Solution:

• Transformers providing three-phase secondary power, which are used for residential service in the European system, have three primary windings and are attached to all three primary phase wires. The windings are almost always connected in a ‘wye’ configuration, with the ends of the three windings connected and grounded.
• A distribution transformer or service 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.
• Delta-Star transformers are commonly used for distribution because they provide a way to step down the voltage for consumer use.
• The primary delta winding allows for the transmission of three-phase power at high voltages, which is efficient for long-distance transmission.