The FEM Analysis of Grounding System When Considering the Soil Ionization Phenomenon under Different Soil Structures

Abstract

A finite-element mode for the grounding system and soil is built in the software of ANSYS 10.0 to study the performance of grounding systems when considering the soil ionization phenomenon around the grounding system under different soil structures. The calculated results are validated by the simulation results found in the published papers. The performance of the grounding systems when considering the soil ionization effect at high-magnitude current are analyzed under different soil structures. Calculated results show that the distribution of earth surface potential is decreased when the soil ionization occurs. The soil structures are closely related to the performance of the grounding system and the soil ionization phenomenon are not easy to occur in the area of low soil resistivity, where the earth surface potential decreased more once the soil ionization occurs.

The effect of soil ionization on transient grounding electrode resistance in non-homogeneous soil conditions

“…The grounding electrode in the three scenarios is injected by a 10 kA lightning current with 10 μs/50 μs wave shape. The grounding electrode resistance values computed using (15) and (16), R eq , and the electromagnetic field computational model, R EM , are presented in Table I. The difference between the resistances R eq and R EM in the three scenarios is less than 0.9%, which validate the proposed method of computing the equivalent grounding resistance in this study.…”

“…[23,38] is taken into account. The grounding resistance of each portion R i is calculated using (15), and finally, the equivalent grounding resistance value R eq is obtained using (16). This disregard is consistent with the considerations taken in [38,39], where the MoM is applied for the computation of the equivalent radius.…”

“…To consider the soil ionization effect in the computation of the transient Figure 10. The grounding electrode resistance values computed using (15) and (16), R eq , and the electromagnetic field computational model, R EM , are presented in Table I. Comparison between the proposed method and CIGRE formula.…”

“…In addition, the equivalent radius a eq _ i for each portion is obtained using (13). The grounding resistance of each portion R i is calculated using (15), and finally, the equivalent grounding resistance value R eq is obtained using (16). Figure 11 illustrates the electric field values along the profiles for the three scenarios.…”

“…Similarly, the overall lightning and grounding performance of the transmission and distribution lines is improved when soil ionization occurs [7,8]. Given the importance of this phenomenon, soil ionization effect is being considered in the grounding system analyses [9][10][11][12][13][14][15] and in the computation of the transient grounding resistance [5,6,[16][17][18][19][20]. These investigations covered both theoretical and experimental studies and resulted in new computational methods and formulas, which explain the mechanism and influence of soil ionization on the grounding transient resistance value.…”