Reduction of magnetic fields from electric power and installation lines
Two methods of reducing the magnetic fields around electric power transmission lines and installation lines are discussed, splitting of conductors, and twisting. General design parameters and criteria are derived. The division of each phase conductor into a pair, at equal distance from a centre, makes the far field decay as the inverse cube of the distance as compared to the inverse square for an ordinary line. It is shown that all split phases should have a common centre, but that the separation distances may be different for individual phases and also the angles between the phase planes may be arbitrary. Applications to existing power lines are discussed. Twisting of telephone cables has long been practised to reduce crosstalk. It is shown that twisting of cables and installation lines also results in a drastic reduction of the external magnetic field. Both methods also result in a great reduction of the sensitivity to disturbances from external sources.
