A procedure for analyzing the reliability of a digital substation (DSS) and smart grid devices that makes it possible to take into account such poorly formalized factors as the environment temperature and humidity is developed. The procedure applies to digital substations, static compensators, static thyristor compensators installed at DSS, as well as united power flow controllers, synchronous compensators and thyristorcontrolled series compensation devices installed in distribution electric networks. The reliability analysis of electric power facilities is based on using the conventional reliability assessment methods and the “cloud” theory. The availability factor is an integral parameter that makes it possible to judge about the reliability of DSS and Smart Grids devices. The article presents the results of estimating the reliability of 110/20 kV DSS structurally consisting of the primary part (the main electrical equipment) and the secondary part (control and data transmission components at the DSS) in accordance with the IEC 61850 standard and implemented according to the “ring” and “star” configurations. The reliability indicators of the active Smart Grids devices for certain climatic conditions, as well as the availability factors of an electric network containing DSS and Smart Grids devices, have been determined. It is advisable to apply the proposed procedure for estimating and analyzing the reliability of electric power facilities, including Smart Grids elements with taking into account the influence of poorly formalized environmental factors on them.