This paper describes the theory of reliability, the application of network rules to obtain reliability indicators, the basics of the NEPLAN program, and reliability analysis, illustrated by an example of obtaining reliability indicators in the NEPLAN program. The second chapter discusses reliability in power systems, how reliability is predicted, what reliability indicators are in the theory of reliability itself, and how to obtain them for non-repairable and repairable elements. Every power system must fulfill the task of ensuring reliable and constant power supply to its consumers, therefore operators (service providers) of distribution and transmission systems must fulfill network rules. With regard to network rules, general and individual reliability indicators are determined, as described in the third chapter. In subsequent chapters, the NEPLAN program is described, how to create certain schemes, how to enter data for elements, and how to obtain results. After that, an example in the NEPLAN program is shown, which shows the basic parts of the main circuit diagrams, in which a reliability analysis was performed. Based on the reliability analysis in the NEPLAN program, tabular and graphical results are obtained, which show reliability indicators for each individual element in the system and for the system as a whole.