ABSTRACT
Main sources of high voltage surges are generally confined to intentional and unintentional switching operations in power systems as well as those induced by lightning phenomenon. Current and voltage surges are usually of high amplitude and short in time duration, and of different span in frequency spectrum with a broad band in harmonies and as special distorted wave forms. Voltage or current surges initiated by switching or lightning will propagate at a velocity close to that of the velocity of light in overhead systems and at about half of that through underground installations. However, regarding long distance propagation of voltage or current surges, it is essential to carry out analytical calculations to obtain reliable information about disturbances inflicted by electromagnetic surges. The Process of Reignition may generate a higher voltage surge, especially in underground cable systems where the line capacitance is a more significant portion of the surge impedance than that of overhead line.
