What is the percentage increase in circuit capacity when converting a substation transformer from delta to wye?

When converting a substation transformer from delta to wye configuration, the transformation can affect the circuit's capacity, which is often expressed in terms of voltage and current. In a delta configuration, the voltage across the windings is equal to the line voltage, while in a wye configuration, the voltage across the windings is equal to the phase voltage, which is lower than the line voltage by a factor of the square root of three. This change in configuration results in a different handling of the current.

In delta, the current capacity is effectively higher because each phase handles the same current, while in wye, the current per phase is less due to the division of load among the three phases. When switching to a wye configuration, the line current increases, leading to a significant increase in circuit capacity.

The percentage increase in capacity between these two configurations can be calculated based on the differences in voltage and current handling capabilities. When calculated, the transformation yields a 73% increase in capacity, which reflects how the wye connection effectively manages power distribution with enhanced safety and reliability.

This makes the correct answer 73%, which indicates a substantial increase in efficiency and handling ability when pivoting from delta to wye configurations in transformer setups.