New information regarding the effects of tellurics has been discovered by the use of special equipment to measure the true polarized pipe-to-soil potential even in the midst of a severe geomagnetic disturbance. [The Aurora Borealis (northern lights) is a manifestation of this occurrence.] Heretofore such information was not available and indeed the effect of the often observed tellurics was strictly a matter of conjecture and speculation.

We have now discovered that tellurics can and do pose a serious threat to coated pipelines in the auroral zone, extending from Northern Montana to Great Bear Lake, and of course elsewhere at similar (geomagnetic) latitudes.

The paper discusses tellurics, their origin, magnitude and frequency of occurrence, the equipment utilized to determine their effect on cathodic protection levels and more importantly, their ability to depolarize apparently well protected pipelines.

Means for successfully controlling the adverse telluric effect are also discussed.

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