This work presents a Probabilistic Three-Phase Power Flow based on the Unscented Transformation and the OpenDSS software's use, considering the uncertainty of loads. The application of the Unscented Transformation allows for a reduction in the number of samples of uncertain variables. OpenDSS, a free software, provides greater flexibility in modeling the unbalanced distribution network. The developed tool is used to evaluate the effect of inverters Volt/Var control, which connects photovoltaic systems to distribution systems. The results obtained for a 13-bus system are compared with those provided by the Monte Carlo Simulation, allowing for a  significant reduction in computational effort while maintaining the accuracy of the estimated statistical variables.