In our experience undergrounding a power significantly reduces the electric and magnetic fields. The electric field is very easy to attenuate and the earth will easily absorb it. In addition, the cables are usually contained in an earthed conductive sheath, often lead, which results in little or no emitted electric field.
The magnetic fields are reduced by virtue of the close coupling of the conductors which are often arranged in trefoil. Of course, it is possible get closer to the cable as it is buried at about a metre deep. Therefore, there maybe some elevation of the fields close to the cable. However, in general, these will be less than an overhead implementation where the cable separations are much greater and there is less cancellation. The levels from an undergrounded cable will be less than 10 uT at 5m distance. The electric fields will be negligible. At least that is my view. Hope this helps. John McAuley Compliance Engineering Ireland Ltd/Field Management Services www.fms-uk.com Also see www.cei.ie Hi Robert: > Later the high tension towers have been replaced with > underground transission lines as part of the Guadalupe > corridor beautification plan. Hmm. I don't believe burying transmission lines attenuates either the magnetic or electric fields. Obviously, something must be done to attenuate the electric field to prevent shocks above ground due to a body crossing too many equipotential lines. Attenuating the electric field may or may not also attenuate the magnetic field. Comments on attenuation of electric and magnetic fields of buried high-tension lines as compare to overhead lines? Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
