Theoretical Model to Calculate Steady-State and Transient Ampacity and Temperature in Buried Cables

The temperature distribution and ampacity in a multilayered soil surrounding a system of three cables is calculated in the steady state in emergency situations. We present the mathematical model that solves the heat diffusion equation in cylindrical coordinates inside the cables and in Cartesian coordinates in the surrounding soil. The finite difference method is used to solve the equations. In order to reduce the number of points studied that are of no interest to the results, a variable step discretization is used. We present the development of the model and the effect of some of the parameters that influence the convergence and accuracy of the method. The application of the model in different configurations and situations is given in the second part of this work. The model is applicable to the study of buried cab in both the steady state and transient states for short circuit and overload situations.

[1]  J. Mitchell,et al.  Temperature Distributions Around Buried Cables , 1979, IEEE Transactions on Power Apparatus and Systems.

[2]  A. Y. Chikhani,et al.  Thermal analysis of power cables in multi-layered soil. I. Theoretical model , 1993 .

[3]  M. H. McGrath,et al.  The calculation of the temperature rise and load capability of cable systems , 1957, Transactions of the American Institute of Electrical Engineers. Part III: Power Apparatus and Systems.

[4]  J. Lyall.  Two dimensional modelling of three core cable transient temperature rise , 1990 .

[5]  M. Kellow,et al.  A Numerical Procedure for the Calculation of the Temperature Rise and Ampacity of Underground Cables , 1981, IEEE Transactions on Power Apparatus and Systems.

[6]  B. M. Weedy.  An economic method for simulating the soil transient temperatures in a water cooled self-contained cable system , 1988 .

[7]  W. Black,et al.  Emergency Ampacities of Direct Buried Three Phase Underground Cable Systems , 1983, IEEE Transactions on Power Apparatus and Systems.

[8]  E. C. Bascom,et al.  A Fourier transform technique for calculating cable and pipe temperatures for periodic and transient conditions , 1991 .

[9]  B. M. Weedy.  Air temperatures in a deep cable tunnel , 1988 .

[10]  D. Mushamalirwa,et al.  A 2-D finite element mesh generator for thermal analysis of underground power cables , 1988 .

[11]  Conrad A. Bauer,et al.  A study of the superposition of heat fields and the Kennelly formula as applied to underground cable systems , 1957, Transactions of the American Institute of Electrical Engineers. Part III: Power Apparatus and Systems.

[12]  M. A. El-Kady.  Calculation of the Sensitivity of Power Cable Ampacity to Variations of Design and Environmental Parameters , 1984, IEEE Power Engineering Review.

[13]  J. Nougier,et al.  Méthodes de calcul numérique , 1987 .

[14]  L. L. Grigsby,et al.  An algorithm for steady-state thermal analysis of electrical cables with radiation by reduced Newton-Raphson techniques , 1994 .

[15]  A. Y. Chikhani,et al.  Thermal analysis of power cables in multi-layered soil. III. Case of two cables in a trench , 1994 .

[16]  S. Grzybowski,et al.  Calculation of Temperature Distributions Within Cable Trench Backfill and the Surrounding Soil , 1985, IEEE Transactions on Power Apparatus and Systems.

[17]  A. Lombardi,et al.  Heat transfer in forced cooled cables , 1990 .

[18]  J. J. Dai,et al.  Calculation of thermal fields of underground cables using the boundary element method , 1988 .

[19]  M. A. Hanna,et al.  Thermal analysis of power cables in multi-layered soil. II. Practical considerations , 1993 .