Further developments in conductor management
of underground cable systems
(2013)Abstract
Conductor management is an efficient way to reduce electromagnetic fields (EMF) directly at the
source, acting on the geometry of the cables that generate the resulting field. In the case of multiple
circuits, the phase sequence becomes relevant and must be taken into account from the early design
step of the system.
At the previous EMF-ELF conference in 2011, the author presented a paper and tutorial to assess the
influence of EMF basic parameters. Typical and more complex configurations were illustrated.
Based on this experience, the present paper deals with the maximum magnetic field calculation of
further configurations: two-phase circuits, stand-by links, twisted bundled cables.
The influence of solid bonding is also discussed, taking into account circulating currents into metallic
sheaths or parallel earthing conductors. Recommendations are given for unbalanced circuits or to
upgrade two-phase to three-phase systems.
The maximum value of exposure of general public is illustrated with a very unfavourable
configuration, which would reach 100 μT: reduced depth of cable laying, flat formation with large
spacing between cables, high current rating and penalizing phase sequence. This practical exercise
shows in what manner conventional cable installations lead to magnetic fields whose magnitude is
well under the recommended value.
Calculations are performed with a very user-friendly software application, convenient to search
automatically the optimal arrangement of multiple circuits, to plot visual results of analysis of
sensitivity to one parameter, or to compare alternative technical solutions. The application has become
an actual tool of e-learning for the cable engineer.
