Investigation of Heat Dissipation of Power Cable Laid in the Tunnel with Ventilation
To increase the current carrying capacity of the power cable, more and more power tunnel are installed with ventilation. Hence in the paper the heat dissipation of power cable is investigated. Firstly the model to calculate the thermal field of power cable with natural ventilation is presented based on the fluid mechanics and heat transfer, and the governing equations and boundary conditions are inferred. Then the thermal field for six-loop cables in power tunnel was calculated, which verified the accuracy of the model. In addition, the factors influencing the thermal field with ventilation is investigated, including the size of the power tunnel, the distance between the cable. Finally the current carrying capacity of the power cable is calculated and the economic benefit of the operation mode of power cable is analyzed.
Calculation of thermal fields of underground cables using the boundary element method
The boundary-element method (BEM) is used to solve the underground cable thermal field problem. Because attention is focused on the region boundaries rather than on its interior, the computational effort is reduced very significantly. Examples of application of the BEM include homogeneous soil and multimedia systems. Single and multicable geometries are investigated. The results exhibit accuracy better than can be expected for commonly used domain-type methods, since region truncation with an artificial boundary is not needed. >
Variable Soil Thermal Resistivity - Steady-State Analysis
The detrimental effects of moisture migration in soils on the ampacity of buried cable systems is an old fact recognized by cable engineers. Yet, no direct method to take this phenomenon into consideration has been available in the past to determine the proper ratings of power cables. The effects of soil moisture content on the variation of the thermal resistivity of the soil are discussed and equations established to determine the effective thermal resistivity when moisture migration has occurred and a final steady state has been reached.