The assessment of equipment trip probability due to voltage sag is a complicated matter because of the uncertainties both from voltage sag in power systems and sensitive equipment in customer side. The uncertainties of influencing factors are difficult to determine especially the stochastic distribution of voltage tolerance of equipment. The characteristics of voltage sag are determined by sag severity indices and the probability density function of voltage tolerance of equipment is determined by maximum entropy model. An impersonal assessment method is proposed in this paper. As a case study, PC is simulated and the simulation results are compared with the current methods. ©2010 IEEE.