Читать книгу Electrical Safety Engineering of Renewable Energy Systems - Rodolfo Araneo - Страница 22

Two identical hemispherical electrodes of radius r₀ are connected in parallel into a uniform soil of resistivity ρ, and each leaks the current i/2. The electrodes are buried at a distance d.

The hemispheres attain the same ground-potential rise, which can be calculated by superimposing the potentials of each electrode, supposed isolated from the other (Eq. 1.13).

(1.13)

Thus, the total ground resistance is given by Eq. 1.14.

(1.14)

If d > 5ro, the second factor in Eq. 1.14 is ≈1, and R _G is mathematically expressed by the formula of the parallel of the ground resistances of each electrode.

If the electrodes are closer than d > 5ro, they are not independent from each other, and their total resistance is greater than their mere parallel (Figure 1.11).

Figure 1.11 Ground-electrodes in parallel.