Method and apparatus for monitoring power quality in an electric power distribution system
First Claim
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1. A method of monitoring power quality in an electric power distribution system comprising:
- repetitively determining values of a plurality of selected parameters of the electric power distribution system;
generating a composite power quality indicator from the values of the plurality of selected parameters;
generating an output representing the composite power quality indicator;
wherein generating the composite power quality indicator comprises generating a power quality component for each of the plurality of selected parameters and combining the power quality components to produce the composite power quality indicator; and
wherein combining the power quality components to produce the composite power quality indicator comprises assigning each power quality component an associated weighting factor selected to produce a selected weighting of the power quality component, multiplying each power quality component by that power quality component'"'"'s selected weighting factor to generate the power quality component and adding the weighted power quality components to generate the power quality index.
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Abstract
A composite power quality indication generated from user weighted statistical contributions of selected system parameters provides an overall indication of power quality in an electric power distribution system. The user defined weightings are maintained over time by continually updating sensitivities that normalize the component contributions to the composite power quality indication. The current composite power quality indication is displayed in relation to its long-term mean and to dynamic thresholds determined as multiples of the standard deviation of the long-term mean.
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Citations
14 Claims
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1. A method of monitoring power quality in an electric power distribution system comprising:
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repetitively determining values of a plurality of selected parameters of the electric power distribution system; generating a composite power quality indicator from the values of the plurality of selected parameters; generating an output representing the composite power quality indicator; wherein generating the composite power quality indicator comprises generating a power quality component for each of the plurality of selected parameters and combining the power quality components to produce the composite power quality indicator; and wherein combining the power quality components to produce the composite power quality indicator comprises assigning each power quality component an associated weighting factor selected to produce a selected weighting of the power quality component, multiplying each power quality component by that power quality component'"'"'s selected weighting factor to generate the power quality component and adding the weighted power quality components to generate the power quality index. - View Dependent Claims (2, 3, 4, 5)
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6. A method of monitoring power quality in an electric power distribution system comprising:
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repetitively determining values of a plurality of selected parameters of the electric power distribution system; generating a composite power quality indicator from the values of the plurality of selected parameters; generating an output representing the composite power quality indicator; and wherein generating the composite power quality indicator further comprises generating at least one dynamic threshold for the composite power quality indicator and wherein generating the output comprises generating a representation of the composite power quality indicator relative to the at least one dynamic threshold. - View Dependent Claims (7, 8, 9, 10)
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11. A power quality monitor for an electric power distribution system comprising:
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sensors for sensing currents and voltages in the electric power distribution system; processing means comprising means for repetitively determining values of selected parameters from the currents and voltages and for statistically generating a composite power quality indicator from the values of the selected parameters; output means providing a representation of the composite power quality indicator, wherein the process means comprises means generating a long-term mean of the composite power quality indicator and the output means comprises a display displaying the composite power quality indicator relative to the long-term mean of the composite power quality indicator; and wherein the processing means further comprises means generating a standard deviation of the long-term mean of the composite power quality indicator and at least one dynamic threshold as a function of the standard deviation, and the display further displays the composite power quality indicator relative to the at least one dynamic threshold. - View Dependent Claims (12, 13, 14)
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Specification