Analysis of Lightning Grounding Values Using Variations in Frequency, Distance Ratio, and Measurement Methods

The aim of this research was to determine the frequency, distance ratio, and measurement method on the grounding measurement results for the lightning protection system. The methods used in this study were the 3-poles, 4-poles, and impedance impulse methods. Referring to the fall of potential (FOP) theory, the measurements were conducted by placing the current probe at a variation of the distance ratio of $56 \%, 59 \%, 62 \%, 65 \%$, and 68 %. The frequency ranges were from 55 Hz to 15.4 kHz, except for the impedance impulse method. The result that the impedance increased from 1.87Ω to 7.36Ω as the frequency increased from 55 Hz to 15.4 kHz. The impedance also increased from 1.66Ω to 2.78Ω as the distance ratio increased from 56 % to 68 %. The graph indicated that the 4-poles method generally produced the lower impedance compared to the 3 -poles method. Thus, the performance evaluation of lightning protection system should consider the characteristics of grounding values which could vary depending on the given variables.