Most of the time the voltage collapse phenomena are studied by means of computer programs designed for the calculation of steady state conditions. But in the real world, the simultaneous occurrences of losses of synchronism, of AVR dynamics or of transformer tap changes call for a full dynamic simulation of voltage phenomena. The present paper shows some examples of dynamic simulations of voltage phenomena using a new general purpose stability program (EUROSTAG) covering in a continuous way the classical fields of transient, mid-term and long-term stability, and also the quasi steady state conditions of a power system.