A fuzzy model for power system operation is presented. Uncertainties in loads and generations are modeled as fuzzy numbers. System behavior under known, while uncertain, injections in dealt with by a DC fuzzy power flow model. System optimal, while uncertain, operation is calculated with linear programming procedures where the problem's nature and structure allow some efficient techniques such as Dantzig Wolfe decomposition and dual simplex to be used. Among the results, a fuzzy cost value for system operation and possibility distributions for branch power flows and power generations are obtained. Some risk analysis is possible, as system robustness and exposure indices can be derived and hedging policies can be investigated.< >