Contents 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.
