Distribution Transformer

A distribution transformer is a transformer that provides the final voltage transformation in the electric power distribution system, stepping down the voltage used in the distribution lines to the level used by the customer. Distribution transformers normally have ratings less than 200 kVA,[2] although some national standards can allow for units up to 5000 kVA to be described as distribution transformers. They are often used for the power supply of facilities outside settlements, such as isolated houses, farmyards or pumping stations at voltages below 30 Kv

These are attached to the overhead wires with two different types of connections. –

• Wye – On a wye distribution circuit, a ‘wye’ or ‘phase to neutral’ transformer is used. A single phase wye transformer usually has only one bushing on top, connected to one of the three primary phases.

• Delta – On a delta distribution circuit, a ‘delta’ or ‘phase to phase’ transformer is used. A single phase delta transformer has two bushings on top which are connected to two of the three primary wires, so the voltage across the primary winding is the phase-to-phase
  voltage.