Using the Siemens DIGSI software package, all the most important steps that need to be taken to set up the relay protection system of a typical single-phase high-voltage transmission line in a transmission network are shown in detail. A Siemens 7SA6x numerical relay device was used. The following protection functions were calculated and selected: distance protection (quadrilateral tripping characteristic with three stages of operation), distance protection communication scheme (PUTT Z1B), directional homopolar overcurrent protection (ANSI 67), ordinary overcurrent protection (ANSI 50/51), power swing blocking. The parameters of the associated current and voltage measuring transformers were also selected. All necessary parameters were set on the aforementioned relay device, in offline mode, using the Siemens DIGSI software package.