Abstract
Utilities apply an additional fee for medium and large customers with low power factors. However, unfair financial charges may occur in installations subjected to voltage unbalance and harmonic distortion. The objective of this paper is to determine the fairest PF definitions and their corresponding measurement algorithms in the case in which a constant impedance load or an induction motor is supplied with unbalanced and nonsinusoidal voltages. Fairness is defined considering that the meter (built based on a particular definition and measurement method) under nonideal supply should lead to very close values as if it was submitted to an ideal balanced sinusoidal supply. We performed computational simulations to emulate several conditions in which a balanced customer (modeled as a constant impedance load or an induction motor) is charged due to a voltage supply no longer balanced and sinusoidal. We also performed experimental tests with an induction motor subjected to a wide range of unbalanced nonsinusoidal supply conditions to ratify the conclusions drawn from the simulations. Based on the simulation results and the experimental tests, we indicate some power factor definitions and measurement methods that are not significantly affected by voltage unbalance and harmonic distortions. These indicated PF definitions provide the fairest billing for conditions with unbalanced nonsinusoidal voltages.
Highlights
Under unbalanced and distorted voltage conditions, different power factor (PF) meters may give different readings for the same condition
A delta connection is used, and the reference PF is set by declaring each individual impedance branch with an angle of cos−1(0.95)
EVALUATION OF THE EFFECTS OF MEASUREMENT ALGORITHMS ON THE FAIREST POWER FACTOR DEFINITIONS This section evaluates the accuracy of the measurement methods discussed in Section III-B considering unbalanced and nonsinusoidal voltage and current signals in conditions with noise and in conditions without noise
Summary
Under unbalanced and distorted voltage conditions, different power factor (PF) meters may give different readings for the same condition. In [1], it is reported an experience in which an industry’s PF dropped from 0.95 to 0.88 after the meter replacement. The new meter would have led to a 4% surcharge in the customer’s bill had the technician not noticed this discrepancy. One thing that stands out is that these meters were approved for commercialization and usage. As pointed out by [1], “Utilities must be able to install any meter in any electrical environment (sinusoidal or nonsinusoidal) with full confidence that they will all give the same readings for the same load. To achieve such level of confidence, it is necessary to understand the possible causes for measurement divergences
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