General Electric Company

David Jeremiah Hoeweler

Gerald Burt Kliman

William James Premerlani

Rudolph A Koegl

James Patrick Lyons

Albert Andreas Esser

Mark Gerald Adamiak

A method for obtaining a power system phasor includes sampling a power system signal at instants determined by a nominal power system frequency to provide a plurality of data samples; using the data samples to estimate a phasor having an elliptical trajectory; generating a deviation formula representing a frequency deviation between actual and nominal power system frequencies; and using the deviation formula to perform a coordinate transform of the estimated phasor to provide a scaled phasor having a substantially circular trajectory. If the data samples are unevenly spaced, a method in another embodiment includes minimizing squares of errors between the unevenly spaced data samples and an approximating sinusoidal function of the data samples. Power system phasors can be used to detect turn faults by providing scaled current and voltage phasors; extracting fundamental voltage and current phasors; and applying a symmetrical component transform to the fundamental voltage and current phasors to obtain symmetrical component voltage and current phasors for use in determining the existence of a turn fault. Variance calculations and/or trigonometric function fits can be used to increase sensitivity of fault detection.

Method and apparatus for compensation of phasor estimations

A method for detecting turn faults in an induction motor includes obtaining motor current and voltage waveforms and converting the motor current and voltage waveforms to digitized current and voltage waveforms. Fundamental phasors of the digitized current and voltage waveforms are extracted and, a symmetrical component transform is applied to the fundamental phasors to obtain symmetrical component current and voltage phasors including a negative sequence voltage phasor (V.sub.-) and negative sequence current phasor (I.sub.-). A fault injected negative sequence current (Ii.sub.-) is estimated according to the following equation:

Self-tuning and compensating turn fault detector

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Encino, CA, United States of America

David Jeremiah Hoeweler