Finite Difference Time Domain Method for the Analysis of Transient Grounding Resistance of Buried Thin Wires

For the analysis of grounding resistance with the finite-difference time-domain (FDTD) method for solving Maxwell's equations, an equivalent radius of a naked thin wire in a lossy medium is derived by means of the static field approximation, proposed for derivation of that of an aerial thin wire. It is 0.23 times the size of each cell employed, which is the same as that of an aerial thin wire. The validity is tested by comparing the grounding-resistance values obtained through FDTD simulation on simple buried structures with the theoretical values.