CORRECTION OF THE IEC FORMULA FOR THE EDDY-CURRENT LOSS FACTOR: THE CASE OF SINGLE-CORE CABLES IN TREFOIL FORMATION WITH METALLIC SCREENS BONDED AND EARTHED AT ONE END

Marko Šućurović, Dardan Klimenta, Dragan Tasić

DOI Number
https://doi.org/10.2298/FUEE2402391S
First page
391
Last page
408

Abstract


The purpose of this paper is to propose and apply the correct formula for the eddy-current loss factor for the case of three single-core cables in trefoil formation with metallic screens and armourings bonded and earthed at one end. This metallic screen bonding design is contrasted to the design where metallic screens and armourings are bonded and earthed at both ends, that is, the eddy-current loss factor is contrasted to the circulating-current loss factor. Ampacity calculations are carried out for 12 different underground lines with power cables of the type Cu/XLPE/CTS/PVC/AWA/PVC 1/C 19/33 kV (BS 6622), assuming that the 33 kV cables are installed directly in the soil without drying out. The ampacity is calculated analytically in accordance with IEC 60287-1-1 and IEC 60287-2-1, and numerically in accordance with IEC TR 62095. The numerical calculations are carried out to verify the accuracy of the proposed formula using the finite element method (FEM) in COMSOL 4.3. A validation of the proposed formula is conducted based on the manufacturer's technical data for the considered cables. The calculated ampacity values determined the incompleteness of the current IEC formula for the eddy-current loss factor, and verified the accuracy of the proposed one.


Keywords

ampacity, circulating-current loss factor, eddy-current loss factor, finite element method (FEM), metallic screen bonding design, power cable

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References


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