CN103245691B - Method for measuring thermal resistance of three-core cable packing layer - Google Patents
Method for measuring thermal resistance of three-core cable packing layer Download PDFInfo
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- CN103245691B CN103245691B CN201310129598.XA CN201310129598A CN103245691B CN 103245691 B CN103245691 B CN 103245691B CN 201310129598 A CN201310129598 A CN 201310129598A CN 103245691 B CN103245691 B CN 103245691B
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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
Technical field
The present invention relates to the thermal resistance measurement technology of cable filling layer, particularly relate to a kind of method measuring triple cable packed layer thermal resistance.
Background technology
The most direct characteristic quantity of power cable conductor current-carrying capacity amplitude change is conductor temperature change, once determine cable conductor steady temperature, is just easy to determine power cable line stable state current-carrying capacity.But directly measuring cable conductor temperature remains at technical difficulty, especially triple cable, generally by measuring the surface temperature of cable, then can only calculate its conductor temperature, and for the calculating of three-core cable conductor temperature, the most difficultly to determine and the parameter had the greatest impact is the thermal resistance of packed layer.
Determine the means Measurement accuracy power cable line hull-skin temperature of triple cable current-carrying capacity many employings optical fiber temperature-measurement at present, what then provide according to IEC standard determines conductor temperature by the method for cable hull-skin temperature acquisition conductor temperature, and then determine current-carrying capacity of cable, the determination mode of this standard to conductor steady temperature is under stable state prerequisite, uses heat transfer principle to obtain the conductor temperature of cable.In recent years in view of single core has more regular structure, have method---the Re Lufa proposing new calculating cable conductor temperature, this method is based on the correction of actual parameter to IEC standard.
No matter be IEC standard or Re Lufa, its accuracy is all based on each layer thermal resistance parameters of reliable cable, due to triple cable and single core cable difference structurally, the irregular structure of triple cable packed layer makes the determination of its thermal resistance very difficult, therefore the setting of triple cable current-carrying capacity, engineer applied is on the thermal circuit model basis of single core cable, add coefficient correction, three of triple cable conductors are equivalent to single core to calculate, draw a normative reference, but there is larger error in this equivalence, does not also meet the thermo parameters method of actual triple cable simultaneously.Also having in addition is the experimental study being fixed against simulated field running environment, and experimentally result is run as guidance.But the method for simulated field is cured the symptoms, not the disease all the time, and needs the financial resource and material resource that waste is very large, general valid conclusion can not be drawn.Therefore Chinese scholars hankers after the thermal circuit model working out triple cable calculating conductor temperature at present, but the prerequisite of the accuracy of checking thermal circuit model is then hold the thermal resistance parameters of each layer of triple cable accurately, the especially thermal resistance of packed layer.
Summary of the invention
In order to overcome the problem that triple cable packed layer thermal resistance in prior art is difficult to measure, the invention provides a kind of method measuring triple cable packed layer thermal resistance, measuring process of the present invention is direct, and result is accurate.
The present invention adopts following technical scheme:
Measure a method for triple cable packed layer thermal resistance, comprise the steps:
S1 chooses the arbitrary xsect of triple cable as measuring object;
S2 obtains according to the profile convex and concave feature of triple cable the radial direction that in this xsect, packed layer is the thickest, and bores three holes along this direction, and described three holes lay respectively at armor, inner sheath and closed region central point;
In three holes of S3 in S2 and the epidermis of this xsect of triple cable lay thermopair respectively;
S4 when triple cable reaches hot stable state, record thermopair survey skin temperature T1, armor temperature T2, inner sheath temperature T3 and closed region central point temperature T4;
S5, according to the thermal resistance R ' of the armor temperature, skin temperature of three-core cable and the oversheath that record, obtains heat flux P=(the T2-T1)/R ' of triple cable radial direction heat transfer under stable state;
S6, according to the heat flux of closed region central point temperature, inner sheath temperature and triple cable radial direction heat transfer, utilizes the fourier theorem of thermal conduction study, obtains thermal resistance R=(T4-T3) * R '/(T2-T1) of this xsect packed layer;
S7 repeats S1-S6 many times, obtains the packed layer thermal resistance of the multiple xsect of this triple cable, calculates the thermal resistance that its mean value obtains this triple cable packed layer.
In described S2, the diameter in three holes is 0.2 ~ 0.4cm.
Beneficial effect of the present invention:
(1) the present invention is all applicable to the triple cable of any model, the material properties of packed layer and geometric configuration on measurement result all without impact;
(2) convenient experimental operation of the present invention, does not need expensive device, and process and the calculating of experimental data are simple;
(3) thermal resistance of the packed layer measured by the present invention can directly apply to the stable state thermal circuit model setting up selected triple cable, when epidermis point for measuring temperature is selected at the point in the radial direction that packed layer is the thickest, can calculate the temperature of stable state lower conductor according to thermal circuit model, and reliability is good compared with the computing method of IEC standard;
(4) the present invention is slight to triple cable structural damage degree, so be both applicable to the experiment cable of theoretical analysis, is also applicable to the measurement of actual motion cable.
Accompanying drawing explanation
Fig. 1 is the structural representation of triple cable;
Fig. 2 utilizes ANSYS simulation software to obtain the thermo parameters method figure of triple cable 90 DEG C time;
Fig. 3 is that the thermopair measuring triple cable packed layer thermal resistance in the specific embodiment of the invention lays figure.
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; The Central Closed region 7 that each core is metal screen layer 61 from outside to inside respectively, the metal screen layer 61 of insulation course 62, conductor shield 63, conductor 64, three cores is linked to be.
As shown in Figure 2, the thermo parameters method figure of the triple cable utilizing ANSYS simulation software to obtain 90 DEG C time, wherein conductor temperature is 90 DEG C, cable skin temperature is 58 DEG C, the heterogeneity phantom feature in the cross section under triple cable stable state is same layer isothermal beyond armor, and this is that even temperature effect is good because armor temperature conductivity is high, armor with beyond inner wire because the irregular distribution of internal heat resource is not then same layer isothermal, but three, triple cable center conductor defines the isothermal region of a plum blossom-shaped.
As shown in Figure 3, according to the heterogeneity phantom feature of above-mentioned triple cable, the central point in the radial direction epicuticle that the packed layer that is laid in by temperature thermocouple 8 is the thickest, armor 2, inner sheath 3 and Central Closed region 7;
The present embodiment measures the method for triple cable packed layer thermal resistance, comprises the steps:
S1 chooses the arbitrary xsect of triple cable and measures;
S2 obtains according to the profile convex and concave feature of triple cable the radial direction that in this xsect, packed layer is the thickest, this side up bore three holes, described pore diameter size is 0.2 ~ 0.4cm, three holes lay respectively at the central point in triple cable armor, inner sheath and Central Closed region, and the degree of depth in hole is determined according to surveyed object;
The epidermis of three holes of S3 in S2 and this xsect of triple cable lays thermopair 8;
S4 works as triple cable and runs under a certain steady current, and reaches hot stable state, the temperature under record stable state measured by thermopair: be this xsect of triple cable skin temperature T1, armor temperature T2, inner sheath temperature T3 and central point temperature T4 respectively;
S5 passes through the temperature difference T2-T1 of surveyed armor and epidermis and the thermal resistance R ' of oversheath, and under calculating steady state conditions, the heat flux of triple cable radial direction heat transfer is P=(T2-T1)/R ';
The heat flux that S6 is conducted heat by triple cable radial direction under the temperature difference T4-T3 between institute's measured center point and inner sheath and steady state conditions, according to the fourier theorem of thermal conduction study, the thermal resistance obtaining packed layer is R=(T4-T3) * R '/(T2-T1).
S7 repeats above-mentioned steps many times, obtains the packed layer thermal resistance of the multiple xsect 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 multiple packed layer thermal resistance value is then the thermal resistance parameters of triple cable packed layer.
Above-described embodiment is the present invention's preferably embodiment; but embodiments of the present invention are not limited by the examples; change, the modification done under other any does not deviate from Spirit Essence of the present invention and principle, substitute, combine, simplify; all should be the substitute mode of equivalence, be included within protection scope of the present invention.
Claims (2)
1. measure a method for triple cable packed layer thermal resistance, it is characterized in that, comprise the steps:
S1 chooses the arbitrary xsect of triple cable as measuring object;
S2 obtains according to the profile convex and concave feature of triple cable the radial direction that in this xsect, packed layer is the thickest, and bores three holes along this direction, and described three holes lay respectively at armor, inner sheath and closed region central point;
In three holes of S3 in S2 and the epidermis of this xsect of triple cable lay thermopair respectively;
S4 when triple cable reaches hot stable state, record thermopair survey skin temperature T1, armor temperature T2, inner sheath temperature T3 and closed region central point temperature T4;
S5, according to the thermal resistance R ' of the armor temperature, skin temperature of three-core cable and the oversheath that record, obtains heat flux P=(the T2-T1)/R ' of triple cable radial direction heat transfer under stable state;
S6, according to the heat flux of closed region central point temperature, inner sheath temperature and triple cable radial direction heat transfer, utilizes the fourier theorem of thermal conduction study, obtains thermal resistance R=(T4-T3) * R '/(T2-T1) of this xsect packed layer;
S7 repeats S1-S6 many times, obtains the packed layer thermal resistance of the multiple xsect of this triple cable, calculates the thermal resistance that its mean value obtains this triple cable packed layer.
2. a kind of method measuring triple cable packed layer thermal resistance according to claim 1, it is characterized in that, in described S2, the diameter in three holes is 0.2 ~ 0.4cm.
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| CN104462796A (en) * | 2014-11-24 | 2015-03-25 | 广州供电局有限公司 | Method and system for obtaining thermal resistance of three-core cable packing layer |
| CN104636555B (en) * | 2015-02-06 | 2017-10-20 | 华南理工大学 | A kind of 10kV three-core cables models for temperature field method for building up |
| CN104634470A (en) * | 2015-02-06 | 2015-05-20 | 华南理工大学 | Method for accurately measuring temperature of cable conductor |
| CN104732080B (en) * | 2015-03-18 | 2017-10-20 | 华南理工大学 | A kind of approximate evaluation method of three-core cable packed layer Transient Thermal Circuit model |
| CN104730388A (en) * | 2015-03-25 | 2015-06-24 | 广州供电局有限公司 | Method and device for evaluating influence of environment thermal resistance on three-core cable core temperature |
| CN106339575A (en) * | 2016-08-15 | 2017-01-18 | 华南理工大学 | Method for establishing steady-state thermal circuit model of 10kV three-core cable based on segmentation method |
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| JPH04242013A (en) * | 1991-01-16 | 1992-08-28 | Sumitomo Electric Ind Ltd | Sheath electric wire |
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Effective date of registration: 20210105 Address after: 510000 Shop No. 6, Yichun First Lane, Qianjin Road, Haizhu District, Guangzhou City, Guangdong Province Patentee after: GUANGZHOU JUMTOP ELECTRIC POWER TECHNOLOGY Co.,Ltd. Address before: South China University of technology 381 Wushan Road Tianhe District Guangzhou City Guangdong Province Patentee before: SOUTH CHINA University OF TECHNOLOGY |
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Effective date of registration: 20220420 Address after: 510000 Shop No. 6, Yichun First Lane, Qianjin Road, Haizhu District, Guangzhou City, Guangdong Province Patentee after: GUANGZHOU JUMTOP ELECTRIC POWER TECHNOLOGY Co.,Ltd. Patentee after: Foshan Power Supply Bureau of Guangdong Power Grid Co., Ltd Address before: 510000 Shop No. 6, Yichun First Lane, Qianjin Road, Haizhu District, Guangzhou City, Guangdong Province Patentee before: GUANGZHOU JUMTOP ELECTRIC POWER TECHNOLOGY Co.,Ltd. |