What happens to a grounded wye high side of a wye-delta three phase transformer bank during imbalance?

When there is an imbalance in a wye-delta three-phase transformer bank, the grounded wye high side is designed to help maintain stability within the system. The grounded wye provides a neutral point, allowing the transformer to sense variations in the phase currents. In response to an imbalance, the configuration works to mitigate or counteract those variations, effectively attempting to balance the load across all three phases.

The grounded nature allows for the neutral point to respond to the differing currents by providing a return path. This balancing act reduces the risk of overvoltage conditions on the higher voltage side, thereby sustaining operational integrity. By managing the imbalance, the grounded wye configuration can help protect the transformer, as well as connected equipment, from potential harm caused by excess load on any one phase.