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Evaluation of Reactive Power Meters in the Presence of High Harmonic Distortion
Abstract
Four reactive power meters, operating on different principles,
were tested under nonsinusoidal conditions. Different definitions of the
reactive power are discussed. Because the definition and meaning of the
nonsinusoidal reactive power are still being actively debated, the
readings of the tested meters were compared with four nonsinusoidal
reactive powers and the first harmonic reactive power, to verify whether
these readings can be interpreted as approximate measures of the
different definitions. A digital instrument, programmed to measure each
of these powers, was used as a reference
... The serious case studies on the evaluation of energy meters' uncertainties under determined and random nonsinusoidal conditions started about 30 years ago. The discussions on the performance of active and reactive energy meters of analog and digital principles, have been highlighted in the scientific literature of the former decades [14][15][16][17]. In [14] the tests were performed for symmetrical and balanced conditions. ...
... In nonsinusoidal experiments the accuracy of the energy meters was not degraded considerably, but large errors as high as −35% were observed during the tests of the kVA demand meters. The research in paper [15] is focused on reactive electric energy measurements. The real-world waveforms were applied, and inaccuracies from − 41% up to + 68% were observed. ...
The influence of distortions in voltage and current waveforms on state-of-the-art single-phase and three-phase power meters, commonly used in the utility power system of the Slovak Republic, was studied. A computer-controlled test system capable of generating nonsinusoidal voltages and currents and a reference power quality analyzer were used for this purpose. The results of the experiments on several revenue meters are presented. Some samples exhibited high errors under the tests, while the others operated within their tolerance limit. The overview of the current standards and previously published related studies on the operation of electric energy measuring equipment under determined and random nonsinusoidal conditions is given. The discussion including possible explanations of the phenomenon supervised under the conducted tests is provided.
... Moreover, distortion in voltage and current signals is enhanced greatly due to improper per phase load distribution by the utility. The presence of different harmonic components in the power line causes an error in measuring electrical quantities in polluted sinusoidal environment [3][4][5][6]. Defining and measuring the harmful electrical pollution is comparable to defining and measuring harmful drinking water. Water we are receiving at our home is not always pure. ...
This paper deals with the human factors in creating electrical pollution and the effect of electrical pollution in human life. It depicts the cause of pollution created in electricity by different electrical home appliances and industrial machineries. The polluted electrical power when transferred through transmission and distribution line to the other sectors then it is proliferated. The high-frequency contamination in the basic power frequency signal pollutes the entire electrical power. Various frequency signal other than fundamental cause many disturbances for the different electrical appliances, connected with the same supply. If the frequency content in the polluted signal is very high, then the human health is also being affected. In this paper, different electrical appliances used in residential buildings are studied. The distortion in the current waveform from proper sine wave is given to show the pollution created by the residential devices. The cause and effect of electric pollution are studied. Specially the effect of the electrical pollution on the human health is elaborated. Finally, the remedies to reduce the pollution effect are given.KeywordsElectric pollutionHarmonicsRadio frequency interferenceElectromagnetic interferenceHarmonic distortionHuman health
... A comparison of different theories can be found in [Wil11]. A comparison of different power meters with different operation principle can be found in [FL92]. A review of definitions and physical meaning of powers in non-sinusoidal conditions can be found in [Ema90]. ...
Power transformers are key components in the interconnected bulk power transmission grid. Moreover, to ensure the reliable and stable operation of the power grid, the interaction of the transformers and the power grid during normal and abnormal operation conditions were studied. To study abnormal operation conditions of power transformers it may be necessary to include the non-linear hysteresis characteristics of the transformer cores in electromagnetic transient studies. The modelling of the hysteresis characteristics of the transformer cores requires detailed information about the transformer core design and material. If this information is not available, it is challenging to establish an adequate electromagnetic transformer model. Especially during deep saturation conditions, typically near two Tesla for gain-oriented steels, an accurate modelling of the hysteresis characteristics can be essential for the calculated phase currents. Such saturation conditions could be caused by geomagnetically induced currents (GIC's) or direct current (DC) bias caused e. g. by power electronic devices. This work is a follow-up investigation, motivated by increased transformer sound, which could be traced back to GIC s in the high and extra high-voltage transmission grid. This work presents a measurement based modelling approach to establish electromagnetic topology models of power transformers, including the transformer’s core hysteresis characteristics. First the AC saturation test was developed with the idea to saturate the outer two legs of a three-phase transformer core by two elevated 180° phase-shifted single-phase voltages. The AC saturation test was successfully used to parametrise the hysteresis model of two transformer topology models, using the inductance-reluctance and the capacitance-permeance analogy. Because the AC saturation test requires a sufficiently large power source, it was further developed to the DC hysteresis test. Instead of using a 50/60 Hz sinusoidal voltage, a DC with reversal polarity was used. The DC hysteresis test was also successfully used to parametrise the transformer hysteresis models. The implementation of the DC hysteresis test in a portable transformer test allows to conduct this test in the laboratory and in the field. Together with the principle of variable core gap inductance the transformer topology models of a 50 kVA reveal a high accuracy of the calculated and measured current waveforms during the AC saturation and the standard no-load test, as well as the corresponding power demand. For the measurement of transformer neutral point currents, including geomagnetically induced currents (GICs), an existing measurement system was further developed to minimise the constraints of the monitoring system on grid operations. The utilisation of a split-core current transducer around the earthing switch, together with a software-supported correction of the offset drift, reveals a low long-term offset drift of the measured transformer neutral point current. In addition to the measurement of the transformer neutral point current, the measurement system was extended to monitor a direct current compensation (DCC) system, installed in several transformers in the transmission grid. The analysis of the DCC measurements, which allows a calculation of the DC per phase, reveals an equal distribution of the DC between the high-voltage phases and the capability of the system to minimise the effects of GICs in transformers.
... Earlier publications [18,19] considered the differences in the readings of electromechanical and electronic meters. It was revealed that in active energy meters of the electromechanical type a flux weakening causes a large negative relative error in the registration of active harmonic energy. ...
The paper considers the influence of harmonics on the operating of electrical energy meters in a network with nonlinear loads. It is shown that electronic static meters of active energy are tested in the presence of distortions, and electronic static meters of reactive energy accuracy requirements do not take into account the possible presence of harmonics. It is revealed that the maximum influence on the error in active energy metering is exerted by the number of harmonics taken into account and their amplitude, and the error in reactive energy metering is additionally influenced by the phase angle at the fundamental and harmonic frequencies, which has been confirmed in laboratory conditions. Additionally, experimental studies of the capacitor bank’s influence on reactive energy metering has been carried out in the presence of nonlinear electrical loads. It is shown that when capacitor banks are connected, the error in reactive energy measurement and variation range of the phase shift angle of harmonics significantly increases. The assessment of the computational error of reactive power metering according to various equations were carried out based on the field measurements. If the voltage and current distortion values do not exceed the permissible values, the error can be estimated at, at most, 5–7%.
Power transformers are key components in the interconnected bulk power transmission grid. Moreover, to ensure the reliable and stable operation of the power grid, the interaction of the transformers and the power grid during normal and abnormal operation conditions were studied. To study abnormal operation conditions of power transformers it may be necessary to include the non-linear hysteresis characteristics of the transformer cores in electromagnetic transient studies. The modelling of the hysteresis characteristics of the transformer cores requires detailed information about the transformer core design and material. If this information is not available, it is challenging to establish an adequate electromagnetic transformer model. Especially during deep saturation conditions, typically near two Tesla for gain-oriented steels, an accurate modelling of the hysteresis characteristics can be essential for the calculated phase currents. Such saturation conditions could be caused by geomagnetically induced currents (GIC's) or direct current (DC) bias caused e. g. by power electronic devices. This work is a follow-up investigation, motivated by increased transformer sound, which could be traced back to GIC s in the high and extra high-voltage transmission grid. This work presents a measurement based modelling approach to establish electromagnetic topology models of power transformers, including the transformer’s core hysteresis
characteristics. First the AC saturation test was developed with the idea to saturate
the outer two legs of a three-phase transformer core by two elevated 180° phase-shifted single-phase voltages. The AC saturation test was successfully used to parametrise the hysteresis model of two transformer topology models, using the inductance-reluctance and the capacitance-permeance analogy. Because the AC saturation test requires a sufficiently large power source, it was further developed to the DC hysteresis test. Instead of using a 50/60 Hz sinusoidal voltage, a DC with reversal polarity was used. The DC hysteresis test was also successfully used to parametrise the transformer hysteresis models. The implementation of the DC hysteresis test in a portable transformer test allows to conduct this test in the laboratory and in the field. Together with the principle of variable core gap inductance the transformer topology models of a 50 kVA reveal a high accuracy of the calculated and measured current waveforms during the AC saturation and the standard no-load test, as well as the corresponding power demand. For the measurement of transformer neutral point currents, including geomagnetically induced currents (GICs), an existing measurement system was further developed to
minimise the constraints of the monitoring system on grid operations. The utilisation
of a split-core current transducer around the earthing switch, together with a software-supported correction of the offset drift, reveals a low long-term offset drift of the measured transformer neutral point current. In addition to the measurement of the transformer neutral point current, the measurement system was extended to monitor a direct current compensation (DCC) system, installed in several transformers in the transmission grid. The analysis of the DCC measurements, which allows a calculation of the DC per phase, reveals an equal distribution of the DC between the high-voltage phases and the capability of the system to minimise the effects of GICs in transformers.
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.
Este articulo presenta algunas consideraciones con respecto al flujo de potencia cuando existen armónicos de tensión y/o corriente en el sistema de distribución. Se enfatiza el hecho de que las relaciones de potencia reactiva clásicas definidas para el caso sinusoidal dejan de ser válidas y que la descomposición espectral de la potencia instantánea puede contribuir a establecer, comprender e interpretar las componentes de la potencia.
The paper describes the recent development of a system for calibration of electrical instruments with harmonics measurement capability, such as revenue meters and power analyzers, under non-sinusoidal test conditions at National Research Council (NRC) Canada. The improvements implemented with respect to an earlier NRC calibration system are aimed at increasing the calibration accuracy in a wider frequency range.
Technology and Engineering / Power Resources / General Key Features • Includes innovative research outcomes, programs, algorithms, and approaches that consolidate current status and future of modern power systems • Discusses how uncertainties will impact on the performance of power systems, • Offers solutions to significant challenges in power systems planning to achieve the best operational performance of the different electric power sectors Uncertainties in Modern Power Systems brings together several aspects of uncertainty management in power systems at planning and operation stages within an integrated framework. Providing state-of-the-art aspects in electric network planning including timescales , reliability, quality, optimal allocation of compensators and distributed generators, mathematical formulation, and search algorithms this book introduces innovative research outcomes, programs, algorithms, and approaches that consolidate the present status and future and opportunities and challenges of power systems. With a comprehensive description of the overall process in terms of understanding, creating, data gathering, and managing complex electrical engineering applications with uncertainties this reference is useful for researchers, engineers and operators in power distribution systems.
It is pointed out that the term apparent power does not have a
unique meaning when used to describe polyphase, nonsinusoidal systems;
in a general case it is an artificial concept with no physical
interpretation. It is shown that this ambiguity can have implications
for power factor calculations, reactive current compensation, and
revenue metering. The time-domain based method of defining and measuring
the apparent power is discussed. The necessity of a critical revision of
terms relating to apparent power in the IEEE Standard Dictionary is
pointed out
The Budeanu definitions of reactive and distortion power in circuits with nonsinusoidal waveforms have been widely used for almost 60 years. There have been objections, concerned mainly with the questions of whether these powers should be defined in the frequency domain and whether they can be measured as defined. The main drawbacks of these definitions include the fact that the Budeanu reactive and distortion powers do not possess any attributes which might be related to the power phenomena in the circuit; that their values do not provide any information which would allow the design of compensating circuits; and that the distortion power value does not provide any information about waveform distortion. It is concluded that Budeanu's concept has led the power theory of circuits with nonsinusoidal waveforms into a blind alley.
Various definitions of reactive power in nonlinear systems for power-factor improvement are shown to be inadequate. A new analysis of apparent poweer is presented. It is concluded, however, that, for power-factor compensation, the definition of reactive power is superfluous, and a direct approach of minimizing the apparent power is preferable.
In nonsinusoidal systems, a commonly used formula for reactive power is Q equals SIGMA E//nI//n sin PHI //n where n assumes values from 1 to n. It is contended that this widely quoted formula is based on a fallacy. It is an arbitrary mathematical value that does not represent any physical quantity. The compensation of Q does not not lead to maximum-power-factor operation. An alternative expression for reactive power is proposed that is claimed to be scientifically based.
A new method of defining reactive power under non- sinusoidal conditions is proposed. It consists of sub- dividing the current into components which would have the same waveform as the current in a resistance and either an inductance or a capacitance when the voltage is applied to them, and into a residual component. An instrument for subdividing and measuring each current component and its corresponding power is described. The method permits the power system operator to determine if the possibility of improving the power factor by means of a shunt capacitance or inductance exists and to easily identify the proper value required to realize the maximum benefit.
The influence of harmonics on commonly used three-phase watthour
and kVA demand meters was studied using a computer-controlled
three-phase test system capable of generating nonsinusoidal voltages and
currents. A description of the three-phase test system and results of
preliminary tests of several revenue meters are presented. The
performance of the tested meters is compared with the response of
time-division and thermal reference meters for different harmonic
conditions, primarily field-recorded data. Errors up to 2% were observed
during the testing of energy meters and up to 35% for kVA demand meters
Experimental measurements of solid-state and induction VArhour
meters operating in the presence of steady-state nonsinusoidal currents
are presented. A computer-based data-acquisition and analysis system is
used to determine the various electrical quantities of some common
nonlinear three-phase loads. The basic operating principles of the
VArhour meters are reviewed along with the nature of reactive power and
energy for nonsinusoidal waveforms. Test results confirm that for
nonlinear loads driven by sinusoidal voltages, both types of VArhour
meters register the fundamental displacement voltampere hours only and
do not respond to distortion voltampere hours
The author expands on the physical meaning of the reactive power
in nonsinusoidal situations. The sinusoidal waveform case is surveyed,
viewing the active current as a component of identical waveform with the
voltage. This approach, when extended to nonsinusoidal waveforms,
supports Fryze's model for apparent power, S <sup>2</sup>= p
<sup>2</sup>+ Q <sup>2</sup><sub>F</sub>. It is proved that
the total reactive power Q <sub>F</sub> is composed from four
distinctive types of elementary reactive powers. Each of the basic
reactive powers is identified as the amplitude of an oscillation of
instantaneous power. The separation of Q <sub>F</sub> in Q
<sub>1</sub>, the reactive power at the system frequency, and in
Q <sub>H</sub>, the reactive power at harmonic frequencies, is
recommended as an effective mean for monitoring filter efficacy and
power-factor compensation. Two major recommendations are supported by
the results of this study: abolish the power model using distortion
power, and measure the active power of the system frequency separately
from the active power of the harmonics
This paper discusses the strong and weak points of the time-domain and frequency-domain approaches to the energy transmission investigations in nonsinusoidal systems. The comprehension of possibilities relevant to these approaches is fundamental for the metrological tasks in nonsinusoidal systems formulation. It was shown, that despite a more complex instrumentation, the frequency-domain approach provides a theoretical basis not only for a conspicuous physical elucidation of the energy transmission decreased efficiency, but also for power-factor improvement in situations where the time-domain approach proves ineffective.