Experimental study on transient impedance of grounding rods encased in ground enhancing compounds

• This study provides useful information for the design of a grounding system.
• Benefits of ground enhancing compounds on grounding systems are presented.
• Full-scale impulse current tests have been performed on vertical grounding rods.
• Slurry bentonite, foundation concrete and natural soil have been tested.
• Concrete and, secondarily, bentonite achieve high decrease in impulse impedance.

Aim of this research work is the study on the variation of the impulse impedance and its parameters of grounding rods which are driven in ground enhancing compounds. From the analysis of the measurement results, this work aspires to investigate the possible earned benefits from the usage of these materials on grounding systems, especially in the field of Lightning Protection Systems (LPS). Moreover, the validation of the results of preceding experimental studies on grounding systems transient impedance is another objective of this project. For this purpose, full-scale impulse current tests of a standard waveform have been performed on single vertical grounding rods, driven both into soil and in ground enhancing compounds. The injected current into the grounding systems and the developed electric potential on them have been recorded, resulting in the determination of the time variation of impulse impedance. The results provide useful information for the design and the behavior of a grounding system, encased either in bentonite or in conductive concrete under lightning impulse currents, as well as for the protection measures of installations from lightning strokes.