Improvements of an FDTD-Based Surge Simulation Code and Its Application to the Lightning Overvoltage Calculation of a Transmission Tower

This paper presents new features recently added to a general-purpose surge simulation code based on the FDTD (Finite Difference Time Domain) method. The added features include various-shape conductor models, lumped-parameter circuit-element models, a lightning-channel model, and an integrated analysis environment (IAE). For precisely modeling the shapes of various conductors, the following conductor models have been added: inclined thin wire, disc, square plate, cylinder, cone, and quadrangular pyramid. The lumped-parameter circuitelement models allow the user to represent the lumped impedance of an apparatus placed inside the analysis space. The lightningchannel model realizes a return-stroke development at a speed slower than the light speed. The IAE includes a GUI (Graphical User Interface) which allows the user to enter geometrical data in a visual way. It also provides a waveform plotting program for viewing voltage, current, electric-field, and magnetic-field waveforms and a movie program for displaying the animation of a transient electric/magnetic-field intensity distribution. For an illustrative example, the lightning overvoltage calculation of a transmission tower is presented.