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Southampton, United Kingdom

Pilgrim J.A.,University of Southampton | Lewin P.L.,University of Southampton | Larsen S.T.,Southampton Dielectric Consultants Ltd. | Waite F.,UK National Grid Corporation | Payne D.,Southampton Dielectric Consultants Ltd.
IEEE Transactions on Power Delivery | Year: 2012

Cable circuits installed in unfilled troughs must often support high current ratings. To achieve higher ratings in unfilled troughs in the U.K., trough lids can be replaced by ventilated grilles, provided that the trough is within a substation site. While several methods exist for rating the traditional covered trough design, no standard method exists for naturally ventilated installations. To examine the possible uprating available, a coupled numerical model has been created for cable trough installations. Following successful benchmarking tests where the covered trough was modeled, the method has been extended to troughs with full natural ventilation. The results have been compared to commonly used engineering assumptions in order to validate simpler analytical methods. It was found that by allowing full natural ventilation of existing covered troughs, the continuous rating could be increased by as much as 28%. © 2012 IEEE.

Pilgrim J.A.,University of Southampton | Swaffield D.J.,University of Southampton | Lewin P.L.,University of Southampton | Larsen S.T.,Southampton Dielectric Consultants Ltd. | And 2 more authors.
IEEE Transactions on Power Delivery | Year: 2010

Over the last decade, there has been a notable rise in the number of forced ventilated cable tunnel schemes in the U.K., with new construction at transmission and distribution levels. The ability to accurately calculate continuous and emergency circuit ratings for these installations is vital in ensuring that their full operational benefit can be realized. While the Electra 143 calculation method in present use is fast and easy to use, it relies on several simplifying assumptions which make it unsuitable for application to tunnels with multiple independent cable circuits. This paper details a series of modifications to the present method which allow the direct calculation of ratings for tunnels containing multiple independent cable circuits. Significant benefits can be obtained from using this approach to calculate emergency ratings in these circumstances, as demonstrated by the example calculations provided. Implementation of an axially varying ac resistance also improves the accuracy of loss calculations. A number of key tunnel design considerations are illustrated through the results of the example calculations. © 2010 IEEE.

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