Series impedance of distribution cables with sector-shaped conductors

Andrew J. Urquhart; Murray Thomson

Series impedance of distribution cables with sector-shaped conductors

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Author(s): Andrew J. Urquhart ¹ and Murray Thomson ¹
- Affiliations: 1: Centre for Renewable Energy Systems Technology (CREST), School of Electronic, Electrical and Systems Engineering, Loughborough University, Loughborough LE11 3TU, UK
Source: Volume 9, Issue 16, 03 December 2015, p. 2679 – 2685
DOI: 10.1049/iet-gtd.2015.0546 , Print ISSN 1751-8687, Online ISSN 1751-8695

This is an open access article published by the IET under the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0/)

Received 26/04/2015, Accepted 18/06/2015, Revised 03/06/2015, Published 03/12/2015

Models of power distribution networks require accurate cable impedance data. For unbalanced networks, both the self-impedances and the mutual impedances are needed. However, published studies use differing approaches to determine cable impedances, leaving uncertainty over the level of detail required. This study compares impedances provided by the manufacturer with those from several analytical methods, showing the impact of modelling the non-circular geometry and of including corrections allowing for the AC resistance. The analysis is compared to results from a freely available finite element (FE) solver where the current distribution is modelled in detail, taking account of eddy currents and the rotation of the cores relative to the neutral due to the cable lay. At 50 Hz, the analytical methods provide a good approximation, but the FE results show that eddy currents affect the impedance at harmonic frequencies. The results also show the impact of including the ground path in the impedance calculation. The current distribution in the ground has a wide cross-sectional area, suggesting that the assumption of a perfect multi-grounded neutral is inappropriate for low voltage networks with short cable lengths.

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Series impedance of distribution cables with sector-shaped conductors

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