Which transformer connection is used for a transformer rated at 2400/4160Y-120/240 connected to a 4160 volt system?

A transformer connection that is specified as 2400/4160Y-120/240 indicates that it has a primary winding rated for 2400 volts and is designed to be connected to a 4160 volt system with a wye configuration (the "Y" indicates that it is a wye connection). Using a wye connection allows for a neutral point to be created, which can be beneficial for grounding and provides a means for supplying single-phase loads alongside three-phase loads.

In this case, connecting to a 4160 volt system typically requires a transformer that can handle the line-to-line voltages present in that system. The wye connection ensures that the transformer can effectively manage the phase relationships and voltage levels required for such a setup. Each phase in a wye configuration sees one-third of the total voltage, which fits within the operational parameters of the transformer.

The other options, such as delta connections, do not have the neutral point that is often critical for safety and balanced loading in systems like this. Open delta, which consists of only two transformers instead of three, is generally used as a reduced capacity method and would not provide the full three-phase capability or performance expected in most nominal applications. These considerations make the wye connection