The document describes a Spanish utility's experience implementing an offline state estimation tool to build distribution-level base cases from diverse data sources. The tool estimates system states like voltages and transformer taps using measurements including power flows, injections, currents, and taps. It detects and eliminates bad data. The tool generates base cases for network studies and improves the utility's data. Case studies demonstrate the tool's advantages over previous manual methods.
Fault diagnosis of a high voltage transmission line using waveform matching a...ijsc
This paper is based on the problem of accurate fault diagnosis by incorporating a waveform matching technique. Fault isolation and detection of a double circuit high voltage power transmission line is of immense importance from point of view of Energy Management services. Power System Fault types namely single line to ground faults, line to line faults, double line to ground faults etc. are responsible for transients in current and voltage waveforms in Power Systems. Waveform matching deals with the approximate superimposition of such waveforms in discretized versions obtained from recording devices and Software respectively. The analogy derived from these waveforms is obtained as an error function of voltage and current, from the considered metering devices. This assists in modelling the fault identification as an optimization problem of minimizing the error between these sets of waveforms. In other words, it utilizes the benefit of software discrepancies between these two waveforms. Analysis has been done using the Bare Bones Particle Swarm Optimizer on an IEEE 2 bus, 6 bus and 14 bus system. The performance of the algorithm has been compared with an analogous meta-heuristic algorithm called BAT optimization on a 2 bus level. The primary focus of this paper is to demonstrate the efficiency of such methods and state the common peculiarities in measurements, and the possible remedies for such distortions.
Fault Diagnosis of a High Voltage Transmission Line Using Waveform Matching A...ijsc
This paper is based on the problem of accurate fault diagnosis by incorporating a waveform matching technique. Fault isolation and detection of a double circuit high voltage power transmission line is of immense importance from point of view of Energy Management services. Power System Fault types namely single line to ground faults, line to line faults, double line to ground faults etc. are responsible for transients in current and voltage waveforms in Power Systems. Waveform matching deals with the approximate superimposition of such waveforms in discretized versions obtained from recording devices and Software respectively. The analogy derived from these waveforms is obtained as an error function of voltage and current, from the considered metering devices. This assists in modelling the fault identification as an optimization problem of minimizing the error between these sets of waveforms. In other words, it utilizes the benefit of software discrepancies between these two waveforms. Analysis has been done using the Bare Bones Particle Swarm Optimizer on an IEEE 2 bus, 6 bus and 14 bus system. The performance of the algorithm has been compared with an analogous meta-heuristic algorithm called BAT optimization on a 2 bus level. The primary focus of this paper is to demonstrate the efficiency of such methods and state the common peculiarities in measurements, and the possible remedies for such distortions.
Optimal Capacitor Placement for IEEE 14 bus system using Genetic AlgorithmAM Publications
Genetic Algorithm (GA) is a non-parametric optimization technique that is frequently used in problems of combinatory nature with discrete or continuous variables. Depending on the evaluation function used this optimization technique may be applied to solve problems containing more than one objective. In treating with multi-objective evaluation functions it is important to have an adequate methodology to solve the multiple objectives problem so that each partial objective composing the evaluation function is adequately treated in the overall optimal solution. In this paper the multi-objective optimization problem is treated in details and a typical example concerning the allocation of capacitor banks in a real distribution grid is presented. The allocation of capacitor banks corresponds to one of the most important problems related to the planning of electrical distribution networks. This problem consists of determining, with the smallest possible cost, the placement and the dimension of each capacitor bank to be installed in the electrical distribution grid with the additional objectives of minimizing the voltage deviations and power losses. As many other problems of planning electrical distribution networks, the allocation of capacitor banks are characterized by the high complexity in the search of the optimum solution. In this context, the GA comes as a viable tool to obtaining practical solutions to this problem. Simulation results obtained with a electrical distribution grid are presented and demonstrate the effectiveness of the methodology used.
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
Solve Production Allocation and Reconciliation Problems using the same NetworkAlkis Vazacopoulos
Production allocation is a business accounting practice used throughout the processing world to proportionately and quantitatively assign measurement error and production expenditures or overheads to internal and external business owners. Reconciliation is a scientific function to vet production data of gross errors or non-random variation if it occurs and to find more precise estimates of the measured values. The consequence of our proposed technique is to allow these two functions the capability to use the same production network or flow-path. Only one model is required to be maintained eliminating the possibility that potentially costly mis-allocation will occur due to business and engineering model-mismatch. Mis-allocation due to measurement errors can still be problematic as we illustrate in an example, but should be reduced over time because of the reconciliation measurement diagnostics.
Fault diagnosis of a high voltage transmission line using waveform matching a...ijsc
This paper is based on the problem of accurate fault diagnosis by incorporating a waveform matching technique. Fault isolation and detection of a double circuit high voltage power transmission line is of immense importance from point of view of Energy Management services. Power System Fault types namely single line to ground faults, line to line faults, double line to ground faults etc. are responsible for transients in current and voltage waveforms in Power Systems. Waveform matching deals with the approximate superimposition of such waveforms in discretized versions obtained from recording devices and Software respectively. The analogy derived from these waveforms is obtained as an error function of voltage and current, from the considered metering devices. This assists in modelling the fault identification as an optimization problem of minimizing the error between these sets of waveforms. In other words, it utilizes the benefit of software discrepancies between these two waveforms. Analysis has been done using the Bare Bones Particle Swarm Optimizer on an IEEE 2 bus, 6 bus and 14 bus system. The performance of the algorithm has been compared with an analogous meta-heuristic algorithm called BAT optimization on a 2 bus level. The primary focus of this paper is to demonstrate the efficiency of such methods and state the common peculiarities in measurements, and the possible remedies for such distortions.
Fault Diagnosis of a High Voltage Transmission Line Using Waveform Matching A...ijsc
This paper is based on the problem of accurate fault diagnosis by incorporating a waveform matching technique. Fault isolation and detection of a double circuit high voltage power transmission line is of immense importance from point of view of Energy Management services. Power System Fault types namely single line to ground faults, line to line faults, double line to ground faults etc. are responsible for transients in current and voltage waveforms in Power Systems. Waveform matching deals with the approximate superimposition of such waveforms in discretized versions obtained from recording devices and Software respectively. The analogy derived from these waveforms is obtained as an error function of voltage and current, from the considered metering devices. This assists in modelling the fault identification as an optimization problem of minimizing the error between these sets of waveforms. In other words, it utilizes the benefit of software discrepancies between these two waveforms. Analysis has been done using the Bare Bones Particle Swarm Optimizer on an IEEE 2 bus, 6 bus and 14 bus system. The performance of the algorithm has been compared with an analogous meta-heuristic algorithm called BAT optimization on a 2 bus level. The primary focus of this paper is to demonstrate the efficiency of such methods and state the common peculiarities in measurements, and the possible remedies for such distortions.
Optimal Capacitor Placement for IEEE 14 bus system using Genetic AlgorithmAM Publications
Genetic Algorithm (GA) is a non-parametric optimization technique that is frequently used in problems of combinatory nature with discrete or continuous variables. Depending on the evaluation function used this optimization technique may be applied to solve problems containing more than one objective. In treating with multi-objective evaluation functions it is important to have an adequate methodology to solve the multiple objectives problem so that each partial objective composing the evaluation function is adequately treated in the overall optimal solution. In this paper the multi-objective optimization problem is treated in details and a typical example concerning the allocation of capacitor banks in a real distribution grid is presented. The allocation of capacitor banks corresponds to one of the most important problems related to the planning of electrical distribution networks. This problem consists of determining, with the smallest possible cost, the placement and the dimension of each capacitor bank to be installed in the electrical distribution grid with the additional objectives of minimizing the voltage deviations and power losses. As many other problems of planning electrical distribution networks, the allocation of capacitor banks are characterized by the high complexity in the search of the optimum solution. In this context, the GA comes as a viable tool to obtaining practical solutions to this problem. Simulation results obtained with a electrical distribution grid are presented and demonstrate the effectiveness of the methodology used.
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
Solve Production Allocation and Reconciliation Problems using the same NetworkAlkis Vazacopoulos
Production allocation is a business accounting practice used throughout the processing world to proportionately and quantitatively assign measurement error and production expenditures or overheads to internal and external business owners. Reconciliation is a scientific function to vet production data of gross errors or non-random variation if it occurs and to find more precise estimates of the measured values. The consequence of our proposed technique is to allow these two functions the capability to use the same production network or flow-path. Only one model is required to be maintained eliminating the possibility that potentially costly mis-allocation will occur due to business and engineering model-mismatch. Mis-allocation due to measurement errors can still be problematic as we illustrate in an example, but should be reduced over time because of the reconciliation measurement diagnostics.
Power System State Estimation Using Weighted Least Squares (WLS) and Regulari...IJERA Editor
In this paper, a new formulation for power system state estimation is proposed. The formulation is based on
regularized least squares method which uses the principle of Thikonov’s regularization to overcome the
limitations of conventional state estimation methods. In this approach, the mathematical unfeasibility which
results from the lack of measurements in case of ill-posed problems is eliminated. This paper also deals with
comparison of conventional method of state estimation and proposed formulation. A test procedure based n the
variance of the estimated linearized power flows is proposed to identify the observable islands of the system.
The obtained results are compared with the results obtained by conventional WLS method
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Fault diagnosis is very important for development and maintenance of safe and reliable electronic circuits and systems. Many k-fault diagnosis methods were put forward such as branch method, node method, loop method, mesh method, cut set method. But the tolerance effect as well as non-linear problems exist and are difficult to deal with
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
Ijeee 28-32-accurate fault location estimation in transmission linesKumar Goud
Accurate Fault Location Estimation in Transmission Lines
B. Narsimha Reddy Dr. P. Chandra Sekar
Sr. Assistant Professor, Dept. of EEE Associate Professor, Dept. of EEE
Mahatma Gandhi Institute of Technology Mahatma Gandhi Institute of Technology
Hyderabad, TS, India Hyderabad, TS, India
babubnr@gmail.com Pcs_76@rediffmail.com
Abstract: In trendy power transmission systems, the double-circuit line structure is increasingly adopted. However, owing to the mutual coupling between the parallel lines it is quite difficult to style correct fault location algorithms. Moreover, the widely used series compensator and its protecting device introduce harmonics and non-linearity’s to the transmission lines, that create fault location a lot of difficult. To tackle these issues, this thesis is committed to developing advanced fault location strategies for double-circuit and series-compensated transmission lines. Algorithms utilizing thin measurements for pinpointing the situation of short-circuit faults on double-circuit lines square measure planned. By moldering the initial net-work into 3 sequence networks, the bus ohmic resistance matrix for every network with the addition of the citations fault bus may be developed. It’s a perform of the unknown fault location. With the increased bus ohmic resistance matrices the sequence voltage amendment throughout the fault at any bus may be expressed in terms of the corresponding sequence fault current and also the transfer ohmic resistance between the fault bus and the measured bus. Resorting to tape machine the superimposed sequence current at any branch may be expressed with relevancy the pertaining sequence fault current and transfer ohmic resistance terms. Obeying boundary conditions of different fault sorts, four different categories of fault location algorithms utilizing either voltage phasors, or phase voltage magnitudes, or current phasors or section current magnitudes square measure derived. The distinguishing characteristic of the planned methodology is that the information measurements need not stem from the faulted section itself. Quite satisfactory results are obtained victimisation EMTP simulation studies. A fault location rule for series-compensated transmission lines that employs two-terminal asynchronous voltage and current measurements has been implemented. For the distinct cases that the fault happens either on the left or on the right aspect of the series compensator, 2 subroutines square measure developed. In addition, the procedure to spot the proper fault location estimate is represented during this work. Simulation studies disbursed with Matlab Sim Power Systems show that the fault location results square measure terribly correct.
Keywords: Ohmic Resistance, Transmission Lines, PMU, DFR, VCR, EMTP, MOV.
Monitoring and Control of Power System Oscillations using FACTS/HVDC and Wide...Power System Operation
Power oscillations are a growing concern among power system operators worldwide. Traditionally, the
main countermeasure against dangerous power oscillations has been the installation of power system
stabilizers (PSS). Essentially, the potential for inter-area power oscillations depends on the strength of
the tie lines between different areas and the load on the ties. From a European perspective, with the
anticipated integration of remote renewable energy sources such as offshore wind power from the
North-sea region and solar power from southern Europe or Africa, we can expect the average
transmission distances to grow and consequently also tie line flows. Unless tie lines are also reinforced
we expect more oscillation events in the European grid in the future.
From an operational point of view, it is of high priority to be able to estimate the damping of
oscillatory modes reliably in real-time in order to take appropriate and timely measures in case
damping becomes poor. Recent developments in wide-area phasor monitoring have resulted in a new
power oscillation monitoring algorithm that uses multiple measurements from different locations in
the grid. An equivalent system model of the power grid is estimated in real-time and based on this
model, the damping and frequency as well the activity of oscillatory modes can be determined from
ambient process variations. As basis for this, a wide-area measurement system (WAMS) can provide
time synchronized signals from phasor measurement units (PMUs) that can measure voltage, current
and frequency with adequate accuracy and resolution in time. This paper shows results from pilot
operation of the new application at swissgrid, including recordings from an actual and representative
event in the continental ENTSO-E interconnected power system. This example demonstrates the
performance of the new application as well as provides information about the oscillatory modes
present in the continental ENTSO-E system today.
A Pilot Experience for the Integration of Distributed Generation in Active Di...davidtrebolle
The last years in Europe, the growing penetration of Distributed Generation (DG), (mainly q combination of heat and power (CHP) and renewable), has demonstrated the necessity of facing the impacts and opportunities of new distributed energy resources connected to medium and low voltage grids by means of research projects. The need of demonstration projects on voltage control with DG to increase the hosting capacity has been identified and a noteworthy number of initiatives have been carried out in the European Union. This paper presents the experience of Unión Fenosa Distribución in PRICE-GDI, a pilot project which aims for the integration of DG in active distribution systems. Besides the adopted solution for the monitoring and control of the generation, this paper explains the main results regarding the voltage control in low and medium voltage grids with distributed energy resources
Power System State Estimation Using Weighted Least Squares (WLS) and Regulari...IJERA Editor
In this paper, a new formulation for power system state estimation is proposed. The formulation is based on
regularized least squares method which uses the principle of Thikonov’s regularization to overcome the
limitations of conventional state estimation methods. In this approach, the mathematical unfeasibility which
results from the lack of measurements in case of ill-posed problems is eliminated. This paper also deals with
comparison of conventional method of state estimation and proposed formulation. A test procedure based n the
variance of the estimated linearized power flows is proposed to identify the observable islands of the system.
The obtained results are compared with the results obtained by conventional WLS method
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Fault diagnosis is very important for development and maintenance of safe and reliable electronic circuits and systems. Many k-fault diagnosis methods were put forward such as branch method, node method, loop method, mesh method, cut set method. But the tolerance effect as well as non-linear problems exist and are difficult to deal with
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
Ijeee 28-32-accurate fault location estimation in transmission linesKumar Goud
Accurate Fault Location Estimation in Transmission Lines
B. Narsimha Reddy Dr. P. Chandra Sekar
Sr. Assistant Professor, Dept. of EEE Associate Professor, Dept. of EEE
Mahatma Gandhi Institute of Technology Mahatma Gandhi Institute of Technology
Hyderabad, TS, India Hyderabad, TS, India
babubnr@gmail.com Pcs_76@rediffmail.com
Abstract: In trendy power transmission systems, the double-circuit line structure is increasingly adopted. However, owing to the mutual coupling between the parallel lines it is quite difficult to style correct fault location algorithms. Moreover, the widely used series compensator and its protecting device introduce harmonics and non-linearity’s to the transmission lines, that create fault location a lot of difficult. To tackle these issues, this thesis is committed to developing advanced fault location strategies for double-circuit and series-compensated transmission lines. Algorithms utilizing thin measurements for pinpointing the situation of short-circuit faults on double-circuit lines square measure planned. By moldering the initial net-work into 3 sequence networks, the bus ohmic resistance matrix for every network with the addition of the citations fault bus may be developed. It’s a perform of the unknown fault location. With the increased bus ohmic resistance matrices the sequence voltage amendment throughout the fault at any bus may be expressed in terms of the corresponding sequence fault current and also the transfer ohmic resistance between the fault bus and the measured bus. Resorting to tape machine the superimposed sequence current at any branch may be expressed with relevancy the pertaining sequence fault current and transfer ohmic resistance terms. Obeying boundary conditions of different fault sorts, four different categories of fault location algorithms utilizing either voltage phasors, or phase voltage magnitudes, or current phasors or section current magnitudes square measure derived. The distinguishing characteristic of the planned methodology is that the information measurements need not stem from the faulted section itself. Quite satisfactory results are obtained victimisation EMTP simulation studies. A fault location rule for series-compensated transmission lines that employs two-terminal asynchronous voltage and current measurements has been implemented. For the distinct cases that the fault happens either on the left or on the right aspect of the series compensator, 2 subroutines square measure developed. In addition, the procedure to spot the proper fault location estimate is represented during this work. Simulation studies disbursed with Matlab Sim Power Systems show that the fault location results square measure terribly correct.
Keywords: Ohmic Resistance, Transmission Lines, PMU, DFR, VCR, EMTP, MOV.
Monitoring and Control of Power System Oscillations using FACTS/HVDC and Wide...Power System Operation
Power oscillations are a growing concern among power system operators worldwide. Traditionally, the
main countermeasure against dangerous power oscillations has been the installation of power system
stabilizers (PSS). Essentially, the potential for inter-area power oscillations depends on the strength of
the tie lines between different areas and the load on the ties. From a European perspective, with the
anticipated integration of remote renewable energy sources such as offshore wind power from the
North-sea region and solar power from southern Europe or Africa, we can expect the average
transmission distances to grow and consequently also tie line flows. Unless tie lines are also reinforced
we expect more oscillation events in the European grid in the future.
From an operational point of view, it is of high priority to be able to estimate the damping of
oscillatory modes reliably in real-time in order to take appropriate and timely measures in case
damping becomes poor. Recent developments in wide-area phasor monitoring have resulted in a new
power oscillation monitoring algorithm that uses multiple measurements from different locations in
the grid. An equivalent system model of the power grid is estimated in real-time and based on this
model, the damping and frequency as well the activity of oscillatory modes can be determined from
ambient process variations. As basis for this, a wide-area measurement system (WAMS) can provide
time synchronized signals from phasor measurement units (PMUs) that can measure voltage, current
and frequency with adequate accuracy and resolution in time. This paper shows results from pilot
operation of the new application at swissgrid, including recordings from an actual and representative
event in the continental ENTSO-E interconnected power system. This example demonstrates the
performance of the new application as well as provides information about the oscillatory modes
present in the continental ENTSO-E system today.
A Pilot Experience for the Integration of Distributed Generation in Active Di...davidtrebolle
The last years in Europe, the growing penetration of Distributed Generation (DG), (mainly q combination of heat and power (CHP) and renewable), has demonstrated the necessity of facing the impacts and opportunities of new distributed energy resources connected to medium and low voltage grids by means of research projects. The need of demonstration projects on voltage control with DG to increase the hosting capacity has been identified and a noteworthy number of initiatives have been carried out in the European Union. This paper presents the experience of Unión Fenosa Distribución in PRICE-GDI, a pilot project which aims for the integration of DG in active distribution systems. Besides the adopted solution for the monitoring and control of the generation, this paper explains the main results regarding the voltage control in low and medium voltage grids with distributed energy resources
The paper outlines key considerations that should be taken on board in the European network codes currently being drafted by ENTSO-E within the scope of the ACER Framework Guidelines on System Operation published in December 2011.
Decentralised storage: impact on future distribution gridsdavidtrebolle
Decentralised storage systems could affect the management of the distribution grid in a number of functional areas, including energy management, system services and the internal business of the DSO:
Energy management refers to energy arbitrage by decoupling electricity generation from its instantaneous consumption, as delivered by electricity storage facilities.
System services cover the support storage could offer to quality of service and security of supply in the electric power system.
Finally, for some special and well defined applications which cannot be provided by the market, storage devices could be installed as a grid asset to primarily support the core operational tasks of the grid operator.
Voltage control of active distribution networks by means of disperse generationdavidtrebolle
The aim of this paper is to analyze how the dispersed generators can be used to effectively control the voltage of the distribution network. The technical and economical viability of this proposal can be assessed throughout a systematic analysis of how the voltage of the point of common coupling (PCC) increases as a function of the injected active power, and the required reactive power needed to maintain the voltage of the PCC to a given value
EURELECTRIC Views on Demand-Side Participationdavidtrebolle
In our vision of demand-side participation, smart grids will provide the infrastructure that enables decentralised producers, customers/‘prosumers’, suppliers and service providers to meet on an open market place, while giving grid operators more advanced tools to manage their grids.
El acoplamiento de transformadores es una actividad habitual en la red de distribución. Las principales razones que obligan al acoplamien- to de dos transformadores son la mejora de la continuidad en el suministro, evitar la sobrecar- ga de instalaciones y la realización de manio- bras en la red de distribución. Previamente al acoplamiento de dos transformadores el distri- buidor debe responder a dos criterios básicos: el aprovechamiento de potencia útil debido a posibles diferencias en el reparto de carga y las tomas óptimas de acoplamiento que minimi- cen la intensidad de circulación en transforma- dores y por ende, las pérdidas. En el presente artículo se van a analizar los fundamentos teó- ricos del acoplamiento de transformadores y los resultados prácticos sobre transformadores reales en la red de distribución.
This EURELECTRIC report addresses a number of fundamental questions that arise from the integration of distributed generation (DG) and other distributed energy resources (DER) into the energy system:
How can DSOs make the most efficient use of the existing network?
When are new infrastructure and changes in system architecture needed to better
integrate DG and DER?
Which types of system services are needed and how can they be procured?
How can renewable energy sources (RES), DG, and DER contribute to system security?
How should the regulatory framework develop?
Centralized voltage control in medium voltage distribution networks with dist...davidtrebolle
The growing shares of distributed generation represent new challenges to distribution grids operation regarding estimation and control of voltage profile along medium and low voltage feeders. This fact leads distribution networks to become active distribution systems in order to increase monitoring and control in medium and low voltage networks. In addition, Distributed Generation (DG) may be a new resource to provide a voltage control ancillary service to Distribution System Operators (DSOs). This issue is one of the main objectives of PRICE-GDI project. This paper presents analyses carried out within this project in order to determine the benefits of voltage control provided by DG.
The new regulatory framework which is being stated in
European Network Codes includes some requirements
for DSOs regarding voltage control. This paper analyses the impact of these requirements on voltage control provided by DG
Analysis of Distribution System Operator Unbundlingdavidtrebolle
One of the key regulatory changes as consequence of the liberalisation of the electricity industry has been the unbundling regime. This organisation model aims to separate the potentially competitive core activities from the natural monopoly distribution and transmission activities and other coordination activities like system and market operation.
Since then, European Directives oblige Member States to adopt unbundling requirements in the electricity sector. In particular since the European Commission proposed the option of full ownership unbundling for Transmission System Operators (TSO), there is some uncertainty around Distribution System Operators (DSO) unbundling.
In light of all this changes, this Master Thesis reviews the regulatory and legislative context for unbundling in Distribution System Operators, in both Europe and Spain.
Besides, identifies the current performance of distribution companies, mainly in terms of distributed power, customers served, market influence and compliance of unbundling requirements. Moreover, analyses how some particular countries have experienced the implementation of unbundling regime. All this experiences reveal a still clear insufficient level of Distribution System Operators unbundling and as a consequence a seriously limit on network operation effectiveness and market well-functioning.
In addition, a regulatory methodology is proposed for allowing Regulatory Authorities to monitor the unbundling process. This approach analyses the performance of current unbundling regime in the distribution business and provides regulatory changes when needed. A set of Key Performance Indicators (KPIs) and a benchmarking technique (DataEnvelopment Analysis-DEA) are the tools identified to measure the companies’ behaviour
towards their organisation model. These tools provide regulators an acknowledgement of the performance of Distribution System Operators and rank the companies according to efficiency ratios.
To test the robustness of the methodology designed, a case study is carried out. In particular, this practical survey aims to contribute to the discussion on current model of
unbundling in Spanish electricity distributors in comparison with other European distributors with both similar and different unbundling regimes. In this study, 10 Distribution System Operators, from 6 European Member States, are benchmarked by using DEA model. The results or technical efficiency scores rank distribution companies
according to efficient frontier firms. The main two findings rated Legal Unbundling DSOs slightly more efficient in terms of costs, and Ownership Unbundling DSOs remarkable more efficient in terms of market orientation.
El uso que hacemos de la electricidad depende fundamentalmente de nuestra actividad en los distintos ámbitos, indus- tria, comercio, residencial, etc. Esta activi- dad presenta unos patrones que varían con el calendario laboral, la estacionalidad o climatología, y en menor medida con el coste de la energía. En otras palabras, la demanda presenta una baja elasticidad.
El aumento de los costes de la ener- gía, la cada vez mayor penetración de energías de carácter renovable y dis- tribuido, y una necesidad de mejorar el aprovechamiento de las infraestruc- turas, junto con el despliegue de solu- ciones de comunicación y de los con- tadores inteligentes y la aparición del vehículo eléctrico, están impulsando soluciones tecnológicas y mecanismos que permiten flexibilizar la demanda e integrarla en el mercado eléctrico (de energía y de reservas), es decir, impul- sando la gestión de la demanda.
The paper highlights the need for an Active System Management (ASM) of distribution networks as a key tool for the efficient and secure integration of a high share of Distributed Energy Resources (DER). The paper provides technical and regulatory recommendations that mainly focus on distributed generation but are also largely applicable to flexible loads, electric vehicles and storage.
La planificación de la distribución con Generación Distribuida y Gestión Acti...davidtrebolle
La actual preocupación por el me- dio ambiente así como la necesidad de diversificar los mixes energéti- cos ha propiciado el desarrollo de las energías renovables. Estas tecnologías pueden encontrarse dispersas geo- gráficamente por la red de distribu- ción, constituyendo unidades de Ge- neración Distribuida. Su conexión cer- ca del consumo les permite disminuir la demanda neta y retrasar de esta forma las inversiones del distribuidor en elementos de red. Se trata de un tema que afecta actualmente a las de- cisiones de los distribuidores, ya que según la directiva europea 2009/72 CE el distribuidor debe considerar la presencia de GD a la hora de dimen- sionar sus redes.
Para que la GD sea implementada exitosamente se le exige firmeza, se- guridad, fiabilidad y suficiencia. En el presente artículo se evalúa el retraso que provoca la implantación de GD en las inversiones en red a través de la metodología “opciones de fiabili- dad para la generación distribuida” (RODG) que tiene como fin solven- tar el problema de firmeza. Se anali- za por tanto, desde la perspectiva del DSO, la rentabilidad de la opción de inversión en GD frente a la inversión en red, así como a la decisión de no inversión, pagando las penalizaciones consecuentes.
El control de tensión en redes de distribución con generación distribuida (1/3)davidtrebolle
Esta publicación en una serie de tres artículos.
En este primer artículo se explican los fundamentos del control de tensión en las redes de distribución
El control de tensión en redes de distribución con generación distribuida (1/3)
2Building Distribution-Level Base Cases Through a State Estimator
1. Building Distribution-Level Base Cases Through a
State Estimator
O. Ru´z Garc´a
ı ı E. Romero Ramos A. G´ mez Exp´ sito
o o A. Abur
Applus Norcontrol, SLU University of Sevilla University of Sevilla Northeastern University
Madrid, Spain Sevilla, Spain Sevilla, Spain Boston, USA
M. Ordiales Botija D. Trebolle Trebolle
Soluziona, SA Uni´ n Fenosa Distribuci´ n
o o
Madrid, Spain Madrid, Spain
Abstract—This paper describes the experience of a Spanish a different moment or day. Sometimes, the data is incomplete
distribution utility, Uni´ n Fenosa Distribuci´ n, when implement-
o o and/or contradictory.
ing an off-line state estimation tool intended to work on cases ´
This paper describes the experience of Union Fenosa Dis-
comprising a diversity of voltage levels and coming from a
variety of sources (own SCADA, external equivalent provided by tribuci´ n which decided to resort to a customized state estima-
o
the TSO, past records, etc.). This implies manipulating current tion tool to deal with this challenge, in an attempt to reduce the
magnitudes and transformer tap changer settings along with burden and frustration of former time-consuming procedures
more usual information such as voltage magnitudes and power based on trial-and-error load flow studies and engineering
measurements. This tool has made it possible the automatic experience.
generation of suitable base cases, which can be subsequently
used to undertake routine network studies (contingency analysis, First, noteworthy features of the state estimator developed
planning problems, etc.). for this off-line application, oriented to subtransmission and
distribution networks, are described. These include incorpora-
I. I NTRODUCTION tion of multiple measurements, ampere flows and injections,
In present day electric energy systems two somewhat contra- estimation of transformer taps, bad data detection, pseudomea-
dictory trends are consolidating regarding the type and volume surement generation from historic data, detection of suspect
of data which are handled by the different partners. On the one parameters, etc. A brief explanation will be provided of the
hand, many data that vertically integrated companies used to Windows interface specially designed to help the user when
share are becoming now strictly confidential. On the other, preparing base cases. Then, several application examples are
a much larger volume of data coming from heterogeneous presented and discussed, showing the advantages of using a
sources must be handled by planners and operators. state estimator in this context.
This is aggravated by the relevance and implications of
many decisions nowadays, which makes decision-taking more II. BACKGROUND ON STATE ESTIMATION
risky than ever. State estimators are widely used in today’s Energy Man-
Distribution companies, managing subtransmission and dis- agement Systems. Their role has become significantly more
tribution networks ranging from 400V to 132 or even 230kV, important due to the need to closely monitor power transac-
constitute a good example where this situation applies. They tions during the daily operation. State estimators commonly
are investing in new monitoring, protection and automation use measurements such as power flows, injections and voltage
systems, aimed at increasing the quality of service standards. magnitudes at system buses. These measurements are then
This means that systematic network studies are being extended used to obtain the optimal estimate of the system state,
to portions of networks formerly excluded or, at most, man- which is defined as the set of complex voltage phasors at all
ually solved. On the higher voltage side, they receive from system buses. While not as common, there are other types
the ISO, upon demand, snapshots of the bulk power system, of measurements such as line current magnitudes and bus
typically including an equivalent of electrically distant buses. current injection magnitudes, which are available as additional
In this situation, a major problem distribution utilities are measurements at certain control centers. Furthermore, taps
facing is how to efficiently match such a diverse information in associated with some transformers with off-nominal taps may
order to build coherent base cases from which reliable network have to be closely monitored, i.e. they may have to be
studies can be performed. For instance, as getting the right data estimated along with the conventional system states.
from the ISO may be difficult, if not impossible, planners may This paper describes a software development project which
have to integrate data corresponding to the transmission system was undertaken in order to address the above mentioned
peak loading condition with those coming from a regional unconventional measurements and unknown variables. In ad-
subtransmission network where the peak demand took place at dition to being able to estimate the system state and unknown
2. transformer taps based on the available conventional and detect, identify and eliminate bad analog measurements. Bad
unconventional measurements, the program aims to detect, data detection is accomplished based on the largest normalized
identify and eliminate any bad data or tap in the system. residual test. If the detection test fails, then the measurement
Hence, it provides a tool which can be used not only to monitor corresponding to the largest normalized residual will be de-
the system operation, but also to improve the system data base. clared bad and its value will be corrected as given in Chapter
5 of [1]:
A. State estimator and bad data processor corrected bad Rkk bad
zk = zk − r
Consider the measurement equation given by: Ωkk k
z = h(x) + e where:
Rkk is the diagonal entry of the measurement error covariance
where: matrix,
z is a vector of power injections, power flows, voltage Ωkk is the diagonal entry of the residual covariance matrix,
magnitudes, line current magnitudes, bus current injection which is defined in Chapter 5 of [1],
magnitudes and monitored taps of some transformers. x is a bad bad
rk = zk − h(ˆ) is the measurement residual,
x
vector of voltage magnitudes and phase angles, plus a set of bad
zk is the bad measurement,
taps associated with those transformers whose taps are to be k is the measurement index for the largest normalized residual.
estimated. State estimation will be repeated as many times as needed
h is the nonlinear function relating error free measurements to after each identification and correction of a bad datum. Note
the state variables given in vector x. that, repetitive solutions will start from the most recent esti-
e is the vector measurement errors. mate instead of flat start, and hence will take fewer iterations
Measurement errors are assumed to be independent and have to converge.
a Normal distribution with zero mean and known variance. A Following the bad data identification and correction phase,
diagonal covariance matrix, R is assumed as below: transformer taps which are estimated, will be checked to en-
R = E[eeT ] = diag(σ1 , σ2 , . . . , σm )
2 2 2 sure that the estimated taps are within maximum and minimum
operating limits. If there are limit violations, tap values will be
where σi is the standard deviation of the error associated set at the respective limit. If taps are found to be within limits,
with the measurement i and m represents the total number then their values are rounded to the nearest discrete tap value
of measurements. that is physically viable. This will not significantly change
Note that multiple measurements of the same quantity are the state estimation solution while providing a physically
allowed and fully compatible with the above formulation. For meaningful answer for the estimated taps.
instance, bus voltage magnitudes may be available from two
or more measuring instruments at a given substation bus. B. Practical issues
Instead of ignoring the extra measurements or using a simple The estimator developed for this project incorporates line
averaging, these measurements are included as separate entries current magnitude and bus current injection magnitude mea-
in the measurement vector z and respective standard deviations surements, which are typically not considered by conventional
of errors are assigned to them. estimators. Furthermore, selected transformer taps are included
The weighted least squares (WLS) estimator will minimize in the unknown variable list, so that their values can be
the weighted squares of residuals of the measurements given estimated as part of the solution. These features call for
below: m derivation of new terms in the measurement Jacobian. Detailed
J= 2
ri derivation of all Jacobian entries can be found in Chapters 2
i=1
and 7 of [1] for the current magnitude measurements and tap
variables respectively. It is worth noting that clever application
where:
of shortcuts proposed in [9] leads to very efficient code for
ri = zi − hi (ˆ) is the measurement residual,
x
computing and updating Jacobian entries for those columns
ˆ
x is the estimated state vector.
corresponding to taps.
The state estimate can be obtained by iteratively solving the
A great deal of effort has been devoted to certain practical
following equation:
aspects of the state estimator that, in spite of not involving new
Gδx = δt
knowledge, play an important role in achieveing a reliable and
where: really accurate application. This is the case of the subroutine
G = H T R−1 H is the gain matrix, devoted to ensure unique observability. After numerous tests it
H = ∂h is the measurement Jacobian,
∂x
has been checked that certain pseudomeasurements result more
δx = xk+1 − xk , k being the iteration counter, appropriate than others in order to get the right estimate. In
δt = H T R−1 [z − h(xk )]. this respect, complex power pseudomeasurements, computed
Iterations are terminated when an appropriate tolerance is from actual current measurements and assumed power factor,
reached on δx. Once the iterations are converged, bad data in places of the system where the power flow direction is well-
processing function is activated. This function’s role is to known, have allowed the state to be estimated in zones where
3. only current measurements exist. It is well documented in the detected and eliminated/substitued. Two different working files
literature (see references [5], [6], [7]) that ampere measure- result from this preliminary phase of the application:
ments alone are not enough to guarantee unique observability. • A raw data file containing power flow system specifica-
Also a systematic study has been undertaken to select adequate tion data.
standard deviations for each measurement type. In this sense, • A measurement file where the available measurements,
not only the precision class of the measurement device, but their values and their standard deviation are listed. The
also its nominal power have been used to better tune this handled measurements can be voltage magnitudes, active
important parameter. In general, all tests have confirmed the and reactive power flows and injections, current flow
improvement of the state estimation results and the bad data and injection magnitudes and transformer taps. Multiple
detection and elimination capability in those cases where measurements for the same magnitude, very frequent in
current measurements are incorporated. practice, are obviously allowed.
Regarding the detection and identification of bad data, the
implemented application allows typical bad performance of Next, the system state is calculated from the state estimator
meters, wrong scale factor or bias, reversed connections, etc., function. At the end of each estimation cycle a bad data pro-
to be identified. Additionally, topology errors, and in some cessor is executed. If a measurement is identified as erroneous
cases outstanding parameter errors, have been detected after it is eliminated and a new estimation takes place. This process
carefully and individually analyzing the results of the estimate. ends when no more bad data are detected.
Almost always, those errors were identified after noticing that Figure 1 depicts a display sample of the application where
large measurement residuals accumulated at certain specific the state estimator provides the data associated to a particular
points. As the the implemented tool does not incorporate in a bus. In this diagram, actual measurements are shown in blue
systematic manner the topology error and network parameter while estimated ones are green. If a measurement is detected as
estimation functions, this task has been carried out manually. erroneous, it is drawn in red. Notice that several voltage mea-
Examples of such errors include wrong status information surements are available (one for each incident line besides that
transmitted by a switching device or a drastic change in the measured at the bus). Regarding the transformers connected to
parameters of a line that has been redesigned without the new this bus, not only the tap setting but also the regulated voltage
values been adequately updated at the data base. and the percent regulation range are shown. More variables
could be visualized when activating other options offered by
III. S OFTWARE I NTEGRATION the application.
One of the aims of the developed application is to generate
The following modules, characteristic of any estimator, are a power system model so that the PSS/E simulator can operate
developed: topological and observability analysis, the applica- on it. The results of the estimation (voltages magnitudes and
tion of a gross error filter, the state estimator strictly speaking, power injections) are used to produce the respective power
bad data detection and identification and the presentation of flow Raw Data File.
results to operators. However, from the point of view of the
The implemented application also allows working by areas,
system where the state estimator is integrated, three main
that is, by electrical zones that can comprise different voltage
functions can be distinguished:
levels. This possibility is very attractive owing to, among other
1) First, the input data for the state estimator are elaborated. questions, the need to save computation time.
This phase includes the observability analysis and the A final remark about the modelling of the external trans-
elimination and correction of gross errors. mission system is needed. As previously pointed out, a net-
2) Secondly, the state estimator is run including the sub- work equivalent could be considered, but keeping the entire
routines of identification and detection of bad data. connected network unreduced is another possibility. Both
3) Finally, a power flow network model is built from the possibilities have been considered in this project. However,
state estimation results. a third option proposed in [11] has proved finally to be the
The data corresponding to the network elements under study most successful. In this last methodology, named “the two-
(e.g. generator, transformer, transmission line, circuit breaker, pass state estimation method”, the state estimator produces an
etc.), their connectivity and the associated measurements are initial estimate of the internal system state. The external model
extracted from the SCADA data base for a particular instant. is then attached in two phases: first, branch power flows are
The external equivalent of the higher voltage networks, in- computed for the unobservable network interconnecting the
cluding eventually that of the TSO, is also taken into account internal and external systems; second, a state estimation is
for the specified day and hour (external equivalents are not run using the internal estimated states as pseudomeasurements
updated so frequently as the SCADA data). Then, a topology along with the power flows of the external system, in order
processor is used to aggregate this detailed model back to a to match the two parts of the network model. The scheduled
bus-branch representation. Moreover, a measurement input file injections at the inner boundary nodes are used as target
is created by using an observability processor. This procedure values and external telemetry is included when available.
is aimed at adding pseudomeasurements where necessary Additionally, exact null injections for both networks are treated
to make the system fully observable. Gross errors are also as pseudomeasurements.
4. Fig. 1. Detailed bus view display
TABLE I
T ESTED CASES
Tested cases Buses/Branches Variables Measurements
V θ t Total V Pi Qi Ii Pij Qij Iij t
Small case 76/85 76 75 29 180 110 46 41 1 87 86 113 22
Large case 1454/1747 1454 1453 556 3463 3053 851 815 14 2517 2475 2846 446
IV. C ASE STUDIES voltage level is,
The state estimator has been executed on many different • 193 buses with voltage levels greater than or equal
cases. Two of them are discussed here. The first one refers to to 220kV. This part of the system is the transmission
a relatively small case on which the main features of the im- network, most of them owned by the Spanish TSO.
plemented system can be tested. This 76-bus network has four • The subtransmission network, comprising voltage levels
voltage levels (in brackets the number of buses for each level): from 132kV to 45kV, contains 754 buses, 470 of them
400kV (3), 132kV (7), 45kV (48) and 15 kV (18); its one-line having a nominal voltage of 45 kV.
diagram is provided in the Appendix, figure 2. There are a total • Finally, there are 508 buses associated to the distribution
of 85 branches, 56 lines and 29 transformers, all of them with network with voltages lower than 33kV. This part of the
tap changers. The set of 506 measurements is composed of system is usually operated in a radial manner. There are
voltages, power flows and injections (active and reactive), rms several rated voltages at this level: 33kV, 20kV and 15kV,
current flows and injections, as well as transformer taps (see being 16, 88 and 331 the number of nodes respectively.
the details in table I). Forty complex power injections are exact The rest of the 508 buses are associated to other voltage
null injections. None pseudomeasurement has been needed in levels corresponding to different generating stations. The
this case to make the whole system fully observable. Note also entire network comprises a total of 26 three-winding
the large number of current flow measurements compared to transformers. The star resulting from the electrical model
power flows, reflecting the fact that current measurements are of these devices has a rated voltage of 1 kV.
more common than power ones as the voltage goes down. Regarding the largest test case (1454-bus system), the
The largest system presented here incorporates voltage distribution of its 14171 measurements are also detailed in
levels from 440kV to 1kV with a total of 1454 buses. This high table I. Once more, it is to be noted the large number of current
number of buses results from including the subtransmission measurements (2860) and the great deal of exact null complex
power system and a huge number of nodes corresponding power injections (701), over a total of 851 power injection
to lower voltage levels (medium voltage); it is well known measurements. For this system 76 pseudomeasurements have
that the lower the voltage level the higher the ratio of buses been added in order to have a single observable island.
to branches. More specifically, the number of buses for each Some of them, specifically 23, are power flow measurements
5. computed from actual current measurements as explained in • Not only measurement errors have been corrected but also
section II-B. errors contained in the information provided by switching
Finally, some comments regarding the tap estimation pro- devices.
cess and identification of bad tap measurements are worth • The accuracy of the system data base has been improved
mentioning. Taps of transformers connecting the subtransmis- by correcting parameter errors at specific points where an
sion network to the distribution feeders usually shift auto- accumulation of bad data were detected.
matically by the action of automatic controllers that try to • Building coherent base cases from which reliable network
maintain voltages as close as possible to specified values. studies can be performed by different utility departments
As there are so many transformers of this type, not all of (operation, planning, protection, etc.).
their tap settings are telemetered. On the other hand, some • The estimation of tap measurements has also allowed
of these transformers are equipped with two tap changers, associated errors to be detected and corrected.
one at the high voltage side (on-load tap changer), and the The success achieved with the implemented tool has en-
other at the low side that can only be changed upon previous couraged the utility to enhance the possibilities offered by the
disconnection. The state estimator has turned out to be a great estimator, for example: trying to incorporate new functions
help to estimate all these unknown taps, no matter if they are such as estimation of parameters; improving the numerical
fixed or not, since measurement redundancy is sufficiently high robustness of the estimator by implementing a QR factoriza-
around these transformers. Other off-nominal tap transformers tion; elaborating a pseudomeasurement data base, etc. Some
are those that step up voltages at generator terminals. Their of these tasks are just being undertaken.
taps are not monitored on-line, but are conveniently estimated
A PPENDIX A
by the developed state estimator.
O NE - DIAGRAM OF THE 76- BUS SYSTEM
The following cases illustrate performance of the state
estimator in detecting tap measurement errors: The meaning of the different symbols used in figure 2 are:
1) Incorrect model for the transformer. This case may occur
when the initial tap position is assumed to be the upper Voltage measurement
limit of the variable tap range whereas it actually is at Current measurement
the lower limit or vice versa. More specifically, suppose 6P Active power measurement
a transformer with rated voltages 43/15kV, the regulation Reactive power measurement
6 Q
voltage lying between 38.7kV and 51.3kV. The first tap Complex power measurement
6
value could be assigned to the lower value, 38.7kV, when
in fact it should be matched with 51.3kV, or viceversa. A “t” next to a transformer means a tap measurement is
2) Some of the values sent to the SCADA are not exactly available. The color code for the different levels of voltages
the tap setting, but the change in tap position (number of is: red for 440 kV, blue for 132 kV, brown for 45 kV and
steps). If one of those changes is lost for some reason, green for 15 kV.
the next changes will be taken into account by the ACKNOWLEDGMENTS
SCADA from an erroneous tap position. The application
The authors would like to thank the support provided by
has allowed this misleading situation to be detected.
the Spanish MCYT under grant ENE2004-06951/CON.
V. C ONCLUSIONS R EFERENCES
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