CN103245691A

CN103245691A - Method for measuring thermal resistance of three-core cable packing layer

Info

Publication number: CN103245691A
Application number: CN201310129598XA
Authority: CN
Inventors: 刘刚; 胡倩楠
Original assignee: South China University of Technology SCUT
Current assignee: GUANGZHOU JUMTOP ELECTRIC POWER TECHNOLOGY Co.,Ltd.; Foshan Power Supply Bureau of Guangdong Power Grid Corp
Priority date: 2013-04-15
Filing date: 2013-04-15
Publication date: 2013-08-14
Anticipated expiration: 2033-04-15
Also published as: CN103245691B

Abstract

The invention discloses a method for measuring a thermal resistance of a three-core cable packing layer. The method comprises the following steps of: selecting any cross section of a three-core cable, acquiring the thickest radial direction of a packing layer in the cross section according to the appearance fluctuated characteristic of the three-core cable, drilling three holes along the radial direction, and respectively measuring the temperature of an armoring layer, an inner jacket and a central point in a closed area of the three-core cable by adopting a thermocouple respectively in the three holes; and on the basis of the steady thermal field distribution of the three-core cable and the principle that the heat conduction heat flow rate of each layer in the radial direction is identical at the steady state, calculating the thermal resistance of the packing layer in the thickest radial direction by utilizing the measured data. Due to the adoption of the method, the difficulty for sampling parameters of the packing layer of the three-core cable in the process for calculating the temperature of a steady conductor can be overcome, the measuring process is more direct, and the measuring result is more accurate.

Description

A kind of method of measuring triple cable packed layer thermal resistance

Technical field

The present invention relates to the thermal resistance measurement technology of cable packed layer, relate in particular to a kind of method of measuring triple cable packed layer thermal resistance.

Background technology

The most direct characteristic quantity that power cable conductor current-carrying capacity amplitude changes is that conductor temperature changes, in case determined the cable conductor steady temperature, just is easy to determine power cable line stable state current-carrying capacity.But directly measuring the cable conductor temperature remains at technical difficulty, especially triple cable generally can only be calculated its conductor temperature again by measuring the surface temperature of cable, and for the calculating of triple cable conductor temperature, the most difficult parameter of determining and having the greatest impact is the thermal resistance of packed layer.

Determine that at present the triple cable current-carrying capacity adopts the means of optical fiber temperature-measurement accurately to measure the power cable line hull-skin temperature more, the method of passing through cable hull-skin temperature acquisition conductor temperature that provides according to the IEC standard is determined conductor temperature then, and then definite current-carrying capacity of cable, this standard is under the stable state prerequisite to definite mode of conductor steady temperature, uses heat transfer principle to obtain the conductor temperature of cable.In view of single core the structure of rule is arranged in recent years, have to propose new calculating cable conductor method of temperature---Re Lufa, this method is based on actual parameter to the correction of IEC standard.

No matter be IEC standard or Re Lufa, its accuracy all is based on reliable each layer of cable thermal resistance parameters, because triple cable and single core cable difference structurally, the irregular structure of triple cable packed layer makes the definite very difficult of its thermal resistance, therefore the setting of triple cable current-carrying capacity, engineering is to add the coefficient correction on the model basis, hot road of single core cable on using, three conductor equivalences of triple cable are calculated for single core, draw a normative reference, but there is bigger error in this equivalence, and the temperature field that does not also meet actual triple cable simultaneously distributes.Also having in addition is the experimental study that is fixed against simulated field running environment, moves as instructing according to experimental result.But the method for simulated field is cured the symptoms, not the disease all the time, and needs the very big financial resource and material resource of waste, can not draw general valid conclusion.Therefore Chinese scholars hankers after working out the hot road model of triple cable calculating conductor temperature at present, but verifies that the prerequisite of the accuracy of hot road model then is to hold the thermal resistance of the thermal resistance parameters of each floor of triple cable, especially packed layer accurately.

Summary of the invention

In order to overcome the problem that triple cable packed layer thermal resistance is difficult to measure in the prior art, the invention provides a kind of method of measuring triple cable packed layer thermal resistance, measuring process of the present invention is direct, and the result is accurate.

The present invention adopts following technical scheme:

A kind of method of measuring triple cable packed layer thermal resistance comprises the steps:

S1 chooses the arbitrary xsect of triple cable as measuring object;

S2 obtains the thickest radial direction of packed layer in this xsect according to the profile convex and concave feature of triple cable, and bores three holes along this direction, and described three holes lay respectively at armor, inner sheath and closed region central point;

The epidermis that reaches this xsect of triple cable in three holes of S3 in S2 lays thermopair respectively;

When S4 reaches hot stable state when triple cable, skin temperature T1, armor temperature T 2, inner sheath temperature T 3 and closed region central point temperature T 4 that the record thermopair is surveyed;

S5 obtains the heat flux P=that triple cable radially conducts heat under the stable state (T2-T1)/R ' according to the thermal resistance R ' of the armor temperature, triple cable skin temperature and the oversheath that record;

S6 is according to the temperature of armor, and the heat flux that triple cable skin temperature and triple cable radially conduct heat is utilized the Fu Shi theorem of thermal conduction study, obtains thermal resistance R=(T4-T3) the * R ' of this xsect packed layer/(T2-T1);

S7 repeats S1-S6 many times, obtains the packed layer thermal resistance of a plurality of xsects of this triple cable, calculates the thermal resistance that its mean value obtains this triple cable packed layer.

The diameter in three holes is 0.2～0.4cm among the described S2.

Beneficial effect of the present invention:

(1) the present invention all is suitable for the triple cable of any model, and the material properties of packed layer and geometric configuration all do not have influence to measurement result;

(2) convenient experimental operation of the present invention does not need expensive device, and the processing of experimental data and calculating are simple;

(3) thermal resistance of the measured packed layer of the present invention can directly apply to the steady state thermal road model of setting up selected triple cable, when the epidermis point for measuring temperature is chosen in the thickest in the radial direction the point of packed layer, can calculate the temperature of stable state lower conductor according to hot road model, and reliability is good than the computing method of IEC standard;

(4) the present invention is slight to triple cable structural damage degree, so both be applicable to the experiment cable of theoretical analysis, also is applicable to the measurement of actual motion cable.

Description of drawings

Fig. 1 is the structural representation of triple cable;

Fig. 2 utilizes the ANSYS simulation software to obtain the temperature field distribution plan of triple cable in the time of 90 ℃;

Fig. 3 lays figure for the thermopair of measuring triple cable packed layer thermal resistance in the specific embodiment of the invention.

Embodiment

Below in conjunction with embodiment and accompanying drawing, the present invention is described in further detail, but embodiments of the present invention are not limited thereto.

Embodiment

As shown in Figure 1, the structure of triple cable is followed successively by oversheath 1, armoring tape 2, inner sheath 3, band 4, packed layer 5, three cores from outside to inside; Each core is respectively the closed region, center 7 that the metal screen layer 61 of metal screen layer 61, insulation course 62,

conductor shield

63,64, three cores of conductor is linked to be from outside to inside.

As shown in Figure 2, the temperature field distribution plan of triple cable in the time of 90 ℃ that utilizes the ANSYS simulation software to obtain, wherein conductor temperature is 90 ℃, the cable skin temperature is 58 ℃, the thermal field distribution characteristics in the cross section under the triple cable stable state is to be with layer isothermal beyond the armor, and this is that samming is effective owing to armor temperature conductivity height, armor with beyond the inner wire because the irregular distribution of internal heat resource then is not with a layer isothermal, but three conductors in triple cable center have surrounded the isothermal region of a plum blossom shape.

As shown in Figure 3, according to the thermal field distribution characteristics of above-mentioned triple cable, with the be laid in central point of the thickest radial direction epicuticle of packed layer, armor 2, inner sheath 3 and closed region, center 7 of temperature thermocouple 8;

Present embodiment is measured the method for triple cable packed layer thermal resistance, comprises the steps:

S1 chooses the arbitrary xsect of triple cable and measures;

S2 obtains the thickest radial direction of packed layer in this xsect according to the profile convex and concave feature of triple cable, bore three holes in that this side up, described pore diameter size is 0.2～0.4cm, three holes lay respectively at the central point of triple cable armor, inner sheath and closed region, center, and the degree of depth in hole is decided according to the survey object;

S3 in S2 three holes and the epidermis of this xsect of triple cable lay thermopair 8;

S4 works as triple cable and moves under a certain steady current, and reaches hot stable state, the measured temperature of thermopair under the record stable state: be respectively this xsect skin temperature of triple cable T1, armor temperature T 2, inner sheath temperature T 3 and central point temperature T 4;

The thermal resistance R ' of the armor that S5 passes through to survey and the temperature difference T2-T1 of epidermis and oversheath, calculating the heat flux that triple cable radially conducts heat under the steady state conditions is P=(T2-T1)/R ';

The heat flux that S6 radially conducts heat by triple cable under the temperature difference T4-T3 between institute's measured center point and inner sheath and the steady state conditions, according to the Fu Shi theorem of thermal conduction study, the thermal resistance of obtaining packed layer is R=(T4-T3) * R '/(T2-T1).

S7 repeats above-mentioned steps many times, obtains the packed layer thermal resistance of a plurality of xsects of this triple cable, calculates the thermal resistance that its mean value obtains the packed layer of this triple cable.The mean value of finally trying to achieve a plurality of packed layer thermal resistance value then is the thermal resistance parameters of triple cable packed layer.

Above-described embodiment is preferred implementation of the present invention; but embodiments of the present invention are not limited by the examples; other any do not deviate from change, the modification done under spiritual essence of the present invention and the principle, substitutes, combination, simplify; all should be the substitute mode of equivalence, be included within protection scope of the present invention.

Claims

1. a method of measuring triple cable packed layer thermal resistance is characterized in that, comprises the steps:

S1 chooses the arbitrary xsect of triple cable as measuring object;

2. a kind of method of measuring triple cable packed layer thermal resistance according to claim 1 is characterized in that the diameter in three holes is 0.2～0.4cm among the described S2.