A Technique for Representing Coaxial Cables for FDTD-Based Surge Simulations

The finite-difference time-domain (FDTD) method is a very effective tool for predicting surge phenomena in 3-D structures such as buildings and transmission line towers and in grounding systems such as grounding grids. In this paper, we propose a new technique for representing a coaxial cable for FDTD-based surge simulations. In this technique, the metal sheath of the cable and the electromagnetic field outside the metal sheath are simulated in the FDTD method, while the surge phenomena inside the metal sheath are solved on the basis of transmission line theory. Therefore, this technique can take into account the effect of the metal sheath of the coaxial cable, the traveling wave inside the cable, and wires connected to the internal conductor of the cable at the same time. Using the proposed technique, we predicted the surge phenomena in a coaxial cable and compared them with measured results for the purpose of validation.