Static control and protection of aircraft electric power systems

THE generation end of a conventional aircraft electric-power system consists of several basic units. These are the generator, voltage regulator, generator circuit breaker, and the control and protection panel. The basic functions of the control and protection panel are those of opening and closing the field of the generator, and supervising the opening and closing of the generator circuit breaker. In a parallel-generator system, supervising the opening and closing of the bus tie circuit breaker is another basic function. In order that these control functions be performed in a logical manner, a control and protection panel must sense voltages and currents throughout the electric system. These various voltages and currents are measured, compared with standards, time-delayed if necessary, mixed with each other in logic circuits, amplified, and finally used to perform the necessary control functions. The panel protective functions include such circuits as overvoltage protection, undervoltage protection, overexcitation protection, underexcitation protection, underspeed protection, stability protection, and differential current protection. The panel control functions include lockout circuits to prevent cycling of circuit breakers, and a circuit for automatic paralleling of generators.