An analysis of influence between the instants of contacts separation during opening on the probability density function of arcing times and the interrerrelation of arcing times between three poles are presented.Analysis indicates that the essintial of the influences is the unbalance of stresses imposed on each pole. The influence is Affected not only by the obsolute values of the differences

but sequences of opened poles.An example for getting the density function of arcing times under certain differences is shown

and 23 figures of density functions under various differences are givep.