Logic control of Static Excitation System (SES) in Power Alternators deals with the use of PLC to control the terminal output voltage of the Alternator in a more simplified and efficient manner using a closed loop system. A closed loop control with negative feedback is designed, which involves AVR, Pulse Generator, Pulse Amplifier, Limiters, Power System Stabilizers with an Auto and a Manual channel. Disruption in the terminal voltage is caused by faults. These faults were rectified earlier by Electro Mechanical relays. Now we are at a major technological Change of Analog to Digital control. It reduces the complexity of the control system, and eliminates the need of wide range of contactors and coils to energies the relay. The best way to maintain the stability of the system is to identify the need and rectify it. This paper proposes an easy and an efficient design for fault detection and elimination using PLC based excitation system in power alternators.