Reliability modeling of power transformers with maintenance outage

Power transformers are critical equipment of the electric power transmission system, because they adjust the electric voltage to a suitable level on each stage of the power transmission from generation station to the end user. Reliability modeling of power transformers is very important for the electric grid design and risk assessment. In this paper, we propose a reliability model of power transformers with maintenance outage incorporated. The power transformer is divided into two groups of components described by different Markov state space models. Both types of state space models are combined to implement the whole power transformer modeling. Reliability indices such as probabilities of full, derated, and zero capacity as well as system unavailability are derived, and numerical evaluation of selected indices is presented with respect to different parameters. The developed models and analysis method are expected to serve as a useful component for the electric grid system design, assessment, and operation.