The generator automatic control (GAC) function, one of the main functions of the generating plant management system (hereafter referred to as “GAC system”), works with various input signals for generators which are sent by digital multiplex transmission or as individual signals. GAC functions include generator voltage monitoring, bus voltage and frequency monitoring, generator synchronizing (paralleling), load sharing control, and load shift control (Jiang 2005). The GAC system is composed of the two sets of programmable controller and one set of the digital synchronizer and one set of check synchronizer CSQ-3.