Theoretical description of ac arcs in mercury and argon

Abstract

The energy balance and circuit equations, together with Ohm’s law, are solved numerically to obtain temperature profiles, current, and voltage as functions of time for wall−stabilized ac arcs. Experimental measurements of current and voltage oscillograms and also temperature profiles have been made for 1.5− and 7.5−A rms arcs in mercury vapor. Derived net emission coefficients of radiation as a function of temperature for the 1.5− and 7.5−A arcs are consistent with one another; furthermore, the experimental temperature profiles for both arcs are in good agreement with our theoretical predictions. Theoretical current and voltage waveforms and central temperatures for a 20−A rms arc in argon are in good agreement with the experimental results of Detloff and Uhlenbusch. Radial convection has little influence on these results. An approximate criterion for arc extinction or reignition at current zero is given in terms of the steady−state V−I characteristic and the arc time constant. By relating the present analysis to methods using the Cassie−Francis and the Mayr equations, expressions are derived for the undetermined constants used in these equations for arcs dominated by thermal conduction losses.

Static modelling of AC flashover on contaminated insulators covered with ice using intelligent identificat ion methods =

“…With the first category, a certain group of investigators were interested in modeling the dynamic arc by expressing the instantaneous arc states in terms of ordinary or partial differential equations to be solved in proper initial and boundary conditions [78,43,72,8]. The results of these methods (referred to as analytical arc models) have provided the theoretical basis for the investigations carried out on designing power system apparatuses such as high voltage breakers [3,68], as well as the dynamic modeling of insulators' flashover under various atmospheric conditions [16,101,60,4,35].…”

Dynamic modeling of AC arc development on ice surfaces

“…Having obtained the required material functions of density, p; specific heat, C p ; thermal conductivity, A; and the radiation emission coefficient, u; the value of/3 may be obtained using the following relation [95]:…”

“…3.6). In this model, for the sake of simplicity, the current instead of voltage was considered to be the independent parameter [95]. …”

“…3.5 The dependence \rj as a function of temperature [119]. 40 3.6 Variations of central temperature and voltage of arc versus time 42 for a 1.5 A mercury arc [95]. 3.7 Form Factor plotted against creeping distance for a cap and pin 43 insulator [22].…”

Modeling of AC arc inside wet snow =

“…• Ayrton's Equation [39,42] • The Rao and Gopal Model [43] • The Cassie-Francis and Mayr Equations [44,45] • LTE and Saha's Equation [48] • The Elenbaas-Heller Equation [46,47,48] • Numerical Solution [45] Many researchers have used Ayrton's arc gradient equation to model the arc [49]:…”