Lightning Current Observations in Buried Cable

References are listed at end of paper. 278 LIGHTNING CURRENTS IN BURIED CABLE 279 lightning trouble expectancy in the earlier cables was due to one or more of the following conditions: a higher rate of occurrence of lightning strokes during thunderstorms, higher stroke currents than in other parts of the country, a longer duration of the lightning currents than assumed, or a higher incidence of strokes to buried cable than predicted theoretically. The observations described here, the larger part of which have extended over a period of three lightning seasons, were intended to secure information on these points. The data forming the principal subject of this paper were obtained from a section of the coaxial cable mentioned above, which for a number of reasons was particularly suitable for the purpose. 1.0 General As mentioned above, the observations were made on a cable route through territory of high thunderstorm rate and high earth resistivity, both of which facilitate measurements of currents along the cable. As a result of the high thunderstorm rate, the incidence of strokes to ground is high, and because of the high earth resistivity, the number of strokes to ground near the cable which flash to latter is also high. Another result of the high earth resistivity is that the attenuation of current along the cable is relatively low, so that currents and voltages may be observed at appreciable distances along the cable from the points of the lightning strokes. The rate of attenuation is, furthermore, smaller the longer the duration of the lightning current, that is, the longer the time to half-value.