A Comparison of Peak Electric Fields and GICs in the Pacific Northwest Using 1‐D and 3‐D Conductivity. Issue 11 (22nd November 2017)

• Record Type: Journal Article
• Authors: Gannon, J. L.; Birchfield, A. B.; Shetye, K. S.; Overbye, T. J.
• Is Part Of: Space weather. Volume 15:Issue 11(2017:Nov.)
• Page Start: 1535
• Page End: 1547
• Publication Date: 2017-11-22
• Subjects: GIC -- electric fields -- conductivity -- space weather; Space environment -- Periodicals; 551.509992
• DOI: 10.1002/2017SW001677
• Languages: English
• ISSNs: 1542-7390

Abstract

Abstract: Geomagnetically induced currents (GICs) are a result of the changing magnetic fields during a geomagnetic disturbance interacting with the deep conductivity structures of the Earth. When assessing GIC hazard, it is a common practice to use layer‐cake or one‐dimensional conductivity models to approximate deep Earth conductivity. In this paper, we calculate the electric field and estimate GICs induced in the long lines of a realistic system model of the Pacific Northwest, using the traditional 1‐D models, as well as 3‐D models represented by Earthscope's Electromagnetic transfer functions. The results show that the peak electric field during a given event has considerable variation across the analysis region in the Pacific Northwest, but the 1‐D physiographic approximations may accurately represent the average response of an area, although corrections are needed. Rotations caused by real deep Earth conductivity structures greatly affect the direction of the induced electric field. This effect may be just as, or more, important than peak intensity when estimating GICs induced in long bulk power system lines. Key Points: The use of 3‐D conductivity in electric field estimates can result in large differences in field magnitude and direction Layer‐cake, 1‐D conductivity models may accurately represent the average induction response of a region Shorter period (10 s to 1 min) magnetic field variation can contribute 50% of the induced electric field