Provides information to users about: certain fundamental service characteristics of different transformer connections and magnetic circuit designs, with particular reference to zero-sequence phenomena; system fault currents in transformers with YNynd and similar connections; parallel operation of transformers, calculation of voltage drop or rise under load, and calculation of load loss for three-winding load combinations; selection of rated quantities and tapping quantities at the time of purchase, based on prospective loading cases; application of transformers of conventional design to converter loading; measuring technique and accuracy in loss measurement.