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Power Systems, Energy Markets and Renewable Energy Sources in South-Eastern Europe

ISBN 978-615-80340-7-4
Volume 3 (December 2016)
Pages 1-389
Edited by Fotis Mavromatakis and Kyriakos Siderakis


Chapter I. Power System Operation and Control

The SCADA System at the Generation Center of Hydro North
Author(s): Siniša Sekulić, Krešimir Vrdoljak

The Generation Center North has recently been revitalized. Apart from all new hardware, the revitalized center includes a new SCADA system, the expansion of the telecommunications system and the adaptation of process control and information systems in hydro power plants (HPPs). SCADA’s communication with process stations in HPPs is done using the IEC 60870-5-104 communication protocol, while communication with external centers is done using the ICCP communication protocol. The SCADA system PROZA NET is based on the newest computer technology and openness standards in order to provide the possibility of long-term upgrade and improvement, hence ensuring the necessary safety in system operation.

Smart Centralized Control System for Active Distribution Networks with Adaptive Multi-Objective Optimization
Author(s): Abdelfatah Ali, Raisz David, Karar Mahmoud

The growth of distributed generation (DG) in distribution systems has great impacts on several practical issues, such as voltage rise/drop and system efficiency. In this paper, a smart centralized control system (SCCS) is proposed for optimizing the performance of distribution systems without violating constraints. The SCCS manages the voltage control devices (VCDs) as well as dispatchable DG sources in a cooperative manner to guarantee security and optimality of system operation. A multi-objective function with adaptive weighting factors (WFs) is introduced, which involves active losses, reactive losses, and voltage deviations. The SCCS optimizes the real-time operation of distribution systems by following a smart strategy that optimally resets the WF values as a response for violating system constraints; hence, the distribution system security is enhanced. Comprehensive simulation studies and comparisons with a time series simulation of a 24-hour period are performed to demonstrate the efficiency of the proposed SCCS for optimizing and securing distribution systems.

Possible Role and Effects of Synthetic Inertia on the Future’s Power System
Author(s): Istvan Taczi, Istvan Vokony

The growing share of renewable energy sources leads system operators to previously-unknown challenges. Beside the well-known issues of balancing and capacity adequacy, the security of supply, reliability and stability are also essential and the electric power grid’s operation must meet the expectations. Some of the emerging technologies are connecting to the grid via power converters so they are practically decoupled from the system and its frequency changes. The electric power system has not been designed for that: stability relied heavily on the inertial response of synchronous generators which decreases the rate of change of frequency (ROCOF). The rotating mass of those generators is directly coupled to the system and functions as a kinetic energy storage component which was incredibly useful. Renewable energies such as wind and solar have to be augmented with synthetic inertia to provide such a useful function otherwise stability issues, load shedding and outages will occur. The questions are so current that ENTSO-E listed this problem as one of three main focus topics in their research and development plan from 2015 to 2017 so the transmission system operators across Europe are all thinking about the possibilities. This study introduces the policy, physical and technical background, the possible role of the implemented synthetic inertia and also provides simulation results for further understanding.

A Sensitivity Analysis of Dynamic Thermal Rating Procedures Using a Probabilistic Monte Carlo Approach
Author(s): Paolo Pelacchi, Davide Poli

The Dynamic Thermal Rating (DTR) algorithm proposed in this paper combines the CIGRE thermal model of conductors with a complex multi-span mechanical model of the line that takes into account the mechanical interaction between spans, due to the possible rotation of strings, and that the temperature of conductors can vary span by span, for different weather conditions. The developed tool is able to forecast the time trend of conductor temperatures, tensions, sags and clearances at each span. Since the weak point of DTR algorithms is the proper forecast of weather conditions about to be present on the different spans of the line, this paper investigates the possibility of using a probabilistic approach to assess the robustness of the thermal and mechanical outputs of the DTR procedure.  A sensitivity analysis of results is carried out considering many different weather scenarios, properly drawn and weighted by a Monte Carlo technique. A case study based on a 400-kV overhead transmission line is shown and discussed.

Inclusion of Phasor Measurements in the State Estimator of the Serbian TSMO SCADA/EMS System
Author(s): Miloš Stojić, Jelena Veselinović, Ninel Čukalevski, Goran Jakupović

Although nowadays, within the transmission system smart grid efforts, new DSP (Digital Signal Processing) based ultra-fast remote terminal units (known as PMU) are increasingly installed in the power systems, the use of their data is mostly limited to phasor visualization at the system control centre. Within the steady state domain, their first practical use might be within the state estimation (SE) application of the classic SCADA/EMS system. This can be justified due to the importance of SE for all of the real time/study network applications.
Due to their high accuracy and existence of phase angle measurements, PMU measurements offer a potential benefit to the quality of state estimation solution. In Serbian TSMO, a new WAMS system has been implemented with PMU devices installed during the Project phase in several substations. Two classical SCADA/EMS systems are in operation in the Serbian TSMO NCC, where one serves as a primary, while the second one is a backup for SCADA/EMS, but at the same time it serves as a primary one for SMM Block load frequency regulator. The backup system is open for upgrade, so the State Estimator has been modified to include voltage phase angle measurements, using approach with no reference bus specified. The influence of phase angle measurements on state estimation accuracy has been investigated, using system snapshots taken from the real-time system.
The results of this study and practical consequences for the Serbian TSMO NCC will be presented in this paper, as well as problems identified.

The Metering Interface between the SCADA and SRAAMD Systems
Author(s): Mirela Đurđević, Vladimir Grujić

The SCADA System (Supervisory Control and Data Acquisition) is a system which provides real-time monitoring and control capabilities for distributed industrial systems such as electric power transmission. The SRAAMD System is the System for the Remote Acquisition and Accounting of Metering Data.
The Metering Interface is the interface between the SCADA NCC system and the SRAAMD system. SCADA and SRAAMD are systems for data acquisition. Exchanged data between these two systems is considerable for the entire TSMO. This interface provides a better quality and redundancy for collected data.

CCT Estimation Based on Principal Components Analysis
Author(s): Teodora Dimitrovska, Urban Rudez, Rafael Mihalic

In recent years, a number of factors such as transitioning energy policies and slow transmission expansion have caused more frequent closing of operation of power systems due to their technical limits. Thus, the awareness of critical clearing time of contingencies, which is concerned with the ability of a power system to maintain synchronism after being subjected to a large disturbance, is gaining importance. On-line critical clearing time (CCT) estimation belongs to these types of applications, which give an extensive insight into system vulnerability, thus enabling early decisions and coordination of corrective control actions. This study presents a novel approach for estimating CCT applying data mining techniques. The proposal is tested on the IEEE New England 39-bus system. Results demonstrate the feasibility of the methodology in fast CCT estimation, suitable for on-line applications.

The Integration of Applications for the Revitalization of the Hydro North Remote Control Centre on the Drava River in Croatia
Author(s): Bruno Pavlović, Branko Horvat

Planning the optimal production schedule, the execution, and supervision for a hydropower system on the Drava River is highly important for the Croatian power system operation. The optimization is performed within the Production Centre North and its result is the generation of the Hydro North area schedule’s power plants and power units. The main goal of the optimization is to minimize water usage while maximizing electrical energy production, taking into account the hydro energetic system’s physical, technical, and operational constraints. The mixed integer linear programming method is used for optimization.

The Tool for the In-Depth Understanding of Electromechanical Wave’s Propagation and Inter-Generator Oscillations
Author(s): Urban Rudez, Maj Osolin, Rafael Mihalic

When dealing with wave propagation in power systems, one usually thinks of electro-magnetic waves whose predictable characteristics are successfully implemented in several existing protection applications. However, when dealing with large interconnected power systems, different kind of events are considered under the term “disturbance,” such as trip of a large generating unit or a highly-loaded transmission line outage. After such disturbance, synchronous generators connected to the system react with a rotor angle deviation, which is not simultaneous all over the system. This invokes the so-called electromechanical wave whose propagation speed depends on transmission system impedances and the inertia of the involved generators. When the electromechanical wave reaches the boundaries of the system, it is reflected back towards the origin and the sum of inclined and reflected waves results in inter-generator oscillations. In this paper, a description of an educational tool that provides a dynamic simulation of the power-system model with arbitrary topology is given. The tool sets-up both steady-state conditions as well as second-order differential equations required to calculate rotor angle deviations of all included generators with respect to time after selected disturbance occurs. The three-dimensional visualization of the results enables one to analyse the situation in detail and especially to gain a physical understanding of the phenomenon.

Chapter II. Energy Markets, Economics and Legislation

Information System Supporting the Local EIC Issuing Office
Author(s): Ivan Fućek, Boris Golub, Đordana Miličić, Nela Bilčar

This article gives an overview of an information system which supports the standard operation processes of a local issuing office including data maintenance of EIC (Energy Identification Coding) objects and data synchronization with the central issuing office.
Although well-defined, EIC regulations are subject to change. Special attention will be given to recent changes in EIC model definition, local issuing office responsibilities and data exchange workflow as well as their impact on existing information systems.
The first part of the article describes business processes according to the Energy identification coding scheme (EIC) reference manual with a description of recent regulation changes.
This description will include object types which are uniquely identified using the Energy identification coding scheme (EIC), issuing a new EIC codes workflow and the data synchronization process with the Central Issuing Office (CIO).  In addition to the implementation guide, the process of providing data to other systems will also be described, thus showing the importance of stored information for other business processes.
The second part of the article gives an overview of the information system architecture as well as its integration with other systems. The information system for the local issuing office architecture is described through all the layers -- starting from the data layer, then the layer of business logic implemented using the Java platform and data display layer implemented using modern JavaScript frameworks on a Java Enterprise Edition containers. The information exchange with the Central Issuing office in the process of synchronization through the Enterprise Service Bus platform is described, together with the integration with other information systems.

More details about the modular structure of the information system will be given, with stress on achieving high availability of the information system, as well as different options available when deciding which system components are used to implement on and run the information system.

Assessment of the implementation of Guarantees of Origin (GOs) in Europe
Author(s): Konstantinos Gkarakis, Athanasios Dagoumas

The aim of the paper is to provide an analysis about the operation of Guarantees of Origin (GOs) from renewable energy sources (RES) in the European Union. It provides a description of the different schemes that have been elaborated and provides an assessment of their effectiveness as a tool for diffusion of green electricity in the energy mix. It examines the benefits and limitations of the GOs for different categories of market participants: providers/suppliers and end users of electricity. Moreover, it provides suggestions for the better functioning of the GO system. The paper concludes that voluntarily purchased renewable electricity products like GOs may create an increase in the demand of renewable electricity by end-customers.

Cooperative Game Theory Solutions in Regional European Capacity Markets
Author(s): Giorgos Stamtsis, Vassilis Lychnaras

The present paper investigates the use of cooperative game theory and its methods in the emerging landscape of the capacity markets in Europe. In order not to hinder the development of Europe’s internal electricity market and to reduce the costs of ensuring the security of supply in electricity, the coordination between the continent’s countries is deemed necessary on regional or even European level. Cooperative game theory methods are ideal to support the establishment of such coordination initiatives and then to allocate the savings occurring from this coordination in the most robust and rational way.

Assessing Electrical Distances - A Small Step Toward Online Dynamic Security Assessment
Author(s): Valentin Azbe, Rafael Mihalic

Impedances are one of the key parameters for various phenomena in electric power systems. In the propagation of electromechanical oscillations, electrical distances—which are usually calculated from inverse admittance matrix—are the key parameter. In this paper, an existing rapid method for obtaining diagonal elements of inverse matrix was successfully applied for the calculation of electrical distances in the ENTSO-E network of continental Europe. This method was proved to be 4 to 22 times faster than the classical procedure of admittance matrix inversion. A computer software—which uses the presented method—was developed for the calculation and presentation of electrical distances in the ENTSO-E network. It is based on an interactive map and it gives clearer information on the electrical distances in the ENTSO-E network.

Chapter III. Renewable Energy Sources, Distributed Generation, Smart Grids

Electrical Modelling Of a Photovoltaic Module
Author(s): P. Acharya, M. N. Shaikh , S. K. Jha, A. P. Papadakis

This paper presents a generalized photovoltaic (PV) model using non-linear equations of current and voltage for the array. The current-voltage (I-V) and power-voltage (P-V) characteristics of the array are determined considering the effect of sunlight irradiance and cell temperature. Within the model, different electrical parameters such as maximum power (Pmp), current at maximum power (Imp), voltage at maximum power (Vmp), open-circuit voltage (Voc) and short-circuit current (Isc) are obtained in terms of solar irradiance and environment temperature changes. These electrical parameters are obtained through an equivalent circuit model which consists of a photocurrent source, a diode, a series resistor and a shunt resistor. The performance of the solar cell is evaluated under the standard test conditions with an average solar spectrum of air mass (AM) coefficient of 1.5, normalized irradiance of 1 kW/m2 and cell temperature of 25oC. A comparative study of the simulation results with the manufacturer’s data is performed in order to validate the proposed equivalent electrical model. Furthermore, an experimental test bench is built and the obtained experimental results are compared with simulation results and are found to be in good agreement.

Spectral Performance of PV Modules of Different Technologies
Author(s): Fotis Mavromatakis, Frank Vignola

The power produced by a photovoltaic array depends, among other factors, upon the spectral responsivity of the modules and the spectral distribution of the irradiance at the plane of the array. The spectral responsivity is related to the type of solar cell used for the module. The spectral composition of the incident irradiance onto the module depends on the atmospheric conditions, the path length of the solar irradiance through the atmosphere and the spectral characteristics of the ground and diffuse components. Data acquired by the Aerosol Robotic Network are employed to examine the variability of aerosols and water vapor at selected sites. A software spectral model is used to explore the effects of these atmospheric constituents upon a spectral correction factor. The analysis found that the water vapor content of the atmosphere affects the spectral correction factor more than the aerosol optical depth.

Typical Lightning Protection System for Wind Turbines
Author(s): Sokratis Pastromas, Ioannis Naxakis, Eleftheria Pyrgioti

Wind turbines are tall structures with heights exceeding 120m. They are usually installed on high altitudes or isolated areas. In these areas, lightning activity could be high and the installation conditions wind turbines are vulnerable to lightning strikes. Furthermore, these areas do not have ideal soil conditions and the efficiency of wind turbine lightning protection system (LPS) can be affected. Additionally, the LPS shall be compatible with IEC61400-24 as minimum; furthermore, the earthing system shall keep step and touch voltages within the limits defined in IEEE80-2000. Considering the high amounts of wind turbines installed annually and also the limited project time-schedules, it is needed to have a typical LPS for wind turbines that complies with the relevant standards; based on this, wind turbines are armoured against lightning strikes. In case of non-effective LPS, damages can be caused in vital wind turbine components like blades which can lead to downtime and loss of energy production. This paper will present a typical LPS for wind turbines. This system can be applied in every site condition up to a pre-defined level, provided that it respects local legislation and can protect the structure in a reliable way. This proposal does not replace the site specific design of LPS but can be used as basis for further adaption in local conditions.

Designing Grid Protections to Accommodate Distributed Generation
Author(s): Papastefanakis Dimitrios, Orfanoudakis George, Siderakis Kiriakos

The operation of electric power systems has considerably changed after the integration of renewable energy sources in transmission and distribution networks. Considering fault conditions, the fault current can now be supplied from both the centralized power plants and the distributed energy sources. Currently, a “rule of thumb” used by the industry, is that inverter-based DG systems contribute two times their rated current to the amount of the fault current.  This study aims at further investigation of the fault current contribution of PV systems under different fault conditions, with the aim of providing guidelines for setting the thresholds of the grid protections. An example of low-voltage grid section and PV inverter are simulated in MATLAB-Simulink. The results illustrate that in parts of the grid where PV systems are connected, protection levels may have to be reduced to appropriately react to high-impedance phase to ground faults.

Energy Savings in Municipal Road Lighting: The Case of the Municipality of Hersonissos
Author(s): Sofia Yfanti, Nikos Sakkas, Anastasia Nistikaki

In an era governed by economic crisis, deep recession and lack of funds, the perspective of sustainable development drives local government to a more focused and constant effort to adapt to their daily requirements not only in respect to the central state but also towards the growing needs of the local society. Thereupon the vision of the Municipality of Hersonissos was the development, adoption and application of the basic principles of sustainable development. At the same time the Municipality’s rigid vision, oriented by environmental protection, highlighted the need for networking on European level as although cities are different, their problems are often common. Thus on 2011, the Municipality  joined the European Union initiative "Covenant of Mayors» [1] with the common aim of the fight against climate change. This article presents the initiatives taken in this direction in the past five years and their results. It also aims to point out a municipality’s vital role in knowledge and technology diffusion within the local society as sustainable energy development can be deployed not only by the private sector but also by the public.

Phase Change Materials in Photovoltaics: The Assessment of System Performance in the Present Mediterranean Climate Conditions
Author(s): Nikolaos Savvakis, Theocharis Tsoutsos

The operating temperature of photovoltaics is amongst the most important parameters affecting their energy output, efficiency and life cycle. This paper is focused on the design, development and evaluation of a modified photovoltaic system, combining a photovoltaic module coupled with a phase change material. The performance of the proposed, the life system has been assessed in the present Mediterranean climate conditions. Moreover cycle assessment has been conducted to estimate its environmental burden.
The obtained results provide important findings on the benefits of the proposed system and complement the existing gap in the literature in terms of the real field experience of this configuration’s operation.

Estimation of Hosting Electric Vehicles Capacity in the Transformers on the Island of Crete
Author(s): Marianna Dimitropoulou, Antonios Tsikalakis, Antiopi Gigantidou, Emmanuel Thalassinakis, Dionysios Pylarinos

Electric Vehicles (EV) penetration gets higher and higher as the battery technology advances and more sophisticated market schemes are proposed. However, increased number of EVs simultaneously charging from the Grid poses also a challenge for the power system operation.

The limitations of the additional demand caused by the charging of EVs on the island of Crete are presented in this paper. Thus, any necessary investments in equipment or more sophisticated control strategies based on the number of the customers served, can be timely scheduled so that the Autonomous Power System of Crete can adapt to the electricity mobility era.

A Reversible Self-assembling Light-Harvesting System Based on a Diphenylalanine – Porphyrin Motif
Author(s): Athanassios G. Coutsolelos, Anna Mitraki, Teodor Silviu Balaban

Herein we describe a very simple diphenylalanine-dipeptide construct to which a meso-tetraphenylporphyrin (TPP) has been attached and which self-assembles to fibrils, platelets or nanospheres depending on the solvent composition. The fibrils, gave intense excitonic couplets in the electronic circular dichroism (ECD) spectra. By slightly increasing the solvent polarity, these light-harvesting fibers disassemble to spherical structures with silent ECD spectra. A single crystal X-ray structure shows that a combination of hydrogen bonding with π-stacking of the porphyrin rings is responsible for the head-to-head arrangement which explains their excitonic coupling. By unraveling the exact supramolecular architecture our study may help devise artificial antenna systems with an on/off capability.

An Experimental Evaluation of a Flexible Wind Turbine Rotor
Author(s): C. Condaxakis, I. Kougioumtzoglou, N. Papadakis

This paper studies the design concept of a flexible wind turbine blade. The aim of the blade structural design is to optimize the geometrical and inertial property distribution for each cross section of the blade; furthermore, its aim is to effectively control the wind rotor and reduce the aerodynamic loads on the blade.

Due to its design, the blade achieves a deformed geometry that satisfies the optimisation criteria in a wide range of aerodynamic load conditions. The aerodynamically-induced bending moment coupled with the eccentricity between the elastic and aerodynamic centre of each blade cross-section results in a deformation. The deformation increases with the load. The resulting deformation is bending and twisting, and results in the change of the pitch along the blade, depending on the aerodynamic loads. The Solidworks commercial package was used for the structural blade design and the Finite Element analysis of the blade. Small-scale models (320 mm rotor diameter) were designed, manufactured and tested in the Wind Energy Lab’s wind tunnel. The behavior of the miniature rotors was compared to the behavior of equal diameter conventionally-shaped rigid rotors.

Problems, Barriers and Perspectives of RES Development in Poland
Author(s): Waldemar Dolega

This paper describes selected current problems, barriers and perspectives of the development of renewable energy sources (RES) in Poland, while an analysis of the RES in Poland is done. The technical, economic and market potential of renewable energy sources in Poland is defined.  Furthermore, the analysis and assessment of renewable energy sources in Poland in technical, economic and environmental aspects is made. The perspectives of the development of renewable energy sources up to 2020 in the context of the Polish implementation of EU’s “3 x 20%” climate package and the national quantitative target for RES development by 2020 are described. This paper also discusses selected technical, economic and legal problems, as well as certain barriers of the development of renewable energy sources in Poland. The conclusions contain the analysis of the barriers and perspectives of the development of renewable energy sources in Poland in the future.

The Study and Evaluation of the 3phase Induction Motor Controlled by an Inverter to Identify Power Losses and Energy Saving
Author(s): Lamas G.,  Syllignakis J., Karapidakis E.

The control of induction motors through an inverter has many advantages. By changing the frequency and size of the supply voltage, a better efficiency at load conditions can be achieved outside the rated operation. In this study, tests were conducted on a laboratory device for a three-phase induction motor of 1Hp capacity that was driven by an inverter. The induction machine loading was done via a magnetic brakes machine, while all the necessary measuring devices were used in order to record the necessary electrical magnitudes with accuracy and detail. Through specific tests, the components of the detailed electrical equivalent circuit were determined. The vector control technique was used on inverter operation. Through this study, the authors concluded that a drive system can be driven on different frequency levels without a great loss of torque. Furthermore, energy can be saved by operating in lower frequencies for smaller loading, having an equally satisfactory level of performance. It is also worth to mention the friendliness of the inverter to control the motor speed, the smooth (soft) starting and the high degree of efficiency in all frequency ranges.

Chapter IV. Islands and Small Scale Power Systems

The Effect of Pumped Hydro Storage Units Installation on the Operation of the Autonomous Cretan Power System
Author(s): Y. A. Katsigiannis, E. S. Karapidakis

Pumped hydro storage (PHS) units represent the most mature technology for large scale energy storage. The ideal criteria for a PHS unit installation include: (a) the existence of an autonomous power system with local power stations, (b) the current high electricity production cost, (c) the high potential of renewable energy sources (mainly wind), and (d) the non-flat terrain morphology. Cretan power system represents an ideal case for the installation of PHS units, as it fulfils all of the above criteria. This paper shows the effect of the installation of a planned PHS unit in Malia, Heraklion, Crete. The calculations are based on real data provided by the Cretan power system operator, whereas the results show the effect of PHS units operation on the energy mix, as well as the economic viability of the project which is combined with significant environmental benefits.

Laboratory Tests, Modeling and the Study of a Small Doubly-Fed Induction Generator (DFIG) in Autonomous and Grid-Connected Scenarios
Author(s): Syllignakis J., Sergis A., Orfanoudakis G., Karapidakis E., Kanellos F.

Doubly-Fed Induction Generators (DFIGs) are widely used in wind power production nowadays. Their key advantages are the low power rating of the converter used for connecting to the network, and the ability to produce and feed the network with reactive power. This paper investigates the capabilities of DFIGs in low-cost wind turbine systems. Namely, it examines the performance and constraints of using general-purpose motor drives instead of back-to-back connected inverters in such systems. A small laboratory DFIG machine is studied in this context, assuming both autonomous and grid-connected scenarios. The analytical model of the machine is initially calculated, and the system is simulated in MATLAB-Simulink, using a uni-directional power converter. Simulation results are presented, accompanied by an analysis of the control technique of the power converter. Experimental results from a laboratory setup based on a low-cost commercial inverter, normally used for controlling a 1kW 3-phase induction motor, are also presented. Finally, the system efficiency - optimal operation points and limitations on the turbine range of operation are discussed.

A Cost-effective Standalone Multisensory System for Energy Consumption and CO2 Emissions Control in Smart-Homes via Internet and Mobile Devices, Using a Network of Arduino Microcontrollers
Author(s): Emmanouil Skounakis, Stavroula Moutsoula, Dimitrios Makris, Nikolaos Bolanakis, Evangelos Kandounakis, Antonios Konstantaras, Emmanuel Karapidakis, Emmanuel Maravelakis

Because of the global climate change, there is increasing need to control energy consumption and the rate of CO2 emissions into the atmosphere.
This research presents a novel cost-effective multisensory system using a smart network of four Arduino microcontrollers to collect information from multiple sensors measuring temperature, light, humidity, dust, tilt (for earthquakes) and gas in order to control energy consumption of several household devices, using new technologies such as the Internet and smartphones.
A number of electromechanical components including a colour TFT-LCD display, a DC motor, a step servomotor, boards, photoresistors, switches & LEDs, etc. are connected, to control the whole system.
The ability to monitor energy consumption in real time is designed to easily inform the users regarding gas release that contributes to global warming as well as to allow consumers to change their attitudes towards energy usage in the near future.

Differential Protection Schemes and Techniques for Power Transformers – Educational Aspects
Author(s): Nikolina Arapoglou, Kiriakos Siderakis

A simulation model for the study of the differential protection in the case of power transformers has been developed. In this direction MATLAB Simulink has been employed and the operation during fault has been investigated, in the case of a two phase fault for different windings connections. The simulation results reveal the influence of the delta winding connection, which limits the asymmetrical loading experienced.

Automatic Speed Controller of a DC Motor Using Arduino, for Laboratory Applications
Author(s): Syllignakis J., Panagiotakopoulos P., Karapidakis E.

This work presents a simple speed control application for a DC motor in laboratory use. The purpose of this application is to maintain the desired speed on a generator operating on the same axis to the motor.    
Two small laboratory DC machines of 1kw and 300W nominal power have been used for testing the controller. Close loop control has been applied by using appropriate speed encoder. The controller functions as a DC chopper and PWM signal is produced by an Arduino UNO controller. The nominal input voltage was 200Volt, so igbt switching devices were used.  
There are over voltage and over current protections and, moreover, a mode without speed metering is available (open loop control scheme).
A detailed analysis is provided on the equipment and the techniques that have been used for the control of the power electronic device. The scope of this work was to plan and test the controller, in terms of energy efficiency and economical operation.

This study presents the critical results of the tests focusing on the best operational point and discusses the related conclusions. The controller’s operation was efficient in both low and high speeds that were tested.

Energy Management System for Water Distribution Systems: Application to Crete
Author(s): A. Pouliezos, F. D. Kanellos, S. Papaefthimiou, Y. A. Katsigiannis

Water distribution systems represent one of the largest infrastructure components of an industrial country. In such systems, significant part of their operational cost is related to energy costs for pumping. As a result, significant cost and energy savings can be achieved with the optimization of pump operation, as well as with the exploitation of renewable energy technologies in order to reduce electricity consumption from the grid. This paper presents measures in both ways that are applied to the water distribution system of Western Crete. The results show that there exists a large potential for cost savings that is combined with a more environmental friendly operation of the whole system.

Composite Outdoor High Voltage Insulators in Crete - 37 Years of Experience
Author(s): Kiriakos Siderakis, Dionysios Pylarinos, Ioannis Pellas, Emmanuel Thalassinakis, Nikolaos Mavrikakis

Power transmission reliability and system integrity are essential requirements in high voltage transmission and distribution networks. Outdoor insulation has a critical role, since the majority of these installations incorporate open air systems and there are many factors able to trigger deterioration mechanisms, which may finally conclude to a system failure. It is important to notice, that although the initial investment for the insulation systems is low in comparison to other types of equipment, an insulation failure may result in considerable costs for the utility. A strategy that is followed by more and more utilities nowadays is the incorporation of composite insulators, in transmission and distribution systems, where the influence of pollution is considerable. In Crete, this action started 37 years ago, experienced intense action; 15 years ago and today the majority of outdoor insulators are composite. This large scale application is presented in this paper, especially with reference to the problems experienced and the testing and maintenance procedures applied.

The Region of Crete: An Integrated and Sustainable Energy Planning
Author(s): Virginia Manasaki, Maria Apostolaki, Michael Golovanis

The island of Crete is a special case concerning energy due to its geopolitical position, size and energy self-efficiency, the sharp fluctuation in energy demand, but mostly due to the absence of electrical interconnection with the mainland. An integrated Energy Planning is therefore essential for providing a key tool for implementing sustainable regional development. The Region of Crete is the first Region in Greece that has developed an integrated Regional Energy Planning, which examines the current energy needs, considers and evaluates all the possible sources of electricity production and their participation in the energy mix up to 2050. Following the National and European energy policies, guidelines and goals, and taking advantage of the large capacity of renewable energy, the Region of Crete through its Energy Planning aims to maximize renewable energy production and promote energy efficiency for reducing dependence on fossil fuels and greenhouse gas emissions. Through collaboration with research and academic institutions and European partners, the Region of Crete develops and implements innovative actions and programs for achieving the goals set by the European Directive “20-20-20” for Energy and Environment.