A new finite difference time domain scheme for the evaluation of lightning induced overvoltage on multiconductor overhead lines

LEMP to transmission line coupling equations can be dealt with either in the frequency domain or in the time domain. A time domain approach allows handling in a more straightforward way non-linearities which appear when considering corona effect, and/or when protective devices such as surge arresters are present. This is the approach proposed by Agrawal et al. to solve their transmission line coupling equations. In particular, Agrawal et al. proposed a 1 order point centered Finite-Difference Time Domain (FDTD) integration scheme. In this paper, we propose a 2 order FDTD scheme for solving the Agrawal coupling equations. The algorithm applies to multiconductor lines above a frequency-dependent lossy ground, with multiple grounding of shielding wires. 1 and 2 order FDTD techniques are compared. It is shown that the proposed 2 order technique leads to more stable numerical results when considering frequency-dependence and/or non linearities. The developed 2 order FDTD algorithm for the analysis of overhead multiconductor lines illuminated by an external electromagnetic field is also interfaced with EMTP96.