In this thesis, power system transients are considered as an opportunity for development of on-line diagnostics of power components and specifically the insulation systems of power transformers and bushings. A new technique for on-line dielectric response measurement of power transformer bushings is proposed which utilizes natural transients in the power system, such as lightning and switching surges, as stimuli. Laboratory investigations are done on implementation of the proposed technique. Measurement considerations, data acquisition and processing involved in achievement of reasonable accuracy in the Dielectric Response (DR) are presented. Capability of the technique in tracking of the degradation signatures such as moisture content in the insulation has been evaluated and it has shown a good level of accuracy by being compared to the Frequency Domain Spectroscopy (FDS).  The proposed technique is tested on the service-aged 150 kV bushings and feasibility of the technique for monitoring of dielectric properties of power transformer bushings has been assessed; the results are promising for the technique to be used in the real application.  Partial Discharges (PD) behavior under transients has been also studied for different materials in this project. PD behavior of different defects, at different insulation condition, responding to the overvoltage transients in form of superimposed impulses on ac voltages was investigated and it was perceived how their distinctive response and the interpretation of  that, can be useful for their identification. Besides the conventional materials, surface ac PD properties of modified paper with silica and zinc oxide nanoparticles under the superimposed impulses have been assessed in this project. Proper type and optimum concentration level of nanoparticles in the paper are the factors that lead to the improvement of PD behavior in the modified paper under overvoltage transients. / <p>QC 20160525</p>

Examensarbetet har genomförts på ABB Components i Ludvika. ABB Components är en affärsenhet inom ABB-koncernen som tillverkar nyckelkomponenter till transformatorer, bland annat genomföringar som kan ses som en isolerande hylsa vars uppgift är att föra högspänd ström genom jordade plan. Examensarbetets syfte är att utföra en förstudie som sedan ska fungera som underlag för ABB Components utvecklingsarbete vad gäller genomföringar av typen RIP (Resin Impregnated Paper). Bakgrunden till förstudien är ökade miljökrav världen över vilket innebär en marknad där miljöfrågor får allt större inverkan. Följden av marknadens utveckling är att ABB Components har insett att de har ett glapp i produktportföljen vad gäller genomföringar av typen RIP. För att skapa det underlag som är nödvändigt för att nå målet med förstudien har metoder som intervjuer, observationer och sökningar i databaser tillämpats. Målet med förstudien har sedan uppnåtts genom att generera lösningskoncept i form av CAD-modeller. Utifrån lösningskoncepten har sedan en identifiering av begränsningar i tillverkningsprocesser varit möjlig. Identifiering av begränsningar i tillverkningsprocesser har sedan konstaterat att ABB Components har kunskapen och de resurser som krävs för att tillfredsställa marknadens behov vad gäller genomföringar av typen RIP. / This thesis has been carried out at ABB Components in Ludvika. ABB Components is a business unit within ABB Group, which manufactures key components for transformers, including bushings that can be seen as an insulating sleeve whose function is to bring high-voltage current through a grounded plane. The thesis aims to carry out a pilot study that will serve as basis for ABB Components development of bushings of type RIP (Resin Impregnated Paper). The background to the pilot study is increased environmental requirements worldwide, which means a market where environmental issues are increasingly impact. The consequence of market developments is that ABB Components have recognized that they have a gap in the product portfolio in terms of bushings of type RIP. To create the information that is necessary to achieve the aim of the pilot study, methods such as interviews, observations, and searches in databases has been applied. The aim of the pilot study has been achieved by generating solution concepts in the form of CAD models. Based on solution concepts, an identification of limitations in manufacturing processes has been possible. Identification of limitations in manufacturing processes has determined that ABB Components have the knowledge and resources necessary to satisfy the market's needs in terms of bushings of type RIP.

This diploma thesis deals with the measurement of the torsion stabilizer characteristics. The beginning of the thesis explains the function of a torsion stabilizer in a vehicle and introduces various technical options of stabilization. Next part is focused on computational simulation of representative stabilizers. Next parts are devoted to proposition of measuring device for torsion stabilizers in the laboratory and execution of the experiment. In the final part multibody model is created to demonstrate achieved results.

The thesis focuses on investigating and optimizing a bushing script implemented as a tool in MSC ADAMS/Car. The study provides an insight on the representation of a rubber bushing and identify parameters which can be used to define the properties of a bushing in a simulation environment such as ADAMS/Car. The tool being studied here can be used to implement different kind of bushings such as a hydro bushing and a general rubber bushing, but optimization was implemented for the rubber bushing only. With an increasing reliance on Computer Aided Engineering (CAE) tools in the designing process, it is necessary that the vehicle behaviour can be predicted without relying on physical testing. CAE tools reduces the need of prototypes and provides a faster approach to designing vehicles. MSC ADAMS/Car is one such tool, which has been used here to predict the vehicle dynamic behaviour, which will influence the ride, handling and comfort characteristics of the vehicle. Rubber bushings, which have been studied here, have a significant contribution to the overall stiffness of the vehicle and as such, it is imperative that the tool being used here, is accurate and makes the designing process easy. The rubber bushing can be imagined to be a combination of a non-linear elastic spring, a frequency dependent Maxwell component and an amplitude dependent frictional element. In order to ease the design of the bushing properties, a reduced number of input properties are used to calculate the bushing properties internally. While trying to validate the force hysteresis loop obtained through the model with the measured data, it was seen that the accuracy was quite poor for the model when loading it with dynamic loads corresponding to amplitudes of0.2 mm and lower. The quasi-static loading and dynamic loading above 0.2 mm is shown to have a satisfactory accuracy when compared to the measured data.

Bushings are a necessary component of the transformers in the power grid. A bushing is used to control the electric field's strength and shape. It is also an insulator for high-voltage conductors. The bushing enables a conductor to be safely brought through a grounded barrier. In this report, several methods for creating a 2D axi-symmetrical bushing core geometry in COMSOL Multiphysics were developed. The geometry includes the conductor, hollow area inside the conductor, the RIP, the mold and aluminum foils. First, the base-geometry was constructed, which includes all geometry parts except the foils. Afterward, two different approaches were used to construct the foils. The first approach was to automatically build a requested number of foils. The second approach was to create the foils based on data from excel-sheets. The developed method should be able to create both full foils and partial foils. A total of four foil methods were developed. The first method used COMSOL's Model Builder to create a requested number of foils uniformly distributed within the base-geometry. The second method used COMSOL's Application Builder to create a requested number of foils based on mathematical expressions. The third method reads data from an excel sheet to create the foils in COMSOL. Method four is an improved version of method three that can create partial foils as well as the base-geometry. Foil methods II, III, and IV, created every foil as a separate geometrical object. As a result, an associated method that deletes the foils were also developed for each of these methods. A conclusion that the fourth method was the most realistic method of creating a bushing core could be draw due to, among other factors, it is the only method that can build partial foils.

Development of the power gridtowards a more reliable and smarter system requires frequent on-line monitoring of the power components. Power transformers and their bushings are particularly important components in a power transmission system and their insulation degradation may lead to catastrophic failures. Time consuming and costly replacement of these components raise the importance of their frequent monitoring. A fault in a power transformer bushing can also involve in the failure of the transformer. Therefore, on-line diagnostics of power transformers and their bushings is of great interest. Several methods exist for diagnostics of these components. However, some of them can only be done off-line in maintenance periods, and the existing on-line methods generally provide less information, especially on the internal solid insulation parts. In this project, a new technique for on-line diagnostics of the power transformer and the bushing insulation is proposed. In this technique, natural transients happening in the power system such as lightning and switching surges can be used as stimuli for on-line dielectric response measurements. This technique can provide information on insulation close to what Dielectric Spectroscopy offers in off-line measurements. The wide-ranging frequency content of power system transients is their advantage for being usedas stimuli when measuring the Dielectric Response. The response can have particular signatures due to different types of defects in the insulation varying with frequency. Oil-impregnated paper as a major insulation component in power transformer and its bushing has been investigated in this project. Moisture content and temperature, as two important degradation factors in this type of insulation, have been studied to evaluate the performance of the proposed technique in the diagnostics of the oil-impregnated paper. The results are verified with the dielectric response obtained through commercial instruments. The results show that the proposed technique has the ability to track the changes in dielectric response due to the moisture content and temperature. Measurements were done at both highvoltage (40kV) and low voltage (10V) levels, and the corresponding circuit models to achieve reasonable accuracy for the results are discussed. Moving on from the material samples, a further study was done on three service-aged 150 kV bushings to investigate the feasibility of the technique on the diagnostics of power transformer bushings. Their dielectric response measured by the transient stimuli showed good agreement with their response obtained by the commercial instruments. The effect of the transformer winding on the transient response of the bushing is a further aspect of the real conditions for on-line diagnostics. This has been investigated through the simulation of transient models for transformers and bushings, and possible solutions for distinguishing the responses are presented. The proposed new on-line diagnostics technique by utilizing natural transients can provide information about the insulation system in a certain range of frequency without interrupting the operation or requiring an external voltage source. However, the validity range of the results depends on the bandwidth of the applied transients and other measurement considerations. This approach can be valuable in frequent monitoring of dielectric properties of the power transformers and their bushings as a complement to the other available on-line techniques. / <p>QC 20140409</p>

An electrical bushing is one of the most important elements in a power transformer. Steep front surges such as transient impulse voltage from lightning strikes is an inevitable electromagnetic transient mostly happening in power transmission and distribution system. The bushing might lead to be degraded due to such kind of surge. This project deals with overvoltage stress distribution on the transformer bushing under the effect of electromagnetic transient response such as lightning impulse.  To understand the behavior of transient response on the bushing, a proper model of power transformer bushing is built-in Comsol multiphysics to authenticate the stress distribution. The electromagnetic wave of impulse propagates onto the overhead line that connects with the transformer. Some understanding of the transient behavior of a conductor bushing has been achieved through studying the influence of inductance property and the skin effect characteristics of a multi-layer coaxial cable on the wave propagation, which has been structured in this project to simplify the model. On the other hand, the skin effect analysis on the conductor of the bushing has been taken also into account in this project using real conductor simulation in the Comsol model. Thus, it will be interesting to compare the real conductor model with the perfect conductor of the bushing through analyzing the current density effect on it.  In this project, multi-layer of coaxial cable and transformer bushing are simulated. The simulation is carried out for time domain and frequency domain in Comsol based on the model characteristics. / En elektrisk genomföring är ett av de viktigaste elementen i en transformator. Spänningsvågor med branta fronter som impulsspänningar från blixtnedslag är ett oundvikligt elektromagnetiskt övergående fenomen som oftast sker i kraftöverförings- och distributionssystem. Genomföringen kan leda till att degraderas på grund av en sådan våg. Detta projekt handlar om fördelning av överspännings på transformatorgenomföringen under påverkan av elektromagnetisk transient respons, såsom blixtimpuls.  För att förstå beteendet hos övergående respons på genomföringen är en korrekt modell av transformatorgenomföring inbyggd Comsol-flerfysik för att autentisera spänningsfördelningen. Den elektromagnetiska impulsvågen fortplantas från luftledningen som ansluter till transformatorn. Viss förståelse för det övergående beteendet hos en ledargenomföring har uppnåtts genom att studera påverkan av induktansegenskaper och hudeffektegenskaperna hos en flerskikts koaxialkabel på vågutbredningen, vilket har strukturerats i detta projekt för att förenkla modellen. Å andra sidan har hudeffektanalysen på genomföringens ledare beaktats i detta projekt med användning av verklig ledarsimulering i Comsol-modellen. Således blir det intressant att jämföra den riktiga ledarmodellen med den perfekta ledaren för genomföringen genom att analysera strömtäthetseffekten på den.  I detta projekt simuleras flerskikt av koaxialkabel och transformatorgenomföring. Simuleringen utförs för tidsdomän och frekvensdomän i Comsol baserat på modellegenskaperna.

Tato diplomová práce byla psána při studentské zahraniční stáži, pod záštitou Evropské Unie – program „ERASMUS Student Mobility for Placement“. Stáž byla absolvována mezi prosincem 2010 a květnem 2011 ve společnosti a.d.Tramontana, mající sídlo v Palau de Santa Eulália, Španělsko. Pro kompletní návrh podvozku a odpružení jakéhokoli vozidla je nezbytná znalost mnoha technických disciplín. Tato diplomová práce se zabývá dvěma z nich – odpružení a řízení. Nejprve je rozebrána teorie, na kterou se může navázat v praktické části práce. Velká pozornost byla věnována srozumitelnosti textu a názornosti obrázků, bez zbytečných detailů, avšak bez vynechání důležitého. Tuto práci je tedy možné užít jako prvního kroku před návrhem podvozku. V další části je popsáno, jak byla probraná teorie využita při návrhu řízení u skutečného vozu, přičemž největší pozornost je věnována Ackermannově teorii řízení a geometrii zabraňující samořízení při propružení. V závěrečných částech je pozornost věnována ukázce některých z každodenních činností v malosériové výrobě automobilů – jde o zjištění maximálně možného pohybu kola při propružení a proces výroby příčných trojúhelníkových ramen včetně návrhu jejich připevnění k šasi.

The work considers pulse wire-guided electromagnetic (EM) waves. The main contribution of the work is the original design of the isolation bushing for maximizing of the received wave (echo) thanks to the results of the numerical simulations, the acquirement of the new acknowledges of the reflections of the guided EM wave from the various boundaries, the construction of PML layers for FDTD simulations in rotational coordinates, the advances made in temporary excitation sources for FDTD and the formulation of the program code for FDTD in rotational coordinates in Matlab environment. The rightness of the numerical simulations was verified in practical experiments. The practical exploitation of the results is supposed in instrumentation and control technology - the level measurement in reservoirs.