Sag effects on protection system in distributed generation grids

Distributed Generators (DGs) are sensible to voltage sags, so the protection devices must trip fast to disconnect the faulted part of the grid. The DG disconnection will not be desirable in the near future with a large penetration, so it will be necessary to lay down new requirements that should be based on avoiding unnecessary disconnections. Therefore, to prevent unnecessary tripping when inverter-based DGs are connected to the Medium Voltage (MV) grid, reliable and effective protection strategies need to be developed, considering the limited short-circuit current contribution of DG. The initial goal of this study is to employ different possible control strategies for a grid-connected inverter according to the Spanish grid code and to analyze the output voltage behavior during symmetrical and unsymmetrical voltage sags. The analytical development of the proposed strategies shows the impacts of the sag on currents, voltages, active and reactive powers. Another goal of this research is to propose a protection strategy based on Artificial Intelligence for a radial or ring distribution system with high DG penetration. The protection strategy is based on three different algorithms to develop a more secure, redundant, and reliable protection system to ensure supply continuity during disturbances in ring and radial grids without compromising system stability. In order to classify, locate and distinguish between permanent or transient faults, new protection algorithms based on artificial intelligence are proposed in this research, allowing network availability improvement disconnecting only the faulted part of the system. This research introduces the innovative use of directional relay based on a communication system and Artificial Neural Network (ANN). The first algorithm, Centralize algorithm (CE), collects the data from all the PDs in the grid in the centralized controller. This algorithm detects the power flow direction and calculates the positive-sequence current of all the PDs in the grid. Significant benefits of this system are that it consolidates the entire systems security into a single device, which can facilitate system security control. However, the CE will not pinpoint the exact location of the fault if there is any loss of information due to poor communication. Therefore, the systems redundancy can be improved by cooperating with a second algorithm, the Zone algorithm (ZO). ZO algorithm is based on zone control using peer-to-peer connectivity in the same line. The faulty line in that zone may be identified by combining the two PDs data on the same line. The most relevant advantage of this algorithm is its flexibility to adapt to any grid modification or disturbance, even if they are just temporary, unlike the CE, which is fixed to the existing grid configuration. The third protection algorithm, Local algorithm (LO), has been proposed without depending on the communication between the PDs; then, the protection system can work properly in case of a total loss of communication. Each PD should be able to detect if the fault is located in the protected line or another line by using only the local information of the PD. According to the type of fault and based on local measurements at each PD of abc voltages and currents, different algorithms will be applied depending on the calculation of the sequence components. The main advantage of this algorithm is the separate decision of each PD, and avoiding communication problems. In case of radial grids, both mechanical breakers and Solid State Relays (SSRs) are used to verify the protection strategies, and in the case of ring grids, mechanical breakers are used, due to the limitations in required voltage difference of SSR. The proposed protection algorithms are compared with conventional protections (Overcurrent and Differential) protections to validate the contribution of the proposed algorithms, especially in reconfigurable smart grids.El objetivo inicial de este estudio es emplear diferentes estrategias de control posibles para un inversor conectado a la red segun el código de red español y analizar el comportamiento de la tensión de salida durante caídas de tensión simétricas y asimétricas. El desarrollo analítico de las estrategias propuestas muestra los impactos de los huecos de tensión en las corrientes, tensiones, potencias activas y reactivas. Otro objetivo de esta investigación es proponer una estrategia de protecclón basada en lnteligencia Artificial para una red del Sistema de Distribución, radial o en anillo, con elevada penetración de Generación Distribuida. La estrategia de protección se basa en tres algoritmos diferentes para desarrollar un sistema de protección más seguro, redundante, y fiable, que asegure la continuidad de suministro durante perturbaciones en redes radiales o en anillo sin comprometer la estabilidad del sistema. Para clasificar, localizar y distinguir entre faltas permanentes o transitorias, se proponen en este trabajo nuevos algoritmos de protección basados en inteligencia artificial, permitiendo la mejora de la disponibilidad de la red, al desconectar sólo la parte del sistema en falta. Esta investigación introduce la innovación del uso del rele direccional basado en un sistema de comunicación y Redes Neuronales Artificiales (ANN). El primer algoritmo, Algoritmo Central (CE), recibe los datos de todos los PDs de la red en un control central. Este algoritmo detecta la dirección de flujo de cargas y calcula la corriente de secuencia positiva de todos los PDs de la red. El entrenamiento de ANNs incluye variaciones en la corriente de cortocircuito y la dirección del flujo de potencia en cada PD. Los beneficios mas significativos de este sistema son que concentra la seguridad total del sistema en un único dispositivo, lo que puede facilitar el control de la seguridad del sistema. Sin embargo, el CE no determinara con precisión la localización exacta de la falta si hay alguna perdida de información debida a una pobre comunicación. Por lo tanto, la redundancia del sistema se puede mejorar cooperando con un segundo algoritmo, el algoritmo de Zona (ZO). El algoritmo ZO se basa en un control de zona usando la conectividad entre dispositivos de protección de una misma línea. La línea en falta en esa zona puede identificarse combinando los datos de los dos PDs de la misma línea.. La ventaja mas relevante de este algoritmo es su flexibilidad para adaptarse a cualquier modificación de la red o perturbación, incluso si sólo son temporales, a diferencia del CE, que se ha adaptado para la configuración de la red existente. El tercer algoritmo de protección, algoritmo Local (LO), ha sido propuesto sin dependencia de la comunicación entre PDs; por lo tanto, el sistema de protección puede operar correctamente en el caso de una pérdida total de comunicación. Cada PD debe poder detectar si la falta esta ubicada en la línea protegida o en otra línea, utilizando sóIo la información local del PD. Según el tipo de falta, y en base a medidas locales en cada PD, de tensiones y corrientes abc, se aplican diferentes algoritmos en función del cálculo de las componentes simétricas. La principal ventaja de este algoritmo es la actuación por separado de cada PD, evitando los problemas de comunicación. En el caso de las redes radiales, se utilizan tanto interruptores mecánicos como réles de estado sóIido (SSR) para verificar las estrategias de protección, y en el caso de las redes en anillo se utilizan interruptores mecánicos, debido a las limitaciones de tensión para su conexión. Los algoritmos de protección propuestos se comparan con protecciones convencionales (Sobrecorriente y Diferencial) para validar la contribución de los algoritmos propuestos, especialmente en redes inteligentes reconfigurables.Postprint (published version

NEW INVERSE-HEUSLER MATERIALS WITH POTENTIAL SPINTRONICS APPLICATIONS

Spintronics or spin-electronics attempt to utilize the electronic spin degree of freedom to make advanced materials and devices for the future. Heusler materials are considered very promising for spintronics applications as many highly spin-polarized materials potentially exist in this family. To accelerate materials discovery and development, The Materials Genome Initiative (https://www.mgi.gov/) was undertaken in 2011 to promote theory-driven search of new materials. In this thesis work, we outline our effort to develop several new materials that are predicted to be 100% spin-polarized (half-metallic) and thermodynamically stable by theory. In particular, two Mn-based Heusler families were investigated: Mn2CoZ (Z= Ga, Sb, Ge) and Mn2FeZ (Z=Si,Ge), where the latter is potentially a new Heusler family. These materials were synthesized using the arc-melting technique and their crystal structure was investigated using the X-ray diffraction (XRD) method before and after appropriate annealing of the samples. Preliminary magnetometry measurements are also reported. We first developed a heat-treatment procedure that could be applied to all the Mn-based compounds mentioned above. Mn2CoGa was successfully stabilized in the cubic inverse-Heusler phase with a=5.869 Å and magnetic moment of 2.007 /fu. This is in good agreement with prior literature reports [1]. However, cubic phases of Mn2CoSb and Mn2CoGe could not be stabilized within the annealing temperature range that is accessible in our lab. We successfully synthesized a cubic Mn2FeSi phase using an annealing procedure similar to Mn2CoGa. The measured cubic lattice parameter of Mn2FeSi was 5.682 Å. This is the first experimental report of this material to the best of our knowledge. Detailed analysis of relative intensities of different X-ray peaks revealed that the structure is most likely in an inverse Heusler phase, in agreement with theory. However, a substantial atomic-level disorder was also uncovered from XRD analysis that requires further investigation to understand its effect on its magnetism and half-metallicity. Mn2FeGe showed the existence of non-cubic phases that substantially weakened at high annealing temperatures

Analisis Pendapatan Usaha Kerajinan Tempurung Kelapa di Desa Bakka – Bakka Kecamatan Wonomulyo Kabupaten Polewali Mandar

Penelitian ini dilaksanakan pada Usaha Kerajinan Tempurung Kelapa Di Desa Bakka-Baka, Kecamatan Wonomulyo, Kabupaten Polewali Mandar yang berlangsung selama 3 bulan yaitu bulan April sampai dengan bulan Juni 2016. Penelitian ini bertujuan untuk mengetahui berapa besar pendapatan yang diterima serta untuk mengetahui nilai R/C Ratio yang diperoleh dari USAha kerajinan tempurung kelapa. Penentuan lokasi penelitian ini menggunakan metode purposive yaitu tehnik penentuan sampel dengan pertimbangan tertentu. metode yang digunakan adalah metode observasi, wawancara (dengan Quesioner yang telah disiapkan), dan dokumentasi. Dilanjutkan dengan pengolahan data dengan menggunakan metode analisis kuantitatif untuk menentukan berapa besar pendapatan dan nilai R/C Ratio yang diperoleh dari USAha kerajinan tempurung kelapa yang dijalankan. Hasil penelitian menunjukan bahwa rata-rata pendapatan perbulan yang diperoleh dari USAha kerajinan tempurung kelapa adalah sebesar Rp. 347.333,- dari total penerimaan sebesar Rp 1.320.00,- dan total biaya sebesar Rp. 972.667,- sedangkan nilai R/C Ratio yang diperoleh sebesar Rp. 1,36 artinya setiap penambahan biaya Rp. 1,- maka akan memperoleh penerimaan sebesar Rp. 1,36,- sehingga USAha kerajinan tempurung kelapa dikatakan layak (untung) sehingga dapat dijalankan dan dikembangkan

Development of a virtual reality milling machine for knowledge learning and skill training

Current methods of training personnel on high cost machine tools involve the use of both classroom and hands on practical training. The practical training required the operation of costly equipment and the trainee has to be under close personnel supervision. The main aim of this project is to reduce the amount of practical training and its inherent cost, time, danger, personal injury risk and material requirements by utilising a virtual reality technology. In this study, an investigation into the use of Virtual reality for training operators and students to use the Milling Machine was carried out. The investigation has been divided into two sections: first the development of Milling Machine in the 3D virtual environment, where the real machine was re-constructed in the virtual space. This has been carried out by creating objects and assembling them together. The complete Milling machine was then properly modelled and rendered so it could be viewed from all viewpoints. The second section was to add motion to the virtual world. The machine was made of functions as for the real machine. This was achieved by attaching Superscape Control Language (SCL) to the objects. The developed Milling machine allows the users to choose the material, speed and feed rate. Upon activation, the virtual machine will be simulated to carry out the machining process and instantaneous data on the machined part can be generated. The results were satisfactory, the Milling Machine was modelled successfully and the machine was able to perform according to task set. Using the developed Virtual Model, the ability for training students and operators to use the Milling Machine has been achieved

Structural health monitoring of Attridge Drive overpass

Vibration-based damage detection (VBDD) comprises a family of non-destructive testing methods in which changes to dynamic characteristics are used to track the condition of a structure. Although VBDD methods have been successfully applied to various mechanical systems and to simple beam-like structures, significant challenges remain in extending this technology to complex, spatially distributed structures such as bridges. In the present study, numerical simulations using a calibrated finite element model were used to investigate the use of VBDD methods to detect small-scale damage on a two-span, integral abutment overpass structure located in Saskatoon, Saskatchewan. The small scale damage was defined in this study as the removal of a concrete element from the top surface of the bridge deck, resembling the spalled clear cover of concrete deck of the overpass. Five different VBDD techniques were evaluated, including the Change in Mode Shape, Change in Flexibility, Change in Mode Shape Curvature, Change in Uniform Flexibility Curvature and Damage index methods. In addition, the influence of the size of damage, the orientation of damage geometry, sensor spacing (3 m, 5 m and 7.5 m), the approach used for mode shape normalization, and uncertainty in the measured mode shapes was investigated. It was found that localized damage could be reliably detected and located if the sensors were located within 3 m of the damage (the distance between adjacent girders) and if uncertainty in the mode shapes was attenuated through the use of a sufficient number of repeated trials. Furthermore, studies using a limited sensor installation that could be achieved without interrupting the flow of traffic indicated that small scale damage could be detected and potentially located using sensors that are placed well away from the damaged area, provided uncertainty in mode shape was attenuated

Creativity-enhancement in media organizations: A study of the perception of journalists and media managers in Saudi Arabia.

This dissertation examines creativity enhancement in the context of media organizations in Saudi Arabia. In the empirical component of this study, managers and employees in seven Saudi media organizations were surveyed for their perceptions of creative climates in media organizations. The Situational Outlook Questionnaire (SOQ) was used as an instrument to collect the study data. The questionnaire explores nine dimensions of the organizational creative climate. A total of 209 participants (43 managers and 166 employees) responded to the SOQ by answering 53 questions about their assessments of the organizational climate. They also answered general demographic questions, and three open-ended narrative questions. Research questions focus on describing how managers and employees in Saudi organizations perceive the climate in their organizations. In addition, the research questions stress the effect of demographic factors on the participants' perception, and the differences between managers and employees. Statistical tests show that gender is a significant factor in defining differences between managers and employees in perceiving creative climate, especially regarding challenge, trust, and freedom dimension of the SOQ. This finding reflects a unique situation for gender in Saudi media organizations. When comparing their perceptions to those reported in other international organizations, managers and employees in Saudi media organizations report significantly lower levels of challenge, risk-taking, idea support, freedom, playfulness/humor, and trust/openness on the SOQ, and significantly higher levels of conflict. Employees, and not managers, reported significantly low levels of debate. Differences between males and females, as well as managers and employees on these dimensions are explained in terms of the situation of Saudi media organizations. The study conducts an extensive literature review of factors that lead to creative climates in organizations in order to introduce a model of making of a creative organization. This model includes three major factors: (a) the management system of the organization, (b) daily work activities, and (c) organizational life. These factors are connected to a specific degree of creativity needed for an organization, based on the special nature of the organization. An explanation of the model's strengths and weaknesses is offered

Safety performance of electrical utility in Tenaga Nasional Berhad, Distribution Division Melaka

This research is a case study research, focused on the Distribution Division in Tenaga Nasional Berhad (Melaka). There are only two technical units under the Distribution Division which comprised of the Operation and Maintenance Unit and Construction and Planning Unit. A total of 131 respondents from the technical staff of TNB Melaka were randomly selected to be involved in the survey. The reason these units were selected is because, they were the frontier who directly involve with electrical hazards between the ranges of 230 volt to 33,000 volt. The research framework is management commitment, safety training, safety rules and procedure, safety compliance, and safety participation towards safety performance. Statistical Package for Social Science (SPSS) version 19 is used to generate and analyzed data collected. In summary, from the findings, there is positive correlation on the relationship between management commitment, safety training, rules and procedure, safety compliance safety participation, and safety performance. The findings also proven that the independent variables, management commitment, safety training and safety rules and procedure did not influence safety performance. However safety compliance and safety participation do influence safety performance at TNB Melaka Distribution Division. The implication of this study is very beneficial to TNB Melaka Distribution Division in improving their safety performance level in the workplace. By improving their safety performance in their workplace, TNB Melaka Distribution Division can reduce the risk, the injury and the cost of accident which will lead TNB Melaka Distribution Division to the growth of profits

Ontology-based information extraction from learning management systems

In this work we present a system for information extraction from Learning Management Systems. This system is ontology-based. It retrieves information according to the structure of the ontology to populate the ontology. We graphically present statistics about the ontology data. These statistics present latent knowledge which is difficult to see in the traditional Learning Management System. To answer questions about the ontology, a question answering system was developed using Natural Language Processing in the conversion of the natural language question into an ontology query language; Sumário: Extração de Informação de Sistemas de Gestão para Educação Usando Ontologias Neste dissertação apresentamos um sistema de extracção de informação de sistemas de gestão para educação (Learning Management Systems). Este sistema é baseado em ontologias e extrai informação de acordo com a estrutura da ontologia para a popular. Também permite apresentar graficamente algumas estatísticas sobre os dados da ontologia. Estas estatísticas revelam o conhecimento latente que é difícil de ver num sistema tradicional de gestão para a educação. Para poder responder a perguntas sobre os dados da ontologia, um sistema de resposta automática a perguntas em língua natural foi desenvolvido usando Processamento de Língua Natural para converter as perguntas para linguagem de interrogação de ontologias

Attitudes of Students at Sultan Qaboos University towards the Nursing Profession

Objectives: The aim of this study was to explore the attitudes of Sultan Qaboos University (SQU) students towards the nursing profession. Methods: A sample of 377 students (male = 130; female = 247) were selected from different colleges of SQU, including the College of Nursing. A questionnaire was constructed and validated to assess the attitudes of SQU students towards the nursing profession. Results: Findings revealed that both male and female students in all academic years and colleges had positive attitudes toward the nursing profession. The findings also revealed that gender and academic year created no significant differences (P <0.05) among the study participants, but that the students’ college affiliation did have a significant effect on their attitudes. In particular, nursing students had more positive attitudes than students of other colleges. Conclusion: Findings indicated that the attitudes of SQU students towards the nursing profession were positive, especially those of the nursing students. This means that serious efforts should be made to continue to promote the nursing profession and so ensure that it remains positively regarded by all concerned