Why do we float the neutral on closed wye/delta banks?

Floating the neutral in closed wye/delta banks is primarily done for safety and system protection. When the neutral is floated, it eliminates the direct path for fault currents that can occur during a fault condition. This reduces the risk of dangerous voltage levels on the system, which can cause equipment damage or pose safety hazards to personnel working on or near electrical systems.

In the case of a closed wye/delta system, floating the neutral also helps maintain the balance of the three-phase system. Without a grounded neutral, the system can continue to operate reliably under certain fault conditions, minimizing disruptions. This approach helps to prevent ground faults from affecting the entire system, allowing for a safer operational environment.

In contrast, the other choices relate to different aspects of system operation or concerns that are not the primary reason for floating the neutral. For example, increasing system stability or managing overload situations can be related to other operational strategies, while reducing transformer size pertains more to design considerations than direct safety and protection issues.