The purpose of this bachelor thesis was to investigate the PLC systems used in ABBs breaker factory in Ludvika and to create a system specification suitable to be used in the procurement of a back-up solution for this workshop. This work involved information gathering from different sources, such as archives, physical installations and interviews of maintenance personnel and operators. The results included the requested system specification (in Swedish) including suggestions for pilot test installations and evaluations. The work also resulted in an extensive listing of all PLC systems with placement, typedesignations, expansion modules and other pertinent information. This information ismade available as a macro enabled multipage Microsoft Excel document. A summary and suggestions for follow up work is also included.

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / Magnetic tape is the primary medium used to capture and store unprocessed data from remote sensing satellites. Recent advances in digital cassette recording technology have resulted in the introduction of a range of data recorders which are equally at home working alongside conventional recorders or as part of more advanced data capture strategies. This paper shows how users are taking advantage of the convenience, economy and efficiency of this new generation of cassette-based equipment in a range of practical applications.

Genetic algorithm has been widely used in different areas of optimization problems. Ithas been combined with renewable energy domain, photovoltaic system, in this thesis.To participate and win the solar boat race, a control program is needed and C++ hasbeen chosen for programming. To implement the program, the mathematic model hasbeen built. Besides, the approaches to calculate the boundaries related to conditionhave been explained. Afterward, the processing of the prediction and real time controlfunction are offered. The program has been simulated and the results proved thatgenetic algorithm is helpful to get the good results but it does not improve the resultstoo much since the particularity of the solar driven boat project such as the limitationof energy production

The increasing demand for electricity over the last few decades has not been followed by adequate growth in electric infrastructure. As a result, the reliability and safety of the electric grids are facing tremendously growing pressure. Large blackouts in the recent past indicate that sustaining system reliability and integrity turns out to be more and more difficult due to reduced transmission capacity margins and increased stress on the system. Due to the heavy loading conditions that occur when the system is under stress, the protection systems are susceptible to mis-operation. It is under such severe situations that the network cannot afford to lose its critical elements like the main generation units and transmission corridors. In addition to the slow but steady variations in the network structure over a long term, the grid also experiences drastic changes during the occurrence of a disturbance. One of the main reasons why protection relays mis-operate is due to the inability of the relays to adjust to the evolving network scenario. Such failures greatly compound the severity of the disturbance, while diminishing network integrity leading to catastrophic system-wide outages. With the advancement of Wide Area Measurement Systems (WAMS), it is now possible to redesign network protection schemes to make them more adaptive and thus improve the security of the system. Often flagged for exacerbating the events leading to a blackout, the back-up distance protection relay scheme for transmission line protection and the loss-of-field relay scheme for generator unit protection can be greatly improved from an adaptability-oriented redesign. Protection schemes in general would benefit from a power re-distribution technique that helps predict generator outputs immediately after the occurrence of a contingency. / Ph. D.

A market review on Hybrid Inverters with Back-Up (HIBU) is presented, selecting products from eleven global inverter manufacturers. A systemic review of all the productsis performed, along with a general comparison of their main features. Trends in power ranges, battery voltages, back-up connection scheme and switching times are then highlighted and other more peculiar characteristics are assessed. A focus on potential applications in the Swedish market is put, considering an average Swedish household consumption profile. Ten from the available software for modeling photovoltaics applications are then reviewed finding PVsyst, Homer and SAM the most suitable tools for computing systems with HIBU. Finally, a case study is simulated on PVsyst showing the influence of the battery size on the percentage of covered load for different values of grid availability. The influence of different locations and different battery discharging strategies is also assessed, critically evaluating the reliability of the model used on PVsyst and stating the main shortcomings.

This document explores Hidden Failures in protection systems, which have been identified as key contributors in the degradation of Power System wide-area disturbances. The Hidden Failure Modes in which the protection systems may fail to operate correctly and their consequences are identified in a theoretical approach. This theoretical side has its practical counterpart since a number of Hidden Failure Modes are found in real wide-area disturbances. The original definition of Hidden Failure, which is a failure that remains undetected and is uncovered by another system event, is included as well as developments on Hidden Failure sequence of events and a methodology for Hidden Failure identification. This method is based on Protection Element Functionality Defects (PEFD), which are applicable to all the elements included in the protective chain. PEFD are classified in two main groups. Primary and Back-up protection schemes applied for Generators, Buses, Transformers and Transmission Lines are analyzed. The abnormal Power System conditions that each Power System element may have are enumerated. A catalogue of the relays or relay systems, in charge of detecting and stopping the continuous presence of the abnormal conditions is developed. Relay families organize this catalogue. The relaying schemes for five Special Protection Systems are described. Thirty-three Hidden Failures Modes are included based on the relaying implementation for Primary protection, Back-up protection and Special Protection Systems. These Hidden Failures Modes are based on PEFD-A. Hidden Failures related to PEFD-B are included in a general fashion. Wide-area disturbances based on NERC reports are analyzed and Hidden Failures are identified employing the developed methodology. The mechanisms in the disturbances are summarized and are applicable to Primary protection, Back-up protection and Special Protection Systems. Regions of Vulnerability and Areas of Consequence definitions are included and are identified for a Power System wide-area disturbance. For some protection schemes the term Condition of Vulnerability was developed. Regions of Vulnerability and Areas of Consequence will bring the initial steps towards the problem solution. Further research directions are oriented towards the development of a computer-based tool to track the regions of vulnerability in real time. / Master of Science

En tant qu'utilisateurs d'ordinateurs, nous générons des données en quantité de plus en plus abondante. Leur importance dans notre vie quotidienne est telle qu'une méthode de sauvegarde s'avère nécessaire. La création de sauvegardes locales est une approche commune, mais insuffisante en cas de vol ou de destruction. Dans cette thèse, nous concevons un système de sauvegarde distribué qui permet de restaurer l'état d'un système de fichiers de manière simple, grâce à la constitution d'instantanés. Nous stockons ces instantanés sur les passerelles résidentielles et utilisons un tracker centralisé pour les coordonner. Nous présentons le concept de fichiers d'indexes qui permet la correspondance entre l'état complet d'un système de fichiers et une structure de donnée. Nous divisons notre système en swarms, rendant l'accès aux données, et son suivi, simple. Les fichiers à sauvegarder sont traités différemment suivant leurs tailles, afin d'améliorer la performance globale du système, et de réduire les ressources nécessaires. Tous les fichiers, ainsi que leurs méta-données, sont chiffrés avant d'être téléchargés afin de garantir leur confidentialité. De plus, nous utilisons les techniques de l'état de l'art afin de rendre le tracker résistant aux pannes, et de pouvoir le remplacer s'il quitte le système. La charge sur le tracker ne dépend que du nombre de participants, et donc pas de la quantité de données stockée. Nous évaluons le système sur base de traces provenant de passerelles résidentielles réelles, avec lesquelles nous démontrons un faible impact global sur les ressources. En leur adjoignant des simulations, nous prouvons la faisabilité de notre service. / As computer users, we create increasing amounts of data, such as digital documents, pictures, and videos. Because these data have high value in our daily life the need for back-ups arises. The creation of local back-ups, e.g. on external hard drives, is a common approach, but is insufficient in the event of natural disasters or theft. In this thesis, we provide a proof of concept for a distributed back-up system that induces only low overhead, and respects user needs to easily recover a state of a file system in a snapshot-based manner. We store distributed back-ups on residential gateways and use a central tracker as coordinator. We introduce index files in order to map the full state of a file system to a single data structure. We divide the system into swarms of flexible size so that accessing data and monitoring is easy. Files are handled differently depending of their size in order to increase the system performance and reduce resource requirements. All files and their metadata are encrypted before being uploaded, so that data confidentiality is ensured. We use state-of-the-art technologies in order to design a tracker that is scalable, fault-tolerant, and is replaceable in case it entirely leaves the system. The load of the tracker only depends on the number of participants, not on the amount of data stored in the network. The system allows configuring a time span within which a user needs to recover his data in case of local data loss. We analyze this approach by using real world connectivity traces of residential gateways and show that it results in low resource demands. Together with simulations on these traces, we underline the feasibility of our service.

M. Tech. (Electronic Engineering, Faculty of Engineering and Technology), Vaal University of Technology| / The lack of electricity in off-grid rural communities in South Africa (SA) and Africa as well as the budget constraints on these communities restrict these communities from connecting to any online resources (internet and e-books) for educational purposes, thus creating a major contributor to the global digital divide. Renewable energy sources such as solar energy, wind energy and biomass were presented as potential alternatives to grid-connected electricity for remote rural locations. Solar energy was identified as the amply available alternative energy resource in SA. Solar radiation was converted by photovoltaic technology to electricity. National power grid isolation (off-grid) was achieved by using a stand-alone photovoltaic system. Photovoltaic technology classification, material categorisation and system sizing for an e-learning centre was presented. Practical set-ups were utilised to determine the most cost-effective equipment mix of power utilization, power management/storage and ICT equipment to build a pilot e-learning centre. It was established that one photovoltaic panel can be employed to fully recharge a battery of a pilot e-learning centre with an operational period of 7 hours using the available sunlight hours. Owing to the susceptibility of the Vaal Triangle region to thunderstorms causing overcast conditions for days, a ratio of back-up battery capacity (Ah) to number of days (seven hours per day) without sunlight was determined. An algorithm was also derived for sizing the pilot e-learning centre for full scale implementation. Future research recommendations based on this study for a reduced system costs of an off-grid e-learning for rural communities powered by a renewable energy resource were presented. This will increase access to basic education in SA and reduce the global digital divide.

The growing demand for hydrocarbon fluids, and the future expectation of insufficient onshore reserves, is driving the exploration and development of off-shore oil and gas fields. A significantly increasing number of the new fields are situated in deep water, placing significant constraints on the application of conventional platform (sea surface) systems. This has, by necessity, generated the rapid growth of sub-sea processing technology. / An integral part of a novel sub-sea natural gas dehydration project is the need to design and develop a communications, monitor and control system that is extremely reliable within a harsh marine environment. The off shore gas gathering and processing facility will be unmanned, therefore the entire ongoing operation of the sub-sea facility, and any sea surface equipment, will be dependent on the proper functioning of the communication system. System redundancy and low power consumption are also important issues. / The continuous bi-directional transmission of information between the field and shore-based control centres, together with the complexity of any maintenance / repair missions requires an extremely highly reliable system. The prospect of false alarms must be maintained at an absolute minimum. / Within this thesis the history and development of ocean based communications up to current state-of-the art technology is reviewed. Based on the unique and demanding requirements of the sub-sea gas processing facility, detailed recommendations are made for both a primary and back-up communication systems that meet the given criteria of being robust and having very low power requirements.