Paper Title
Impulse Characteristics of Tropical Countries’ Soil Under Seasonal Variation

This paper presents the experimental results of the impulse characteristics of andisols under seasonal variation when a 1.2/50㎲ impulse voltage is applied to the sample of andisols. The soil resistivity changes seasonally, lightning current is function of both time and current magnitude. For this study, laboratory experiments were carried out based on the factors that affect the transient behavior in soils. The tested andisols is composed by sand 21%, silt (30%) and clay (49%) and the sample soil with different water content was subject to 5kV, 500A impulse generator. The impulse tests were performed on hemispherical test cells of 1m diameter, with inner rod of 10cm diameter and depth of penetration of 10cm. The magnitude of voltage to breakdown the soil was measured for soil with different water content. It was found that, the time-lag in soils decreases when soil water content increases and when the amplitude of applied voltage increases as the increment of the soil water content results in decreasing the soil resistivity.The impulse characteristics of the soil depends not only on the soil resistivity and its moisture content but also on the amplitude of the impulse voltage and rise time of conduction current. When the test impulse voltage is applied repeatedly, andisols breakdown occurs along different impulse paths. It expected that, the effective grounding system can be obtained in future by considering the rising time and impulse current magnitude under seasonal variation in the design of grounding systems. (Abstract) Keywords - Grounding System, Soil Impulse Impedance, Rising Time, Time-Lag, Low Resistivity Material (LRM)