Perpustakaan Digital ITB

Understanding the impulse characteristics of the soil where ground will be planted under seasonal variation is a key factor in the determination of the lightning performance of transmission lines and the safety voltages near high voltage towers. The earthing impedance is usually measured by either switching DC to the earth rod or injecting low currents with frequencies close to the power frequency. This resistance helps to estimate the behavior of the grounding system under low frequencies. However, under lightning and impulsive transient conditions, the grounding system exhibits different behavior. Many factors significantly affect the performance of the grounding system, such as the resistivity and permittivity of the soil, the shape of earthing electrode, the current magnitude and rise time of the impulse current. These aspects cause many challenges in designing an effective grounding system to meet the safety operation requirements. This thesis investigates both AC and impulse characteristics of the soil with different water content when the soil is subjected to AC variable frequency and impulses voltage respectively. The prepared soil with different water content was mixed LRM. The results obtain before adding the LRM compared with the developed models available in literature exhibited close agreements with them. However, the impulse experiment tests show that, the impulse characteristics of the soil before and after adding LRM were totally different. The impulse impedance decreases with soil water content, additional of LRM, and amplitude of impulse current. Effect of moisture contents on the resistivity of soil and the electrical soil parameters depend on the frequency due to the soil permittivity. Both AC and impulse characteristics of the soil under season variation are the paramount parameters to be considered in designing the effective ground system to improve the withstand and performance of power system.