Lightning Arrester Spark Gaps

This paper describes a new form of high-voltage lightning arrester gap which has been called the ``impulse protective gap'' because of its particular effectiveness in protecting against line disturbances of steep wave front. The paper opens with a brief resumé of some of the results of previous investigations of the subject of impulse voltages. A discussion of the points involved in securing adequate protection against transient voltages of steep wave front follows. Particular reference is made to some of the conditions that may exist when a high-frequency impulse is superimposed on a low-frequency wave. In this connection is shown the desirability of a gap having a selective action, making it sensitive to steep wave fronts, and a number of forms of gap having this selective property are described. Methods employed in testing these gaps are described and the results of a large number of experiments are tabulated. Tests on the action of a high-frequency impulse combined with a 60-cycle wave are included in the experimental work. From the experimental data a number of curves are plotted showing the discharge characteristics of the impulse protective gap under many different conditions. The results of the tests are highly favorable and indicate that the new gap may have a wide application in the field of lightning protection.