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SES Research and Development Team

Using Fall-of-Potential Measurements to Improve Deep Soil Resistivity Estimates

Robert D. Southey, Member, IEEE, Majid Siahrang, Simon Fortin, Member, IEEE, and Farid P. Dawalibi, Senior Member, IEEE

When measuring the ground impedance of an electrically isolated grounding system, it sometimes happens that the test electrodes are placed at considerably greater distances from the installation under test than the maximum electrode spacing used during the soil resistivity measurements carried out during the pre design phase of the grounding system. As a result, ground impedance measurements carried out with the fall-of-potential method may contain valuable supplemental information about deep soil strata that can improve grounding system performance predictions made during the design phase with computer modeling software and explain discrepancies encountered between predicted and measured ground impedance values. These data can be also used during subsequent grounding design work associated with facility expansion. It is shown in this paper how, in the absence of interfering metallic infrastructure, such ground impedance measurements can be converted into apparent soil resistivity values corresponding to deeper soil layers, with an example showing how dramatic improvements in grounding system performance predictions can be obtained.

Published in IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL.51, NO.6, NOVEMBER/DECEMBER 2015.

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Analysis of Grounding Systems in Horizontal Multilayer Soils Containing Finite Heterogeneities

Simon Fortin, Member, IEEE, Nina Mitskevitch and Farid P. Dawalibi, Senior Member

SES technologies ltd. Quebec, Canada

 

This paper presents a theoretical model for the analysis of grounding systems located in multilayer soils in which arbitrary heterogeneities (finite volumes) are embedded. The presence of the heterogeneities is handled through a Boundary Element Method while that of the horizontal soil layers is handled analytically, using Image Theory (or any other equivalent technique). Numerical results are presented for several cases, and are shown to agree with limiting cases. The results also clearly show that the presence of finite heterogeneities in multilayer soils can have a very strong impact on the safety performance of a grounding system.

Published in IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL.51, NO.6, NOVEMBER/DECEMBER 2015, p. 5095-5100.

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Analysis of Grounding Systems in the Vicinity of Hemi-Spheroidal Heterogeneities

Amir Hajiaboli, Simon Fortin, Farid Paul Dawalibi, Peter Zhao and Adrian Ngoly

Safe Engineering Services & technologies ltd.

Laval, Canada

 

This paper presents a method of analysis of grounding systems located inside or near a hemi-oblate spheroidal soil heterogeneity. This type of soil is particularly useful for modeling grounding grids close to certain types of finite inhomogeneities, such as lakes or some types of backfill material. The developed analytical framework is based on the moment method and involves solving Poisson’s equation in an oblate spheroidal coordinate system. Computation results obtained using this modeling approach for several electrodes and hemi-spheroidal geometries are compared with those obtained using other numerical and analytical techniques. In all cases a good agreement has been achieved.

Published in IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL.51, NO.6, NOVEMBER/DECEMBER 2015, p. 5070-5077.

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Numerical Techniques for the Analysis of HVDC Sea Electrodes

Amir Hajiaboli, Simon Fortin and Farid Paul Dawalibi

 

Safe Engineering Services & technologies ltd.

 

This paper presents an analysis of HVDC sea electrodes using different numerical techniques. The large volume of sea water that must be included in the analysis is represented using infinite (Inclined Layer model) and finite models (Finite Volume and Hemi-Spheroidal models). The comparison between the results obtained using these models are based on the potential rise of the electrode, the sea potential rise in the vicinity of the electrode and on the computational burden for utilizing each model. The analysis shows that the results obtained using finite models can predict the performance of the electrode more accurately and realistically.

Published in IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL.51, NO.6, NOVEMBER/DECEMBER 2015, p. 5075-5181.

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