The thesis deals with the use of cable sections in the overhead transmission route of the 400 kV transmission system in the Czech Republic, with the design of the arrangement of the cable route and with the solution of the crossover of the cable line with other networks of the technical infrastructure or natural obstacles. The thesis shows what the construction of a 400 kV cable line in the overhead transmission route - which has not been implemented in the Czech Republic as of yet - entails in practice. The first, general part deals with the electrical properties of both the cable lines and the combined overhead transmission lines with intermediate cable sections, and this sets out limitations on the maximum possible length of the cable sections. The following chapters provide an analysis of the magnetic field of the cable line, its impact on the surrounding environment and the possibilities of its shielding. On the basis of this knowledge optimization of the designed cable route arrangement is carried out in order to make the route comply with hygiene limits. The next part uses selected locations on a real route of overhead 400 kV transmission line to show what the construction of cable sections inserted into the route of overhead 400 kV line would involve. The design includes a professional estimate of the time and financial demands of the construction.

This thesis considers how an assessment method for reinvestments in the distribution grid can be designed and implemented. The assessment method was created to give long-term estimations of the amount overhead lines that could be substituted with underground cables and how to prioritize between different areas. The regulation of power grid companies was reviewed to highlight important factors for profitable reinvestments. The assessment method was implemented for overhead lines in Ellevio´s distribution grid using the database program FME and validated against real reinvestment decisions in a case study area called Sinntorp. The resulting reinvestment proposals mainly consist of replacing older grid sections and sections where expensive maintenance is planned in the future. The script show similar results as real reinvestment decisions but small differences are noticed related to the script’s hard focus on older grid sections. The script has potential to be used on Ellevio´s entire overhead line network but this requires work to complete essential data. Further validation on new areas are also desired to see if results are reasonable and if the script can be developed to consider more reinvestment factors.

This thesis describes an investigation into the influences of arcing and conductor deflection due to magnetic forces on the accuracy of fault locator algorithms in electrical distribution networks. The work also explores the possibilities of using the properties of an arc to identify two specific types of faults that may occur on an overhead distribution line. A new technique using the convolution operator is introduced for deriving differential equation algorithms. The first algorithm was derived by estimating the voltage as an array of impulse functions while the second algorithm was derived using a piecewise linear voltage signal. These algorithms were tested on a simulated single-phase circuit using a PI-model line. It was shown that the second algorithm gave identical results as the existing dynamic integration operator type algorithm. The first algorithm used a transformation to a three-phase circuit that did not require any matrix calculations as an equivalent sequence component circuit is utilised for a single-phase to ground fault. A simulated arc was used to test the influence of the non-linearity of an arc on the accuracy of this algorithm. The simulations showed that the variation in the resistance due to arcing causes large oscillations of the algorithm output and a 40th order mean filter was used to increase the accuracy and stability of the algorithm. The same tests were performed on a previously developed fault locator algorithm that includes a square-wave power frequency proximation of the fault arc. This algorithm gave more accurate and stable results even with large arc length variations. During phase-to-phase fault conditions, two opposing magnetic fields force the conductors outwards away from each other and this movement causes a change in the total inductance of the line. A three dimensional finite element line model based on standard wave equations but incorporating magnetic forces was used to evaluate this phenomenon. The results show that appreciable errors in the distance estimations can be expected especially on poorly tensioned di stribution lines.New techniques were also explored that are based on identification of the fault arc. Two methods were successfully tested on simulated networks to identify a breakingconductor. The methods are based on the rate of increase in arc length during the breaking of the conductor. The first method uses arc voltage increase as the basis of the detection while the second method make use of the increase in the non-linearity of the network resistance to identify a breaking conductor. An unsuccessful attempt was made to identifying conductor clashing caused by high winds: it was found that too many parameters influence the separation speed of the two conductors. No unique characteristic could be found to identify the conductor clashing using the speed of conductor separation. The existing algorithm was also used to estimate the voltage in a distribution network during a fault for power quality monitoring purposes.

The global mean surface temperature rise was observed in the past century and proved the warming of the earth climate system. Global warming is believed to continue into the next decades due to unprecedented increases in greenhouse gas emissions. As a consequence of global warming, extreme weather scenarios are also expected to occur more frequently. In such a context, it is of vital importance to assess the impacts of climate change on the operational performance of power systems. This thesis investigates the impacts of climate change on the operational performance of power systems. The future climate is simulated based on emission scenarios and is then used as an input to the thermal models of power system components to assess their ratings and ageing, and further the reliability of the system. This research contributes to a number of areas in power system research. In the literature review, the risks that climate change may cause to power systems are identified. The models used for the simulation of future climate are firstly introduced. The weather variables that can be simulated from the models include air temperature, solar radiation, wind speed and direction, soil moisture and soil temperature. Among the models, the one for soil temperature is originally developed in this thesis. Following this, the component thermal models of overhead line, cable and transformer, from different standards are compared and selected. After that, the sensitivity of component ratings to individual weather variables is investigated, as a preliminary study for the later research in this thesis. Then, the impacts of climate change on component ratings (including both static and dynamic rating) are comprehensively and probabilistically assessed. The assessment results indicate the reduction of component ratings due to climate change. The impacts of climate change on system reliability is further examined on the IEEE Reliability Test System. Results demonstrate and quantify the reduction of both component ratings and system reliability, and prove that the dynamic rating can be used to mitigate the reduction. Finally, the preliminary exploration of transformer ageing is carried out and shows an increased ageing rate due to air temperature rises.

A novel insulating cross-arm (ICA) has been developed for new and existing overhead transmission lines of up to 400 kV. The cross-arm consists of four insulating members, end fittings, field grading devices and a nose connection for the attachment of the conductor. The two main structural elements of the assembly have a unique non-cylindrical geometry which gives them improved mechanical characteristics compared to conventional overhead line insulators. The profile for the compression insulator has been designed. After examining six profile variations, it was determined that the lateral orientation which would give the best performance would be with the flat face of the core facing upwards and tilted by 6o. Using the results obtained from performing flashover tests on a conventional 145 kV insulator, the elevation angle for the compression insulator was set to 6o. The dimensions of the compression insulator were calculated based on the assumption that the ICA would be used to uprate an OHL with L3 towers from 275 kV to 400 kV. The optimal insulator profile was determined to be an alternating profile with three different shed sizes, an arcing distance of 3083 mm and a creepage distance of 12470 mm. Electric field grading devices for the ICA were designed. For the LV end, a grading device resembling a ring which follows the general shape of the cross-section of the insulator was designed. For the HV end, an iterative process yielded two designs. First, the ‘butterfly’ grading device was a unibody piece of cast aluminium for all four ICA members. FEA simulations and tests in the laboratory showed that it could effectively control the electric field at voltages of up to 132 kV. The design was patented and the device was used on six cross-arms installed on a live line in Scotland in August 2013. Second, the ‘M-W’ grading device, was a solution made out of four components for managing the field at voltages of up to 400 kV. The device was designed to be easy to install and service, easy and cheap to manufacture and to have minimal visual impact. The compression insulator and the cross-arm assembly were subjected to a multitude of tests adapted from international standards and the Technical Specifications of National Grid. The performed tests aimed to test the electrical characteristics of the cross-arm and the quality of the materials and manufacturing process of the compression insulator. All of the tests were completed successfully except from the corona extinction test for which the appropriate equipment was not available at the time. Two trials were commissioned to examine how the cross-arm performs in a service-like environment. The snow and ice accretion patterns recorded at the mechanical trial site were used for optimising the profile of the compression insulator. The results after a year of continuous monitoring of leakage current and weather conditions at the live trial site showed that there were humidity and visibility thresholds, above 93% for the former and below 400 m for the latter, which increased the average leakage current by 15% on the tension insulators and by 20% on the compression insulators. It was found that when the longitudinal axis of the cross-arm was perpendicular to the weather the leakage current was higher because more of its surface was exposed. The performance of the novel compression insulators was found to be as good as that of the industry standard tension insulators, reaffirming the potency of the design. Finally, on-site observations showed that the ‘butterfly’ grading device could not effectively manage the electric field on the cross-arm at 400 kV, confirming the results of the FEA simulations and testing.

Made available in DSpace on 2016-06-02T20:18:14Z (GMT). No. of bitstreams: 1 3866.pdf: 6310029 bytes, checksum: 1dbae2c10aceb4a83b1489edc0b7fb1d (MD5) Previous issue date: 2011-10-24 / Universidade Federal de Minas Gerais / Electrical energy is an essential good that may affect people s life and the economy. Overhead line workers and construction electricians are the workers responsible for the availability of this good. To perform their occupational tasks these workers are exposed to fatal accidents and musculoskeletal overload. Although of high rates of accidents and musculoskeletal injuries among these workers, few studies evaluated the presence of risk factors in the occupational settings of line workers and electricians. In this sense, it is necessary to identify the risk factors in the electricians activities (Study 1), quantify the exposure using valid direct methods (Study 2, 3 and 5) and verify the importance of the found results for clinical applications (Study 4 and 5). Study 1 was developed to determine the prevalence of musculoskeletal symptoms among line workers and to identify the risk factors for musculoskeletal disorders. The results of this study showed postural overload and high prevalence of musculoskeletal symptoms at shoulders and neck. Based on these results, Study 2 was purposed to quantify the postural overload in the five main tasks performed by line workers. Loading and unloading the ladder on the vehicle support was deeply investigated by means of posture and force measurements in Study 3, due its higher frequency in line workers schedule. Postures and movements were recorded by four inclinometer sensors at a sampling rate of 20Hz. Inclinometer sensors were previously calibrated and them attached at workers head, upper back and right and left upper arms. Study 2 and 3 identified that line workers are exposed to shoulder and neck awkward postures during all evaluated tasks. However, both studies were performed in simulated settings. By this way, Study 4 was developed to verify if the postures recorded in the simulated conditions are representative of the posture recorded in occupational environment. The results of Study 4 showed that whether the tasks are possible to be reproduced in simulated conditions the postural overload is representative of occupational overload. Besides the representativeness, Study 5 focused the comparison between posture exposure among Brazilian and Norwegian electricians to verify whether the same job type evaluated by the same method under the same procedures would present the same overload disregard the culture differences. The results of this study would allow inferring about external validity of the recordings. According to the found results, Brazilian and Norwegian posture exposure is similar. The results of Study 5 also indicated the high postural overload that these workers are submitted. Therefore, the present thesis showed the need for ergonomic interventions to reduce biomechanical risk factors presented at electricians work activity and the representativeness of the found results to occupational environmental conditions and to other populations. / A disponibilidade de energia elétrica é um serviço básico que afeta diretamente a vida e a economia da população. Para a manutenção deste serviço, eletricistas das empresas de distribuição de energia e eletricistas de construção são expostos aos riscos de acidentes fatais e à alta sobrecarga musculoesquelética. Apesar do reconhecimento dos altos índices de acidentes e de lesões musculoesqueléticas nestes trabalhadores, poucos estudos que avaliam a exposição destes sujeitos aos fatores de risco presentes no ambiente ocupacional estão disponíveis na literatura. Neste sentido, é necessário conhecer os fatores de risco presentes na atividade ocupacional (Estudo 1), quantificá-los por medidas diretas válidas (Estudos 2, 3 e 5) e verificar a importância dos resultados encontrados para a prática clínica (Estudos 4 e 5). O Estudo 1 foi desenvolvido para determinar a prevalência de sintomas musculoesqueléticos em eletricistas de distribuição e identificar os fatores de risco para desordens musculoesqueléticas presentes nas atividades mais freqüentemente desenvolvidas por estes. Os resultados deste estudo mostraram alta prevalência de sintomas musculoesqueléticos em ombros e cervical associados à alta sobrecarga postural, identificada por observação. Com base nestes resultados foi proposto o Estudo 2 para quantificar a sobrecarga postural a que estes trabalhadores estão submetidos durante cinco das atividades freqüentemente realizadas. Maior detalhamento da atividade de remoção e reposição da escada foi realizado no Estudo 3, que envolveu, além do registro postural, a medida da força e esforço requeridos. As posturas e movimentos da cabeça, tronco superior, cervical e ombros direito e esquerdo foram registrados por inclinometria por meio de 4 transdutores previamente calibrados e fixos na cabeça, tronco superior e braços direito e esquerdo, respectivamente. Os Estudos 2 e 3 identificaram a exposição dos eletricistas de distribuição a posturas inadequadas para ombros e cervical nas atividades avaliadas. No entanto, como estes dois estudos foram realizados em ambiente simulado, foi realizado o Estudo 4, para verificar a representatividade destes resultados encontrados em ambiente simulado quando comparados ao registro realizado em ambiente ocupacional real. Os resultados do Estudo 4 mostraram que as atividades desenvolvidas em ambiente simulado podem apresentar a mesma sobrecarga postural do ambiente ocupacional desde que a atividade possa ser simulada. Além da representatividade, no Estudo 5 foi realizada a comparação da exposição postural entre eletricistas de construção Brasileiros e Noruegueses, para verificar se o mesmo tipo de trabalho, avaliado pelo mesmo instrumento a partir dos mesmos procedimentos, indicam a mesma exposição independente da cultura, o que permite inferir sobre a validade externa dos resultados encontrados. De acordo com os resultados encontrados, a exposição de eletricistas Brasileiros e Noruegueses é similar. Os resultados do Estudo 5 também indicam a alta sobrecarga postural a que os eletricistas de construção estão expostos. Portanto, a presente tese revelou a necessidade de intervenções ergonômicas para redução dos fatores de riscos biomecânicos presentes na atividade de eletricistas e a representatividade dos resultados encontrados para situações ocupacionais reais e para outras populações.

The aim of this work is the reconstruction and development of the distribution network of DS to ensure electricity supply in the required quality to existing customers and new customers connecting to the planned industrial zone Šlapanice. The first part deals with the inclusion of a distribution network in power system, its distribution and composition. Subsequently, the work deals with the description of the management of distribution networks, cable and outdoor leadership and their parameters. It also contains guidelines for the design of high voltage networks. The end of the first part is devoted to calculating the steady operation of the network. In the second part, the proposed project using the PAS DAISY Off-line v 4.00 Bizon. Based on the available evidence is developed steady state operation. We found that lines are overloaded and need to be strengthened with regard to the development of industrial zones and adjusting the network to ensure safe and reliable operation. The conclusion focuses on the economic evaluation of proposed alternatives.

The aim of this Master’s thesis is the design and reconstruction of the high voltage distribution network for the company E. ON with focus on calculation of the stabilized operation and on the planning of new cable taps from the transformer substation Moravany u Brna. The first part of the theoretical analysis of the work deals with the inclusion of the distribution network into the power system and with principles of development and construction of high voltage networks. The second part includes a general calculation of stabilized operation of the power distribution network and a familiarization with the program PAS Off - Line Bison 4.0. The practical part of the thesis is focused on the calculation of the stabilized operation at the current state of transformer substation Moravany u Brna using the PAS Off - Line Bizon 4.0 V programme. This part also contains the design of six new cable lines which are needed to strengthen the power distribution in the southern part of the city Brno. The closing part of this chapter constitutes of a outdoor and indoor cable line renovation. These cables are connected to the transformer substation Moravany u Brna and a calculation of stabilized operation is also included in this part.

The aim of this Master’s Thesis is to describe protections for overhead lines in distribution networks. Here are described requirements for the protection and the basic protections. Protections are divided according to their protective function. For each protection is given its use and its power plans. It is stated in the work setting of protection in the real network. On this network is simulated place with short-circuit and described the action of protection. The work also deals with the coordination of protection with automatic circuit breakers. This chapter shows that, given the selectivity is not possible to deploy two or more reclosers (remotely-operated switches) to the core network management. The next chapter describes two representatives reclosers available on the Czech market OSM 27 and GVR 27. Chapter describes and compares their performance characteristics. Conclusion the work includes a proposal protected the lead in incorporating automatic circuit breakers (remotely operated circuit breakers and reclosers). The proposal is based on two different levels of annual number of interruptions and duration of annual general interruption of electricity supply. For these levels the company EGÚ Brno, a.s. proposed several variants of the use of remote-controlled in terms of reducing the cost of the penalty. Our task was to choose a variant that would be applicable in the real network. Reducing costs is feasible only in the limits Ln = 6 failures / year and Lt = 720 min / year, where the selected option No. 4. The limits Ln = 8 failures / year and Lt = 1,080 min / year, not in the real network may no option in terms of selectivity.

Master's thesis proposes a new operation state of distribution network 22kV in Prostějov district after connection of the new Prostějov – Západ substation. The PASS DAISY OFF-LINE Bizon program is used to calculate power losses, optimal network possibilities, as well as to create a new model of Prostějov district's distribution network and to design a modification of a current state of given location. A description of this calculating and simulation program is also included in this paper. The theoretical part describes calculating methods of distribution network’s condition, with emphasis on mathematical method used by PASS DAISY OFF-LINE Bizon program, the modified Newton-Raphson method. The aim of this paper is to prepare technical documentation for E.ON company, with respect to new operation disconnection, planned overhead and cable lines of corresponding parameters. These changes in network's configuration will cause a new distribution of feeding areas. As a result, related changes of provided power from individual feeding points and changes of power currents in electric lines will occur. Due to new operation connection, a reduction of losses and, simultaneously, an improvement of voltage ratios are expected. One of the aims of this paper is to update network's model in PASS DAISY OFF-LINE Bizon program to match the current network’s state of a given area. The outcome of this work is a comparison between the current condition and the new operation condition, with new Prostějov – Západ substation connected, from perspective of distribution network's operator.