Harmonic-adjusted power factor meter
First Claim
1. A method for measuring electric power consumed by a power consumer, comprising the steps of:
- a. measuring time-domain current samples from time-domain current consumed by the consumer;
b. transforming the time-domain current samples to frequency-domain current;
c. storing current adjustment tables;
d. adjusting the frequency-domain current for forming an adjusted current having a predetermined relationship to the frequency-domain current;
e. measuring time-domain voltage samples from time-domain voltage consumed by the consumer;
f. transforming the time-domain voltage samples to frequency-domain voltage;
g. storing voltage adjustment tables;
h. adjusting the frequency-domain voltage for forming an adjusted voltage having a predetermined relationship to the frequency-domain voltage; and
i. calculating an adjusted power factor using the adjusted current and the adjusted voltage.
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Abstract
An electric power measuring system wherein power factor measurements are adjusted to reflect the adverse economic effects of harmonic currents and voltages. Well-known techniques are used to acquire frequency spectra that represent the voltages and currents present at the measuring point. These spectra are weighted in such a way that non-fundamental currents are increased and non-fundamental voltages are decreased. The weighted spectra are used to calculate a harmonic-adjusted volt-ampere measurement, which is then accumulated to form a harmonic-adjusted volt-ampere-hour measurement. The weighting functions for voltage and current are selected to approximate the economic impact on the AC power generating, transmission, and distribution system of non-fundamental currents and voltages. The resulting harmonic-adjusted volt-ampere-hour measurement is used to calculate a harmonic-adjusted power factor measurement.
88 Citations
1 Claim
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1. A method for measuring electric power consumed by a power consumer, comprising the steps of:
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a. measuring time-domain current samples from time-domain current consumed by the consumer; b. transforming the time-domain current samples to frequency-domain current; c. storing current adjustment tables; d. adjusting the frequency-domain current for forming an adjusted current having a predetermined relationship to the frequency-domain current; e. measuring time-domain voltage samples from time-domain voltage consumed by the consumer; f. transforming the time-domain voltage samples to frequency-domain voltage; g. storing voltage adjustment tables; h. adjusting the frequency-domain voltage for forming an adjusted voltage having a predetermined relationship to the frequency-domain voltage; and i. calculating an adjusted power factor using the adjusted current and the adjusted voltage.
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Specification