of the three cores, λ is the thermal resistance coefficient of the filling layer, and y ₀ is the seabed The distance from the center of the cable to the outer diameter of the filling layer (ie, the origin), x and y are the horizontal and vertical coordinates of the center of the optical unit (ie, the composite optical fiber), and x=0.

3. Calculate the temperature at the outer diameter of the armor layer, the specific method is as follows:

(1) Let X be the ratio of the material thickness between the lead alloy sheath and the armor layer to the outer diameter of the lead alloy sheath. For the lead alloy sheaths that do not touch each other, calculate the geometric factor

(2) The thermal resistance of each layer of material between the outer diameter of the filling layer and the inner diameter of the armoring layer is calculated by the following formula

where _ρT is the thermal resistivity coefficient.

(3) Calculate the temperature of the armor layer

t _a =t _s -Q·T _s1

Among them, T _s1 is the sum of the thermal resistance from the outer diameter of the filler layer to the inner diameter of the armor layer.

4. Calculate the thermal resistance between the isothermal surface at the composite optical fiber and the isothermal surface at the outer diameter of the armor layer as

Among them, Δt is the temperature difference between the isothermal surface at the optical fiber and the isothermal surface at the armor layer;

5. Calculate the thermal resistance of the filling layer inside the composite optical fiber T _f =T _s -T _fa .

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Any technical personnel familiar with this profession, without departing from the technical essence of the present invention, can make any changes to the above embodiments. Amendments, equivalent changes and modifications all belong to the protection scope of the technical solution of the present invention.

Claims (2)

1. in three core submarine cables within composite fiber packed layer thermal resistance computational methods, it is characterised in that comprise the following steps：

Step 1：The thermal resistance of packed layer internal diameter to armor external diameter is calculated, concrete grammar is as follows：

(1) assume that packed layer internal diameter to the thermal resistivity between armor external diameter is all the thermal resistivity of packed layer, calculate filling Layer internal diameter is to the thermal resistance between armor external diameter

$T_s^{\′}=\frac{ln(R/r_1)-\frac{1}{n}ln(nr/r_1)}{2\mathrm{\π}\mathrm{\λ}}$

Wherein, R is the half of armor external diameter, r₁It is distance of the core center to submarine cable center, n=3 is the number of core Amount, r is the radius of core, and λ is the heat conductivity for filling layer material；

(2) using thermal resistance sum T of IEC60853 criterion calculation packed layer external diameters to armor external diameter_s", it is equal to band, pyrite The thermal resistance sum of band, armouring bed course and armor；

(3) assume that packed layer external diameter to the material between armor external diameter is filling layer material, using IEC60853 criterion calculation Thermal resistance T_s”’；

(4) packed layer internal diameter is calculated to true thermal resistance sum T between armor external diameter_s=T_s’-(T_s”’-T_s”)；

Step 2：Packed layer outer radius temperature is calculated, concrete grammar is as follows：

As y-axis, y-axis is origin with the intersection point of packed layer external diameter to extended line with light unit center to the submarine cable line of centres, The tangent line of packed layer external diameter is x-axis at origin, sets up coordinate system；Calculate packed layer outer radius temperature be

$t_s=t(x,y)-\frac{Q}{2\mathrm{\π}\mathrm{\λ}}ln\sqrt{\frac{x^2+{(y+y_0)}^2}{x^2+{(y-y_0)}^2}}$

Wherein, t (x, y) is the temperature of composite fiber, and Q is the total losses of three cores, and λ is the thermal resistivity of packed layer, y₀For sea To the distance of packed layer external diameter, x and y is the transverse and longitudinal coordinate at light unit center, and x=0 for bottom cable center；

Step 3：Armor outer radius temperature is calculated, concrete grammar is as follows：

(1) set X as lead alloy sheath to material thickness between armor and lead alloy sheath external diameter ratio, for not connecing each other Tactile lead alloy sheath, computational geometry factor

(2) packed layer external diameter is all calculated as follows to the layers of material thermal resistance between armor internal diameter

$T=\frac{{\mathrm{\ρ}}_T}{2\mathrm{\π}}\stackrel{\‾}{G}$

Wherein, ρ_TIt is thermal resistivity；

(3) armor temperature is calculated

t_a=t_s-Q·T_s1

Wherein, T_s1For the thermal resistance sum of packed layer external diameter to armor internal diameter；

Step 4：Calculating the thermal resistance at composite fiber between isothermal level and armor outer radius isothermal level is

$T_{fa}=\frac{\mathrm{\Δ}t}{Q}$

Wherein, Δ t is the temperature difference at optical fiber at isothermal level and armor between isothermal level；

Step 5：Calculate packed layer thermal resistance T within composite fiber_f=T_s-T_fa。

2. according to claim 1 in three core submarine cables within composite fiber packed layer thermal resistance computational methods, its feature It is that composite fiber is single mode, multimode or other kinds of optical fiber, the temperature of composite fiber passes through distributed optical fiber temperature measuring Equipment is measured, and these equipment are based on fiber raman scattering, based on optical fiber Brillouin scattering or based on the relevant detection of fiber Rayleigh The distributed optical fiber temperature measurement equipment of principle or instrument.