Sundstrand Corporation

Jef W Good

David J Mrowiec

A shorted rectififing diode protection system for a synchronous generator having a stationary exciter field which induces a voltage in a rotating exciter armature when energized by an exciter drive current, the voltage being rectified by a plurality of rotating rectifiers and applied to a rotating field winding to induce an output voltage in a plurality of main stator output phase windings, the output voltage being controlled by a voltage regulator having peak excitation current protection means, comprises a circuit for detecting actuation of the excitation current protection and generating a field protection monitor signal, a circuit for discriminating a shorted exciter field and generating a protection lock-out signal, and a logic circuit responsive to the field protection monitor signal and the protection lock-out signal for generating a shorted rectifying diode protection signal. Upon generation of the protection signal, the system disables the voltage regulator to preclude collateral damage to the generator. The method of detecting a shorted exciter field rectifying diode comprises the steps of a) monitoring the peak current supplied to the exciter field from the voltage regulator, b) generating a field protection monitor signal when the peak current exceeds a given threshold, c) generating a protection lock-out signal if the exciter field is discriminated as shorted, d) de-energizing the generator in response to the field protection monitor signal, and e) inhibiting the step of de-energizing the generator in response to the protection lock-out signal.

Protection system for a shorted rectifying diode within a synchronous

A system of protection for an electric power generating system having a poly-phase generator switchably coupled through a generator control breaker to a load distribution bus, wherein the generator output voltage is controlled by a generator control unit which utilizes isolated voltage and current sense signals having a magnitude proportional to the output voltage and current for each phase of the poly-phase generator, the isolated voltage and current sense signals being generated by isolated voltage and current sensors, comprises a first circuit for monitoring the magnitude of each of the isolated voltage sense signals and generating a first output control signal if the magnitude of any isolated voltage sense signal is below a first predetermined threshold. The system further comprises a second circuit for monitoring the magnitude of each of the isolated current sense signals and generating a second output control signal if the magnitude of any isolated current sense signal is below a second predetermined threshold. A logic circuit is included which is responsive to the first and the second control signals, and to the generator control breaker for generating a protective trip signal for de-exciting the generator and opening the generator control breaker. Preferably, this signal is delayed for a predetermined period of time which is set to a value based on maximum generator output voltage and applicable standards for abnormal voltage transients to ensure that the standards are not exceeded by the maximum generator output voltage.

Protection system for undetected over voltage in an isolated voltage

A system of protection for an electric power distribution system which has at least two parallel power feeders for each electrical phase coupling a source of electrical energy through a contactor device to a load distribution bus comprises a controller, and a parallel feeder current sensor for each parallel power feeder which sense electrical current conducted therein. The parallel feeder current sensors produce output parallel current sense signals proportional to the magnitude of the parallel feeder current sensed, and are coupled to the controller by conductors which communicate the output parallel current sense signals thereto. The controller comprises circuitry which compares the magnitudes of the output parallel current sense signals for each electrical phase. This comparison circuitry generates a first output protection signal when the magnitudes of the output parallel current sense signals differ by at least an amount sufficient to indicate a high impedance fault on at least one of the parallel power feeders. The protection system further comprises circuitry to isolate the high impedance fault by opening the contactor device and de-energizing the source of electrical energy.

System of protection for electric power distribution failures

A protection system minimizing utilization equipment's exposure to, and power interruption resulting from, an under voltage condition in an electric power generating system includes generator current sensors, generator speed information, an exciter current sensor, voltage sensors, and a controller. The controller utilizes a voltage level detector which calculates an average voltage magnitude and generates a control signal when the average voltage magnitude drops below a threshold, and which monitors the peak value of each phase voltage and generates a lock out signal when any one of the phase voltages exceeds a threshold; a current detector which generates an enable signal when the magnitude of the highest phase of the generator current is less than a threshold; an exciter current detector which generates a second enable signal when the exciter current is outside an acceptable operating range; a generator speed monitor which generates a control signal when the generator speed is above a minimum regulation speed; protection logic which generates a protective trip signal; and breaker drivers which control the position of system breakers to isolate the fault and re-energize the system loads. The protection logic discriminates between an under voltage condition caused by an overload or a through fault on a main load bus, and one caused by a failure in the controller or associated wiring.

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Beloit, WI, United States of America

Jef W Good