Using IEC 61850 standard would increase the reliability and availability of electricity network and put a huge impact on network automation. Even though much research works has been done in substation system reliability, there is a few works in automated substation control system reliability. This paper evaluates the reliability of substation automation system based IEC 61850 comparatively considering vender's different intelligent electrical devices. The technique is based on fault tree analysis approach and the tie sets methodology is used to evaluate quantitatively. In this paper proposed method is implemented on Mianeh Aydoghmush substation automation system in 5 different scenarios. Comparative studies are used to establish the most reliable architecture compared with others. Using IEC 61850 Standard in substation automation system provides us to use different manufacturers’ products with identical protocols. Furthermore, producers’ different intelligent electrical devices, in 3 different ranges of mean time between failures, are tested in various scenarios and reliability of system is evaluated quantitatively. Proposed method provides rate of change of system mean time to failure index. Using this index can be a useful tool to choose the best range of intelligent electrical devices.