Quality Of Electric Power Supply Research Articles

Enhanced thermal modeling of power transformers: A comparison of bond graph and IEEE methods considering external environmental factors

The optimal and secure operation of electrical power system is largely affected by the reliability of power transformers in operational and economic terms. The continuous monitoring of power transformer is crucial for ensuring the quality of electrical power supply. Hence, the thermal modeling of power transformer is very essential to prevent their failure. This paper aims to design thermal models of operating power transformer by considering the two external influencing parameters of solar irradiation and wind flow. This paper presents a Bond Graph (BG) method-based design of thermal models for power transformer under operating condition by comparison with the results obtained from IEEE Std. based thermal models and also with the practical readings. The models have been implemented on a 5MVA, 33/11 kV power transformer running at 33 kV Substation, Sardarpura, Jodhpur, by initially considering the input hourly dataset of load and ambient temperature. The designed thermal models were subsequently updated by integrating the impact of solar radiation and wind incident on the surface of power transformer. Comparative study of all the designed thermal models has been done that indicates improved accuracy of the model if the impact of solar radiation and wind flow are included. Also, the effectiveness of the BG based thermal models in accurately predicting the system behaviour validates their applicability for real world engineering applications.

Design and Implementation of Hybrid Harmonic Filter for Converter System

Quality of power is essential for all electrical systems towards their reliable operation. In specific voltage/current magnitude, frequency and waveforms are the key parameters that decide the quality of electric power supply. Recently enormous nonlinear loads such as converters, inverters, variable frequency drives, and uninterrupted power supply are used in all modern industrial sectors which leads to power quality disturbance in power systems In particular, harmonic distortion is one of the main power quality causes produced by nonlinear loads which will affect the reliable operation of industrial electrical equipment. Harmonic filters help to maintain the harmonic limits as per the IEEE 519-2014 standard. This research article overviews the various types of harmonic filters and the design procedure for the passive harmonic filter. Also, this research paper briefly converses the design and control technique procedure for the proposed hybrid harmonic filter, used to control the harmonic distortion produced by the three-phase converter system. The results of the experimental setup with the implementation of a hybrid harmonic filter clearly show that the harmonic distortion is greatly reduced. The high accuracy power quality analyzer used in this research work measures the real-time voltage/current waveforms, power/energy, and harmonic profiles.

Susceptibility Characteristics of 500 kV Transmission Lines to Forced Outages Caused by Wildfires

Wildfires are one of the main causes of transmission line outages in Brazil. However, not every wildfire will result in the outage of a transmission line. Understanding this phenomenon is fundamental to improve the quality of electric power supply. This work aims to identify the characteristics of spans of twelve 500 kV transmission lines that make them more susceptible to outages caused by wildfires. Based on the analysis of construction data, fire outbreaks, vegetation index, restrictions on the cleaning maintenance of the rights-of-way, weather conditions and terrain characteristics, the main characteristics that make a given transmission line span vulnerable to an outage caused by wildfires could be identified. The results show that spans located on land classified as savanna formations have a greater chance of leading to transmission line outages caused by wildfires. The number of fire outbreaks and the NDVI index were the variables with the greatest influences on the occurrence of transmission line outages in spans exposed to wildfires.

ENHANCEMENT OF POWER QUALITY USING FUZZY LOGIC CONTROLLED DSTATCOM

End users of electricity want to receive a quality and reliable electric power without interruption all the time throughout year. Even though, power generation station maintains quality, some natural and man-made sources affect the quality of electric power supply being distributed. Various conventional devices are available to improve electric power quality, but their performance is inadequate.  The main aim of the work is to design and simulate a system which provides quality and reliable electric power. The system uses Distribution STATic COMpensator (DSTATCOM) to maintain the power at near sinusoidal voltage and at designed frequency. DSTATCOM is a shunt connected Voltage Source Inverter (VSI) based custom power device, used to mitigate power quality issues. The system also uses the fuzzy logic control algorithm, to control the Pulse Width Modulation (PWM) controllers used in VSI of DSTATCOM.

Smart Metering Systems Optimization for Non-Technical Losses Reduction and Consumption Recording Operation Improvement in Electricity Sector.

One of the keys of enhancing the quality of electric power supply resides in the accuracy of the consumption metering. Nowadays development of the sensors, devices and systems for electricity metering offers the basis for this service. Nevertheless, this achievement in many situations is altered such that appropriate measures must be adopted even if already significant costs have been registered. In this paper is proposed and discussed an optimal solution based on the identification and minimizing the measurement errors for increasing the electricity readings accuracy and lowering the electricity losses and related costs. In this regard, a mathematical model was developed and a particular algorithm for the mentioned problem is proposed and tested in the case of a power distribution company where an enhancement on average of the own technological consumption with 4% was recorded.

Static VAR compensator for improving voltage profiles and transmission losses: Case study in Batam

Batam has companies engaged in the industry and requires a good quality of electrical power supply. FACTS Devices such as SVC can be mounted to absorb/produce reactive power to control the flow of power to the electrical system of Batam to solve the voltage drop in power transmission in Batam. Newton Raphson method is one method of power flow that is available in the ETAP to simulate the Batam electrical system before and after the addition of the SVC. The Simulation result suggested installing an SVC on bus 20 kV GI Tj. Uban with generated QC and QL values are 15,699.2 kVAR and 31,358.18 kVAR. With these values, the voltage can be improved about 1.132 kV with an active power difference of 6 kV.

Сравнительный анализ результатов экспериментального исследования несимметричных режимов работы трехфазного трансформатора и данных полнофазного моделирования

Achieving better energy efficiency and quality of electrical power supply in distribution networks is a multipronged problem, which should be solved with reference to unbiased criteria. Data obtained from load flow analysis of the network under study serve as the main criterion in estimating the efficiency of technical solutions and administrative measures aimed at decreasing technical and commercial losses and improving the key electric energy quality indicators. At the same time, achieving better accuracy of a numerical analysis of electrical networks with loads unevenly distributed among the phases, including, in particular, distribution networks, still remains a significant problem in the electric power industry. The single-line equivalent circuits, which are conventionally used in engineering applications, do not allow the steady-state operating conditions of a three-phase electric network containing multiple sources of imbalance to be analyzed with sufficient accuracy. Under such conditions, it is reasonable to make a shift for using a three-phase representation of the network under study. This approach involves the need to construct three-phase equivalent circuits of electrical equipment, determine their parameters and use them for analysis. The article describes a conceptual approach for constructing the three-phase model of a three-phase two-winding transformer with a wye - grounded wye winding connection circuit, which is widely used in distribution networks. The following experiments were carried out on the test bench: open-circuit test, short-circuit test, load operation tests, open-circuit test under zero sequence supply voltage, and open-circuit test and load operation tests with one phase disconnected. Part of the experimental data was used to calculate the parameters of the three-phase equivalent circuit and to model a three-phase transformer in the MATLAB environment based on the described method.A comparison between the simulated and the experimental data testifies that the performed simulation of various transformer operating conditions yields highly reliable and accurate results. In the balanced mode, the maximum and minimum errors of simulating the main parameters were found to be 4.78 and 2.13%, respectively. In the unbalanced mode, the maximum and minimum errors of simulating the main parameters were found to be 6.6 and 0.78%, respectively. The obtained results allow a conclusion to be drawn that the proposed model of a three-phase two-winding transformer with the wye - grounded wye winding connection circuit adequately reflects the properties of a real transformer. The proposed technique allows the key properties of a three-phase transformer to be revealed, namely, the redistribution of magnetic fluxes among the magnetic core legs and the presence of voltage across the secondary winding when one of the primary winding phases is open. It can also be inferred that a three-phase transformer has a balancing effect.

UPQC: A Custom Power Device for Power Quality Improvement

Power Quality (PQ) has increased concern amongst utilities at all levels of usage. The development of power electronic devices has made a notable impact on the quality of electric power supply. The operation of nonlinear loads generates harmonics and thus, deteriorates the quality of distribution system. In such cases both utilities and end users of electric power are gradually more concerned about the quality of power. This suggests that few course of action has to be taken so that the power quality can be improved. In this paper the main focus is on UPQC, which is a combination of series and shunt active power filters. The series APF alleviates voltage based distortions, while shunt APF mitigates current based distortions. UPQC alleviates the voltage and current based distortions concurrently as well as independently. UPQC improves power quality by compensating both harmonics and load current which thereby makes source current and load voltage sinusoidal at the required voltage level.The modelling of series APF, shunt APF and the UPQC has been carried out using MATLAB/Simulink.

Analytical Complex Distribution System Reliability Evaluation Considering Stochastic Interruption Durations and Network Reconfigurations

A reliability enhancement scheme for an electric distribution system is impossible to be cost-effective without the guidance of accurate reliability index estimations. As one of the widely used basic reliability indices, average interruption duration is of foremost concern, due to being a straightforward indicator of the electric power supply quality in the aspect of customer satisfaction to the incident response capability of electric utilities to outage events. This paper proposed an analytical distribution system reliability evaluation method that allows for considering stochastic load point interruption durations together with stipulated network reconfiguration constraints. Through case studies on the Roy Billinton Reliability Test System, advantages of the proposed method over a traditional section technique-based reliability evaluation method are discussed. The proposed method is validated to yield more realistic estimations in the case of considering stochastic interruption durations and post-fault network reconfigurations, thus is expected to be capable of supporting economical system reliability-enhancing decision-making.

LIFETIME OF AUXILIARY MACHINES OF AC ELECTRIC TRAINS

Purpose. In this paper it is necessary to analyze increase the efficiency of auxiliary machines of AC electric trains, series ER 9M during operating under the real conditions. Methodology. An engineering method to determine the relative reduction of the lifetime of asynchronous motors, selected with a certain design factor of power reserve, under normal operating conditions and with decrease of the electric power supply quality in auxiliary circuits of rolling stock, which takes place in real operation in sections of Ukrzaliznytsia was proposed. Findings. As a result of a study, conducted by the author it was found that long-term operation of asynchronous motors, selected with a sufficient reserve of power k з = 1,6, when the supply voltage unbalance is 16 … 20% leads to a reduction of their lifetime on 9,5…33,2%, depending on the type of motors. It proves that the choice of auxiliary machines with a large margin of power is not a rational way to increase the efficiency of auxiliary machines of electric trains, series ER9M. Recommendations were suggested for the introductions of symmetry-balancing and protective devices based on modern microprocessor and microcontroller hardware components. They make impossible operation of auxiliary machines during a low level of electric energy quality in onboard electric circuits of AC electric train in general, and on the trains, series ER9M in particular. Originality. The issues of the analytical study of the energy supply quality effect on the lifetime of auxiliary machines of AC electric trains, series ER9M through the determination of the relative reduction of the lifetime of auxiliary machines, depending on the general overheating temperature were highlighted firstly. The effect of safety factor for motor capacity on the average overheating and on the heating process of electrical machines on the whole was taken into consideration. Practical value. Obtained results allow forming critical opinion about the existing protection of auxiliary machines of AC electric train and develop recommendations for the implementation of complex organizational and technical measures to improve operability of auxiliary machines of AC electric trains, series ER 9M.

Performance Verification of Power Quality Signals Classification System

Power quality has become a greater concern nowadays. The increasing number of power electronics equipment contributes to the poor quality of electrical power supply. The power quality signals will affect manufacturing process, malfunction of equipment and economic losses. This paper presents the verification analysis of power quality signals classification system. The developed system is based on linear time-frequency distribution (TFD) which is spectrogram that represents the signals jointly in time-frequency representation (TFR). The TFD is very appropriate to analyze power quality signals that have magnitude and frequency variations. Parameters of the signal such as root mean square (RMS) and fundamental RMS, total waveform distortion (TWD), total harmonic distortion (THD) and total non-harmonic distortion (TnHD) of voltage signal are estimated from the TFR to identify the characteristics of the signal. Then, the signal characteristics are used as input for signal classifier to classify power quality signals. In addition, standard power line measurements are also calculated from voltage and current such as RMS and fundamental RMS voltage and current, real power, apparent power, reactive power, frequency and power factor. The power quality signals focused are swell, sag, interruption, harmonic, interharmonic, and transient based on IEEE Std. 1159-2009. The power quality analysis has been tested using a set of data and the results show that, the spectrogram gives high accuracy measurement of signal characteristics. However, the system offers lower accuracy compare to simulation due to the limitation of the system.

THE IMPROVEMENT OF MAINTENANCE SERVICE FOR TRACTION NETWORKS EQUIPMENT ON THE BASE OF PROCESS APPROACH

Purpose. The new methods development for improving the maintenance service for equipment of traction networks in order to increase its efficiency and quality. Methodology. In world practice of solving problems related to the quality of products and services is usually achieved by introducing quality management system in to the enterprises. The provisions of quality management system were used for solving the problem. The technologies of process engineering were used for describing the main stages of maintenance service. Findings. The development of high-speed movement and growth of its intensity, the use of electric rolling stock of a new generation require the introduction of new methods diagnostics of equipment technical state and improvement of the existing maintenance system and repair of power supply. Developing a model of business-processes, their optimization with using techniques of process engineering and system management is needed for the transition to the management system based on the process approach. From the standpoint of the process approach and in accordance with the requirements of the quality management system (ISO 9001-2009), the operation of the E (Department of electrification and power supply) infrastructure sector is represented as a scheme of business-processes in which the guaranteed supply with electricity of railway and third-party consumers is defined as the main business-process of management. Each of the sub-process of power supply for consumers is described in details. The use methods and main stages of process approach for sample management system reorganization were investigated. The methodology and the application method of PDCA (Plan-Do-Check-Act) closed loop to the equipment maintenance system were described. The monitoring process of traction networks maintenance using the process approach was divided into components after investigations. The technical documentation of maintenance service was investigated in details. Ways to improve business-processes of E (Department of electrification and power supply) management were described. Originality. Maintenance improvement ways for equipment of traction networks using process engineering technologies and quality of electric power supply were proposed. Practical value. Using the provisions of the quality management system to the process of maintenance equipment will let ensure the improvement of process quality by increasing the reliability indices of electric equipment, the service level of consumers and changes of production processes focused on the efficiency increase of the sector activity.

Operación Remota de la Distribución basada en la Supervisión y Control remotos de Reconectadores

Una de las tareas históricas de la Operación de los sistemas eléctricos de distribución ha sido garantizar la continuidad y calidad del suministro de energía eléctrica. La tendencia de los años recientes ha sido aprovisionar las redes de distribución con equipos de maniobra y protección “inteligentes” con funcionamiento autónomo pero aislado. Los Centros de Control, con sus componentes tales como los SCADAs, han sido otro pilar en la optimización de la Operación. Actualmente, con el apoyo de las nuevas tecnologías de la Informática y las Telecomunicaciones, el siguiente paso, casi obligatorio, es articular estas dos herramientas en un solo instrumento para la Operación de la Distribución. Esta integración puede no ser sencilla. Factores como la ubicación de los equipos de maniobra y protección, los sistemas de supervisión y control disponibles, el grado de avance de las telecomunicaciones, influyen en la adopción de la solución más apropiada. Es decir, la realidad de cada Sistema Eléctrico de Potencia condiciona fuertemente la adopción de la plataforma de control y automatización de dichas redes. La solución sugerida en el presente trabajo se enfoca como una guía general para la aplicación en la mayoría de realidades. El caso práctico de éxito de una empresa distribuidora del país confirma la premisa.

Selected Indicators of the National Distribution System Dependability

The article discusses a significant problem, which is the analysis of the dependability of the national distribution system. The distribution of selected failure rates was analysed in two perspectives: dependability analysis at the local utility company level, and for the distribution power system. In the first part of the paper failure rates are analysed for five domestic utility companies. The second part presents an analysis of the distribution of SAIDI, SAIFI and MAIFI indicators for domestic distribution system operators in 2007–2012. DOI: 10.12736/issn.2300-3022.2013403 Introduction A power system (SEE) is one of the most important engineering systems developed and operated by man. The SEE primary role is reliable delivery of demanded electricity with the required quality to each customer. In market conditions the SEE operation and further development requires the assurance of quality energy supply to consumers in a commercially reasonable manner. The quality of electric power supply consists of: quality of supplied electricity, dependability of supply, and quality of customer service. The quality of supplied electricity and dependability of the supply is essentially determined by the SEE dependability [1]. Dependability of the entire SEE consists of the operability degrees of individual system components responsible for electricity generation, transmission and distribution to customers. Unfortunately, in general, the importance and role of individual SEE elements is visible only at the time when they do not perform their functions properly, for example when there is no electricity supply caused by a failure. Unexpected depriving consumers of electricity supply may cause serious damage to property, and constitute a threat to people and equipment. Precise and unambiguous definition of dependability measures for each group of power equipment enables the identification of critical SEE items. This knowledge enables SEE performance improvement by way of upgrading the most failure-prone items, or use of newer technologies, thereby raising the dependability level of the entire SEE. Pursuant to current legal regulations, the domestic distribution system operators (DSOs) are responsible for the level of electricity supply dependability. The ongoing changes in the energy sector can be seen both in terms of changes in the ways of organizing its operations, as well as of a search for the best ways to improve the existing grid infrastructure’s performance. Not without significance is the current issue of the SEE implementation based on Smart Grid premises. The dependability indicators most frequently determined for power distribution systems include: number of shutdowns in a certain period of time, total duration of interruptions in the supply of electricity in a specified time period, number of faulty equipment items (in each group), and SAIFI, SAIDI and MAIFI indicators widely used in international practice. A very important problem encountered in the determination of grid dependability indicators is the lack of available data, due to the general absence of dependability services in utilities (ZE). Analyzing network failure, one should also be aware that this data is collected in a hierarchical manner, i.e. from individual energy districts (RE) to ZE headquarters, and then to the respective DSO branches. Typically only the averages of received dependability data are disclosed in reference publications. The lack of details of this data’s distribution between individual ZE utility companies does not allow for a complete analysis of the issue. This paper discusses the analysis of selected failure rates in two perspectives: dependability analysis as seen from the local utility company level, and for the entire domestic distribution power system. In the first part of the paper failure rates are analysed for five ZE utility companies operated by domestic DSOs. The second part presents an analysis of SAIDI, SAIFI and MAIFI indicators developed for the national distribution system on the basis of data posted on DSO websites in 2007–2012. Selected standards and legislation concerning the dependability One of the documents explaining notions related to dependability issues is PN-N-50191 93 standard “Glossary of electrical M. Kornatka | Acta Energetica 4/17 (2013) | 27–32

Application of an Active Power Filter on Photovoltaic Power Generation System

This paper deals with the Photovoltaic (PV) power generation system ( PVGS) , it is a promising source of energy with great interest in clean and renewable energy sources and an electromechanical active power filter (APF). The rising number of power electronics-based equipment has posed a problem on the quality of electric power supply. Both high power industrial loads and domestic loads cause harmonics in the utility. Power quality problems may arise in the system or may be caused by the consumer itself. The proposed PVGS with APF is able not only to track the maximum power point of the photovoltaic energy but also to dampen harmonic currents from the grid line. To attain these purposes, for the first time in order to increase the output voltage of PV generator this paper presents the design, simulation and implementation of a simple power electronic interface connected PV array using boost converter. The controller extracts maximum power from the solar array. A closed loop scheme employing a PI controller has been modeled to regulate the DC-bus voltage feed the converter, in the second time the paper provides a study to a PV system combined with the function of the active power filter system which permits the cancellation of the most noteworthy harmonics from the utility current. To demonstrate the performance of abovementioned PVGS with APF, a Matlab/Simulink model was established and simulated. Results seem to be very promising.

Método da superposição modificado como uma nova proposta para atribuição de responsabilidades sobre as distorções harmônicas

Diante das orientações contidas em documentos aprovados pela Agência Nacional de Energia Elétrica (ANEEL), o Módulo 8 dos Procedimentos de Distribuição (PRODIST) contempla, dentre outros indicadores de qualidade da energia elétrica, a temática das distorções harmônicas. O referido texto aborda questões associadas com definições, procedimentos de medição, valores de referência, etc. À luz destas determinações e reconhecendo que as soluções mitigadoras para adequação dos indicadores de desempenho envolvem expressivos custos financeiros, surge a questão da busca de meios para a determinação das responsabilidades sobre eventuais violações dos limites pré-estabelecidos para as distorções harmônicas. Dentre as propostas encontradas para se detectar as parcelas de contribuição advindas do supridor e do consumidor ressalta-se que, de um modo geral, as metodologias são fundamentadas em princípios que utilizam o domínio da frequência conciliado com a superposição de efeitos. Não obstante a simplicidade deste procedimento destaca-se que o mesmo se apoia em informações de medições e no pré-conhecimento das impedâncias harmônicas equivalentes da concessionária e do consumidor, sendo estas últimas de difícil, ou mesmo impossível, acesso. Diante disto, o presente trabalho visa viabilizar meios para se contornar tais dificuldades e estabelecer uma sistemática adequada para obtenção do justo compartilhamento de responsabilidades entre as partes envolvidas.

Critical evaluation of the performance of the method of harmonic power flow to determine the dominant source of distortion

In many guidelines contained in documents approved by electrical regulation agencies, harmonic distortions appear as an important issue among other indicators of electric power supply quality. In general, these standards consider specific aspects, such as definitions, measurement procedures, and benchmarks. Overcoming challenges related to voltage distortions and establishing ways to determine the responsibility for possible violations of given limits are also important matters. The literature describes procedures to characterize the major responsibility among the agents involved (supplier and consumer) or, in a more advanced way, the individual contributions. One of the simplest and most widely used methodologies for identification of the major source of harmonics consists of determining the direction of harmonic power flow by comparing the fundamental and harmonic power signals. Most commercial power quality measuring equipment has the ability to quantify fundamental and individual harmonic powers. However, this study shows the weaknesses of this method. Theoretical analyses, as well as computational and experimental studies, were performed for a hypothetical electrical arrangement. The electrical network was investigated under different operating conditions, and the power harmonic approach was used to determine the dominant harmonic source. The results were then used to evaluate the effectiveness of the methodology to find the correct response.

Critical Analysis of the Current and Voltage Superposition Approaches at Sharing Harmonic Distortion Responsibility

Faced with the guidelines contained in documents approved by the National Electric Power Agency PRODIST - Module 8, amongst other indicators of electric power supply quality, the harmonic distortions appear as an important issue. The mentioned regulation takes into account specific matters such as definitions, measurement procedures, benchmarks, etc. Focusing the subject of voltage distortions and the establishment of approaches to determine the responsibility for possible violations of given limits emerges as an important task. This research topic has been taken into account by the literature and a few procedures to characterize the responsibility of a given distortion level due to supplier and consumer has been proposed. The most widespread solutions are based on frequency domain superposition principles. Having this in mind, the current paper conducts a critical analysis performance of the superposition methodology throughout two possible ways of dealing with the subject. The first uses the current contributions and the other by focusing the voltage harmonic found at a given busbar. The studies highlight that the current procedure do not lead to consistent results whereas the voltage method seems to provide a promising manner of dealing with the identification of the harmonic distortion responsibility.

Simulation of Voltage Waveform of Single Phase Synchronous Generator

The electromagnetic field of a Single Phase Synchronous Generator(SPSG) with no-load and rated load is analyzed in this article, the voltage waveforms in both conditions are computed and the harmonics are analyzed. The computation results are close to the test results, which prove the computation method in this article is correct and effective. The results can provide theoretical bases and method to engineers in optimizing the design parameters and improving the electric power supply quality of SPSG.

Electric Power Supply Quality in ship systems: an overview

Power Supply Quality (PSQ) has become an important concern for ship electric systems. Thus, deviations of voltage from nominal values and wave-shapes could cause several problems onboard. Considering that ship system electrification eventually dominates according to the All Electric Ship concept, PSQ will be a key-factor of the normal operation, survivability and safety aboard. The paper provides a coherent description and categorisation of the PSQ phenomena (causes, consequences, characteristic parameters etc.) highlighting similarities and differences between terrestrial systems and ship systems in terms of these phenomena. This overview is enriched by cross-references to relevant standards applied in shipboard applications.