Incorporating demand response effect on transformer replacement planning

Transformer replacement planning is a long-term optimization problem of power system engineering. Therefore, long-term effects as loading and ageing should be considered in the problem. The most crucial reason in such a long term problem in power system is reliability issues. Accordingly, in this paper, long-term effect of loading on transformer failure rates has been modelled and demand response (DR) has been implemented to reduce loading rate of the system. In order to optimize effectiveness of DR, its implementation cost has been added to the objective function of the problem. In addition, reducing the failure rate of existing transformer may decrease the need for a new transformer so that the reliability of the system has a desirable level. On the other hand, a decrease in existing transformer loading rate in the long run, makes them more valuable at the end of the planning horizon. Hence, the value of transformers should be embedded in the objective function. Additionally, reducing loading rate causes lower loss of load at contingencies caused by transformers from two point of view, first reduced failure rate and second reduced peak load. The developed model has been implemented on transformers of THE IEEE 24-bus reliability test system (IEEE RTS) in two case studies. Results show DR can enhance network performance technically by increasing network reliability and decreasing transformer loading and can improve network operation economically by decreasing operational and expansion costs