Finite-difference time-domain method based on telegraph equations and its applications to modelling of large-scale grounding systems

A straightforward and simple time-domain simulation algorithm is proposed, which is similar to the well-established finite-difference time-domain method (FDTD) based on Maxwell equations. Thanks to this simplicity, a three-dimension (3D) simulation domain can be reduced to a one-dimensional (1D) model. This type of time domain method based on the telegraph equations has been successfully used to analyze underground transmission line or overhead transmission line problems. In this work, by introducing the shunt and series connection difference equations into this method, the application of this method is extended from the single transmission line to an entire conductor network. As a result, the method can be used in the modelling of large-scale problems, e.g., grounding systems. As the transmission line theory in the frequency-domain is a valid approximation of Maxwell theory on the condition of low frequency or that the size of models is much smaller than the wavelength, the proposed time-domain method is an approximation of the FDTD method based on Maxwell equations. Generally speaking, it is accurate and effective for frequency below 10MHz. This makes the method very useful in the lightning analysis of grounding systems.