Analyzing the Effect of Lightning Channel Impedance on the Lightning Overvoltages in Wind Turbines

Lightning is a natural phenomenon that can cause serious damage to power systems including wind farms. Wind Turbines (WTs) are tall structures and are often installed in areas with high lightning activity levels which makes them exposed to direct strikes. One of the parameters affecting the performance of the lightning protection system is the impedance of the lightning channel. In this paper, the effects of this impedance on the lightning overvoltages in WTs, and the energy absorbed by Surge Arresters (SAs), as the main lightning protection device, are investigated. The case study is carried out on a WT with 2 MVA of rated power where a direct lightning strike with a maximum current magnitude of 50 kA is struck to one of the WT's blades. Accurate models, designed for transient studies, are used for modeling different parts of the WT. The results of different scenarios are compared, and it is shown that as the value of lightning channel impedance gets higher, the overvoltage caused by the corresponding lightning strike, with the same current magnitude, increases too. In addition, it is shown that the higher the lightning channel impedance, the higher the absorbed energy by the arrester. This shows the importance of the lightning channel impedance's effect on high-voltage studies of WTs, as it can help in selecting proper lightning protection devices.