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Project: T173700 #3723
 

Practicing appropriate rating and placement of working grounds is extremely important both to ensure a safe working environment for employees and the public and to protect power system equipment. Utilities rely heavily on standards such as IEEE, ASTM, and IEC in selecting suitable rated conductors and adopting safe work procedures. However, when utilities face situations that differ from those assumed in the standards, additional guidance or tools may be necessary to recalculate values. This report presents analytical models, simulation results, and spreadsheet tools serving the purpose of guiding utilities in adopting appropriate rating and placement of working grounds, even when conditions differ from those provided in the standards. These include calculating stresses seen by working grounds and staff when X/R ratios differ from rated values, and touch potentials away from Temporary Protective Grounds (TPGs). The project also provides simple quantitative spreadsheet tools to calculate capacitive and inductive coupled voltage and currents considering eleven line and bus configurations. These tools are presented to guide the user to modify the input parameters to any applicable scenarios and calculate the desired outputs. Equipotential zone methodologies to limit touch potentials to safe values are also presented.

Keywords:

Temporary Protective Grounds, X/R ratio, Capacitive coupling, Inductive coupling, Touch potentials, Bracket grounding, Temporary ground rods, Equipotential zones.