Parametric Analysis on Ground Level Safety Near Steel Poles under Fault Conditions

Y. Li, J. Ma, and F.P. Dawalibi (Canada)


Ground potential rise, Touch voltage, Step voltage, Electric lines, Customer neutral, Ground loop


When a fault occurs on a distribution or transmission steel pole, the faulted pole or the adjacent poles can be subjected to very high ground potential rise. The earth surface voltage gradient near the tower is increased and could represent a hazard for a worker or a person who is touching the pole or just happens to be nearby. Appropriate pole grounding design may represent a relatively simple, durable, and economic solution. This paper carries out a detailed parametric analysis that shows how the grounding system can effectively reduce the touch and step voltages on the pole ground level. Generally speaking, installing a buried grounding loop around the pole decreases the touch voltages but increases the step voltages. Increasing the grounding system radius can improve the touch voltage tremendously without increasing significantly the step voltage. Significant variations in soil resistivity with depth have important impact on the performance of the grounding system. Burying the grounding system in a relative low soil resistivity layer can maximize the effectiveness of the grounding system for both touch and step voltages. Not surprisingly, the presence of bare metallic pipes in a residential or urban areas improves the touch and step voltages considerably.

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