A theory of interruption and thermal-arc reignition

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Abstract
The paper describes an analytical and computational investigation of the free recovery and thermal reignition of the positive column of a wall-stabilised cylindrically symmetric d.c. arc. The arc column is assumed to be in local thermal equilibrium, and the energy losses are taken as solely by thermal conduction. By inclusion of the variations of spatial distribution and by allowing movement of the arc boundary within the tube enclosure, it is shown that limitations of previous analyses can be overcome. In particular, it is possible, for the first time, to predict the thermal recovery and reignition characteristics of a suddenly interrupted arc.Computation gives the free recovery characteristics after the sudden interruption of a current of 8–100 A, and from these characteristics a collapse time is defined which gives the period for the collapse of the conductivity to zero. Further computation on the effect of reapplication of unit-function voltages at delayed times after interruption enables reignition-voltage and power-loss-voltage characteristics to be determined. From the computed results, relatively simple analytic functions have been determined for both collapse time and reignition voltage.By extension of the analysis a theory of interruption is proposed which yields an expression for the critical rate of rise for reignition, and consideration is given to the manner in which the theory agrees with practical experience in circuit breaking.

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