The models of the transformers for the Distribution Aerial Networks – Classes 15 and 36.2 kV are single-phase and three-phase types, according to the need to attend to customers of the electricity distribution concessionaire.
In urban areas of medium, high and very high load densities will be installed three-phase transformers. In low-density urban areas and in rural areas, single-phase transformers can be used.
In order to be correctly defined before the installation of single-phase transformers, the existence of consumer units that require three-phase power must be evaluated, or if there is a medium-term increase in load.
With this analysis can be avoided the premature amplification of transformers, from single-phase to two-phase.
The single-phase transformer is the transformer which is supplied by a single phase alternating current system, or by a phase-neutral or phase-phase circuit derived from a polyphase circuit. This type of transformer is used for small consumers requiring a voltage of 127 V to 380 V.
The values assigned for the maximum equipment voltage in kV, nominal voltage and primary and secondary connection of the transformer can be observed.