Implementation of Smart Grid into the power system has made our grid more robust and reliable. Due to integration of two-way, real time communication it is possible to monitor equipment through sensors. Continuous monitoring will help to predict the state of the equipment. Due to this fact and also to ensure the system performance, time based maintenance can be replaced by condition or reliability based maintenance. Contribution of this work is to identify the appropriate standards for to be used for the transformer subcomponents and develop appropriate Weibull distribution parameters for each subcomponent for a modified series-parallel topology of distribution transformer. This modification is done based on the available measurements and standards. Using the developed reliability model, Monte Carlo simulation was performed to evaluate the behavior of these parameters.