| LIGHTNING induced overvoltages may cause damage to the insulation of the distribution lines or other power equipments. Erksson et al. have evidenced that the indirect lightning return strokes, hitting the ground in the vicinity of overhead lines, constitute a more dangerous cause of damage than direct strikes, because of their more frequent occurrence. The research on the calculation of the lightning-induced overvoltages and prediction of the flashover of the distribution power system are very important for the insulation design of power lines.This paper introduces the mechanism of the lightning over-voltage, the importance of lightning induced over-voltage for the voltage level of the distribution overhead line. It assumes that the shape and speed of the lightning current remain the same with height while the amplitude is exponentially decay with the height. As the disadvantage of having a discontinuity at the stroke tip, which is presented in other models, is avoided. The Heidler model is chosen as the lighting base current model. Assuming the lightning channel as a vertical channel to the ground, the electromagnetic is calculated based on the Maxwell equation. The Agrawal model is chosen as the coupling of field-to-line model and the over-voltage induced by lightning strikes was calculated base on FDTD and Agrawal Model. Through a section of a typical calculation of overhead lines and compared with the existing literature, correctness of the method is verified.Discussion is implemented for the effects of the conductivity of the lossy ground to the lightning-induced overvoltages. Furthermore, the method about how to evaluate the flash over probability of the distribution system is presented and the discussion about the effects of the ground wire to the lightning-induced overvoltages is implemented, as a result, the equipment of the ground wire can reduce the overvoltages of the overhead lines and improve the quality of the distribution power system. |
PDF Full Text Request