What is the term for not grounding the common connection of a wye high side of a three phase transformer bank?

The term for not grounding the common connection of a wye high side of a three-phase transformer bank is indeed referred to as "floating." In electrical systems, grounding is crucial for safety and system stability. When the neutral point of a transformer bank, particularly in a wye configuration, is not connected to ground, it is said to be floating. This scenario can lead to voltage imbalances and increased voltage levels that may cause equipment damage or unsafe operating conditions.

Floating systems can experience various issues, such as overvoltage conditions or unpredictable electrical characteristics because the neutral point is not referenced to the earth potential. This can result in dangerous situations, especially in fault conditions.

In contrast, if the wye connection were grounded, it would provide a clear path for fault currents and stabilize the system voltages, reducing the risk of hazards. "Isolated" generally refers to separation for safety but does not specifically express the non-grounded state of the wye connection. "Disconnected" might suggest that the connection is broken, but it doesn't inherently communicate the state of grounding in the way "floating" does. Therefore, floating is the term that correctly describes the situation where the neutral is not grounded.