A Vector Group is a classification system used for three-phase transformers, indicating the phase relationship between the primary and secondary windings. It is represented by a combination of letters and numbers, such as Yd11 or Dd0, where "Y" stands for wye connection, "D" for delta connection, and the numbers indicate the phase shift in degrees. This classification helps in understanding how transformers will operate together in a power system. Understanding the Vector Group is crucial for ensuring compatibility between transformers in a network. Proper matching of vector groups prevents issues like phase imbalances and ensures efficient power distribution. This is particularly important in systems involving multiple transformers, as incorrect connections can lead to operational problems and equipment damage.