Probability evaluation method of equipment failure due to voltage sags considering multi-uncertain properties

The existing problem with probability evaluation of sensitive equipment failure arising from voltage sags is how to measure the uncertain properties and determine the mathematical models of influencing factors. In this paper, the uncertain properties of voltage sags, voltage tolerance of sensitive equipment, and equipment operation states are explored. The intension and extension uncertainties of influencing factors are used to distinguish the mathematical properties. Stochastic and fuzzy variables are introduced to quantify these uncertainties. The corresponding models are proposed. A multi-uncertainty evaluation method of sensitive equipment failure probability is presented also. With the proposed method, the maximum entropy method is used to extract the probability distribution of voltage sag intensity while the determination principle of membership function of fuzzy safety event is applied to determine the multi-uncertainty evaluation model. As a case study, a personal computer is simulated. The results show that the proposed method is feasible and effective, and can be deployed in other fields.