Calculation of grounding involves determination of the number and configuration of ground electrodes, depth of their immersion and and taking into account soil resistivity. All these parameters directly affect the final resistance of the grounding set. However, the question about such a parameter as "minimum distance between ground electrodes" appears at the installation quite often. How should it be? In practice the distance of 3 meters is often taken into account, which confirms the recent question from our site visitor. Is this value true? Let's study this question!
For efficient current spreading, vertical electrodes should be installed at the distance not less than their length. Utilization ratio plays a great role, as it shows mutual interference of ground electrodes in the grounding contour and is directly dependent on the relative distance of the electrodes. Direct instructions for placement of vertical electrodes at the distance greater than their length, are listed in paragraph 2.2 AD 34.21.122-87
the relative distance of the electrodes
Arrangement of the electrodes in a row also contributes to the efficient current spreading, compared to the contour because the work areas of the electrodes do not overlap - the utilization ratio is higher. If several ground electrodes are too close to each other, this ground circuit becomes inefficient because the "electrode work zones" overlap - the working volume of these zones reduces and, therefore, the efficiency of each ground electrode operaton decreases.
Thus, the total length of the electrodes and their correct arrangement are valuable. Each conductor has an electric potential. The lower is the resistance, the better the current spreads in the environment, the greater the potential reduces on the ground electrode. It will get closer to the natural potential of the ground, ie, to zero. As a result,the amount of the dangerous potential on the body of the damaged electric installation will decrease.
Installation of electrodes into a closed contour is suitable to be placed around the object, and serves the purpose of potential equalization, which is important in lightning protection, and provides low ground resistance because large total length of the electrodes may be used.
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