The Dielectric Recovery of Parallel Arcs

Author: Shennum, Robert Herman

Year: 1954

Degree: Dissertation (Ph.D.)

Advisor: McCann, Gilbert Donald

Committee Member: Unknown, Unknown

Option: Electrical Engineering; Physics

DOI: 10.7907/G0V3-BW26

Abstract

A study of the factors which influence the stability of simultaneous, distributed arcs on power lines is reported. The types of arcs studied were through air between iron electrodes, flashover along a wood-air boundary between copper electrodes and arcs confined in expulsion-tube lightning arrestors.

Variations of line geometry influence line characteristic impedance, series and shunt impedances and equivalent length. The studies indicate that of these factors, only the series impedance between the simultaneous arcs is important unless the line length separating the two arcs is very short.

The analysis illustrates that it is possible to calculate approximate critical spacing of a test gap in terms of the geometry and material of arc electrodes and the potential at the gap. This potential was shown to depend upon both the power frequency conduction characteristics of the remainder of the circuit and upon the nature of the surge initiating the arc. The relative importance of these two factors was estimated.

The studies show that it is possible for arcs to rob one another after they have been independently initiated on power distribution systems. Consequently, with appropriate placement of lightning arrestors it is possible to protect a system so that even though a direct stroke of lightning may initiate an arc at a location remote from the arrestors, the arrestors can still rob the open arc of current and hence extinguish it.

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