Reliability evaluation of power system substations is of significant importance when performing asset management. Most of the studies about substation reliability only focus on the substation connectivity. The reaction of protection system is fully neglected, which cannot be true in reality. Failures of the protection system failure or the circuit breakers do have an effect on the substation reliability. In this thesis, the substation reliability with respect to protection failures is evaluated using the event tree method. The basic protection principles for substations are explained first. Then, the event tree analysis is also introduced. Two case studies will be analyzed in this thesis. The effects of different substation configurations on the reliability is analyzed and compared. Then, the reliability of a real substation, Maasvlakte 380kV substation in the Netherlands, will be evaluated using event tree methods. The failure results will be combined with a load flow scenario of Maasvlakte substation in 2020, and indices such as the average lost load, and maximum lost load will be given.