A ‘Hot’ Lightning Flash


    A RECENT report issued by Science Service, of Washington, D.C., states. that the Westinghouse Company has perfected a method, first discovered by P. L. Bellaschi, for producing an artificial electric discharge which imitates natural lightning in its ability to set fire to materials in its path. This form of discharge, which is called ‘hot’ lightning, is used for the routine testing of all high-tension power transformers sent out by the Company. The volt-amperes required for the test are 1½ million volts, 80,000 amperes. In the previous method used of creating discharge flashes, the heat developed was intense and they had enormously destructive explosive effects on whatever they hit unless it was adequately protected, but they did not last long enough to set fire to combustible targets, only leaving a scorched hole. In the ‘hot’ lightning stroke, there is a low-amporage, long-duration stroke following the main and ‘leader’ lightning discharged, similar to natural lightning. The after-stroke of ‘hot’ lightning generates temperatures only half as high as the main stroke, but it lasts between 100 and 1,000 times as long. The long-duration charge is produced by means, of additional condensers or by a transformer from which the charge is ‘soaked’ through a scries of resistance inductance coils in oil and permitted to follow the initial high-current discharge relatively slowly. Demonstrations are shown by the Company of ‘hot’ lightning, fusing sand in a fibre tube, setting fire to cotton cloth and burning holes through copper sheets varying from one thirty-second to one-sixteenth of an inch in thickness.

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    A ‘Hot’ Lightning Flash. Nature 144, 323 (1939). https://doi.org/10.1038/144323b0

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