Protection system for controller and control wiring induced under voltage faults in an electric power generating system

A protection system for an electric power generating system minimizing system exposure to, and power interrupting resulting from, an under voltage condition, comprising:

• means for sensing electrical current generated by a first generator unit, said
• generator current sensing means producing output generator current sense
• signals proportional to the magnitude of the generator current sensed thereby;
• means for sensing an aircraft engine speed signal, said speed sensing means producing
• a generator input speed sense signal therefrom;
• means for sensing generator exciter drive current, said exciter sensing means producing an output exciter drive current sense signal proportional to the magnitude of the exciter drive current sensed thereby;
• means for sensing alternating current voltage generated by said first generator at a point of regulation, said voltage sensing means producing voltage sense signals proportional to the magnitude of the alternating current voltage sensed thereby;
• and
• a controller, responsive to said output generator current sense signals, said generator input speed sense signal, said voltage sense signals, and said output exciter drive current sense signal, for discriminating between an under voltage condition caused by an overload or a through fault on a main load distribution bus and an under voltage condition caused by a failure within said controller or associated wiring;
• and wherein said controller comprises:
• voltage level detection means, responsive to said voltage sense signals, for monitoring
• peak voltage magnitude and for calculating an average voltage magnitude, said voltage level detection means generating an under voltage II lockout signal when said peak voltage magnitude of any phase exceeds a predetermined threshold, and an under voltage control signal when said average voltage magnitude drops below a predetermined threshold;
• high phase detection means for generating an under voltage enable control signal when the magnitude of the highest of said output generator current sense signals is less than a predetermined threshold;
• exciter field current detection means for generating an under voltage II enable signal when said output exciter drive current sense signal is outside a predetermined acceptable operating range;
• generator input speed monitoring means for generating a ready-speed control signal when said generator input speed sense signal indicates that said generator input speed is above a predetermined minimum regulation speed;
• logic means, responsive to said under voltage control signal, said under voltage enable control signal, said under voltage II enable signal, said under voltage II lockout signal, and said ready-speed control signal, for generating a protective trip signal;
• and
• breaker drive means for controlling the position of a first breaker, said breaker
• drive means issuing a first trip drive signal in response to said protective trip signal, said first breaker tripping in response thereto, isolating said under voltage fault thereby.