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s: Grounding impedance is an important component of electrical power systems especially for protection for human safety and the continuity of the operation of power systems. At low frequency current injection the characteristics of grounding impedance is very resistive, however at high frequency it may be capacitive or inductive depending on the frequency. In order to build a grounding system used for lightning protection, it needs a careful and accurate design. It will receive high current and high frequency around hundred kilos up to mega hertz, otherwise it is simple grounding for low frequency. This paper reports the modification of a grounding system with vertical layers configuration. This is the novel issue because the other researchers use horizontal layers configuration. In this experiment, the grounding rod is injected by using low to high frequency AC source The modification is made by filling the soil into a grounding rod (cylinder rod) and therefore it created two soil layers of grounding system, and by using three size variations of cylindrical layers of length (L) of 40, 60, and 100 cm; and three size variations of diameter (D) of 20, 30, and 40 cm. These variations will allow us to understand the characteristic of the grounding impedance at low and high frequency, where usually the composition of inner layer soil have lower resistance than the outer soil. The composition of the outer soil consist of 16.85 % clay, 66.18 % silt, 15.48 % sand, and 1.49 % gravel whereas the composition for the inner/filling soil consist of 34.98% clay, 49.55% silt, 15.35% sand, and 0.16% gravel. The value of soil permittivity and resistivity affect the value of grounding impedance at low and high frequency. In general, the results indicated that the grounding impedance at high frequency was higher than at low frequency, but the fluctuation of grounding impedance depended on the condition of inner soil, length and diameter of cylindrical rod. In this research, the grounding impedance was plotted as the function of the frequency and until now the value of this fluctuation cannot be determined accurately.

Grounding Impedance Characteristics for Two-Layer Soil of Vertical Rod Configuration with Variation of Length and Diameter