Thermal Analysis of Cables in Unfilled Troughs: Investigation of the IEC Standard and a Methodical Approach for Cable Rating

• Published in: IEEE transactions on power delivery Vol. 27; no. 3; pp. 1423 - 1431
• Main Authors: Terracciano, M., Purushothaman, S., de Leon, F., Farahani, A. V.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-07-2012; Institute of Electrical and Electronics Engineers
• Subjects: Ampacity; Applied sciences; cable thermal rating; Electric connection. Cables. Wiring; Electrical engineering. Electrical power engineering; Exact sciences and technology; finite elements; Heating; IEC standards; intensity of solar radiation; Power cables; Soil; Solar radiation; Steady-state; Transient analysis; unfilled troughs; Various equipment and components; Numerical method; Aspect ratio; Electric circuit; Convection; Implementation; Finite element method; Relaxation; Time varying system; cable thermal rating; intensity of solar radiation; Current carrying capacity; Heat radiation; IEC standard; Solar radiation; Power cables; Algorithm; Steady state; unfilled troughs; Ambient atmosphere; Equivalent circuit; Thermal analysis; Room temperature; Heat transfer; finite elements; Ampacity
• ISSN: 0885-8977; 1937-4208
• DOI: 10.1109/TPWRD.2012.2192138

A robust algorithm, based on relaxation, is proposed for the implementation of the IEC Standard method for rating cables installed in unfilled troughs. Through hundreds of finite-element simulations, the validity range of the standardized equations is established. Studies are performed by varying the following parameters over a wide range: trough size, ambient air temperature, trough aspect ratio, position of cables, cable operating temperature, and intensity of solar radiation. A physically consistent analog thermal-electric equivalent circuit is proposed for the thermal rating of cables installed in unfilled troughs. In contrast with the standards, the equivalent circuit offers a methodological approach that considers all heat-transfer phenomena involved in cables in troughs, for example, the conduction of heat through the cable layers, the heat convection and radiation inside the trough, the conduction in the trough itself and soil, the convection to the surface air, and the solar radiation. Extensive finite-element verification in steady state and transients demonstrates the accuracy of the proposed equivalent circuit.