This paper analyzes different types of relay protection devices used to protect components in the power system. In addition to theoretical analysis, these devices are shown on the example of protecting a 110/30 kV substation. Using the DIGSI 5 software package from Siemens, the work with protection devices and the principle of their optimization are shown. At the beginning of the paper, the most important protections used in distribution networks are described. The main division is into overcurrent protection and power transformer protection. The area of application of all protections is stated, in which types of faults occur, and their advantages and disadvantages. The third chapter of the paper refers to the comparison of various 7SJ8x and 7UT8x type protection devices. The differences between them and the area of application for which they are intended are stated. The end of the paper itself and the most important part is dedicated to the description of the procedure and parameterization of all protection devices used to protect a 110/30 kV substation with 5 bays. Three protection devices 7SJ82, 7SJ85 and 7UT85 were used to protect this plant. These are devices of the last generation SIPROTEC 5 of the Siemens brand, which are currently one of the most modern and sophisticated devices for relay protection on the market.