Surge Measurements in High-Voltage Stations

Surge voltage measurements were performed at twenty-six 230- and 115-kV transformer stations. Individual measuring periods varied from four months to 12 years; the number of measuring locations ranged from 1 to 55. From several thousand klydonograph records it is concluded that in systems with operating voltages up to 230 kV and in areas with an isokeraunic level of 20 to 30, lightning is the main cause of surges in high-voltage stations. Information is derived on the effects of surge attenuation as well as the number and lightning outage rate of transmission lines terminating at a station. One direct lightning stroke to a large station must be expected every one to two years, justifying the shielding of such stations.