Among the most important factors affecting the quality of electricity supply and the proper operation of the power system is maintaining voltage within permitted limits. The 400 kV and 220 kV networks play a key role in the transmission network for maintaining voltage conditions. This paper presents the current state and possible ways to solve the above problem in the Croatian power system, with special emphasis on a part of the current transmission network of the Croatian Electric Power Company (the so-called southern branch). It also provides a general overview of the state that can be expected in the HEP transmission network in view of the upcoming changes that will occur in the network and the power system as a whole.