REDUCING LOSSES IN A DISTRIBUTION TRANSFORMER: A CASE STUDY ON SELECTED DISTRIBUTION TRANSFORMER OF JIMMA TOWN, ETHIOPIA

Abstract

Losses in distribution transformers are estimated as 30% of overall transmission and distribution losses. It is further estimated that the losses in all of the world’s electrical distribution systems are about 1715TWh. One-third of these losses occur in the distribution transformers. In this thesis, a mathematical model is done and a new objective function is proposed for minimization of losses in a distribution transformer. This thesis presents a loss-reduced optimal design of three phases, 200kVA, 15/0.4kV, 50Hz, oil-immersed, core type distribution transformer. Two optimization techniques namely, Brute force search and Genetic algorithm are used in MATLAB® to obtain an optimum design of a distribution transformer that has minimum losses which met the requirements and constraints. The loss of a distribution transformer designed using both algorithms is compared, and then a comparison is made with transformer manufacturers’ used design based on analytical method. The results from the optimization algorithm show that the design reduces the total losses on the existing distribution transformer selected for the study from 2,756.50W to 1,994.14W by 762.36W, thus representing a percentage reduction of 27.66%. If this saving is applied to the existing 49, 200kVA distribution transformers of the Jimma town route of the case study area, the saving will be 37,355.64W. If the optimally designed transformer is to be implemented on a larger scale across the electrical distribution networks of Ethiopia, the magnitude of savings would be huge. Moreover, the designed distribution transformer using the optimization algorithm has a slightly increased material cost, but it has the lowest total cost. Thus, the design is cost-effective.