When a three phase transformer bank with a grounded wye high side connection loses one phase, how does it operate?

In a three-phase transformer bank with a grounded wye high side connection, if one phase is lost, the system can still operate, but its capacity is reduced. This occurs because each phase of a three-phase transformer bank contributes equally to the overall power output. When one phase is lost, the transformer can still provide power through the remaining two phases, but the total power output will be limited to what those two phases can supply.

The grounded wye connection allows for some degree of operation during phase loss due to its neutral point, which provides a return path and helps maintain system stability. However, the transformer will not be able to handle the same load as it could with all three phases functioning, leading to limitations on the capacity. Therefore, it operates with reduced capacity, effectively still providing power but at a reduced level and possibly affecting the equipment or systems connected to it.