The paper deals with an assessment of transient current induced along the vertical grounding electrode applying the thin wire antenna model in the frequency domain. The formulation is based on the homogeneous Pocklington integro-differential equation. The influence of an imperfectly conducting half-space is taken into account via the corresponding reflection coefficient arising from the Modified Image Theory (MIT). The Pocklington equation is solved using numerical and analytical approach respectively. The numerical solution is carried out via the Galerkin-Bubnov scheme of the Indirect Boundary Element Method (GB-IBEM). The transient response is obtained by means of the Inverse Fourier Transform (IFFT). Some illustrative computational examples for the transient current induced at the center of a vertical grounding electrode are presented in the paper.