This paper deals with Benders' Decomposition techniques applied to Volt Var Control algorithms for MV distribution networks. This partitioning technique helps to solve certain classes of Mixed Integer Nonlinear Programming problems with decomposable structure. Therefore, this approach can be applied to the standard case of Volt Var Control algorithms in distribution systems which use continuous and discrete control variables. Considering the mathematical properties of prior algorithms, such as mixed continuous and discrete variables, Bender's Decomposition techniques allow an effective global optimum research. The effectiveness of this method is tested on the academic 30 bus distribution system and on a typical French MV network with 150 nodes/ 149 lines/ 5 onload tap changers transformers/ 3 DGs/ 1 capacitor bank.