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The finite-difference time-domain (FDTD) method is a technique for computing space- and time-discretized expressions of Maxwell's equations, which are space- and time-fractional partial differential equations of electric and magnetic fields. It has the following advantages: its computer programming is relatively easy, its computed results can be intuitively well understood, and associated numerical instability, if it occurs, is easily recognized. For these advantages together with recent rapid advancement of high-performing computers, the FDTD method has been employed frequently in analyzing surge phenomena in electrical systems. In this technical report, the fundamental theory of the FDTD method, and techniques for representing thin wires, flashover phenomena, and modeling of arresters, which are indispensable for practical surge analyses, are explained. As examples of applications of the FDTD method, surges analyses in wind-turbine-generation systems, photovoltaic generation systems, intelligent buildings, telecommunication towers, and inverter-equipped apparatuses as well as conventional electric power facilities such as grounding electrodes, transmission and distribution lines, and substations are demonstrated. Also, analyses of propagation of partial-discharge-generated electromagnetic waves in an electric power equipment, and of power-line-communication signals in a power cable, which are difficult to be analyzed appropriately by the conventional circuit theory, are presented. Furthermore, equivalent-circuit modeling of transmission towers and grounding electrodes based on the FDTD-computed results is shown. In the appendix, a recent trend of related researches and developments in other countries is presented. |
