The invention relates to a method for monitoring the opening of a mechanical switching device in an AC high-voltage electrical circuit, having two electrodes that are subjected to an AC electrical potential and to a floating potential, respectively, characterized in that the method comprises: - an initial opening step in which a relative movement of the two electrodes is effected at a first mean speed of separation of more than 0.05 meter per second, preferably more than 0.1 meter per second; - at least one stabilizing step, in which a relative movement of the two electrodes is effected at a stabilizing mean speed of separation of less than 0.03 meter per second. The invention also relates to an electrical installation implementing such a method.