In order to prevent major blackout and enhance system reliability, various types of system protection schemes have been implemented by the utilities around the world. One of the main concerns in the design of a system protection scheme is to assure whether the system could fit with the reliability requirements specification. In this paper, three reliability evaluation techniques, namely, simplified equation, fault tree analysis and Markov modeling, are described and applied to assess the probability that the protection scheme fails to respond as designed in a system implemented by the Taiwan Power Company. A sensitivity analysis technique is also described and used to illustrate the effects of input data uncertainty on the system reliability.