Multistage distribution substations planning considering reliability and growth of energy demand

• Optimal loading of distribution transformers using a new approach in substation allocation.
• Analyzing the effect of considering reliability in the LV networks planning.
• Employing the CDF (customer damage function) in LV network planning to model the imposed cost to the customers.
• Improving the energy interruption cost using the proposed method.

The reliability of energy distribution is not usually considered in the planning of LV (low voltage) networks. However, the reliability cost has increased because of the appearance of the penalty schemes for the customer energy outage. In this paper, an approach is proposed for the planning of the LV distribution networks in which the distribution transformers are optimally organized. The size, number, and placement of the distribution transformers are optimally determined in order to improve the system reliability and to minimize the power and energy losses under the energy demand growth. An objective function is constituted, composed of the investment cost, maintenance cost, losses cost, and reliability cost. The proposed approach is applied to a test system consisting of 42 electric load points. It is observed that the appropriate placement of the distribution substation can reduce the interruption cost considerably, while the investment cost increased slightly. The total cost of the planning also decreased.