For a transformer bank with a rated voltage of 7200/12470Y, how is it connected to the grid if the system voltage is higher than 7200 volts?

In a transformer bank rated at 7200/12470Y, where the lower voltage side is 7200 volts and the higher voltage side is 12470 volts in a Wye configuration, the connection to the grid is typically achieved through a Delta connection on the higher voltage side.

This configuration allows for proper phase balancing and effective distribution of power across the system. When the system voltage exceeds 7200 volts, utilizing a Delta connection for the higher voltage side is advantageous because it accommodates the higher voltage levels while maintaining the necessary phase relationships. The Delta configuration can handle higher voltage and current ratings more effectively and provides a path for transformers to share loads and phase shifts, which is particularly important in three-phase systems.

The other choices do not align with the characteristics necessary for connecting to higher system voltages in this context. A Series connection would not facilitate the necessary phase relationships for a transformer bank, while a Wye connection is primarily suitable for the lower voltage side in this scenario and not preferable for higher voltage connections. A Direct connection does not effectively address the intricacies of transformer operation and voltage management in power distribution systems.