Telluric currents interfere with cathodic protection systems and cause variations in pipe-to-soil
potentials, which can exceed the levels recommended for protection of the pipeline steel. The
amplitudes of telluric currents observed in a pipeline depend on three factors: (1) the level of the
geomagnetic activity, (2) conductivity of the underlying earth and (3) pipeline electromagnetic properties
and geometric parameters. These factors have been incorporated into mathematical models that are
used to estimate the pipe-to-soil potential variations due to telluric activity.
The time when pipe-to-soil potential variations exceed the recommended level can be different
depending on the different telluric activity at the pipeline locations. To evaluate this, a simple model for
the telluric electric field has been set up, based on the geomagnetic data and an earth conductivity
model. A statistical study based on the long records of the geomagnetic data from Canadian magnetic
observatories and conductivity structures of the deep earth allows evaluating telluric activity for 30
years period.
In order to show the geographical areas with different levels of activity, a set of maps has been
produced and is available through Atlas of Canada web page:
http://atlas.nrcan.gc.ca/auth/english/maps/environmentlnaturalhazards/space weather.
The estimated telluric electric fields were used as an input to model pipe-to-soil potential variations on a
pipeline. In order to do this, the developed pipeline model has been incorporated to provide an on-line
service for different users. The on-line service allows the user to evaluate the pipe-to-soil potential
fluctuations at a particular location for a user-defined pipeline.
Keywords: Telluric currents, pipe-to-soil potential variations