Three-dimensional FDTD-based simulation of induced surges in secondary circuits owing to primary-circuit surges in substations

Currently, plenty of sensitive electronic devices are installed in secondary circuits in substations and power plants. Electronic devices may malfunction and become damaged owing to electromagnetic disturbances caused mainly by lightning surges. To protect electronic devices properly, it is useful to predict electromagnetic transient phenomena and evaluate the effectiveness of lightning protection methodologies. Recently, the finite-difference time-domain (FDTD) method, which is one of the full-wave numerical approaches, has become a very powerful tool for analyzing electromagnetic transient phenomena in 3-D structures and grounding systems. In this article, first, we study the modeling of protection relay units and instrument transformers for FDTD-based surge simulations. Second, using an FDTD-based electromagnetic transient simulation code, we model a test platform of a gas-insulated switchgear (GIS), instrument transformers, and a control cable above a grounding grid. By applying a surge voltage to the center conductor of the GIS model, we calculate the transient voltage in the GIS model, the transient response of the grounding grid, and the induced voltage on the control cable, and compare the calculated results with measured waveforms for validation