Lightning phenomena: I — General characteristics

Although Franklin conducted his famous lightning experiments about the middle of the 18th century, little more was learned until about a generation ago when lightning outages on expanding electric-power systems made an intensive study of the phenomena imperative. Many investigators in different parts of the world have studied lightning during that period, many special instruments have been devised for recording various characteristics of the phenomena, and from information obtained through the use of these instruments remedial measures have been devised — to the end that in spite of the continuously expanding network of electric-power lines, outages caused by lightning have been greatly reduced. In a series of three articles, the authors have reviewed and described: (I) the general characteristics of lightning, the accumulation of the charge, and the mechanism of the discharge; (II) instruments available for measuring the properties of lightning; and (III) results of field investigations in which the instruments described in part II were used. Part I appears on this and the following pages; parts II and III are scheduled for subsequent issues. THE physical manifestations of lightning have been with us from the remotest times, but only comparatively recently have the phenomena become even partly understood. Franklin in his electrical experiments between 1740 and 1750 succeeded in identifying lightning as the static electricity of his time. Beyond this fact little was learned until within the past 25 years. The real incentive to obtain additional knowledge lay in the necessity of the electrical industry to protect against its effects. As longer transmission lines were built the need for reduction in outages due to lightning became more acute. This placed more stringent requirements upon lightning arresters and other protective devices. Largely through the co-operation of the utilities and manufacturers and through the use of special instruments such as the klydonograph, cathode-ray oscillograph, surge-crest ammeter, Boys camera, and fulchronograph, information of a very valuable character has been obtained regarding stroke mechanism and the voltages and currents associated with lightning.