The introductory section explains the reasons for the need for voltage regulation in the distribution network so that all consumers have a fairly equal amount of voltage of the nominal amount. The second chapter describes the voltage regulation procedures in general, we touched on the back-up power supply of adjacent MN networks to provide additional protection in the event of a power failure of a substation. Also in the second chapter we have seen some basic voltage regulation schemes of main substations. After introducing the general voltage control modes in Chapter 3, the control modes are explained in more detail, such as automatic control of the main substation HV or LV bus, voltage compensation, and some analyzes of voltage regulation using additional reactive power injection from the HV network to the MN network. In the practical part, the data were analyzed after applying the method of changing the transformer switch. In addition to the above method, the method of simultaneous use of the Booster transformer and the method of changing the transformer switches were used. Both methods proved to be positive and led to an improvement in voltage conditions, as can be seen from the graphical representations. Although both methods are effective, by installing Booster transformers we achieve better voltage opportunities on terminals that have longer lengths and more consumers.