The joint distribution of load-wind generation is modeled by a generic dependency matrix, which can be readily used in contingency analysis. The dependency matrix can be used with the conventional deterministic contingency analysis method based on the DC power flow study so that the joint-probability of load and wind generation can be incorporated, and the system security level on the line overloading can be descried probabilistically. The resultant probability distribution of the system security level can be used for making informed decision. The minimum expected security index criteria is used for decision support. Through case studies, a number of issues are discussed including the impact of the correlation on the system security, the location of FACTS device, capacity constraints, and etc. As a special case, a probabilistic approach is presented that can be used for the decision of the optimal location of Flexible AC Transmission Systems (FACTS) devices in a power system with uncertain large-scale wind generation.