Before we begin to analyze the various malfunctions that can befall a generator and the connected auxiliary system, we must have an understanding of the parameters that define normal operation. Our review of generator and generator auxiliary protection will be based on the sample system shown in Figure 1.1. During normal operations, the generator supplies power to the grid through the Generator Step Up (GSU) transformer and to auxiliary loads at 4.16 kV buses A and B through auxiliary transformers. When the unit is off line, the auxiliary load is supplied from the auxiliary transformer at Bus B.