A fully implicit method for the numerical solution of the MHD problem in an SF/sub 6/ discharge

Summary form only given. A fully implicit method for the numerical solution of the model for the analysis of the discharge in an SF/sub 6/ circuit breaker is presented. The numerical model developed is an essential tool for the understanding of the operation of the device, to improve its efficiency and reliability during nominal operation and during faults. The physical formulation of the model (Borghi et al., 1997) is constituted by the continuity equation of mass, momentum and energy, by the state equations of gas and by the convection-diffusion equation of the magnetic flux density, derived from the Maxwell equations and Ohm´s law. The main difficulties to deal with, are the presence of a moving boundary between hot gas and the surrounding cold gas, and the strong dependency of plasma conductivity and transport coefficients on temperature. When solving numerically the discharge model, due to the mentioned feature, attempts to explicitly perform the time integration, result in an excessively restricted stability condition on time step. An implicit method, which calculates at each time step the fluid dynamics and the electrodynamics, is needed to overcome the stability problem of the time integration.