Statistical Study of Electric Fields from Earth-Return Tests in the Western States Compared with Natural Electric Fields

Preliminary grounding tests have been carried out by the Bonneville Power Administration and by the Bureau of Reclamation in three regions of the western states, in preparation for the installation of a HVDC transmission system linking the Pacific Northwest and Southwest regions. Electric fields observed about ground mat locations in the Washington-Oregon area, the southern Nevada area, and the central California area were analyzed statistically as a function of distance from the ground mat. These fields are compared with the probable levels of natural fields induced by slow variations in the earth's magnetic field-in order to estimate the possible hazards involved in using ground return for current in a HVDC system.