An FDTD Thin-Wire Model for Lossy Wire Structures With Noncircular Cross Section

This paper presents an effective finite-difference time-domain (FDTD) thin-wire model for lossy wire structures with noncircular cross section in transient analysis. Unique correction factors of field quantities and surface electric field of wire structures are introduced in the model. These parameters are both frequency-dependent and position-variant. They are evaluated in an initialization process and are applied in the updating process using an iterative convolution technique. The proposed method is validated with the transmission line theory analytically and the traditional FDTD method numerically. Three types of wire structures are tested, including rectangular, H-shape, and cross-shape structures. Good agreements are observed. It is found that the computation time is reduced to 1% of that with the conventional FDTD method, and the computer memory to 30% in the tested case. General guidelines on wire zone meshing are provided as well. Finally, this method is applied to analyze lightning surges in a light rail system under a direct lightning stroke.