Selection of Asymmetrical Transformers Banks with Emphasis in Losses and Efficiency

In many power distribution systems when three-phases and single-phase loads are combined is common to use asymmetrical transformers banks. Although different connections can be used, the most usual for mixes loads, is the wye/delta-grounded three elements transformer bank where one of the transformers, the one with the higher capacity, is called the lighting transformer and the other two power transformers. The lighting transformer in the secondary side is grounded and also supplies the single-phase loads. In rural and low load systems the open-delta and open-wye connections are frequently used. This paper show an optimization process based on artificial intelligence technique; genetic algorithm, to determinate the most adequate capacity of each transformers of the asymmetrical bank based on losses and life cycle cost reduction. The goal is to increase the efficiency and reduce cost of power transformers banks operating in field conditions. This article exposed as a study case a transformer bank supplying Cienfuegos's University in Cuba. The procedure can be applied to other transformers configuration as well as to three phase power transformers. The result obtained show increased efficiency and reduced cost of the Cienfuegos's installation.