Finite-Difference Time-Domain Simulation of a Lightning-Impulse-Applied ZnO Element

The voltage across a zinc oxide (ZnO) element, in which a lightning impulse current is injected, and the temperature distribution in the ZnO element have been computed using the finite-difference time-domain (FDTD) method. The ZnO element having a length of 36 mm and a radius of 16 mm is represented with many 2 mm × 2 mm × 4 mm rectangular cells, each of which has a nonlinear resistivity in each of the x, y, and z directions dependent on the electric field in each direction and the temperature in each cell. Waveforms of the voltage across the ZnO element and maximum temperatures, computed using the FDTD method, for lightning impulse currents having magnitudes of about 30-65 kA, have been compared with those measured by the authors. Furthermore, the voltage across a 66- or 77-kV transmission-line surge arrester, composed of nine stacked ZnO elements, and the distribution of temperature in the arrester have been computed for a 50-kA lightning impulse current.