A microprocessor-based control system for a gas turbine electrical powerplant. the microprocessor-based control system controls the startup, operation, and shutdown of the gas turbine electric powerplant. The microprocessor-based control system of the present invention dispenses with the need to utilize relays, timers, or other control hardware. Rather, the microprocessor-based control system employs software that replaces the control hardware, and directly reads the inputs, calculates the control actions, and writes the outputs. The microprocessor-based control system is also in electrical communication with an overspeed control system, provided to ensure that a runaway condition of the gas turbine engine does not occur should the gas turbine engine become disconnected from the speed reducer (gearbox) or generator. Sensors are used to monitor multiple operating conditions of the powerplant. The microprocessor-based control system communicates with the sensors, and activates the overspeed control system if an overspeed condition is detected.