A new phase locked loop strategy for power quality instruments synchronisation

Power quality instrumentation requires the accurate fundamental frequency estimation and the signal synchronization, even in presence of disturbances. In the paper the authors present an innovative synchronization technique, based on a single phase software PLL. To evaluate how the synchronization technique is adversely affected by the application of stationary and transient disturbing influences, appropriate testing conditions have been developed, taking into account the requirements of the in-force standards. In the paper the proposed technique is described and PLL performances in presence of stationary and transient disturbances are presented

A prototypal architecture of a IEEE 21451 network for smart grid applications based on power line communications

This paper deals with the development of reliable measurement and communication devices and systems and their integration on a prototypal network architecture for smart grid applications, based on the use of narrowband power line communications (PLCs). The proposed solution is presented and discussed in the framework of the ISO/IEC/IEEE 21451 family of Standards. Currently, PLCs are not properly addressed by the aforesaid Standards; on the other hand, by including such issue, their guidelines could represent a common platform for the integration and interoperability of the proposed systems and devices. This would allow to exploit the benefits of the IEEE 21451 approach also for PLC-based sm…

A New Coupling Solution for G3-PLC Employment in MV Smart Grids

This paper proposes a new coupling solution for transmitting narrowband multicarrier power line communication (PLC) signals over medium voltage (MV) power lines. The proposed system is based on an innovative PLC coupling principle, patented by the authors, which exploits the capacitive divider embedded in voltage detecting systems (VDS) already installed inside the MV switchboard. Thus, no dedicated couplers have to be installed and no switchboard modifications or energy interruptions are needed. This allows a significant cost reduction of MV PLC implementation. A first prototype of the proposed coupling system was presented in previous papers: it had a 15 kHz bandwidth useful to couple sin…

I contatori di energia reattiva in regime distorto: stato dell'arte, misure e confronti teorico-sperimentali

Comparison of Nonactive Powers for the Detection of Dominant Harmonic Sources in Power Systems

This paper deals with an innovative technique for the detection of disturbing loads in distorted power systems. The technique is a single-point strategy based on a comparison among different ldquononactiverdquo power quantities already proposed in the literature, which are measured at the same metering section. In this paper, the effectiveness of the strategy is discussed, which also considered the errors of the measurement transducers; the analysis is supported by simulation tests, which were carried out on both a simple single-phase system and an IEEE standard three-phase test power system. The latter was used by other authors as a benchmark system for the analysis of multipoint measureme…

Measurement Issues for the Characterization of Medium Voltage Grids Communications

This paper is focused on the measurement issues and procedures for the characterization of medium voltage grids for narrowband power line communications (NB-PLCs), in the perspective of the use and integration of such technology into smart grids communication networks. The fundamentals are given for the characterization of the PLC channel, by means of noise and attenuation measurements. Suitable procedures are also developed for the characterization and modeling of the power system components in the frequency range of interest. Furthermore, the complete model of the PLC system is experimentally validated in a real case study.

Contract for the support of household appliances control and monitoring application interworking specification

Experimental Evaluation on Narrow Band Power Line Communication in Medium and Low Voltage Smart Grids

The aim of this work is to perform a feasibility study on the power line communication for the development of a new generation of interface devices (IDs) for smart grid and energy storage applications. More in detail, this paper deals with one of the most important issues on this topic, which is the communication system. Among the existing communication technologies, the study is focused on power line communications (PLCs). After an analysis of the state of the art in the field, the main aspects are analyzed, concerning the open issues on the use of PLCs, especially for medium voltage (MV) and low voltage (LV) systems. In this work the use of PLC in MV-LV networks is investigated, by means …

Individuazione dei carichi disturbanti nei sistemi di potenza. Una strategia basata su misure di potenze non attive

Series arc faults in AC and DC electrical circuits. Characterization and detection methods

This paper analyzes the problem of the arc faults in both AC and DC low voltage electrical circuits. The state-of-the-art of the arc fault detection methods is analyzed together with the UL 1699 and UL 1699B Standard requirements for protection devices against arc faults (AFCIs). An experimental characterization is carried out of the arc fault phenomenon, for both AC and DC systems, focusing the attention on series arcs. The experimental measurements are carried out on a proper test bench, which has been developed in order to reproduce significant arcing conditions, in accordance with the UL 1699 Standard requirements.

Real-Time Power Flow Monitoring and Control System for Microgrids Integration in Islanded Scenarios

This article presents an enhanced system for real-time power flow monitoring and control (PFMC) for microgrids integration in medium-voltage (MV) distribution networks. The developed solution includes both system architecture and the monitoring and control algorithms, and it has low implementation and installation costs. It is based on the use of hardware and software solutions previously proposed by the authors, i.e., a distributed measurement, a control and communication architecture, and a supervisory control and data acquisition (SCADA) software, which have been enhanced and integrated for the considered application. The SCADA implements a load flow (LF) algorithm for real-time power fl…

Medium Voltage Smart Grid: Experimental Analysis of Secondary Substation Narrow Band Power Line Communication

This paper is focused on the possibility of employing narrow band power line communication (PLC) in medium voltage (MV) distribution networks. The topic is investigated by means of both simulations and experimental tests, which were carried out in the distribution network of Ustica Island. In detail, a two-way MV communication was tested between two secondary substations connected by an MV cable power line. Each substation has a by-pass connection at MV bus-bars and an MV/LV oil filled power transformer. In this paper, the MV and the PLC systems under test are described and the experimental tests are presented, which were carried out to evaluate the parameters of the simulation model. The a…

A PC-based wattmeter for accurate measurements in sinusoidal and distorted conditions: Setup and experimental characterization

This paper presents the development of a high-accuracy sampling wattmeter, which can be employed with both sinusoidal and distorted input signals. The proposed personal computer (PC)-based system is a simple, portable, and low-cost solution because it is based on two commercial data acquisition boards connected to a common PC. Owing to this solution, the voltage is sensed directly, avoiding expensive voltage dividers, while the current is sensed by means of a noninductive current shunt. Commercial software is also used for data processing and implementation of the virtual instrument. The setup of the PC-based wattmeter is described, with a detailed description of the correction strategy of …

A low cost and easy re-configurable instrument for power quality survey

In this document the development of a low cost and user friendly PC-based instrument for power quality measurement is proposed, according to IEC 61000-4-7 and standard IEC 61000-4-30. It is an easily re-configurable instrument able to measure harmonics, interharmonics and amplitude disturbances and supply unbalance. In order to verify its accuracy, the instrument has been tested according standard test procedures, by means of a built-up calibration test bench.

Un metodo single-point per l’individuazione delle sorgenti di armoniche nei sistemi elettrici di potenza

I contatori elettronici di energia reattiva in presenza di distorsione armonica

An harmonic test condition for the metrological characterization and the operating principle identification of reactive static meters

This paper faces the problem of the metrological characterization of the static meters for reactive energy in the presence of harmonic distortion. Starting from the only available accuracy test condition in the presence of harmonics introduced in the Standards for active static meters, an experimental approach is proposed for the verification of such meters in the presence of harmonic distortion, as well as for the individuation of their operating principle. A theoretical validation of the obtained results is presented by means of a comparison with a standard and a commercial static meter with a known operating principle.

A Line Impedance Calculator Based on a G3 PLC Modem Platform

Power line communication (PLC) is one of the most today used technologies for both automatic meter reading and many other smart grid applications. In this framework, a characterization of the electrical network in the PLC frequency range is needed in terms of impedance measurement and received signal level. This can allow choosing the most suitable and less noisy frequency ranges for PLC transmission. Usually, these characterization measurements are performed with dedicated instrumentation and in the absence of mains voltage. This article wants to propose an alternative solution, which allows these kinds of measurements to be performed using electronic boards currently used as on-field appl…

Smart interface devices for distributed generation in smart grids: The case of islanding

With the increasing presence of distributed generators (DGs), the implementation of a smart sensors and actuators network in distribution grids has become crucial for different monitoring, management and protection functionalities. For DGs monitoring and control, sensors and actuators are usually embedded in so-called interface devices (IDs) or interface protection systems (IPSs). Existing IDs lack in communication interfaces both to the electrical energy Distribution System Operators (DSOs) and to the DGs inverter. In this framework, the authors have developed a new ID solution and a proper communication architecture, which allow implementing new smart functionalities based on the interact…

Arc Fault Detection Method Based on CZT Low-Frequency Harmonic Current Analysis

This paper presents a method for the detection of series arc faults in electrical circuits, which has been developed starting from an experimental characterization of the arc fault phenomenon and an arcing current study in several test conditions. Starting from this, the authors have found that is it possible to suitably detect arc faults by means of a high-resolution low-frequency harmonic analysis of current signal, based on chirp zeta transform, and a proper set of indicators. The proposed method effectiveness is shown by means of experimental tests, which were carried in both arcing and nonarcing conditions and in the presence of different loads, chosen according to the UL 1699 standard…

An Innovative Coupling Solution for Power Line Communication in MV Electrical Networks

One of the main problems in the diffusion of power line communication (PLC) in medium voltage (MV) networks is the need of a dedicated PLC coupler to be installed all over the network. To avoid this problem, the authors have studied, prototyped and patented an innovative PLC coupling solution which uses electrical elements embedded in most of the switchgears already installed in MV networks, i.e. the capacitive dividers of the voltage detecting systems (VDS). The new solution prototype is described in this paper, highlighting the advantages in terms of a significant reduction of both direct costs of equipment and infrastructures and indirect costs of installation and service interruption. T…

Un approccio sperimentale per la caratterizzazione dei contatori statici di energia reattiva in presenza di distorsione armonica

Comparison of two different approaches for harmonic distortion sources assessment

The paper focuses the attention on the comparison of two approaches for power quality assessment in the electric grid. Both approaches are suitable for investigating the harmonic pollution source and discovering if the harmonic source comes from the customer or the utility grid. The two approaches have the same purpose but they are deeply different. The first approach is based on the knowledge of the customer and utility equivalent impedance while the second is based on single point measurement at point of common coupling PCC. In this paper, the advantages and drawbacks of the two approaches are investigated also supported by a case study.

Harmonic sources detection in power systems via nonactive power measurements according to IEEE Std. 1459-2010: theoretical approach and experimental results.

In this paper an enhanced decision-making strategy is presented for the detection of harmonic sources in power systems able to detect also which is the prevailing nature of the disturbance (nonlinearity or unbalance). It makes use of some simple indices, which are evaluated by means of the measurements of some nonactive power quantities, proposed by the authors and derived from the approach of the IEEE Std. 1459-2010. The decision-making rules for the proposed strategy are presented and discussed by means of simulation and experimental tests. The results obtained are presented, showing the effectiveness of the proposed strategy for the detection of the dominant harmonic source upstream or d…

Realizzazione di un banco di misura e di un modello in Simulink per la ricerca e la caratterizzazione di reti di accoppiamento per la trasmissione di segnali su cavi di media tensione

A Single-Point Strategy for the Harmonic Sources Detection in Power Systems.

A resilient distributed measurement system for smart grid application

Since the production of energy from renewable energy sources is strongly increasing, the migration from the classical electric grid toward the smart grid is becoming a reality. Distribution System Operators, along with the control of the entire network and its stability, need to address the security and the reliability of the communication channels and the data itself. In this paper a solution is proposed to address these issues. It is based on a distributed measurement system that relies on a wireless network as well as a redundant Power Line communication system in order to transfer the electrical measures to a centralized SCADA server. The collected data are used to run a power flow algo…

Experimental EMF characterization of a secondary substation

This paper presents the results of the experimental EMC characterization of a new medium/low voltage (MV/LV) secondary substation, which was developed in the framework of the research project "NEW CAB ELARC". It has two MV/LV transformers, with total rated power of 1000 kVA. To perform the experimental characterization, firstly an analysis was performed of the Italian and European standards recommendations. Different approaches were highlighted and the most appropriate procedures were identified for the measurement of the magnetic fields emissions, at power systems frequency (50 Hz) in steady-state conditions. A dedicated test lab was set up for the secondary substation characterization. Th…

Characterization of DC series arc faults in PV systems based on current low frequency spectral analysis

Abstract This work presents an experimental study focused on the characterization of series arc faults in direct current (DC) photovoltaic (PV) systems. The aim of the study is to identify some relevant characteristics of arcing current, which can be obtained by means of low frequency spectral analysis of current signal. On field tests have been carried out on a real PV system, in accordance with some tests requirements of UL 1699B Standard for protection devices against PV DC arc faults. Arcing and non-arcing current signals are acquired and compared and the behavior of a set of indicators proposed by authors is analyzed. Different measurement equipment have been used, in order to study th…

A single-point approach based on IEEE 1459-2000 for the identification of prevailing harmonic sources detection in distorted three phase power systems

This paper deals with a novel single-point strategy for the detection of prevailing harmonic sources downstream or upstream the metering section in three-phase power systems. It is an enhancement of a previous strategy, already developed by the authors and it is based on the comparison of three non-active power quantities which are based on the IEEE Std. 1459-2000 approach. The method does not require any spectral analysis of voltages and currents because it is based only on the separation of the fundamental components from the harmonic content of voltage and current. In the paper, the effectiveness of the strategy is investigated by means of simulation tests which were carried out on a IEE…

Comunicazione power line in reti di media e bassa tensione: modellizazione e verifiche sperimentali

Development of a high-accuracy PC-based wattmeter with commercial data acquisition boards

This paper presents the development of a high accuracy sampling wattmeter, which makes use of two commercial data acquisition boards (DAQs) connected to a common personal computer. Commercial software is also used for data processing and implementation of the virtual instrument. The set up of the PC-based wattmeter is described and a preliminary evaluation of its metrological performances is made by means of two series of experimental tests, which were carried out with an electric power standard and a high performance multifunction calibrator. © 2011 IEEE.

CZT-Based Harmonic Analysis in Smart Grid Using Low-Cost Electronic Measurement Boards

This paper validates the use of a harmonic analysis algorithm on a microcontroller to perform measurements of non-stationary signals in the context of smart grids. The increasing presence of electronic devices such as inverters of distributed generators (DG), power converters of charging stations for electric vehicles, etc. can drain non-stationary currents during their operation. A classical fast Fourier transform (FFT) algorithm may not have sufficient spectral resolution for the evaluation of harmonics and inter-harmonics. Thus, in this paper, the implementation of a chirp-Z transform (CZT) algorithm is suggested, which has a spectral resolution independent from the observation window. T…

Experimental investigation on PLC signal crossing of power transformers

In this work the use of PLC in MV-LV networks is investigated, by means of experimental tests in the case of a two-ways MV/LV communication between two secondary substations. The two substations are connected by a MV overhead power line. Moreover each substation has a by-pass connection at MV bus-bars and a MV/LV power transformer. A ST7580 transceiver is used to inject the communication signal. The transceiver is embedded in a new interface device developed by the authors. In the paper the communication issues are introduced and some experimental tests are presented and discussed. Such tests have been carried out in the presence of voltage net, i.e. 24 kV, with the aim to verify the possib…

An Innovative Measurement Approach for Load Flow Analysis in MV Smart Grids

This paper proposes a novel measurement procedure for load flow analysis in medium voltage (MV) smart grids. The new approach is based on power measurements at low voltage (LV) side of MV/LV distribution substations. Such measurements are carried out by means of power quality analyzers. If compared with the load flow methods based on measurements at the MV side, the proposed approach has a lower cost and it offers an equally reliable measurement system. The proposed algorithm takes the basic concept of the current summation backward/forward method; some modifications are introduced to use LV load powers measurements. To this aim, the MV/LV power transformer is properly modeled and taken int…

Metrological characterization and operating principle identification of static meters for reactive energy: an experimental approach under nonsinusoidal test conditions

In this paper, an experimental approach is proposed for the metrological characterization of the static meters for reactive energy and for the individuation of their operating principle in nonsinusoidal conditions. The proposed approach was developed by starting from the only available accuracy test condition in the presence of the harmonics introduced by the standards for active static meters. In this paper, the proposed approach is described, and some experimental tests are presented, which were performed on some meters of different accuracy classes and with both known and unknown operating principles.

Comportamento dei contatori elettronici di energia reattiva in presenza di armoniche:problematiche aperte

A time domain approach for IEEE Std 1459-2000 powers measurement in distorted and unbalanced power systems

Behaviour of reactive energy meters in polluted power systems

The reactive energy meters used in electric distribution networks are based on a conventional definition of reactive energy (or power) for sinusoidal voltages and currents, containing only the fundamental frequency component. As a consequence, the performances of reactive energy meters in the presence of harmonic distortion are not tested and their accuracy specifications can be very different from the nominal ones, that are evaluated in sinusoidal conditions. In this paper the authors present a comparative study of the performances of different reactive energy meters, both electromechanical and static, in the presence of harmonic distortion; the study is supported by several simulations an…

Strumento virtuale in ambiente LabVIEW per la gestione automatica di misure di emissione radiata in camera semianecoica

NB PLC and Software Defined Networking for Smart Grid Applications

During the last years, the installation of Distributed Energy Resources (DERs) and the expected diffusion of Electrical Vehicles (EVs), is increasing the complexity of the distribution grid, making the management of the grid operated by Distribution System Operators (DSOs) more difficult. The Smart Grid approach tries to provide a response to these troubles, by means of a strong interaction between the power grid and Information and Communication Technology (ICT) infrastructures. The drawback of this approach is an increase in the management effort of the ICT infrastructures, for which the DSO are not prepared. Software Defined Networking (SDN) is an approach developed to manage complex ICT…

Smart renewable generation for an islanded system. Technical and economic issues of future scenarios

The subject addressed in this paper is the analytical study of the transition of an energy generation system for a real MV/LV distribution system from one that is “fuel-based” to a distributed and smart “renewables-based” system. The paper outlines both the technical and the economic issues related to such a transition from one type of system to the other. The study is carried out for a real islanded network located in the Island of Pantelleria (Mediterranean Sea). The results obtained are presented and discussed, putting into evidence the technical, environmental and economic benefits of using smart technologies and renewable energy sources.

PQ and Harmonic Assessment Issues on Low-Cost Smart Metering Platforms: A Case Study

This paper presents a feasibility study on how to implement power quality (PQ) metrics in a low-cost smart metering platform. The study is aimed at verifying the possibility of implementing PQ monitoring in distribution networks without replacing existing smart metering devices or adding new modules for PQ measurements, thus zeroing the installation costs. To this aim, an electronic board, currently used for remote energy metering, was chosen as a case study, specifically the STCOMET platform. Starting from the specifications of this device, the possibility of implementing power quality metrics is investigated in order to verify if compliance with standard requirements for PQ instruments ca…

Sistemi di comunicazione e dispositivi di interfaccia per l'integrazione della generazione distribuita nelle smart grids

L'integrazione della generazione distribuita (GD) nelle reti elettriche di distribuzione a media e bassa tensione  uno degli elementi chiave per il pieno sfruttamento delle fonti energetiche rinnovabili (FER). Ci˜ implica un ripensamento della gestione e del controllo delle reti elettriche , che devono passare da sistemi " passivi ", con flussi di potenza unidirezionali e un numero limitato di funzioni di monitoraggio e automazione, a reti attive e intelligenti (Òsmart gridsÒ). In tali sistemi, i flussi di potenza possono essere bi-direzionali e, se non correttamente gestiti, possono causare situazioni critiche, quali ad es. problemi di stabilitˆ e di controllo della rete o funzionamento i…

An Improved Load Flow Method for MV Networks Based on LV Load Measurements and Estimations

A novel measurement approach for power-flow analysis in medium-voltage (MV) networks, based on load power measurements at low-voltage level in each secondary substation (SS) and only one voltage measurement at the MV level at primary substation busbars, was proposed by the authors in previous works. In this paper, the method is improved to cover the case of temporary unavailability of load power measurements in some SSs. In particular, a new load power estimation method based on artificial neural networks (ANNs) is proposed. The method uses historical data to train the ANNs and the real-time available measurements to obtain the load estimations. The load-flow algorithm is applied with the e…

An interface protection system with power line communication for distributed generators remote control

The aim of this work is to present a narrow band power line communication (NB-PLC) interface protection system (IPS) for distributed generators (DGs); it has been developed according to the current standard CEI 0-21 and the requirements for smart grid applications. For such applications, the new IPSs have to implement new intelligent functions such as remote monitoring and control of DGs and Energy Storage Systems (ESSs) inverters, not only in terms of disconnection but also of voltage regulation and power modulation by the utility control. The main feature of the developed IPS is the ability to interact with both the grid and the DG's and ESS's inverters. In fact, it can communicate with t…

Detection of disturbing loads in distorted and/or unbalanced power systems: a technique based on a comparison among nonactive powers

This paper presents an innovative technique for the detection of disturbing loads in distorted power systems. It is a single-point strategy, based on a comparison among different "nonactive" power quantities already proposed in literature, that are measured at the same metering section. In the paper, the results obtained with the application of the proposed technique are compared with those of other techniques for the monitoring of the harmonic pollution, both single-point and multi-point. Moreover, the effectiveness of the strategy is discussed, considering also the errors of the measurement transducers.

An enhanced approach based on IEEE 1459 for the detection of disturbing loads in distorted and unbalanced three-phase power systems

This paper presents an enhanced approach for the detection of disturbing loads in distorted and/or unbalanced three-phase power systems in both cases of three and four-wires. It is based on the IEEE Std. 1459-2000 effective apparent power resolution and it requires only the separation of the fundamental components of voltage and current from the remaining harmonic content. In the paper, the formulation of the novel approach is given and some simulation results are presented.

A virtual instruments for the measurementsof IEEE Std 1459-2000 power quantities

Un metodo ibrido per il riconoscimento dell'islanding in reti di media e bassa tensione in presenza di generazione distribuita

Characterization of IP-Based Communication for Smart Grid Using Software-Defined Networking

The smart grid (SG) approach is based on a strong interaction between the network communication infrastructure and the power grid. Usually the management of the infrastructure is done by the distribution system operators (DSOs) that are worried about the increasing managing complexity due to the presence of increasing number of distributed energy resources and electrical vehicles. The use of software-defined networking (SDN) may simplify the network configuration and management for DSO, as highlighted from previous research works. The objective of this paper is to introduce and characterize an internet protocol (IP)-based communication architecture with specialized SDN bridges operating als…

Synchronisation Techniques for Power Quality Instruments

An Experimental Characterization of Time of Arrival Accuracy for Time Synchronization of Medium Voltage Smart Grid Solutions

The time synchronization of smart grid devices is a critical feature for the successful application of advanced grid monitoring and control techniques. Synchronization mechanisms based on the accurate estimation of the Time of Arrival (ToA) of network messages - sent over power line cables - are a promising solution to achieve synchronization tasks over distribution lines. In this paper, a chirp-based synchronization technique over the Medium Voltage (MV) grid has been proposed and characterized. Such approach has the benefit of not requiring the installation of a dedicated infrastructure, thanks to the exploitation of power distribution lines for the transmission of time synchronization da…

Transition of a distribution system towards an active network. Part II: Economical analysis of selected scenario

This paper outlines the economical issues related to the transition of the energy generation for a real MV/LV distribution system from a ‘fuel based’ one to a distributed and smart ‘renewables based’ one. It is the prosecution of a companion paper, which addressed the technical issues connected to such transition. The study has been carried out by University of Palermo and ENEA (Italy), on a portion of real MV/LV distribution system of the research center ENEA of Casaccia (Rome, Italy). The analysis is carried out for a specific scenario chosen among those proposed in the companion paper.

A virtual instrument for the measurement of IEEE Std 1459-2000 power quantities

In this paper, the authors present a PC-based instrument for the measurement of electrical-power quantities defined in IEEE Std. 1459. The instrument is based on a time-domain technique for the detection of the fundamental and harmonic components of voltages and currents. The time-domain strategy was originally developed by the authors for three-phase, three-wire systems. In that paper, the strategy had been extended to both three-phase, four-wire and single-phase systems. Simulation tests were carried out to assess the uncertainty contribution of the proposed strategy in the absence of the measurement transducers. Moreover, the accuracy of the PC-based instrument with its transducers was e…

A New Low Cost Coupling System for Power Line Communication on Medium Voltage Smart Grids

This paper proposes and verifies the performance of an innovative and low cost coupling system for power line communication (PLC) on medium voltage (MV) smart grids. The coupling system makes use of the capacitive divider of the voltage detecting systems (VDSs) to inject and receive the PLC signal. VDS are usually already installed in the MV switchboards of the major electrical manufacturer all over the world according to IEC 61243-5. VDS are used to detect the presence of the mains voltage to guarantee personnel safety. An interface circuit has been developed to be connected between the PLC transceiver and the VDS socket. In this way, the PLC signal can be coupled to the MV network without…

Due problematiche di misura nei sistemi elettrici di potenza in presenza di armoniche: sincronizzazione della strumentazione di power quality - contatori elettronici di energia reattiva

DAQs-based wattmeters for high accuracy measurements. Comparison with the Italian power primary standard

Abstract This paper is focused on the use of data acquisition boards (DAQs) for the development of high accuracy PC-based instruments for the measurements of electrical power. The proposed systems are simple, portable and low cost because they are based on commercial data acquisition boards (DAQs) connected to a common personal computer. Data processing is carried out by a commercial software based on an interpolating windowed FFT. In the paper it is shown how the voltage can be sensed directly, thanks to the DAQ input range, thus avoiding expensive voltage dividers. The set up of the DAQs-based solutions is described and the evaluation of their metrological features is made by means of a c…

Design and Characterization of a New MV PLC Coupler for Smart Electric Energy Systems

This paper deals with the design, modeling and characterization of a new coupling system for medium voltage (MV) narrow band power line communications (NB-PLC). It exploits the capacitive divider of voltage detecting systems (VDSs) normally used to reveal the mains voltage presence, thus avoiding the use of dedicated MV couplers. The proposed coupling system was patented by the authors. In this paper, the modeling of the VDS capacitive divider is presented, using a proper characterization method. Moreover, the interface card design is described, based on simulation of the whole PLC transmission channel. Laboratory tests are also presented and discussed. More in detail, a frequency response …

Implementation of a Management System for Prosumer Energy Storage Scheduling in Smart Grids

Scheduling of energy storage systems of distributed generation is a key element for optimal renewable energy sources (RES) exploitation in smart grids, demand side response strategies implementation and prosumers interaction with Distribution System Operators (DSOs). In this context, this paper presents the implementation of a management system for energy storage scheduling, which allows taking appropriate account of the storage system behavior in real cases. To properly consider the real system operation, the employed battery model is modified, in order to include also the hysteresis phenomena in state of charge estimation in both charging and discharging operation. The validation of the p…

Riferibilità dei contatori statici di energia reattiva in presenza di armoniche. Evoluzione normativa e prove sperimentali

Una tecnica innovativa per misure sui sistemi elettrici di potenza secondo lo standard IEEE 1459-2000

A PC-based wattmeter for high accuracy power measurements

This paper proposes the use of a commercial data acquisition board (DAQ) connected to a common personal computer for high accuracy power measurements. In the paper the set up of the PC-based wattmeter is described and an experimental evaluation of its metrological performances is made by means of the comparison with a simultaneous coherent digital sampling wattmeter realized with two high-precision DMMs Hewlett Packard Model 3458 A. In both cases the power source is a Fluke 6100A/E electrical power standard. © 2010 IEEE.

Un metodo single-point basato sulla IEEE 1459-2000 “effective apparent power resolution” per l’individuazione dei carichi disturbanti nei sistemi elettrici di potenza distorti e/o squilibrati

Caratterizzazione e metodi di riconoscimento degli arc faults per applicazioni in sistemi di bassa tensione

A simplified approach for load flow analysis in MV smart grids based on LV power measurements

This paper presents a simplified approach for load flow analysis in medium voltage (MV) distribution networks. It is a power summation Backward/Forward (B/F) algorithm, based on measurements of active and reactive powers at low voltage (LV) side of MV/LV distribution substations. The proposed solution allows achieving good accuracy, computational efficiency and fast convergence. In order to verify the algorithm performances, simulation studies are carried out in the case of a real test system, i.e. the distribution grid of Favignana Island (Mediterranean Sea, Italy). The compatibility between simulations results and power measurements at the MV bus bars of the generating substation shows th…

Simulation of a Power Line Communication System in Medium and Low Voltage Distribution Networks

The aim of the paper is to study the influence of the power transformer on signal transmission in the case of a power line communication (PLC) system in a overhead Medium Voltage (MV) power network. A model of the PLC system was carried out by means of the Simulink® software. A distributed parameter MV overhead line, two power transformers, the signal coupling networks and the receiving and transmitting line coupling interface of a ST7540 FSK powerline transceiver were included in the model. The performances of the complete PLC communication system are evaluated for different line lengths by means of the attenuation computed as ratio between the received and transmitted voltage signals.

On the calibration of reactive energy meters under non sinusoidal conditions

This paper is focused on the problems related to the calibration of the reactive energy meters on the place of installation of the electricity meter (on-site), using the load of the same electrical system. In the presence of harmonic distortion, the behaviour of the meters can go out of the limits imposed by the theoretical calibration curve depending on the metric used by both reference standard meters and meters under test.

Innovative Solutions for the Integration of Renewable Energies on Tunisian and Sicilian Electrical Grids

The rapid spread of distributed generation from renewable energy sources, combined with their unpredictable behavior, requires the continuous monitoring and control by the Distribution System Operator, in order to guarantee the stability and efficiency of the distribution network. Thus, in this paper a new measurement and communication architecture is proposed, which foresees the use of innovative devices and different technology-oriented solutions, even redundant ones, which allows the transition from passive to active electricity distribution network, with minimal structural changes. The architecture has been developed in the framework of the SInERT project (Italy-Tunisia cross-border coo…

Energy Management via Connected Household Appliances

The study reported hereafter provides results based on a campaign of simulations conducted by University of Palermo on the basis of its knowledge in the field Energy Value Chain and in the field of Energy Management (EM) for household appliances. Inputs from CECED Convergence WG has been fundamental to base that study on realistic data and cases. Moreover, the so called EM study, offers also a clear picture about the opportunity to have energy management applications and services in house, being those opportunities strictly related to the cost of in- frastructure needed and to the benefits belonging to different actors in the energy value chain. Energy savings have been considered both in t…

Realizzazione in ambiente LabVIEW di un sistema automatico di gestione della cella GTEM per prove di compatibilità elettromagnetica

A Phase-Locked Loop for the Synchronization of Power Quality Instruments in the Presence of Stationary and Transient Disturbances

Power quality instrumentation requires accurate fundamental frequency estimation and signal synchronization, even in the presence of both stationary and transient disturbances. In this paper, the authors present a synchronization technique for power quality instruments based on a single-phase software phase-locked loop (PLL), which is able to perform the synchronization, even in the presence of such disturbances. Moreover, PLL is able to detect the occurrence of a transient disturbance. To evaluate if and how the synchronization technique is adversely affected by the application of stationary and transient disturbing influences, appropriate testing conditions have been developed, taking int…

A New Solution for Low-Voltage Distributed Generation Interface Protection System

In this paper, a new solution is proposed for the remote monitoring and control of distributed generators (DGs) and energy storage systems (ESSs) connected to low-voltage distribution networks. The proposed system fulfills the in-force standard requirements for the connection of DGs to the utility grid. Moreover, it allows implementing some enhanced functions for the remote control of inverters of DGs and ESSs, not only in terms of disconnection but also in terms of voltage regulation and power shuttering. The proposed solution is based on a new interface protection system and a dedicated secondary substation concentrator, which allows the communication between the distributed system operat…

Un wattmetro basato su schede di acquisizione commerciali per misure in regime distorto. Sviluppo dello strumento e prove preliminari

Synchronization techniques for power quality instruments

The measurement of voltage characteristics in power systems requires the accurate estimation of the power supply frequency and signal synchronization, even in the presence of disturbances. The authors developed and tested two innovative techniques for instrument synchronization. The first is based on signal spectral analysis techniques performed by means of the Chirp-Z transform analysis. The second is a phase-locked loop (PLL) software based on a time-domain coordinate transformation and an innovative phase-detection technique. To evaluate how synchronization techniques are adversely affected by the application of a disturbing influence, experimental tests were carried out, taking into acc…

The Measurement of Reactive Energy in Polluted Distribution Power Systems: An Analysis of the Performance of Commercial Static Meters

This paper presents a comparative analysis of the performances of both a traditional induction meter and various types of commercial static meters for reactive energy in the presence of harmonic distortion. This is a topical issue, since there are several types of static meters on the market, based on different principles of construction. In accordance with current standards, these meters are designed to operate in sinusoidal conditions and their performance is not tested in the presence of harmonic distortion. However, with the increase of pollution levels in power systems, the meters may be used even in the presence of distorted voltages and/or currents; in such cases, their accuracy may …

FROM FUEL BASED GENERATION TO SMART RENEWABLE GENERATION: PRELIMINARY DESIGN FOR AN ISLANDED SYSTEM. PART II: SELECTION OF FUTURE SCENARIO AND ECONOMICAL ISSUES

The subject addressed in this paper is the analytical study of the transition of the energy generation system for a real MV/LV distribution system from a ‘fuel based’ one to a distributed and smart ‘renewables based’ one. The paper outlines the economical issues related to such transition from one type of system to the other and it is the prosecution of a companion work addressing the technical topics concerning this subject. The study is carried out for a real islanded MV/LV distribution network.

LV Measurement Device Placement for Load Flow Analysis in MV Smart Grids

This paper deals with the issue of measurement device placement for load flow analysis in medium-voltage (MV) distribution networks. The study is carried out using an innovative measurement algorithm for load flow analysis developed by the authors. It is based on low-voltage (LV) load power measurements applied on a backward/forward algorithm for the load flow resolution. The final aim is to identify the most suitable number and placement of the LV measurement points in order to limit the uncertainty on the power flow estimation to a target value. The proposed approach is based on the uncertainty evaluation of the estimated power flows; a sensitivity analysis is performed in order to assess…

Enhanced islanding detection in smart interface protection systems of distributed generation

The widespread presence of distributed generators (DGs) and storage systems (DSSs) in electricity grids has increased the risk of islanding occurrence. This phenomenon must be suitably managed by Distribution System Operators (DSO), in order to avoid adverse situations, in terms of grid-protection problems, equipment damage, safety hazards, power quality problems and so on. Currently anti-islanding protection functions are handled by interface protection systems (IPSs), which are built in accordance with relevant standards for DGs and DSSs connection to power systems. However, some problems may occur in case of operation within the so-called non detection zone (NDZ). This paper presents an …

Hybrid passive and communications-based methods for islanding detection in medium and low voltage smart grids

Islanding condition takes place when a distributed generator (DG) continues to power a part of the grid even if power from electric utility is no longer present. Adverse effects of islanding are power quality deterioration, grid-protection interference, equipment damage, and personnel safety hazards. For these reasons, DG systems must detect an islanding condition and immediately disconnect from the grid (anti-islanding protection). This paper proposes an hybrid solution, for both low voltage (LV) and medium voltage (MV) applications, which makes use of passive and communication-based methods for islanding detection. Among the existing communication technologies, the study is focused on pow…

Polluting loads detection in power systems: a decision-making strategy based on nonactive power measurements

In this paper a novel decision-making strategy is proposed for the detection of polluting loads in three-phase power systems. It makes use of simple indices, which are expressed as a function of some nonactive power quantities, previously proposed by the authors and derived from the approach of the IEEE Std. 1459–2000. The decision-making rules for the proposed strategy are presented and discussed, by means of some simulation tests.

Implementation and Experimental Tests of a Management System for MV/LV Distribution Grids

The continuous monitoring of network power flows and the remote control of Distributed Generators and Energy Storage Systems are the essential elements to allow a full exploitation of Renewable Energy Sources and their real integration in distribution networks. Thus in the paper a management system is presented for load flow monitoring in MV/LV distribution network. Moreover, on the basis of calculated power flows, the management system is able to send control commands to DGs and ESSs, to vary their power production or power factor or eventually to disconnect them in order to maintain the network stability. The proposed solution was really implemented in the MV network of Ustica Island, dev…

IEEE Std 1459–2010. IEEE Standard Definitions for the Measurement of Electric Power Quantities under Sinusoidal, Nonsinusoidal, Balanced or Unbalanced Conditions

Definitions used for measurement of electric power quantities under sinusoidal, nonsinusoidal, balanced, or unbalanced conditions are provided in this standard. Mathematical expressions that were used in the past, as well as new expressions, are listed, as well as explanations of the features of the new definitions.

La verifica dei contatori statici di energia reattiva in presenza di armoniche. Problematiche di misura e possibili soluzioni

An interface protection system based on an embedded metrology system platform

Abstract The aim of this work is to present an interface protection system (IPS) for Distributed Generators (DG) and Energy Storage Systems (ESS). The new prototype of IPS guarantees standard protection requirements, in terms of both voltage and frequency measurement accuracies and trip times. Moreover, it has the additional functionalities of implementing a communication link between the Distribution System Operator (DSO) and the DG and ESS Inverter. The new IPS is based on a smart meter platform with an integrated power line communication modem. Moreover, it has also an integrated metrology section. Experimental tests will show how this last feature allows a significant reduction of the m…

La caratterizzazione dei contatori statici di energia reattiva in presenza di armoniche: problematiche tecniche e normative

On the use of narrow band power line as communication technology for medium and low voltage smart grids

The aim of this work is to perform a feasibility study on the power line communication for the development of a new generation of interface devices (IDs) for smart grid applications. More in detail, this paper deals with one of the most important issues on this topic which is the communication system. Among the existing communication technologies, the study is focused on power line communications (PLCs). After a analysis of the state of the art in the field, the main aspects are analyzed, concerning the open issues on the use of PLCs, especially for medium voltage (MV) and low voltage (LV) systems. In this work the use of PLC in MV-LV networks is investigated, by means of simulations and ex…

A DAQ-based sampling wattmeter for IEEE Std. 1459-2010 powers measurements. Uncertainty evaluation in nonsinusoidal conditions

Abstract This paper presents the evaluation of the metrological performances of a DAQ-based sampling wattmeter (DAQ-SW) for the measurement of IEEE Std. 1459-2010 power quantities in non-sinusoidal conditions. The instrument makes use of two commercial data acquisition (DAQ) boards, a non-inductive current shunt, a personal computer and a commercial software for data processing. Starting from the results of an experimental characterization of the two instrument channels with non-sinusoidal voltages and currents and a correlation analysis, the combined standard uncertainties of IEEE Std. 1459-2010 quantities are evaluated, following the approach of the ISO Guide to the Expression of Uncertai…

Problematiche di misura nei sistemi elettrici di potenza in presenza di distorsione armonica

Studio di fattibilità e progettazione preliminare di dimostratori di reti elettriche di distribuzione per la transizione verso reti attive. Report 1 – Caratterizzazione delle reti attuali e analisi di possibili scenari di sviluppo

A new low cost power line communication solution for smart grid monitoring and management

Modern smart grids require the improvement of measurement and communication infrastructures of distribution networks, at both medium voltage (MV) and low voltage (LV) levels. Distributed sensing and measurement systems are needed to provide all necessary data for grid monitoring, control and management, as well as for the implementation of a number of smart functionalities, such as remote control of distributed generators (DGs), real time analysis of power flows, automatic meter reading (AMR), demand side management (DSM), grid automation and so on [1]-[6]. Acquired network data include typical electrical network quantities and status variables (such as powers, voltages, currents, switches …

ARC FAULT DETECTION EQUIPMENT AND METHOD USING LOW FREQUENCY HARMONIC CURRENT ANALYSIS

An arc fault detection circuit includes a current sensing circuit coupled to a line conductor carrying a current. The current sensing circuit operates to sense current and output data indicative of the sensed current. A processing circuit implements a frequency transform algorithm to transform the output data to frequency data in a low frequency range and with a high spectral resolution where a minimum short time observation window is concerned. The processing circuit identifies an arc fault condition on the line conductor by identifying differences in said frequency data between at least two subsequent observation windows and identifying characteristics which exceed thresholds.

Experimental evaluation of an hybrid communication system architecture for smart grid applications

In this paper a new communication system architecture is proposed for the development of a SCADA system which can remotely monitor and control intelligent electronic devices (IEDs) connected to the low voltage distribution networks, i.e low voltage smart meter (SM), interface protection devises (IPS). New distributed metering systems and interface devices, together with a proper communication infrastructure (HiperLAN and narrowband power line communication (NB-PLC) on low voltage network), have been developed to allow monitoring the whole power system and controlling the distributed generators of a Smart Grid also in the presence of harmonic distortions. In this way, the electrical energy d…

Harmonic sources detection in power systems via nonactive power measurements according to IEEE Std. 1459–2010: Theoretical approach and experimental results

In this paper an enhanced decision-making strategy is presented for the detection of harmonic sources in power systems able to detect also which is the prevailing nature of the disturbance (nonlinearity or unbalance). It makes use of some simple indices, which are evaluated by means of the measurements of some nonactive power quantities, proposed by the authors and derived from the approach of the IEEE Std. 1459–2010. The decision-making rules for the proposed strategy are presented and discussed by means of simulation and experimental tests. The results obtained are presented, showing the effectiveness of the proposed strategy for the detection of the dominant harmonic source upstream or d…

A Smart Sensing Method for Real- Time Monitoring of Low Voltage Series-Arc-Fault

This paper proposes a smart sensing method for real-time monitoring of low voltage series arc fault. It is based on the wavelet coefficient mean-difference algorithm and the four spikes appearing within two fundamental periods criterion with adaptive threshold. The method also uses the hard thresholding wavelet denoising with the universal threshold. An arc fault factor and a load adaptation factor are introduced and combined with a correction factor, so allowing the selection of the adaptive threshold in real-time and the series arc fault detection.

Un approccio semplificato per il calcolo del load flow nelle smart grids basato su misure distribuite in bassa tensione

I sistemi di misura distribuiti sono alla base delle "smart distribution grids", ove la crescente presenza di generazione distribuita e sistemi di accumulo e la conseguente transizione verso sistemi attivi rendono necessarie funzionalità avanzate di monitoraggio, controllo e gestione delle reti. In tale contesto, un elemento essenziale è l'analisi dei flussi di potenza, che, com'è noto, può essere effettuata tramite algoritmi di load flow, noti il modello della rete e le potenze generate/assorbite nei vari nodi. Per la misura di tali grandezze sulla media tensione (MT), si possono utilizzare diversi strumenti (quali phasor measurement units, smart meters, power quality analyzers), che però …

Sistema di misura per l’analisi spettrale di segnali non stazionari: implementazione in VHDL per lo sviluppo di un prototipo su FPGA

Cabine secondarie: nodi intelligenti e sicuri delle smart grid

Nel futuro panorama delle Smart Grid, le cabine secondarie assumeranno il ruolo di nodi intelligenti e sicuri della rete di distribuzione, integrando diverse soluzioni innovative di monitoraggio, comunicazione, controllo e richiedendo maggiori caratteristiche di sicurezza come proposto nei due progetti di ricerca REIPERSEI e NewCabElarc

A New Measurement Method for the Detection of Harmonic Sources in Power Systems Based on the Approach of the IEEE Std. 1459–2000

In this paper, a novel single-point strategy is proposed for the detection of the harmonic sources in power systems. The method is an improvement of a strategy previously proposed by the authors; it is developed from the IEEE Std 1459-2000 approach and it can be entirely implemented in the time domain, thus simplifying the measurement system. The effectiveness of the proposed method is evaluated by introducing simple decision-making rules and by taking the presence of the measurement transducers into account. Several simulations and experimental tests are presented, showing that the enhanced strategy is able to give an useful information on the detection of the dominant harmonic source upst…

Compensation of Nonlinearity of Voltage and Current Instrument Transformers

This paper aims at characterizing and improving the metrological performances of current and voltage instrument transformers (CTs and VTs) in harmonic measurements in the power system. A theoretical analysis is carried out to demonstrate that, due to the iron core nonlinearity, CT and VT output signal is distorted even when the input signal is a pure sine wave. Starting from this analysis, a new method for CT and VT characterization and compensation is proposed. In a first step, they are characterized in sinusoidal conditions and the harmonic phasors of the distorted output are measured; in the second step, these phasors are used to compensate the harmonic phasors measured in normal operati…

Uncertainty evaluation of a Backward/Forward Load Flow algorithm for a MV smart grid

This paper presents the uncertainty evaluation of an innovative measurement algorithm for load flow analysis in MV distribution networks. The measurement procedure is based on Low Voltage (LV) load power measurements applied on a Backward/Forward (B/F) algorithm for the Load Flow (LF) resolution. Furthermore, in the procedure a three phase voltage measurement at the MV generating substation bus-bars is also considered. The accuracy analysis of the LF algorithm is performed in the case of a real load condition in the distribution grid of Ustica island, Italy. The analysis takes into account the uncertainty of the measurement instruments at the LV side of each secondary substation power trans…

A Monitoring and Management System for Energy Storage Integration in Smart Grids

The integration of distributed storage systems (DSSs) at users and prosumers level can significantly contribute to energy efficiency and increase profits from renewable energy exploitation, thanks to suitable scheduling of charging and discharging periods. On the other hand, to preserve network stability and secure operation, Distribution Systems Operators (DSOs) are interested in DSSs control and cooperation with the grid. In this framework this work proposes a simple monitoring and management system for DSSs scheduling and its integration in a distributed measurement and control system architecture for smart grids. In the paper the proposed algorithm is tested on a simple case study at ho…

A New Protection Strategy for Electrical Distribution Systems

In this paper, the authors propose a new protection strategy for electrical Medium Voltage distribution networks, based on a distributed intelligence system composed of a central unit and of many local processing units. The distributed intelligence system can precisely identify and locate faults in suitably limited times. Each local processing unit is composed of a data acquisition system and a data analysis system. The first allows the accurate reconstruction of the fundamental using only 1.5 cycles of under fault transient electrical quantities. The second performs suitably precise on-line fault diagnosis based on the data provided by the data acquisition module. The data acquisition algo…

The metrological characterization of the static meters for reactive energy in the presence of harmonic distortion

For the electricity metering for billing purposes in distribution systems, the static meters are substituting the traditional inductive meters. Thus, the evaluation of the performances of such equipments is required, also in the presence of disturbances affecting the power systems. With respect to this, this paper analyzes the main aspects related to the metrological characterization of the static meters for reactive energy in the presence of harmonic distortion. Particular attention is given to the reference standard meters, that are not considered by the actual in-force Standards. The analysis is supported by several experimental tests.

Disturbing loads identification in power systems: a single-point time-domain method based on IEEE 1459-2000

This paper presents a single-point method for the identification of prevailing disturbing loads in power systems for both single-phase and three-phase applications downstream or upstream from the metering section. It is based on the simultaneous measurement of three nonactive power quantities, which are based on the IEEE Std. 1459-2000 approach. The proposed method is only based on the separation of the fundamental components from the harmonic content of voltage and current; thus, it does not require any spectral analysis of the voltages and current. In this paper, the formulation of the proposed method and its time-domain implementation are described; moreover, some simulation results are …

Uncertainty evaluation in load flow analysis: real MV distribution networks case studies

This work investigates the measurement uncertainty impact on load flow analysis in medium voltage (MV) distribution networks. The considered algorithm is a simplified load flow algorithm (LFA), developed by authors, which is based on the load power measurements at each secondary substation and one voltage measurement at the slack bus (i.e. the voltage at the MV bus bars of the primary substation). In the viewpoint of a real implementation, to reduce monitoring system costs, the LFA makes use of low voltage (LV) load power measurements for all the substations except those of MV users, where MV transducers are usually already installed. The uncertainties on LFA input quantities (load powers a…

PQ Metrics Implementation on Low Cost Smart Metering Platforms. A Case Study Analysis

The increasing interest on the quality of the energy supplied and generated in distribution networks is raising the need of distributed power quality (PQ) measurements. To allow such capabilities with cost effective metering solutions, this paper wants to investigate the feasibility of using smart meters, already installed for energy billing, also for power quality monitoring. To this aim, an electronic board (based on STCOMET metrology device), already used in many energy meters of different countries, has been selected as case study platform. The manufacturer firmware of this board was essentially aimed at implementing energy meter metrics and power line communications functionalities. In…

Problematiche di misura per la caratterizzazione dei contatori statici di energia reattiva in condizioni non sinusoidali

Traceability of static reactive energy meters in the presence of harmonics: theoretical considerations and a DAQ-based reference meter

This paper deals with some problems related to the measurements traceability with static meters for reactive energy. These problems arise when the meters operate in the presence of harmonics, which can negatively affect their performances, depending on implemented metric. The paper analyzes the problem in the light of both in-force and draft standards, from the viewpoint of the performances of both commercial meters and reference standard instruments. The analysis is supported by some experimental tests, which are carried out by means of a reference meter, based on data acquisition boards, which can be used in both sinusoidal and distorted conditions.

Narrowband power line communications for medium voltage smart grids

The aim of the paper is to show how narrowband power line communications (NB-PLCs) can be a valid solution for medium voltage grids. Advantages and drawbacks of this solution are analyzed, starting from some experimental communication results, which were carried out on the medium power system networks of the islands of Ustica and Favignana, in the presence of the net voltage. Furthermore, some communication architectures and hardware prototypes based on NB-PLCs are proposed for different smart grids applications.

Critical issues and future prospects of the secondary substation in smart grid context

This paper is focused on the new role of the secondary substation in the smart grids context. This innovative view has been proposed and developed in the framework of two Research Projects: NewCabELARC Project and Reipersei Project. The latter provides a concrete and comprehensive low cost solutions for the smart grid monitoring and control, allowing the real diffusion and integration of Distributed Generation and the full exploitation of Renewable Energy Sources. In this field, this paper shows how the secondary substation (SS) takes the role of smart transducer node where innovative devices can be located, collecting the measurement data coming from the field devices (power and energy met…

Potenza reattiva in regime deformato

Caratterizzazione dei contatori statici di energia reattiva in presenza di armoniche – studio sperimentale e risultati

On the methodologies for the calibration of static electricity meters in the presence of harmonic distortion

This paper is focused on the problems related to the calibration of static electricity meters with nonsinusoidal test waveforms. This is an up-to-date issue since the harmonic distortion levels are ever increasing, especially in low-voltage power systems, and in such conditions the performances of the modern static electricity meters can be negatively affected, depending on the implemented measurement algorithm. Thus it is important to test the meters with nonsinusoidal waveforms. The paper analyzes the problems related to both the choice of the test signals to be used for calibration and the implemented metric, with a particular focus on the reactive energy meters. The analysis is supporte…

Comportamento dei trasformatori MT/BT in sistemi di comunicazione power line. Caratterizzazione e modellizzazione

Simulation and laboratory experimental tests of a line to shield medium voltage power line communication system

A complete model of a power-line communication (PLC) system on a medium-voltage (MV) network in the case of a line-shield configuration is presented in this paper. An MV cable model in a line-shield configuration is considered together with the power transformers, the signal coupling networks, and the receiving and transmitting line coupling interface of a ST7540 FSK power-line transceiver. Simulations of the complete model of the system under consideration have been carried out for different line lengths, with and without power transformers and derivation branches. The model is validated by experimental tests performed in the laboratory. The measured results confirm the reliability of the …

A set of indicators for arc faults detection based on low frequency harmonic analysis

In this paper a novel set of indicators is presented for arc faults detection in electrical circuits. The indicators are defined starting from an experimental characterization of the arc fault phenomenon and the study of the arcing current in several test conditions, which were chosen in accordance with the UL 1699 Standard requirements. The proposed parameters are measured by means of a high resolution low frequency spectral analysis of the arcing current, which allows to achieve a good spectral resolution even with short observation windows.

A PLC based monitoring and remote control architecture for Distributed Generation and Storage systems in LV smart grids

(Abstract) This paper proposes a new power line communication (PLC) architecture for monitoring and remote control of Distributed Generators (DG) and Energy Storage Systems (ESS) connected to low voltage distribution networks. The final aim is to improve the performance of the PLC link in terms of robustness and efficiency in devices addressing. The proposed solution is based on a concentrator, to be installed in secondary substation, and a new PLC bridge, to be linked both to inverters and interface protection systems of DGs or ESSs. In this way, a communication link is obtained between distribution system operator (DSO) and DG or ESS owners. The proposed system is able to provide advanced…

Development of a Coupling System for Medium Voltage Power Line Communication in the CENELEC A Frequency Band

In this paper the performances of a new power line communication (PLC) coupling system for medium voltage (MV) smart grids are investigated in the CENELEC A frequency band (i.e. 3 - 95 kHz). The new coupling solution is based on the use of the capacitive divider of the voltage detecting system (VDS) as PLC coupler to the MV network. According to IEC 61243-5, VDS are worldwide used to reveal the presence of the mains voltage to ensure the safety of the operators. A proper interface circuit has been invented and patented to couple the PLC signal through the VDS. In this way no dedicated MV PLC coupler is required, thus avoiding the related costs of the coupler, of its installation, and those …

Measurement of Simplified Single- And Three-Phase Parameters for Harmonic Emission Assessment Based on IEEE 1459-2010

This article investigates the feasibility of using a simplified approach, based on the measurement of power ratio parameters, for harmonic emissions assessment at the point of common coupling (PCC). The proposed approach comes from the common concept of power factor correction and the definitions of the IEEE Std. 1459-2010, where line utilization and harmonic pollution levels are evaluated by means of ratios between the power quantities of the apparent power decomposition. In addition to the IEEE Std. 1459–2010 indicators, in this article, the behavior is studied of additional parameters that are conceptually similar to those defined by the IEEE Std. 1459-2010. The suitability of such param…

Rogowski coil current transducer compensation method for harmonic active power error

Abstract In the harmonic active power measurement, the highest uncertainties are generally introduced by the current and voltage transducers. In a previous paper, the authors showed that the current transformer (CT) can introduce significant errors in such measurement, especially if the phase shift between voltage and current is close to ±90°. In such condition the errors on harmonic power measurement are mainly due to the CT phase displacement. This paper shows that better results can be achieved with more linear transducers, such as the Rogowski coil current transducers (RCCTs), whose metrological performance in distorted condition can be improved, by means of a proper compensation method…

Static meters for the reactive energy in the presence of harmonics: an experimental metrological characterization

Electricity metering plays a crucial role for all the commercial transactions on the energy market. Thus, an accurate evaluation of the performance of the electricity metering equipment is required not only in the reference operating conditions but also in the presence of disturbances affecting the power systems. As regards this matter, this paper analyzes the main aspects related to the metrological characterization of the static meters for the reactive energy in the presence of harmonic distortion. Attention is focused not only to the meters covered by the current standards but also to the meters of better accuracy and to the reference standard meters. The analysis is supported by several…

Single-Point Strategies for the Detection of Harmonic Sources in Power Systems

A self-synchronizing instrument for harmonic sources detection in power systems

The deregulation of energy markets holds out new prospects for contract between customers and utilities, in which the price of energy can depend on voltage quality and load characteristics, as well as on the responsibility for disturbances caused to supply voltage in power systems. In this context, harmonic sources detection is one of the main problems, because of equipment sensibility and the proliferation of loads which absorb non-sinusoidal currents. In this paper the authors present a new instrument based on a time domain method for the detection of harmonic active powers in three-phase systems, which can be usefully applied even in the presence of unbalance or asymmetry. The amplitude …

A new PLC-based smart metering architecture for medium/low voltage grids: Feasibility and experimental characterization

Abstract This paper investigates the feasibility of a smart metering architecture for modern power grids in the smart cities framework. A particular focus is made on Automatic Meter Reading, with the aim of facing some costs and safety drawbacks of current solutions (such as dependence from wireless communication providers, reliability problems in bad weather conditions, and exposition to cyber-attacks). The proposed architecture exploits power line communications (PLC) at both low and medium voltage level, thanks to new devices and an innovative medium voltage PLC coupling system. The new coupling solution and the whole smart metering architecture are experimentally verified in a wide freq…

Confronti Teorico-Sperimentali tra Contatori Elettronici di Energia Reattiva in Presenza di Distorsione Armonica

Un metodo single-point basato sullo Standard IEEE 1459-2000 per l’individuazione delle sorgenti di armoniche nei sistemi elettrici di potenza

An Innovative Power Line Communication solution For Medium Voltage Smart Grids Applications

This paper summarizes the authors research activity concerning the design, modeling and experimental characterization of a new coupling system for medium voltage (MV) narrow band power line communications (NB-PLC). The proposed solution has been patented by authors and it exploits the capacitive divider of voltage detecting systems (VDSs) normally used to reveal the mains voltage presence, thus avoiding the use of dedicated MV couplers. In the following, the modeling of the VDS capacitive divider is presented and the interface card design is described, based on simulation of the whole PLC transmission channel. Laboratory tests are also presented. Finally, the results are shown of an on-fiel…

A new phase locked loop strategy for power quality instruments syncronization

A Virtual Tool for Load Flow Analysis in a Micro-Grid

This paper proposes a virtual tool for load flow analysis in energy distribution systems of micro-grids. The solution is based on a low-cost measurement architecture, which entails low-voltage power measurements in each secondary substation and a voltage measurement at the beginning of the medium voltage (MV) feeder. The proposed virtual tool periodically queries these instruments to acquire the measurements. Then, it implements a backward&ndash

Incremental heuristic approach for meter placement in radial distribution systems

The evolution of modern power distribution systems into smart grids requires the development of dedicated state estimation (SE) algorithms for real-time identification of the overall system state variables. This paper proposes a strategy to evaluate the minimum number and best position of power injection meters in radial distribution systems for SE purposes. Measurement points are identified with the aim of reducing uncertainty in branch power flow estimations. An incremental heuristic meter placement (IHMP) approach is proposed to select the locations and total number of power measurements. The meter placement procedure was implemented for a backward/forward load flow algorithm proposed by…

Measurement Uncertainty of Harmonic Emission Indicators based on IEEE Std. 1459-2010

The study presented in this paper is aimed at analyzing the measurement uncertainty impact on the evaluation of some power ratio parameters for harmonic emissions assessment based on IEEE Std. 1459-2010 apparent power decomposition. In addition to power factors for line utilization and harmonic pollution levels evaluation defined in the Standard, the study covers also some new parameters, which have been introduced by the authors as IEEE Std. 1459-2010 power quantities ratios. The measurement of the aforesaid parameters is implemented on a PC-based wattmeter, in order to investigate the measurement uncertainty impact on the evaluation of the power ratios. The obtained results show that, in …

Experimental characterization of series arc faults in AC and DC electrical circuits

This paper presents an experimental characterization of the arc fault phenomenon, for both AC and DC systems, focusing the attention on series arcs. The aim of the study is to find some current characteristics, which can be significant for the purpose of arc detection. The arcing current signal is analyzed in both time and frequency domain. For the AC analysis, the test conditions are chosen in accordance with the “unwanted tripping tests” and the “operation inhibition tests” reported in the Standard UL 1699. The DC study is carried out on the currents waveforms acquired during some on-field tests on a PV plant. Starting from the study herein presented, the authors have found that is it pos…

Metodologie di caratterizzazione dei contatori elettronici in presenza di armoniche

A Time-Domain Approach Based on the IEEE Std 1459-2000 for the detection of Loads Producing Harmonic Distortion

This paper presents a novel strategy for the detection of harmonic sources in power systems for both the single-phase and the three-phase systems. It is based on the IEEE Std. 1459-2000 approach and it is based only on the separation of the fundamental components from the harmonic content of voltage and current. The proposed strategy do not require any spectral analysis of voltages and currents and it can be entirely implemented in the time domain. In the paper, the formulation of the novel approach is given and some simulation results are presented.

Design of a Time Dissemination System Using Chirp Modulation for Medium Voltage Smart Grid Applications

The monitoring and the management of smart grid require an advanced communication infrastructure. The time synchronization is among the most important services such an infrastructure should offer. Several solutions are available to disseminate the time information in a distributed system; for instance, most of the times a global positioning system (GPS) receiver is used to recover accurate time information. However, GPS receivers need a clear view of the sky. Other solutions, like the use of a network-based synchronization mechanism, require a dedicated communication infrastructure, which is not always feasible for economical reason. Thus, the use of the power grid itself to disseminate a t…

Oil filled MV/LV Power Transformer Behavior in Narrow Band Power Line Communication Systems

The aim of this paper is to characterize oil-filled power transformers in the narrow-band power-line communication (PLC) frequency range of 50-150 kHz. A new model is proposed for such type of a transformer, in the aforementioned frequency range of interest, in order to study its influence on the signal transmission and to investigate the possibility that the PLC signal can cross the power transformer itself. The new model is simpler than those previously proposed in literature, and it can be used in the whole frequency range available for NB PLC according to the CENELEC EN 50065-1 A-band. In order to validate the model, simulation and measurement results are compared for four oil-filled po…

Disturbing Load Detection in Three-Wire and Four-Wire Systems Based on Novel Nonactive Powers From IEEE 1459-2000

This paper presents an enhanced approach for the detection of disturbing loads in distorted and/or unbalanced three-phase power systems, both three-wire and four-wire. It is based on the IEEE Std. 1459-2000 effective apparent power resolution, and it requires only the separation of the fundamental components of voltage and current from the remaining harmonic content. In this paper, the formulation of the novel approach is given, and its effectiveness is discussed by means of several simulation tests, which were carried out on a simple test system.

Un nuovo approccio per l'individuazione delle sorgenti di distorsione armonica nei sistemi elettrici di potenza

A novel approach based on nonactive powers for the identification of disturbing loads in power systems

In this paper, a new approach is proposed for the detection of harmonic sources in polluted power systems. It is a single- point strategy, based on a comparison among different "nonactive" power quantities proposed in literature that, in the same working conditions, assume different values at the same metering section. Some simulations tests were carried out on a standard IEEE test system proposed by other authors as a benchmark system for the analysis of multipoint measurement techniques for harmonic pollution monitoring. The obtained results show that the proposed single-point approach is in agreement with other strategies already proposed in the literature and can provide useful indicati…

Implementation of a PLC Field Analyzer on a G3 Modem Platform

Nowadays, power line communications (PLC) are a widely used technology in distribution grids, both for automatic meter reading and automation applications. PLC performances (in terms of capacity, coverage, robustness, and data transmission rate) can be significantly affected by electrical network topologies, connected loads and disturbances. Thus, utilities and modem manufacturers are increasing their interest in electrical network characterization. In this framework, a software tool is proposed in this paper to measure received signal and noise levels. As case study, it is implemented on a G3 PLC transceiver, widely used for smart metering purposes. In this way, a PLC channel characterizat…

Riferibilità dei contatori statici di energia reattiva in presenza di armoniche

Secondary substation power line communications for medium voltage smart grids

In this paper a performance analysis is carried out, in order to evaluate the possibility to employ power line communication (PLC) between secondary substations of a medium voltage (MV) distribution networks in a smart grid. The study is focused on the analysis of PLC technologies and the evaluation of the influence quantities on the communication performance in the most common case of by-pass connection at MV bus-bars of secondary substations. Different quantities have been analyzed as modulation techniques, requested bandwidth and bitrate, coupling device and system attenuation versus frequency in order to find the best solution for a reliable communication system. A complete model of a r…

Measurement and communication interfaces for distributed generation in smart grids

The aim of this work is to perform a feasibility study on the measurement and communication strategies for the development of a new generation of interface devices for distributed generators and their integration on smart grids. The communication system can use one or more technologies, at the various levels, creating a low cost network infrastructure, in the framework of a SCADA (Supervisory Control and Data Acquisition) architecture. As regards the measurements, the attention is focused on the anti-islanding protection, based on a hybrid solution, which makes use of local measurements and communications with the grid, at both MV and LV level by employing the PLC technology. Some simulatio…

A time domain strategy for the measurement of IEEE Standard 1459-2000 power quantities in nonsinusoidal three-phase and single-phase systems

This paper describes a time domain technique for the detection of fundamental and harmonic components of voltages and currents, which is able to evaluate all the quantities required by IEEE standard 1459-2000. The technique does not require any spectral analysis to separate the fundamental positive-sequence components from harmonic, negative-sequence and zero-sequence ones. In the paper the development of the proposed technique is presented for three-phase systems, both three-wires and four-wires, as well as for single-phase systems. The implementation of the proposed technique on a PC-based instrument is also described and experimental results are presented. Finally, accuracy specification…

Un metodo basato su misure distribuite in bassa tensione per il calcolo del load flow nelle smart grids

Con la diffusione della generazione distribuita nei sistemi elettrici di distribuzione e la conseguente loro transizione verso reti attive, è diventato essenziale disporre di opportuni sistemi per il monitoraggio, il controllo e la gestione delle retistesse. In questo ambito, l'unità GMEE di Palermo, in collaborazione con l'ISSIA-CNR e la STMicroelectronics, da alcuni anni si occupa dello sviluppo di sistemi di misura e comunicazione per lo sviluppo delle "smart distribution grids". In particolare, per quanto riguarda il monitoraggio della rete, lo studio è stato focalizzato sull'analisi dei flussi di potenza, che, noti il modello della rete e le potenze generate o assorbite nei vari nodi, …

A theoretical and experimental comparison among reactive energy meters in nonsinusoidal working conditions

Nuove tecniche di sincronizzazione per strumenti di power quality

Campagna di misure sulla rete elettrica dell’isola di Favignana per la caratterizzazione di reti di accoppiamento per la trasmissione di segnali su cavi di media tensione

Uno strumento virtuale per il monitoraggio e il controllo di un impianto fotovoltaico a concentrazione

In questa memoria si presenta una sintesi delle attività condotte nell'ambito del progetto SERPICO ("Sviluppo E Realizzazione di Prototipi di Inverter per impianti fotovoltaici a Concentrazione", PO-FESR Sicilia 2007-2013, Misura 4.1.1.2). Il progetto ha riguardato lo sviluppo di un prototipo di impianto fotovoltaico-termico a concentrazione e del relativo sistema di monitoraggio e controllo. Tale sistema permette di acquisire le quantità sia elettriche che termiche. Inoltre esso implementa un algoritmo per l'inseguimento solare utilizzato per ottimizzare la produzione di potenza.

Un campione di potenza basato su schede di acquisizione commerciali. Prove sperimentali e valutazione dell'incertezza