Reactive power has countless benefits for power systems, which are called reactive power sub-services. One of these services is voltage control. The main goals in this research are to find the suitable price for reactive power and set the voltage of the buses in the allowed range and at the same time consider the suitable amount of reactive power in the generation buses as a reserve for technical and voltage support in the power system. In order to optimize the objective functions, the gray wolf optimization algorithm has been used and 33 bus radial distribution system has been considered and it has been assumed that the load of the power system changes during 24 hours and it is assumed that in this distribution network, generators are placed in some buses. The simulation results show that in addition to the cost of reactive power being minimized, a suitable amount of reactive power is also stored in the generation buses and the voltage deviations of the buses are also minimized.