In Egypt, the insulators of overhead transmission lines and substations are often subjected to the deposition of contamination substances from the desert. This can lead to serious reduction in insulator effectiveness, resulting in flashovers and outages of electricity supply. It is important to mention that a remarkably high rate of interruption of 500 and 220 kV transmission lines, in Egypt, are recorded during spring seasons in desert areas where occasional sandstorms occur (Khamassine). This interruption in the power system will lead to the delay of the development of the community. The flashover characteristics are thoroughly investigated for porcelain insulators exposed to natural sandstorms, as well as to simulated sandstorms with and without charged grids. Test results show that neither natural nor artificial sandstorms affect the fast flashover voltage if the sand particles are not charged, whereas charged particles of sands reduce the flashover voltage of the insulators. To a higher extent, this reduction in flashover voltage will be greater as the grid is charged with DC voltage.