GSC60
EN - 128
Approximate evaluation of intentional rods' contribution
The resistance of an Rd rod can be calculated with the following formulas ( r = average
resistivity of the ground).
a) resistance of a vertical rod
Rd = / L
where L = length of the element touching the ground
b) resistance of a horizontal rod
Rd = 2 / L
where L = length of the element touching the ground
c) resistance of linked elements
The resistance of a complex system made of more elements in parallel is always higher
than the resistance, which could result from a simple calculation of single elements in
parallel, especially if those elements are close to each other and therefore interactive. For
this reason, in case of a linked system the following formula is quicker and more effective
than the calculation of the single horizontal and vertical elements:
Rd = / 4r
where r = radius of the circle which circumscribes the link
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