Power Quality Measurements Research Articles

Estimation of Active Power Loss Due to Supraharmonics in a 22 kV Transmission Line

Power systems in Vietnam's coal mining industrial areas supply power of inferior quality. Supraharmonic voltages and currents in power grids serving electric energy to open-cut coal mines were detected by measuring power quality indicators and operating parameters in the power grid serving electric energy to the open-pit coal mine and coal screening plant operated by "Cua Ong-Vinacomin" company. The active powers of harmonics and supraharmonics do not produce any useful work. They induce extra loss of active power. Coal mining and coal processing companies pay for the loss, which results in diminished rate of return for them. This paper offers a review of published research on the topic. It presents the results of measuring the operating parameters and power quality indicators for non-sinusoidal conditions at the point connecting a 22 kV power line to the power system that serves electric energy to an open-pit coal mine and coal screening plant. The active power loss caused by supraharmonics is calculated and analyzed.

Application of hilbert transform for power quality indicators monitoring in general purpose grids

During the operation of power grids, abnormal modes occur that lead to a decrease or increase in the grid voltage beyond permissible values, the appearance of high-frequency noise components and grid signal fading’s, which fading’s the power quality and can lead to the failure of electrical equipment. This requires constant monitoring of power quality indicators. The methods of measuring power quality indicators have been examined and analyzed in the article, their advantages and limitations have been considered, and the inefficiency of using the Fourier transform for estimating of power quality indicators in time domain has been justified. The application of Hilbert transform has been suggested for monitoring the indicators of power quality in general-purpose grids, which include measuring the duration and magnitude of voltage dips, the duration of voltage fading, localization and determination of the duration of high-frequency noise interference in the power grid, determination of phase shift during voltage dip. A simulation of the process of determining the indicators of power quality in time domain and the time intervals during which these indicators exceed the established limits has been performed, which confirmed the effectiveness of using the Hilbert transform in the systems of their monitoring. Keywords: general purpose power grid, power quality indicators, Hilbert transform.

Enhancing NILM classification via robust principal component analysis dimension reduction

Non-intrusive load monitoring (NILM) techniques estimate the consumption of individual appliances in a household or facility, based on aggregated reading from a centralized meter. Usually, NILM techniques are shown to be improved when various power features and additional power quality parameters are included. However, adding power features leads to increased time complexity which is a disadvantage to real-time operation. Previous attempt to operate a principal component analysis (PCA) method to reduce the dimension of the problem managed to improve the run time but with considerably low accuracy. To this end, we utilize a robust PCA approach, to mitigate the influence of outliers in the data as a measure for improved performance. The proposed procedure achieves extraordinary results with accuracy over 96% for 600 hours long record of power quality measurements of the consumption of seven appliances from the standard AMPds dataset.

Measurement and Evaluation of Voltage Unbalance in 2 × 25 kV 50 Hz High-Speed Trains Using Variable Integration Period

This article addresses the need for a standardized method to measure power quality in railroad systems, which differ from distribution and transmission networks. It evaluates the applicability of existing standards in detecting variations and short-term disturbances in railroad networks powered by the 50/60 Hz AC grid or the 2 × 25 kV AC network used for high-speed trains. The objective is to propose a standardized algorithm capable of accurately identifying disturbances to assess power quality on railway traction substations. A new method is proposed to characterize voltage imbalances more precisely. Practical demonstrations confirm that a short integration period, as used in existing standards, provides a more accurate estimation of disturbance amplitude and duration. Field experiments validate the proposed solution, embedded in equipment installed on the 225 kV line supplying the 2 × 25 kV AC substation for high-speed rail. Comparative analysis of results obtained during high-speed train journeys confirms the algorithm’s potential to aid standards committees in reviewing and updating existing standards, as well as expediting the creation, approval, and implementation of new standards for railway installations. Experimental comparisons of other power quality parameters, such as frequency and voltage harmonics, also underscore the algorithm’s utility in railway power quality assessment.

Research on Building Power Quality Assessment and Control Technology Based on Online Monitoring

This study is to improve the assessment accuracy and control efficiency of building power quality by adopting online monitoring and integrating multiple technical indicators and control methods. A whole set of power quality technical index system is developed in the study, involving voltage deviation, harmonic voltage/current limit, and so on. The power quality indicators are quantitatively evaluated through standardization and weight determination. The assessment results show that the measured power quality indicators vary within the interval of 0 to 9, which verifies the effectiveness of the assessment system. In terms of control technology, this paper discusses in depth the static reactive power compensation (SVC) device and its role in improving building power quality, and confirms its efficacy in optimizing power quality through simulation experiments. This work not only successfully evaluates the building power quality, but also proposes practical control strategies, which provide theoretical and practical guidance for the stable operation of power systems and the further improvement of power quality.

POWER QUALITY MEASUREMENT CAPABILITIES OF “SMART” ENERGY METERS

Power quality measurement integrated in energy meters are presented as a potential benefit by some manufacturers. The Norwegian regulator has considered making minimum requirements for energy meters to include registration of interruptions. SINTEF Energy Research has performed tests on energy meters with power quality measurement capabilities. These tests include the ability to detect interruptions, supply voltage variations, voltage dips, among others. Results presented in this paper show large differences in capabilities for power quality measurement of ‘smart’ energy meters. The results also show that the power quality measurements are not according to international standards for such measurements like EN50160 [1], IEC 61000-4-30 [2] and others.

Short Time Voltage Variations Analysis for the new Brazilian Distribution Procedures (PRODIST) and for the IEC 61000-4-30

This paper presents the analysis of one important requirement of the new Brazilian regulation of Power Quality. The Electric Distribution Procedures (PRODIST), that includes power quality regulation, stipulates the references and methods of measurements to the Electrical Utilities that soon will become a standard that will have limits that must be achieved. The main target of this paper is to compare and propose a specific calculus methodology for a Power Quality Analyzer to precisely identify the amplitude and duration of Short Time Voltage Variations requested in the PRODIST. The PQ Analyzer complies PRODIST technical specifications and the International Standard IEC61000-4-30 for some aspects that PRODIST is not clear. The weak points that are not specified in the PRODIST are also analyzed, showing that they should be more precise, otherwise if different manufactures choose distinct methods, procedures and algorithms, they will not reach the same results. Therefore, power quality measurements could not be compared using equipment of different manufacturers.

Measurement and calculation of harmonics in distribution power system with connected small co-generation facility Etan

Generation of electrical energy in large conventional plants (thermal, hydro, nuclear) in last ten years worldwide is being supplemented by small generation utilities. Etan is a gas refining facility. Power supply is provided by two turbo generators and each of them can independently cover the consumption of Etan. Etan usually works in insular operation, but it can also work parallel to the distribution system, especially in cases of maintenance of generator units. Etan is connected to the MV distribution power system (10 kV bus in substation 35/10 kV Ivanic Grad) through a 4,5 km long cable. Load in Etan consist mostly of induction motors. Power electronic devices are used for control of motor loads. The working process of the refinery is always the same so the load is not varying with time. It is very important to know the influence of this kind of industrial consumers with distributed generation on power quality. Power quality measurements were performed at three measurement points with the power quality analyzer ION 7650 of company Power Measurement. The aim of this paper is to compare harmonic measurements and calculations at all three measuring points in different operating conditions depending on the production of generator in Etan.

A New, Ultra-Low-Cost Power Quality and Energy Measurement Technology Bringing SmartGrid on the Factory and Automation Floor

This paper introduces a new application for Power Quality and Energy Monitoring: embedding power quality monitors inside sensitive industrial, commercial, automation, manufacturing and medical equipment – and bringing SmartGrid to the factory and automation floor. Using power quality monitors to solve intermittent problems has also been limited by the cost of monitors. In this case, the monitors are generally installed at the equipment terminals. So the monitors can either directly interface with the load, or they can interface via e-mail or WebServer with a remotely connected user. In addition the new technology also combines a high accuracy energy monitor that can precisely control loads based on the load profile. It also introduces IEC 61000-4-30 which is an excellent standard that ensures that all compliant power quality instruments, regardless of manufacturer, will produce the same results when connected to the same signal. However, instruments that comply with the Class A requirements of this standard have, until now, been too expensive for common use. Now a new set of technologies developed by an American company, in cooperation with a Japanese company, demonstrate that it is possible to manufacture three-phase power quality instruments that are fully compliant with the Class A requirements of IEC 61000-4-30, and to do so at ultra-low-cost, allowing these monitoring devices to be used even at entry levels of individual loads.

Performance and measurement of power quality due to harmonics from street lighting networks

The municipality government of San Miguel de Tucumán city in Argentina is interested in applying energy saving policies to street lighting facilities. In this frame, devices like astronomical programmable clocks and electronic control gear (ballast) will be used to replace photocells and inductive control gear. Also luminaries in use could be replaced by more efficient ones. A technical-economical evaluation was necessary and the technical aspect was request to the Lighting Department of Tucumán University. The performance of the devices and the power quality impact in the lighting networks evaluation was also necessary to evaluate. The study carried out involved outdoor and laboratory test. During 1,5 month six lighting networks with 273 semi-cutoff luminaires were tested. Network selected belong to residential areas which represent more than 60% of total city lighting facilities (26.000 luminaires). In addition laboratory test were conducted with a sample of inductive (in use) and electronic control gear, for high pressure sodium discharge lamps (HPS) 150W. Performance varying voltage input for aged was analyze. Some results from tests points out that: • The use of programmable astronomical clocks instead of photocell produces 11% of energy saving because of actual time on and off schedule set. • Electronic control gear instead of inductive control gear produces 28% energy saving. • Luminaire replacement of current HPS 150W by HPS 100W with Electronic control gear and photocell control produces 43% in energy saving. Outdoor test results from measurement of electrical input parameters and harmonics of existing inductive control gear in street lighting, indicate that: while THD V voltage is about 2,8%, THD A current can be reduced from 38% to 6,5% even when electronic control gear is set to the lower output power step (70% of power output and 60% of initial average illuminance value). The results obtained will be used as arguments for the widespread replacement in the city which would involve considerable investment and a new experience in the region.

Proposal of a Power Quality Analyzer for the new Brazilian Distribution Procedures (PRODIST)

This paper presents the analysis of the requirements of the new Brazilian regulation of Power Quality. The Electric Distribution Procedures (PRODIST), that includes power quality regulation, stipulates the references and methods of measurements to the Electrical Utilities that soon will become a standard that will have limits that must be achieved. The main target of this paper is to propose a methodology for a Power Quality Analyzer to calculate all the parameters requested in the PRODIST. The PQ Analyzer complies PRODIST technical specifications and the International Standard IEC61000-4-30 for some aspects that PRODIST is not clear. The weak points that are not specified in the PRODIST are also analyzed, showing that they should be more precise, otherwise if different manufactures choose distinct methods, procedures and algorithms, they will not reach the same results. Therefore, power quality measurements could not be compared using equipment of different manufacturers.

Calibration of a Virtual Instrument for Power Quality Monitoring

The paper describes a virtual instrument for power quality monitoring based on NI LabVIEW™ platform and simultaneous measurements of electrical voltages and currents. The virtual power quality analyzer is realized by using National Instruments 9225 and 9227 modules for voltage and current measurements, respectively, NI cDAQ 9174, 4 slot USB chassis and a PC. The created virtual instrument measures power quality characteristics: power frequency, voltage variations, magnitude of rapid voltage changes, flicker severity, voltage unbalance, total harmonic distortion, as well as the elements of voltage dips, short interruptions, and long interruptions defined in the standard EN 50160 for voltage characteristics of supplied electricity. The measurement is according to the general guide on harmonics and interharmonics measurements IEC 61000-4-7. The calibration and verification of the power quality analyzer is a complex task and it is performed by using the laboratory calibrator FLUKE 5500A. The results of calibration and verification of the developed virtual instrument, as well as the results of power quality measurements near different lightning technologies are presented

Power Quality Survey in a State of the Art Microgrid

The power quality in a state of the art microgrid has been examined using power quality analysers from Elspec Ltd and A-Eberle GmbH. The microgrid employs PV, CHP and three battery banks with a total of 120 kW / 204 kWh dividing the microgrid into three subnetworks with different network topologies. Different power quality measurements during different stages of construction shows that there are some power quality issues in the microgrid. These issues relate to transitioning to island mode, increase of harmonic noise during island mode, and undesirable equipment interactions. These are increasingly important issues to address as microgrids are becoming more widely adopted and increasingly complex.

A new, ultra-low-cost power quality measurement technology

IEC 61000-4-30 is an excellent standard that ensures that all compliant power quality instruments, regardless of manufacturer, will produce the same results when connected to the same signal. However, instruments that comply with the Class A requirements of this standard have, until now, been too expensive for common use. Now a new set of technologies developed by an American company, in cooperation with a Japanese company, demonstrate that it is possible to manufacture three-phase power quality instruments that are fully compliant with the Class A requirements of IEC 61000-4-30 at ultra-low-cost (selling price less than 500 Euros in quantity). The development uses technologies from several fields that have not previously been related to power quality, including digital cameras, power-over-ethernet, mobile phones, and submarine sonar systems. These new technologies have been packaged in a demonstration instrument, and may be licensed to instrument manufacturers as well.

Analysis of state of MV distribution system before and after connection of small wind farm Ravna1

In the last two decades, the number of installed wind turbines has grown rapidly all over the world. This was due to the huge improvement in technology and increased interest in using wind energy as an important energy source in the future. Following this worldwide trend, the first small wind farm in Croatia named Ravna1 was installed on the Pag Island. To check its influence on local distribution network, power quality measurements have been made in different points in the network before and after the connection of the small wind farm. In parallel, simulation of the distribution network with its connection to 110 kV network was made, and power flow and voltage analysis were made for cases of network with and without wind farm connected. Analyses were made to check the influence of the connection of the wind park on the relatively weak island network, and were made with different power outputs of wind turbines. Calculated values of power flows and values of voltages in the network match very well with measured ones. Also, measurements show that connection of small wind farm does not affect power quality on the Pag Island distribution network.

Measurement of Energy and Power Quality in the Spanish Des-regulated Market

The spanish electrical sector is, since 1997, becoming opened to a free deregulated market, in a progressive way, step by step, finishing the process the next 2007. One of the keys of this deregulation has been the reform of the Spanish regulation for the electrical metering points, necessary for adapt the energy meter fleet to the new needs of the market. This changes in the regulation have arrived later than the transition date for the different steps. Despite this, the different steps have been accelerated, and, since 1st of January of 2003, any electrical consumer can compete for being in the deregulated market. In this article it is tried to give a practical point of view and summarize, the different types of energy meters, depending of the level of consumer.

Statistical Study of Power Quality in Wind Farms.

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The Impact of Power Quality on VFD Application in Motor Fan Dust Collector

The technology to control the motor speed according to load requirements is variable frequency drive (VFD). The motor fan dust collector operates using a VFD to reduce the speed during idle smelting conditions. In addition to energy efficiency, the power quality of the electrical energy system is important to consider. Nonlinear loads from VFDs cause harmonics in the industry that affect electrical power. Power quality measurement and analysis to determine the harmonic and unbalance values of voltage and current are important for improving power quality. This paper discusses the effect of VFDs on power quality, as a real case study, data from existing VFDs in the steel industry are taken to analyze power quality. A large current harmonic of 45% occurs when the VFD decrease the motor speed during idle smelting operation and drops to 5% when the motor speed returns to full speed during smelting operation on. The average maximum current unbalance value is 10.8% and the voltage unbalance is 0.36%, which is still below the standard maximum limit whether the motor is at full or low speed.

Continuous Harmonic Analysis and Power Quality Measurements in Three-Phase Systems.

A virtual instrument, named Power Quality Meter, is presented for (a) measuring power consumption and harmonics in three-phase systems, under non-sinusoidal and imbalance conditions (b) detecting, classifying and organizes power disturbance events. Measurement of the power consumption follows the formulation proposed by the members of the IEEE Working Group on Nonsinusoidal Situations (1996). So, definitions are based on the analysis of functions in the frequency domain, separating the fundamental terms from the harmonic terms of the Fourier series. The virtual instrument has been developed too for monitoring and measuring power disturbances, which are automatically classified and organized in a database while they are being recorded. Software tools use the database structure to present summaries of power disturbances and locate an event by severity or time of occurrence. Records of actual measurements are included to demonstrate the versatility of the instrument.

Hartley Transform Signal Compression and Fast Power Quality Measurements for Smart Grid Application

Hartley Transform Signal Compression and Fast Power Quality Measurements for Smart Grid Application