Lightning Transient Impulse Problem of Substation Grounding Grid in Multilayer Horizontal Layered Soil Considering Soil Ionization Effect and Frequency Characteristics

This study proposes a novel mathematical model based on time-domain Garlerkin's boundary element method. Our approach accurately computes the lightning current distribution and lightning current impulse response of buried grounding grid conductors in horizontal multilayered soil, accounting for soil ionization effects and electrical parameter frequency characteristics. To enhance computational efficiency, we integrate the quasi-static complex image method and its time-domain Green's function closed form into the model. An analytical method is employed to compute the mutual inductance coefficient between the branch currents of any two conductor segments and the mutual resistance between the leakage currents. The proposed Galerkin boundary element method simulates the lightning transient impulse response of substation grounding grids in multilayer horizontal soil.

I. Introduction

Optimizing substation grounding grid design is imperative for minimizing lightning current-induced damage to power systems. A prerequisite involves scientifically and accurately simulating the transient response of lightning impulses. Numerous numerical approaches based on Fourier transform and frequency-domain electromagnetic field principles have been developed for this purpose. For instance, circuit theory approaches [1], [2], [3], [3], [4], [5], transmission line theory methods (TLM) [6], [7], [8], [9], hybrid methods [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], and electromagnetic field theory techniques [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35]. The frequency-domain electromagnetic field theory-based approaches include the method of moments [20], [21], [22], [23], the finite element method (FEM) [24], [25], [26], and the boundary element method (BEM) [27], [28], [29], [30], [31], [32], [33], [34], [35]. By contrast, the time-domain electromagnetic field theory-based approaches include time-domain finite difference methods (FDTD) [36], [37], [38], circuit theory approaches [39], [40], time-domain TLM [41], [42], [43], and hybrid techniques [44], [45], [46], [47], [48], [49], [50], as well as methods based on electromagnetic field theory [51], [52], [53]. Recently, based on vector fitting approaches, frequency-domain BEM or hybrid methods have been transformed into time-domain methods [15], [54], [55], [56] to simulate the lightning transient impulse response issue of substation grounding grids.