| With the continuous improvement of urbanization infrastructure,the proportion of cables is increasing.In order to ensure the safe and reliable operation of cables,after investigation and research by scholars at home and abroad,it is found that temperature is an intuitive characterizing quantity that restricts the safe operation of cables.When the power cable is overloaded,the temperature will rise,which will affect the aging and life of the cable,and may even cause power supply accidents;when the cable is under-loaded,the load that is due to full-load operation is not reached Flow capacity,resulting in uneconomical energy supply.Therefore,on the premise of ensuring the effective service life of the cable and safe power supply,it is very important to analyze the temperature change of the cable under long-term operation.In order to qualitatively and quantitatively analyze the temperature field change of the cable body and the intermediate joint,the following work is done in this paper:Firstly,this paper expounds the current research status of high-voltage power cables.Based on the basic structure of cable body,the calculation principle of cable loss and three heat transfer modes of heat transfer are analyzed.The current capacity of power cable is introduced.IEC-60287 The shortcomings of the standard calculation method are discussed in the numerical calculation method of the temperature field of the high-voltage power cable.Then,based on the above theoretical analysis,a single loop three-phase cable simulation model was established through the finite element software COMSOL.The study found that when the cable temperature reaches 90℃,its current carrying capacity is900.5A,which is lower than the current carrying capacity under IEC international standards,and the error is only 1.02%,This verifies that the built simulation model is correct and effective.It can be seen in the laying of double-circuit cable exhaust pipes that the temperature of the middle phase of the cable can reach a maximum of 72.5℃ due to the influence of cable heating and proximity effects on both sides.and the temperature on both sides is 64.5℃ and 65.7℃,which are higher The temperature is about 7℃ higher.Under the same conditions,when the cross-section increased from 640mm~2 to 1400mm~2,the temperature decreased by 28.9℃.Secondly,because the temperature of the intermediate joint of the cable is too high,it is one of the main factors that cause the failure of the cable.The existing temperature analysis of the intermediate joint is analyzed from an overall perspective.To analyze real-time changes in temperature.Starting from the structure of the intermediate joint,a temperature field calculation model for the cable intermediate joint was established.At the power frequency voltage of 110kV,the radial temperature difference between the cable intermediate connector core and the cable copper shell is 28.6℃,and the axial temperature difference is 7.1℃;the cable joint temperature and insulation thickness,conductivity,thermal conductivity,current density Factors such as internal defects are directly related.Therefore,by changing the parameter research,the temperature increases with the increase of the insulation thickness.When the thickness of the insulation layer increases from 10mm to 60mm,the temperature rises by 30.11℃;the temperature decreases with the increase of the contact resistance conductivity,when the conductivity is 5.99e~7S/m increases to 10.99e~7S/m,the temperature drops by 10.8℃;the temperature decreases with the increase of the thermal conductivity of the insulation,and the thermal conductivity of the insulation increases from 0.35W/(m·K)to 0.6W/(m·K).The temperature decreased by47.9℃;the temperature increased with the increase of current density.When the current density increased from 1.27e~6A/m2 to 1.52e~6A/m2,the temperature increased by 22.8℃.However,the internal defect of the cable intermediate joint is mainly related to the contact coefficient of the intermediate joint and the ambient temperature.It has been found that when the contact coefficient of the intermediate joint is increased from 1 to 6,the temperature of the main body core is increased by 1.8℃,and the temperature of the joint core is increased by 25.8℃,which is 14.3 times the elevated temperature of the main body cable;When the ambient temperature is raised from 15℃ to 35℃,the temperature of the bulk core is increased by 20.9℃,and the temperature of the joint core is increased by22.6℃.Thus,it can be seen that the joint core is more sensitive than the body in the case of changing the same factor.In summary,this paper is based on the finite element method to analyze the temperature variation of the cable body and the intermediate joint,and obtain the law that affects the temperature distribution change,which provides reference and reference for the design and construction of the cable. |
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