Calculation Methods of Direct Lightning Shielding in ± 800kV Converter Station

The height of electrical equipment in the converter station increases with the increase of voltage level of power transmission system, and the limitation of the existing calculation methods of protection range of lightning rod is gradually being revealed. Based on the theoretical analysis of the electrogeometric model (EGM), a new design scheme of lightning rod for ultra high voltage direct current (UHVDC) converter stations was put forward. This method can calculate maximum allowable stroke current. When a shielding failure of small lightning current occurs, combining installation of arrester and the protection scope of the lightning rod, provides better protection for large stroke current, and ensures that the stroke current is within the range which arresters withstand in the meanwhile. Furthermore, it enables the average height of lightning rod to be lower. That reduces the chance that the lightning rod may attract lightning strike. Therefore, it alleviates the EMI of lightning current to the converter substation.