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Description
Post arc dielectric recovery process is an important stage when vacuum circuit breakers interrupt current, which has decisive effect on the whole interrupting process and causes much concern. much concern. The post arc dielectric recovery process, which contains the physical processes, e.g., the dissipation of residual plasma and metal vapor, begins at the moment of current zero and lasts until the gap recovers its dielectric strength. After current zero, the residual plasma forms an ion sheath in front of the post arc cathode and develops to the post arc anode under the effect of transient recovery voltage, then forms the so called post-arc current.
In order to obtain an in-depth understanding of the post-arc sheath, a one-dimensional particle in cell (PIC) model has been developed to study the basic characteristics of the post-arc sheath expansion process. Firstly, the influence of plasma temperature on the post-arc sheath expansion has been studied. Then the theory of ion rarefaction wave. Then simulations of different residual plasma drift velocity also have been carried out. Because the collisions between electrons and metal vapor and the collisions between ions and metal vapor exist during the post arc sheath expansion process, a PIC-MCC model has been developed to study the influence of metal vapor. Moreover, a two-dimensional cylindrical PIC model has been developed to study the influence of plasma motion in radial direction on post arc sheath expansion.
Then the influences on the characteristics of post-arc current by some factors, e.g., residual plasma density, the rising rate of transient recovery voltage, the plasma temperature and the contacts stroke, have been studied with the one-dimensional PIC model. Because ions can enter the post arc anode, the influence on the proportion of ions and electrons entering the post arc anode of the above factors also have been studied. Besides, the influences on the post arc current density of different factors also have been studied.