H. Hofmann et G. Preston, REDUCTION OF STRAY CURRENTS AND MAGNETIC-FIELDS FROM SINGLE-PHASE POWER DISTRIBUTION-SYSTEMS, IEEE transactions on power delivery, 10(2), 1995, pp. 1112-1118
This paper describes a simple, straightforward method for reducing str
ay currents and external magnetic fields from single-phase power distr
ibution systems through the installation of a 1.1 current transformer.
The current transformer magnetically couples the phase conductor and
neutral conductors of a power cable, thereby forcing the return curren
t to travel through the neutral rather than through other paths. Furth
ermore:, if the phase conductor and neutral are sufficiently close tog
ether (preferably concentric), the magnetic field created by the retur
n current in the neutral cancels the field created by the current from
the phase conductor, thereby eliminating magnetic fields. This isolat
es the power cable from its environment while allowing it to remain so
lidly grounded. The current transformer may be applied to all sizes of
power distribution systems, from underground residential distribution
systems to wiring within buildings. This paper explains the theory be
hind this method, discusses possible practical applications of the met
hod, and reports the results of a test installation by the City of Aus
tin. These results show that the method can virtually eliminate stray
currents and magnetic fields emanating from power distribution systems
. However, more research should be done before the method is put into
practice.