Study On Calculation Of Thermal Distribution And Ampacity For High-Voltage Power Cables In Trenchless Pipe-jacking

High-voltage power cable is an important part of the urban power grid.In recent years,along with the accelerating development of urbanization in China,the use of high-voltage power cables in urban networks is increasing,and the proportion of the power transmission lines is becoming more and more important.Due to the complexity of urban pavement environment and underground pipeline arrangement,when the cable route passes through the non-excavation road section,only the pipe jacking laying scheme can be adopted under the condition of construction limited.Cables are arranged tightly and buried deeper at the place where the pipe is laid,which is often the bottleneck segment that limits the cable ampacity.At present,the research of cable ampacity is mostly based on conventional laying and less involved in pipe jacking.So it is necessary to carry out pertinent research to clarify the temperature and flow of high voltage power cable in pipe jacking,and then provide a reference for the operation and management of Power Grid Corp.In this study,the common methods for calculating the temperature and the discharge of the cable for the pipe laying are first investigated.The IEC standard and the thermal-fluid coupling model to perform two-dimensional temperature field finite element analysis are adopted.At the same time,based on the study of existing calculation methods,a threedimensional temperature field simulation model for pipe jacking laying cables is established.Then,the temperature distribution of the cable under different pipe jacking length,cable section area and cable circuit number is simulated and analyzed after verifying the accuracy of the model by comparing it with the traditional method.The influence of the cable longitudinal heat flow on the temperature and the discharge of the cable in the pipe jacking is studied.If the longitudinal heat flow of the cable is neglected,there will be a large error in calculating the ampacity of the cable pipe jacking by the traditional method.Finally,considering the axial heat flow of the cable conductor and the metal shield,the analytical solution calculation model for cable pipe jacking is proposed,and the accuracy of the model is verified by comparison with the simulation.In this paper,the analysis of the influence factors of the thermal environment and the ampacity of the high-voltage power cable can provide a theoretical basis for the calculation of the temperature and the ampacity of these cables.At the same time,it provides a practical calculation method,which can provide auxiliary reference for the power part to fully utilize the transmission capacity of the cable line.