Power Quality Measurements Research Articles

SOFTWARE BASED EXPERIMENTAL SYSTEM FOR ELECTRICAL POWER QUALITY MEASUREMENT USING THE WIRELESS SENSOR NETWORK MODULES

Experimental system for measurement of standard electrical power quality (PQ) parameters, based on wireless sensor network (WSN), is presented in this paper. System includes generator of reference voltage waveforms, software application for measurement of standard PQ parameters and two microcontroller based wireless sensor modules for transmitting and receiving of measurement results. Reference voltage signals are provided using signal generator with possibility for simulation of typical network disturbances, presented in some previously published papers. This PQ signal generator is functionally supported by the virtual instrumentation software and data acquisition card. Measurements of basic quality parameters for reference test signals are performed using the LabVIEW software application. Time interval for each measurement cycle is 1 s. For communication is used wireless sensor network based on communication standard IEEE 802.15.4 (Zigbee). Hardware configuration includes two wireless sensor modules SPaRCMosquito v.2, based on the microcontroller with Cortex M3 architecture. Transfer of measurement results, between computer and wireless sensor modules on transmitter and receiver points, are provided using standard USB interface.

Power quality measurements in a single-house microgrid

Power quality measurements have been performed during 1 year in a small-scale microgrid in Sweden. The microgrid consists of one residential house that can operate in grid-connected or grid-disconnected (islanded) modes. During the year the microgrid was disconnected from the main grid most of the time.

Dealing with customer's complaints regarding PQ issues – from DNO perspective

During the last two decades the customers have become more aware about the voltage quality that they receive from the grid and its possible (negative) impacts on their household apparatus and on the living environment. The modern customers use sophisticated devices in their day to day life and do not want to comprise on their comfort level. Therefore, any inconvenience that might be caused by the electricity utility service is immediately reported as a 'complaint' to the network operators. When the operational people are convinced that it is voltage-quality related complaint, a week-long power quality monitoring (PQM) is generally done at the customer's point of connection (POC). If the measured power quality (PQ) parameters violate the standard limits of the EN50160 and the Dutch Netcode, an appropriate measure is taken/advised at that installation or in the network to improve voltage quality at the POC. In this study, customer's complaints related to some specific PQ problems are discussed. Furthermore, a PQ complaint handling methodology is discussed briefly, which gives guidelines to tackle customer complaints efficiently. Some national level activities are highlighted at the end of this study.

Detailed power quality measurement of electric vehicle charging infrastructure

Detailed power quality measurement of electric vehicle charging infrastructure

Power Quality Measurements of a Horizontal Axial Small Wind Turbine

As small wind turbines are increasingly used, the assessments of power quality may thus become paramount. Unlike the large-scale wind turbines which are optional required to perform power quality measurements during production certification stage; however the power quality measurements are often neglected in small wind turbines since they are not requested on the certain of national grid codes at low-voltage distribution system level. Considering the high penetrations of small wind turbines may be connected to the future urban electric network, the paper performs the power quality on-site measurements of a horizontal axle small wind turbines. The issues may include the discussion of measurement system structure, the description of measurement method, and the analysis of wind turbine power characteristic, voltage/current trends, harmonics and flicker phenomena. The measured data collected in the study will valuable for the further analysis of power systems connected with the small wind turbines.

Fast Procedure for Characterization of Voltage Sag for Medium Voltage (MV) Distribution Network without Online Monitoring Using Fault and Regression Analyses

Power Quality (PQ) Management undertaken by most utilities including TNB involves monitoring/online measurement, data processing & analysis, reporting and customers’ complaints management. The Malaysian regulator requires proactive communication and PQ disturbance report covering specific details such as percentage remaining voltage, duration, and cause of voltage sag/dip events to be shared with affected customers. The above stipulated requirement can be easily met for substations/exposed areas with online PQ measurements, which capture voltage magnitude and duration that could be corroborated with tripping events. However, it is not practical to have online monitoring facilities as the majority of medium voltage (MV) substations are not equipped with voltage and current transformers where measurements could be tapped. Current procedures of characterizing voltage sag for substations without measurements facilities is time consuming. In this paper, a fast procedure using combinations of fault simulations and regression analysis to characterize voltage sag is proposed. Extensive results from 160 simulation cases comprising 4 network operating configurations, 20 fault distances, and 2 fault types are used in the regression formulation. The results based on the proposed fast procedure for MV distribution network without online monitoring is found to be fairly accurate.

Variable speed drive with PFC front‐end for three‐phase induction motor

A variable frequency drive for an induction motor is proposed. The drive uses a power factor (PF) correction bridgeless single-ended primary inductor converter-controlled rectifier operating in discontinuous inductor current mode as a front-end in order to improve the input power quality and a variation of the constant volts per hertz controller, with feedback to regulate the velocity of the motor shaft. The frequency slip is measured and compensated, since the input stage. Experiments with and without load are carried out and presented. Input power quality measurements are also presented. The proposed system is effective to regulate the velocity and achieving a close to unity PF.

A compact design of multi-feeder data logging system for power quality measurement with a multiplexer and a single PQ transducer

This paper presents a simple and costs effective equipment design multi-feeder data logger for recording and monitoring power quality. The system design uses remote supervising and multi-feeder data logging system (RESMOS). The data collected through resmos portable unit (RMPU) will automatically be saved with the format as binary and comma separated value (CSV). The time setting on the RMPU can be configured with minimum one minute per logging. This data logger uses a single transducer with a multiplexer for recording and monitoring ten channels of power quality at busbar. The system design has been validated with national metrology laboratory scientific and industrial research institute of Malaysia (SIRIM). This tool has the advantage that it can be used to measure harmonic data more than 21st at the same time for ten channels and equipped with software making it easier for analysis data with low operational costs versus another power quality equipment. The experimental results indicate that the proposed technique can accelerate data reading with conversion rate one sample per second for each channel. The device can be used to measure harmonic level and power quality with a confidence level above 95% and percentage error under 2.43% for total harmonics distortion (THD) and 1.72% for voltage harmonics.

Inductive current transformer accuracy of transformation for the PQ measurements

Abstract Inductive current transformer made of magnetic cores with high permeability are used for accurate wideband transformation of distorted current required by the power quality (PQ) measurements. However, such solutions are often characterized by not acceptable additional secondary current distortion in condition of variation of primary current rms value. The problem presented in this paper concerns determination and analysis of mutually exclusive magnetic requirements on inductive current transformer accuracy for transformation of current in both mentioned conditions. To show relevant considerations and support drawn conclusions about source of deterioration of inductive current transformers accuracy of transformation simple and effective procedure for designing inductive current transformer is discussed. The usage of the composited axially magnetic core from the magnetic cores made of permalloy and transformer steel ensured acceptable composite error for transformation of a given harmonic of distorted current and high accuracy in condition of variation of primary current rms value. Obtained resultant magnetization curve, regardless the rms value of primary current and its distortion level, provides proper magnetic permeability to prevent decrease of transformation accuracy for distorted current. The novelty of the paper concerns presentation of designing process and requirement that ensure such operation of inductive current transformer not obtainable without usage of the composited axially magnetic core.

Novel inductive sensor solutions for on-line partial discharge and power quality monitoring

Networks of medium voltage have spread over a long distance through underground cables. The aim to prolong the life span of existing network assets increases the need for condition monitoring to prevent unplanned and long lasting interruptions. Continuous on-line partial discharge (PD) measurement is an excellent way to determine the overall health of the medium voltage (MV) components and to detect developing faults in underground cables. A sensor is an essential part of the PD monitoring system which measures the high frequency PD signals. PD sensors can be used to measure power frequency current and harmonic currents on the MV side to estimate the thermal loading of transformer or incoming cable provided that the sensors have a suitable frequency response for measuring low frequency signals as well. A novel inductive sensor is described in this paper which allows both PD measurements as well as power quality (PQ) measurements at frequency range below 2.5 kHz. Authors did experiments on different ferrite cores in order to design the best possible sensor which can be used for both PD and PQ measurement. Characteristics of the sensors, including sensitivity, saturation current, and frequency bandwidth, as well as relative errors are provided and analyzed under laboratory conditions. At the end, developed sensors are compared with a commercial HFCT sensor, the Rogowski coil and power quality current sensors to show the capability of the sensors to be used for PD and PQ measurements.

Frequency response and harmonic distortion testing of inductive voltage transformer used for power quality measurements

International standards related to power quality measurements define methods and accuracies for the measuring instruments, but do not specify the accuracy of instrument transformers. Therefore, it is not possible to specify an overall accuracy for such measurements. Inductive voltage transformers (IVTs) which are used for power quality measurements should be tested to determine the ratio correction factors (RCFs) and phase angle errors at higher frequencies. In this paper, harmonic distortion and frequency response tests are performed to determine the level of harmonics generated by IVT and its ability to transform harmonics from high voltage (HV) to low voltage (LV) side. Complex voltages consisting of fundamental voltage and certain amount of superimposed harmonic are used to check the frequency response of IVT. RCFs and phase angle errors of the IVT are determined and can be applied to power quality monitors for compensation of errors that occur at high harmonic frequencies. Different test circuits are proposed for generation of HV consisting of fundamental voltage and harmonic voltages with amplitudes in range 5-15 % of the applied fundamental voltage. In order to improve the testing capabilities at higher voltage levels (for equipment with 123 kV≤Um≤420 kV), a compensation for both fundamental and harmonic voltages is proposed with a special connection through blocking and pass filters.

Development of the automatic load modelling system using PQM data on industry site

AbstractLoad modelling is a very important issue for the power system analysis. It affects the results of the several simulations such as a transient analysis, voltage stability, load shedding amounts and etc. And it is very difficult to describe the load models because there are so many components which have different characteristics in the loads. KEPCO installed the power quality measurements on 154 kV industry sites and measured voltage, current, active power and reactive power. In this paper, an automatic load modelling system which uses those data is presented. It includes an algorithm for estimating load model parameters of two induction motors and ZIP load model. Parameters of load model are calculated automatically and are accumulated in the load modelling automation system server. The results of parameter estimation using the data of the real power system are also shown.

Simple Continuous Assessment of Transmission-Network Flicker Levels Caused by Multiple Sources

Transmission system operators (TSO) should be able to assess power quality levels in a network in order to properly address the mitigation of power quality problems. High flicker levels might be a serious power-quality problem in transmission networks and are usually caused by arc-furnace operation. TSO can assess flicker levels in real time only at nodes where power-quality measurements are available. As for the rest of the system, a TSO could calculate flicker levels, if a reliable and relatively simple method is available. Besides, proper summation of flicker levels originating from several flicker sources remains an issue to tackle. The paper proposes a simple method for the calculation of flicker levels at all nodes of a transmission network based on the known flicker values at multiple flicker-sources and based on the known network topology. Different flicker summation coefficients are compared and the one that gives the smallest error is chosen. The proposed method enables a TSO to continuously assess flicker levels at all network nodes and to investigate the consequences of network changes on flicker levels. The method was verified on the Slovenian transmission network where the results of flicker calculation were compared with available flicker measurements.

High voltage coreless transformer for power quality measurement at medium voltage level

High voltage coreless transformer for power quality measurement at medium voltage level

A New Power Quality Instrument Based on Raspberry-Pi

This article describes a new instrument for power quality (PQ) measurements based on the Raspberry-Pi. This is the latest step of a long study started by the Electric and Electronic Measurements Laboratory of “Roma Tre” University 12 years ago. During this time, the Laboratory developed and refined instrumentation for high accuracy power quality measurements. Through its own architecture, the new instrument allows the use of the Raspberry instead of a personal computer (PC). The data acquired and locally processed are then sent to a remote server where they can be shown to users. Imagines of the system and of the data prove the activity of the system.

Real Time Power Quality Phenomenon for Various Distribution Feeders

Power Quality (PQ) brings more challenges to the large- scale and medium scale industries because in the recent years most of them use high efficiency and low energy devices which cause vulnerable PQ disturbances at Point of Common Coupling (PCC). In this paper, the measurement at different times during load condition and analysis of all types of disturbances occurred has been done. When large rated equipments run, the disturbance (harmonics, RMS variations, and switching transients) levels are very high and poor power factor (PF) has also appeared. Due to this poor PF, reactive power consumption in load increases and accordingly total power increases. An electronic device such as LED lights, fluorescent lamps, computers, copy machines, and laser printers also disturb the supply voltage. We are very well known that every PQ problem directly or indirectly must affect economically. Many researchers have investigated PQ audit for over three decades. However these studies and analysis have been done only at simulation level. Hence, the PQ analyzer based study is required to find out the PQ issues at distribution feeders. It will be a valuable guide for researchers, who are interested in the domain of PQ and wish to explore the opportunities offered by these techniques for further improvement in the field of PQ. This paper gives a brief Real Time PQ measurement using PQ analyzer HIOKI PW3198 at Distribution Feeders and it gives an idea to the researcher to optimize problems-related to PQ with respect to the high rated and low rated electric machinery of different feeders at PCC level. This study further extends to analyze the grid disturbances and looks forward to the optimization methods for each individual PQ disturbance.

Analysis of higher harmonics in the power supply system of the administrative building with grouped nonlinear low-power loads

This paper presents the results of the analysis of influences of higher harmonics in the power supplying systems of administration building, obtained on the basis of formed simulation model. It also presents and analyses specific measurements of power quality at the level of distribution substations that feed the typical administration building. Formed simulation model as well as the conclusions drawn on the basis of measurements and simulation calculation for the given administration building, may be of significance both in exploitation and in the planning of distribution networks with significant participation of nonlinear low-power loads in the structure of their consumption.

Evaluation of Measured Power Quality Results of a Wind Farm Connected to Taiwan Power System

This paper presents the power quality measurement results of a commercial wind farm (WF) connected to Taiwan Power System. This 46-MW Jang-Bin WF with 23 2-MW doubly fed induction generators is connected to the Jang-Bin extra high-voltage substation of Taiwan Power Company (TPC) through six feeders and a step-up main transformer. The measured data were recorded from October 2 to November 6, 2013, for a total of 35 days. The recorded results include three-phase voltages, currents, active power, reactive power, apparent power, power factor, frequency, current harmonics, voltage flickers, and voltage variations. According to the measured results, it can be clearly observed that the power quality of the studied Jang-Bin WF during the measurement period can meet the grid code of TPC.

Cyber Security for Smart Grid � The Backbone of Social Economy

Ever-growing population of people and new electronic gadgets demand huge electricity. Existing power grids mostly use non-renewable energy sources for electricity generation which is unidirectional energy flow. Aging equipments and manual meter reading, power line failure detection and power quality measurements result in lot of power losses and delays. Smart Grid assures modern, computerized and automated electricity power generation, distribution and management. It also ensures energy efficiency with quality improvement and reliability. But since it involves some kind of wired and wireless communication, there are the chances of enormous vulnerabilities. Electricity theft, authentication, authorization, trust ranking, distributed denial of service attack, man in the middle attack are the real challenges for smart grid. Cyber Security should ensure security for smart grid system with appropriate levels of trust, privacy and security. This paper puts forth the security challenges for smart grid and discusses about possible security solutions.

Comparative Analysis of Power Quality Instruments in Measuring Power under Distorted Conditions

Abstract This paper aims to evaluate the performance of commercial power quality (PQ) instruments. By using a high precision programmable voltage and current source, five meters from different manufacturers are analyzed and compared. At first, three-phase voltage signals are applied to those PQ instruments, considering harmonic distortion, voltage dip, voltage swell, as well as unbalanced voltages. These events are measured, compared and evaluated considering the different instruments. In addition, voltage and current signals are applied under different conditions, with and without harmonic and unbalances, in order to obtain the measurements of electrical power. After analyzing the data generated in all these tests, efforts are focused on establishing a relationship between the accuracy of the measurements. Considering the percentages of errors, a score is assigned to each instrument. The tests have shown “excellent” and “good” results regarding measuring active and apparent power, as well as power factor. However, for non-active power, almost all instruments had lower performance. This work is relevant considering that Brazil is deploying standardization in terms of power quality measurements aiming towards regulatory procedures and index limits.