The final work covered the topic that includes the methods for voltage regulation in the transmission network of the electrical power system. Voltage and reactive power regulation are very important to us in the entire electrical power system, and not only in the transmission network, but the focus of the final work is primarily on the transmission network and all its aspects. We get an insight into the necessary actions and parameters required to perform good and quality regulation of the transmission system voltage. We can also see that the network rules and norms that cover Croatia and the region and beyond are urgently needed, which should be adhered to in order to improve the quality of electricity in terms of its production, transmission, distribution and consumption. The final paper describes various procedures and devices where a picture is obtained of how individual aspects of the transmission system are affected individually, in groups or in total. It is crucial to monitor voltage conditions and reactive power flows for successful voltage regulation in the transmission system. Regulation is mostly done automatically and is divided into primary, secondary and tertiary regulation. In regulation, we use compensating devices that help us in the production or consumption of reactive power, which affects the increase or decrease of voltage in places in the network where the devices are connected. Some of these compensating devices are high voltage chokes, capacitor banks, control transformers and FACTS devices.