A short-term reliability evaluation is used for power stations, where each power generating unit is presentedby a multi-state Markov model. The main obstaclefor reliability evaluation in such a case is a "curse ofdimensionality"—a great (huge) number of states of entire power station that should be analyzed. A modern approachis proposed based on using Lz-transform that drastically simplifies computation. The proposed approach is useful for power system security analysis and short-term operating decisions. In order to illustrate the proposed approach,the short-term reliability evaluation for a power station with different coal fired generating units is presented.