Lightning Overvoltages due to Direct Strikes to a Hybrid Overhead Line

Inhalt:
This paper analyzes the overvoltages caused by direct lightning strikes to a hybrid overhead line with sub-transmission (138 kV), medium-voltage (13.8 kV), and low-voltage (220 V) circuits. The main focus is on the influences of various parameters, such as the lightning current front time, the ground impedance, and the tower surge impedance, on the overvoltages in the medium-voltage line. Specific models of transmission line towers and high-voltage insulators were developed and validated through laboratory tests and EMTP simulations. The analysis indicates that the line performs well against backflashovers.