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314 Uppsatser om Voltage disturbances - Sida 20 av 21

Förbättrad vakuumtätning mot kabeln under plastextruderingsprocessen

This thesis is about developing a design that provides improved vacuum seal between a lead coating and a plastic coating during plastic extrusion processes of cables. This report is a part of the course MSGC 17 for Bachelor Engineers in mechanical engineering.The work is performed at Nexans Norway AS in Halden where they have a production of high voltage cables for sea-, and offshore industry. A problem they face is that they do not get enough good seal at the attachment to the plastic extrusion machine. They want to achieve a vacuum between a lead coating on the cable and a plastic coating of the cable for plastic extrusion, which is something they do not achieve today. The thesis is thus to come up with a design that provides better sealing against the cable.The work involves a construction part with the phases of product development processes.

SPICA - ARISTO JÄMFÖRELSE studie av analysprogram med avseende på spånningskollaps i elektriska kraftsystem

Safe operation of a large synchronous power system as Nordel is not an easy task.There are several aspects to take into consideration. This thesis focuses on the problems due to voltage collapses in a transmission system.The ability to foresee an upcoming collapse is vital to maintain stable operation of the grid. The grid operator at Svenska Kraftnät (SvK) uses the computer program SPICA to predict the maximum transfer limit at specified transfer sections. SPICA uses actual states from the grid to predict the transfer limitation, and a quarter later a renewed estimate is produced and so on. This means that the operator can se his transfer limits vary every fifteen minutes.Our task in this project is to validate the accuracy of the limitations obtained by SPICA.

Bakre skallgropens form hos hund : en studie av occipital hypoplasi hos hund

Chiari type I malformation is a condition in humans characterized by a small posterior cranial fossa, downward herniation of the cerebellar tonsils, foramen magnum overcrowding and disturbances of cerebrospinal fluid dynamics. Syringohydromyelia is often seen in patients with Chiari type I malformation. Syringohydromyelia is characterized by fluid-filled cavities in the spinal cord. This causes damage to the nervous tissue in the spinal cord. In recent years, a condition similar to Chiari type I malformation has been recognized in dogs. It has mostly been seen in Cavalier King Charles spaniels (CKCS). The condition seen in dogs is usually called occipital bone hypoplasia. The aim of the study was to examine whether there is a difference in the shape of the caudal fossa between CKCS, small bred dogs with a similar head shape and dogs with a normal head shape and if occipital bone hypoplasia is related to a head shape with a steep back of the head. Other aims of the study were to examine the crowding of nervous tissue in the foramen magnum in each breed group, the extent of syringohydromyelia and to what extent the malformation had caused neurological signs. Sculls from dogs on autopsy were divided in halves and the position of the cerebellum compared to the level of the foramen magnum was studied.

Utveckling av Mätmetoder för Färdmotstånd

The student project Elba at KTH started in 2011 and is a project where a battery driven prototype car is developed. The vehicle competes in Eco Shell Marathon in Rotterdam, Holland. In this competition the vehicle that travels a certain distance including several starts and stops with the lowest energy consumption wins. To minimize the consumption is therefore very important, which requires knowledge of the vehicles energy losses.A vehicle's energy losses depends on several factors and can be divided into the powertrain efficiency and the driving resistance. The driving resistance can then be divided in to rolling and air resistance, if smaller losses like vibrations are ignored.

Mätning av partikelmassa i avgaser från en dieselmotor

This master thesis was a continuation of a previous study in the diesel exhaust characterization, which is part of the academical work embedded in the EMIR-1 project. The main objective of this thesis work was to finish the installation and make the proper modifications of the particulate mass measuring system located in one of the engine test cells at KTH, in order to be able to measure the mass of the particles from the exhaust of diesel engines.This experiment requires a diluted flow sample from the exhaust that should be sent to the device that makes possible the measurement of particle mass, called TEOM. In the first stage of this project, the objective was to study and make the proper modifications in the existing KTH diluter because there were several problems to obtain a constant dilution ratio from it during tests.This modifications were made and it resulted in a great improvement in the maximum inlet and outlet flow that this diluter can handle. Therefore another modification is proposed for controlling the inlet exhaust flow so it will be possible to regulate the dilution ratio and make it constant along a wide range of engine loads and speeds.The second and most important stage was to make particulate mass measurements possible by analyzing the frequency signal from the TEOM device. The idea was to obtain the frequency of oscillation from the tapered element in the TEOM, and therefore with the proper correlations, be able to predict the particulate mass concentration in the exhaust flow from the engine.An electrical problem in the TEOM circuit was detected and corrected, so the signal that carries the frequency from the TEOM can be analyzed properly.

Evaluation of an ectomycorrhizal macrofungi as an indicator species of high conservation value pine-heath forests in northern Sweden

Since the 1950s, the development of modern rotation forestry in boreal Fennoscandia has resulted in a severe reduction of older forests, and a high degree of fragmentation among the small patches that remains of old forest. In Sweden, when performing conservation value assessments in order to identify and preserve the remaining forest habitats, the government authorities use to a significant extent a set of indicator species that indicate habitats of high biological conservation value. One species considered to indicate high conservation values in pine-heath forests is the red-listed ectomycorrhizal (EM) macrofungi Sarcodon scabrosus (Fr.) P. Karst. In the present study, the validity of using S.

Modell och analysverktyg för beräkningav frekvensförlopp

The power system modelled in this thesis work has been developed for simulationwhen e.g. the production in some part of the power system is changed. The powersystem has been modelled according to the swing mass of the system, the frequencydependency of the load and the turbine governor. The model determines the systemfrequency, the period of regulation and the power exchange between the differentsubsystems in the Nordic synchronized system.In this model the system frequency is assumed to be the same in all different parts ofthe power system and the voltage conditions in the power system are neglected. Forthat reason power swings does not occur between different subsystems in the powersystem, which usually occur as a result of the swinging connection between thetransmissions line.

Metodutveckling för analys av PBDE och HBCD i sediment

Brominated flame retardants (BFRs) has for many years been used in products to reduce their flammability, mainly in electronic products, textiles and construction materials. In 2003, Sweden imported 300 tons of brominated flame retardants. Leakage of these compounds has polluted natural environments. Fishes has shown increased contents of these substances, especially fat fish, since brominated flame retardants tends to accumulate in fatty tissues. They are also regarded as persistent and that gives them the ability to travel long distances. What also is really scary is that increased levels of brominated flame retardants have been detected in human breast milk. The knowledge of the brominated flame retardants is limited and not so much research has been done in this field. There are many reasons though, to keep the research going. Partly their structural resemblance to well-known toxics as PCB, but also their ability to accumulate in biological systems and enrich in food chains. In which way they affect humans we really don?t know yet.

Automation i Distributionsnät

As a part of Göteborg Energi?s work towards a smarter electric grid, the company has chosen to investigate the possibilities of automation in their middle voltage grid. In Europe, there are example cases where these technologies already are installed which many articles on the CIRED conference 2011 proved. Netcontrol Oy in Finland has, together with Tekla, created an automated SCADA system that Vattenfall in Finland today uses. The grid mainly consists of 10 kV open loop fed city grid and this automation is mainly designed for this type of grid.

Medvind eller motvind? : granskning av fem tillståndsansökningar från vindkraftprojektering i Sverige

The Swedish Government has decided that Wind power should have a higher contribution to the electricity generation in Sweden. Their goal is that, by 2015, the yearly production by Wind power should generate 10 TWh. In year of 2006, the 760 wind mills in Sweden generated only 0,936 TWh. Despite good wind conditions in a large extend of Sweden's land- and coast areas, the slow rate of new wind mills establishments will likely result in unattainable goals. The major problem for new establishments of wind mills is the extensive and complicated permission process. An expert group of environmental studies (Expertgruppen för miljöstudier) was commissioned by the Government to make a report concerning the problems with the expansion of wind power in Sweden.

En kvalitativ utvärdering av det accelerometerbaserade hältdetektionssystemet ?Lameness Locator? :

Background: Evaluation of lameness in horses is traditionally performed by a veterinarian who subjectively evaluates the movements of the horse. Accordingly, lameness diagnosis varies with the veterinarian and circumstances for which the horse is examined. Research within the area has long tried to establish an objective and standardized method for lamenessevaluation in horses. Several methods have been shown to be reliable and are used regularly within research, for example measurement of forces between the hoof and ground, and measurement of movements with high speed cameras or accelerometers. However these methods require considerable preparation, standardization, and expensive equipment as well as produce large amounts of data that are incomprehensible for the clinician.

Jordfelssimulering och modell-validering med PSCAD av ett impedansjordat distributionsnät

Detta examensarbete har utförts hos Vattenfall Eldistribution på avdelningen Kontroll och Skydd med målsättningen att utforma och utvärdera en nätmodell avsedd för jordslutningssimuleringar i PSCAD. Ombyggnationen från luftledningar till markkablar har medfört att kapacitansen i distributionsnätet ökat, vilket ställer högre krav på jordfelsutrustning och på nätanalyser för att kunna försäkra att en säkerställd frånkoppling kan ske enligt de myndighetskrav som föreligger. Syftet med arbetet har varit att undersöka hur en nätmodell bör utformas för analys av stationära in-svängningsförlopp och utvärdera hur stor noggrannhet som kan förväntas gentemot verkliga jordfelsprov vid felresistanser på främst 3 k? och 5 k?. Nätmodellen har ut-formats efter ett verkligt impedansjordat mellanspänningsnät med ?-länkar i PSCAD och utifrån de nätuppgifter som förekommer i Vattenfalls näthanteringsprogram Netbas.

Mikroproducenternas påverkan på Elinorr

The Swedish energy system will be influenced by many future changes, such as energy and climate policy objectives. The installation of more renewable electricity could increase by using solar energy. Over the recent years, grid-connected photovoltaic (PV) systems have increased dramatically in Sweden, partly due to various support systems and compensation models. These support systems have been designed to make it easy for individuals and businesses to invest in self-generated electricity and thus contribute to the transformation of the energy system.The introduction of a higher proportion of solar energy may in turn affect the Swedish electricity system. This could mean that the electricity companies will be facing a number of changes in the near future.

Influence of providing objects to piglets before and after weaning on behaviour and weight gain

Barren rearing environment and early weaning of piglets can lead to a high level of distress, behavioural disturbances and reduction in weight gain. The main aim of this thesis was to study the effects of potential enrichment objects on piglet?s behaviour and weight gain during the pre- and post-weaning period. The second aim was to examine what type of object stimulated the highest frequency of interaction. The study was carried out at the Swedish Livestock Research Centre in Lövsta where a batch of litters from 10 first-parity Yorkshire sows were used.

Sjukdomsfrekvens och utslagningsorsaker hos kor med 12 respektive 15 månaders kalvningsintervall

The incidence of many of the most common diseases in dairy cattle has been proven to be highest during the time closest to calving. It is possible that the current breeding strategy with 12 month calving intervals increases the risk for disease in dairy cattle, which is problematic concerning both animal welfare and for economic reasons. The economic incentives behind a calving interval of 12 to 13 months have mainly been based on milk- and feed- costs and no costs due to diseases or fertility disturbances have been included.The aim of this study was to see if a lengthening of the calving interval would result in lower disease frequency. The hypothesis is that cows with a planned calving interval of 15 months have a lower disease incidence than cows with a calving interval of 12 months due to less number of calvings. Therefore the difference in disease frequency should be larger when compared over a long period of time, such as over lifetime, since cows with a longer calving interval experience fewer calvings.The study was performed between August 17th, 1994, and January 24th, 2007.

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