Laboratory long gaps simulation considering a variable corona region

Different simplified models [1 – 11] have been proposed to simulate long gap discharges under switching-like voltage impulses laboratory experiments [6]. Some models fitted experimental data and others applied the physic of electrical discharges. Nevertheless, the physical models approximate the corona zone as a constant geometrical region; the geometrical shape assumed has been either conical [4] or several parallel filaments [1 – 3]. In the reality, due to the increment or reduction of the electric field, the corona zone should change of geometry and cover a larger or smaller area respectively, instead of keeping a constant region as it has been assumed in previous models. Photographical reports [6–7, 12] of laboratory experiments have shown that the corona zone in a rod - plane arrangement is conical at the initial stage and then its shape becomes hyperboloid and finally cylindrical. The model presented here, analyzes the three dimensional region that fulfils the corona condition for each time step and includes the calculated charge on the leader propagation model. The model was derived from the physical analysis used on [5, 8]. The characteristics of the calculated leader development are compared with experimental results [6], photographical reports [12] and other numerical models [1, 5, 8].