General Electric Company

Rodney A Lawson

William Robert Pearson

Lawrence J Lane

Irving A Gibbs

Michael J D'Antonio

James E Curran

Mohammed Kassem Saleh

Gautam Sinha

John Earl Bittner

Harold Copeland Sanderson

Michael John Ryan

Bruce Allen Gerritsen

Ivan Elmo Freeman, Jr

The field ground fault detector of the present invention detects a ground fault that occurs in the field circuit and in any associated circuits galvanically connected to the field. The field ground fault detector discerns the ground resistance so that it can be monitored to detect gradual degradation of the ground resistance. The detector estimates the resistance of the ground fault and the location of the ground fault. The detector is able to estimate the location of the ground fault during system operation and during periods of non-operation. The invention utilizes a low frequency square wave oscillator to permit measurement of the ground fault resistance when field voltage is not applied, to insure that there are no blind spots when the field is energized, and to provide a method for estimating the ground fault resistance. The field ground detector can differentiate between ground faults that occur on the AC side form those on the DC side of the Thyristor Bridge.

Apparatus and method for detecting and calculating ground fault resistance

A circuit is provided for use in a synchronous generator excitation system. The circuit comprises a three-phase bridge having six legs. The bridge is connected with an AC power supply. A thyristor is provided in each of the six legs, wherein the thyristors provide a path for a device current. A free wheeling diode functions as a de-excitation means connected in parallel with the three-phase bridge. The free wheeling diode provides a discharge path for a field current.

Full thyristor bridge circuit with free wheeling diode for de-excitation control and stability sensing

A method and apparatus for compensating, consistent with variations in cooling conditions, protection and limit functions of a generator. Limits of the capability curve of the generator, including the overexcited region, underexcited region and region limited by stator current heating, are modified in response to changes in coolant pressure or temperature depending on the type of generator being compensated. Feedback signals and setpoints being provided to fixed protection and limit functions are intercepted and modified in accordance with the relationship between generator rated values and generator performance in view of altered coolant conditions. Protection and limit functions are automatically coordinated. As a result, overall generator performance is improved.

Method and apparatus for modifying limit and protection software in a synchronous generator exciter to match the capability of the turbine-generator

A method and apparatus for enabling the continuous monitoring of the operational state of circuit components includes a scheme for generating a plurality of voltage signals representing neutral-to-line voltages of the system and adding to each of those signals a second signal, each second signal being identical. This addition is done vectorially to yield a modified signal. A representation of the modified signal as acted upon by the circuit to be monitored is compared with a representation of the neutral-to-line voltage signal to yield an output signal representative of the operational state of the circuit components.

Method for monitoring operational condition of circuit components

In a system for stabilizing the operation of an electrical generator connected to a power distribution network, which system includes a power system stabilizer operating through a modulator circuit to control generator oscillations, there is included a scheme for testing the integrity of the power system stabilizer and modulator circuit which involves the application of a test signal having known values to the power system stabilizer. This test signal propagates through the circuitry and the resultant output is demodulated to be compared with a stored representation of the test signal to thus yield outputs representing the gain and phase shift of the power system stabilizer and modulator circuit in combination.

Power system stabilizer system having improved integrity checking scheme

Method and apparatus for monitoring an amplifier

A method and apparatus for performing a complete functional test of a power system stabilizer connected to the excitation system of an electrical power generator is disclosed. Two tests are performed, one an on-line modulation test, and the second a system response test. In the on-line modulation test, an internal 0.5 hertz sine wave is generated by a microprocessor which is applied as a frequency modulating input to the continuous wave frequency transducer included in the power system stabilizer. Such a signal acts to stimulate intertie mode oscillations and provide a means of determining the gain and phase shift characteristic of the power system stabilizer. In the second test, a voltage step type of signal is generated and applied to the output of the power system stabilizer where it is then coupled to the excitation system of the generator. This has the effect of stimulating local mode oscillations. The generator response to the local mode oscillation is sensed to determine system damping. Both tests are adapted to verify the operational status of the power system stabilizer and the adequacy of its adjustments. Furthermore, a local terminal and a telephone modem are connected to a communication port associated with the microprocessor for enabling the test to be initiated and the results evaluated either locally or remotely.

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Fincastle, VA, United States of America

Rodney A Lawson