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The normal operation of a surge arrester by a lightning stroke or switching surge requires the arrester to conduct currents, first limited by the system surge impedance and arrester resistance, and then, limited by short circuit impedance and arrester resistance. These currents, whose magnitude and duration are a function of the source impedances and arrester characteristics, can, when the surge impedances are unusually low, pose special problems of durability for the arrester. Some applications where such low surge impedance can exist are tapped and multi-line stations, transferred surges from high to low side, high voltage cables, and large shunt capacitor banks. Arrester performance based on varying surge impedance, as well as system voltage and arrester characteristics, can be explored through laboratory prorated tests and translated into useful application data for all transmission voltages. |
