A method for monitoring an activity of partial electrical discharges in an electric apparatus powered with direct voltage comprises the following steps, repeated in succession at predetermined time intervals: measuring (1) analogue electrical signals and generating corresponding digital signals representative of the wave form of partial discharge impulses; deriving (2) for each of said digital signals, at least one shape parameter and at least one amplitude parameter; separating (3) the set of the measured data into homogeneous sub-sets with respect to the shape parameter; correlating (4) the sub-sets of signals having similar values of the shape parameter and measured in successive steps; selecting (5) the correlated sub-sets for which the amplitude parameter has a predetermined profile over time and attributing the signals of said subsets to partial discharge activities. The methods currently in use do not allow to monitor partial discharge activities in an apparatus in DC, because they do not allow to distinguish the signals relating to the partial discharges from those relating to noise or to disturbances.