989 resultados para Dynamic Operation


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Electricity distribution network operation (NO) models are challenged as they are expected to continue to undergo changes during the coming decades in the fairly developed and regulated Nordic electricity market. Network asset managers are to adapt to competitive technoeconomical business models regarding the operation of increasingly intelligent distribution networks. Factors driving the changes for new business models within network operation include: increased investments in distributed automation (DA), regulative frameworks for annual profit limits and quality through outage cost, increasing end-customer demands, climatic changes and increasing use of data system tools, such as Distribution Management System (DMS). The doctoral thesis addresses the questions a) whether there exist conditions and qualifications for competitive markets within electricity distribution network operation and b) if so, identification of limitations and required business mechanisms. This doctoral thesis aims to provide an analytical business framework, primarily for electric utilities, for evaluation and development purposes of dedicated network operation models to meet future market dynamics within network operation. In the thesis, the generic build-up of a business model has been addressed through the use of the strategicbusiness hierarchy levels of mission, vision and strategy for definition of the strategic direction of the business followed by the planning, management and process execution levels of enterprisestrategy execution. Research questions within electricity distribution network operation are addressed at the specified hierarchy levels. The results of the research represent interdisciplinary findings in the areas of electrical engineering and production economics. The main scientific contributions include further development of the extended transaction cost economics (TCE) for government decisions within electricity networks and validation of the usability of the methodology for the electricity distribution industry. Moreover, DMS benefit evaluations in the thesis based on the outage cost calculations propose theoretical maximum benefits of DMS applications equalling roughly 25% of the annual outage costs and 10% of the respective operative costs in the case electric utility. Hence, the annual measurable theoretical benefits from the use of DMS applications are considerable. The theoretical results in the thesis are generally validated by surveys and questionnaires.

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Cellen har ett s.k. cytoskelett som bl.a. ger stadga åt cellen och deltar i dess form- och rörelsefunktioner. Intermediärfilamenten är en viktig del av cytoskelettet och de har länge varit kända för sina väsentliga roller i att upprätthålla den cellulära organisationen och vävnadernas integritet. På senare år har man insett att intermediärfilamenten har en större funktionell mångsidighet än man tidigare tänkts sig, i och med att en rad olika studier har visat betydelsen av intermediärfilamenten vid olika signaleringprocesser. Dessa proteinnätverk samverkar nämligen med kinaser och andra viktiga signalfaktorer och deltar därmed i cellens signaleringmaskineri. Intermediärfilamentproteinet nestin används ofta som en markör för stamceller men dess fysiologiska funktioner är i stort sett okända. Interaktion mellan nestin och ett signalkomplex bestående av cyklin-beroende kinas 5 (eng. Cyclin-dependent kinase, Cdk5) och dess aktivatorprotein p35 upptäcktes i vårt laboratorium före denna avhandling påbörjades. Därför var syftet med min avhandling att undersöka den funktionella betydelsen av nestin i regleringen av Cdk5/p35 komplexet. Cdk5 är ett multifunktionellt kinas som reglerar både utvecklingen och stressreaktioner i nerver och muskler. Vi visade att nestin skyddar neuronala stamceller under oxidativ stress genom dess förmåga att hämma Cdk5s skadliga aktivitet. Genom att förankra Cdk5/p35 komplexet, reglerar nestin den subcellulära lokaliseringen av Cdk5/p35 och minskar klyvningen av p35 till den mer stabila aktivatorn p25. Vi demonstrerade också aktiveringsmekanismen för Cdk5 under differentiering av muskelceller. Proteinkinas C zeta (PKCzeta) avslöjades ha en förmåga att accelera klyvningen av p35 till p25, och därmed öka aktiviteten hos Cdk5. Nestin kunde genom sin förmåga att reglera Cdk5 signalkomplexet styra muskelcellernas differentiering. Denna doktorsavhandling har på ett avgörande vis ökat förståelsen av de reglerande mekanismer som styr Cdk5 aktivering. Avhandling presenterar nestin och PKCzeta som kritiska faktorer i denna reglering. Vidare innehåller avhandlingen ny information om de cellulära funktionerna hos nestin som vi har visat vara en viktig reglerare av cellernas överlevnad och differentiering.

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Centrifugal pumps are widely used in industrial and municipal applications, and they are an important end-use application of electric energy. However, in many cases centrifugal pumps operate with a significantly lower energy efficiency than they actually could, which typically has an increasing effect on the pump energy consumption and the resulting energy costs. Typical reasons for this are the incorrect dimensioning of the pumping system components and inefficiency of the applied pump control method. Besides the increase in energy costs, an inefficient operation may increase the risk of a pump failure and thereby the maintenance costs. In the worst case, a pump failure may lead to a process shutdown accruing additional costs. Nowadays, centrifugal pumps are often controlled by adjusting their rotational speed, which affects the resulting flow rate and output pressure of the pumped fluid. Typically, the speed control is realised with a frequency converter that allows the control of the rotational speed of an induction motor. Since a frequency converter can estimate the motor rotational speed and shaft torque without external measurement sensors on the motor shaft, it also allows the development and use of sensorless methods for the estimation of the pump operation. Still today, the monitoring of pump operation is based on additional measurements and visual check-ups, which may not be applicable to determine the energy efficiency of the pump operation. This doctoral thesis concentrates on the methods that allow the use of a frequency converter as a monitoring and analysis device for a centrifugal pump. Firstly, the determination of energy-efficiency- and reliability-based limits for the recommendable operating region of a variable-speed-driven centrifugal pump is discussed with a case study for the laboratory pumping system. Then, three model-based estimation methods for the pump operating location are studied, and their accuracy is determined by laboratory tests. In addition, a novel method to detect the occurrence of cavitation or flow recirculation in a centrifugal pump by a frequency converter is introduced. Its sensitivity compared with known cavitation detection methods is evaluated, and its applicability is verified by laboratory measurements for three different pumps and by using two different frequency converters. The main focus of this thesis is on the radial flow end-suction centrifugal pumps, but the studied methods can also be feasible with mixed and axial flow centrifugal pumps, if allowed by their characteristics.

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The goal of the master‘s thesis is to determine and estimate ice accretion influence on the wind turbine blade performance. The thesis describes the technique of ice accretion calculation on the wind turbine blade and determination characteristics of the turbine with ice accreted. The methodology of the classic Blade Element Moment Theory was used. Iced blade experimental data was investigated in order to calculate blade with ice characteristics. The obtained results shows that iced blade power coefficient is lower than clean blade one. The heating system implementation shows that in the particular site in the Lapland region it is efficient.

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The aim of the study was to create and evaluate an intervention programme for Tanzanian children from a low-income area who are at risk of reading and writing difficulties. The learning difficulties, including reading and writing difficulties, are likely to be behind many of the common school problems in Tanzania, but they are not well understood, and research is needed. The design of the study included an identification and intervention phase with follow-up. A group based dynamic assessment approach was used in identifying children at risk of difficulties in reading and writing. The same approach was used in the intervention. The study was a randomized experiment with one experimental and two control groups. For the experimental and the control groups, a total of 96 (46 girls and 50 boys) children from grade one were screened out of 301 children from two schools in a low income urban area of Dar-es-Salaam. One third of the children, the experimental group, participated in an intensive training programme in literacy skills for five weeks, six hours per week, aimed at promoting reading and writing ability, while the children in the control groups had a mathematics and art programme. Follow-up was performed five months after the intervention. The intervention programme and the tests were based on the Zambian BASAT (Basic Skill Assessment Tool, Ketonen & Mulenga, 2003), but the content was drawn from the Kiswahili school curriculum in Tanzania. The main components of the training and testing programme were the same, only differing in content. The training process was different from traditional training in Tanzanian schools in that principles of teaching and training in dynamic assessment were followed. Feedback was the cornerstone of the training and the focus was on supporting the children in exploring knowledge and strategies in performing the tasks. The experimental group improved significantly more (p = .000) than the control groups during the intervention from pre-test to follow-up (repeated measures ANOVA). No differences between the control groups were noticed. The effect was significant on all the measures: phonological awareness, reading skills, writing skills and overall literacy skills. A transfer effect on school marks in Kiswahili and English was found. Following a discussion of the results, suggestions for further research and adaptation of the programme are presented.

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Comprehensive understanding of the heat transfer processes that take place during circulating fluidized bed (CFB) combustion is one of the most important issues in CFB technology development. This leads to possibility of predicting, evaluation and proper design of combustion and heat transfer mechanisms. The aim of this thesis is to develop a model for circulating fluidized bed boiler operation. Empirical correlations are used for determining heat transfer coefficients in each part of the furnace. The proposed model is used both in design and offdesign conditions. During off-design simulations fuel moisture content and boiler load effects on boiler operation have been investigated. In theoretical part of the thesis, fuel properties of most typical classes of biomass are widely reviewed. Various schemes of biomass utilization are presented and, especially, concerning circulating fluidized bed boilers. In addition, possible negative effects of biomass usage in boilers are briefly discussed.

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The purpose of this paper is to gather enough evidence to speculate the future of Nokia, Rim and Apple. The thesis goes over the history, current events and business model of each company. This paper includes differences between the companies and co-operation and rivalry, such as patent infringement cases. The study is limited to smartphones and their future. The result of this study is that Apple will continue its steady increase in market share, while Nokia will first decrease and after the launch of the Windows Phone it will rise again. RIM‟s result has not been as good as in past years and it has lost market share. The decrease of share price may lead to acquisition by a company interested in RIM technology.

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In this thesis, general approach is devised to model electrolyte sorption from aqueous solutions on solid materials. Electrolyte sorption is often considered as unwanted phenomenon in ion exchange and its potential as an independent separation method has not been fully explored. The solid sorbents studied here are porous and non-porous organic or inorganic materials with or without specific functional groups attached on the solid matrix. Accordingly, the sorption mechanisms include physical adsorption, chemisorption on the functional groups and partition restricted by electrostatic or steric factors. The model is tested in four Cases Studies dealing with chelating adsorption of transition metal mixtures, physical adsorption of metal and metalloid complexes from chloride solutions, size exclusion of electrolytes in nano-porous materials and electrolyte exclusion of electrolyte/non-electrolyte mixtures. The model parameters are estimated using experimental data from equilibrium and batch kinetic measurements, and they are used to simulate actual single-column fixed-bed separations. Phase equilibrium between the solution and solid phases is described using thermodynamic Gibbs-Donnan model and various adsorption models depending on the properties of the sorbent. The 3-dimensional thermodynamic approach is used for volume sorption in gel-type ion exchangers and in nano-porous adsorbents, and satisfactory correlation is obtained provided that both mixing and exclusion effects are adequately taken into account. 2-Dimensional surface adsorption models are successfully applied to physical adsorption of complex species and to chelating adsorption of transition metal salts. In the latter case, comparison is also made with complex formation models. Results of the mass transport studies show that uptake rates even in a competitive high-affinity system can be described by constant diffusion coefficients, when the adsorbent structure and the phase equilibrium conditions are adequately included in the model. Furthermore, a simplified solution based on the linear driving force approximation and the shrinking-core model is developed for very non-linear adsorption systems. In each Case Study, the actual separation is carried out batch-wise in fixed-beds and the experimental data are simulated/correlated using the parameters derived from equilibrium and kinetic data. Good agreement between the calculated and experimental break-through curves is usually obtained indicating that the proposed approach is useful in systems, which at first sight are very different. For example, the important improvement in copper separation from concentrated zinc sulfate solution at elevated temperatures can be correctly predicted by the model. In some cases, however, re-adjustment of model parameters is needed due to e.g. high solution viscosity.

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The main focus of this thesis is to define the field weakening point of permanent magnet synchronous machine with embedded magnets in traction applications. Along with the thesis a modelling program is made to help the designer to define the field weakening point in practical applications. The thesis utilizes the equations based on the current angle. These equations can be derived from the vector diagram of permanent magnet synchronous machine. The design parameters of the machine are: The maximum rotational speed, saliency ratio, maximum induced voltage and characteristic current. The main result of the thesis is finding out the rated rotational speed, from which the field weakening starts. The action of the machine is estimated at a wide speed range and the changes of machine parameters are examined.

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The offset printing process is complex and involves the meeting of two essentially complex materials, printing ink and paper, upon which the final product is formed. It can therefore be expected that a multitude of chemical and physical interactions and mechanisms take place at the ink-paper interface. Interactions between ink and paper are of interest to both the papermakers and ink producers, as they wish to achieve better quality in the final product. The objective of this work is to clarify the combined influence of paper coating structure, printing ink and fountain solution on ink setting and the problems related to ink setting. A further aim is to identify the mechanisms that influence ink setting problems, and to be able to counteract them by changing properties of the coating layer or by changing the properties of the ink. The work carried out for this thesis included use of many techniques ranging from standard paper and printability tests to advanced optical techniques for detection of ink filaments during ink levelling. Modern imaging methods were applied for assessment of ink filament remain sizes and distribution of ink components inside pigment coating layers. Gravimetric filtration method and assessment of print rub using Ink-Surface-Interaction-Tester (ISIT) were utilized to study the influence of ink properties on ink setting. The chemical interactions were observed with the help of modified thin layer chromatography and contact angle measurements using both conventional and high speed imaging. The results of the papers in this thesis link the press operational parameters to filament sizes and show the influence of these parameters to filament size distribution. The relative importance between the press operation parameters was shown to vary. The size distribution of filaments is important in predicting the ink setting behaviour, which was highlighted by the dynamic gloss and ink setting studies. Prediction of ink setting behaviour was also further improved by use of separate permeability factors for different ink types in connection to filtration equations. The roles of ink components were studied in connection to ink absorption and mechanism of print rub. Total solids content and ratio of linseed oil to mineral oil were found to determine the degree of print rub on coated papers. Wax addition improved print rub resistance, but would not decrease print rub as much as lowering the total solids content in the ink. Linseed oil was shown to absorb into pigment coating pores by mechanism of adsorption to pore walls, which highlights the need for sufficient pore surface area for improved chromatographic separation of ink components. These results should help press operators, suppliers of printing presses, papermakers and suppliers to papermakers, to better understand the material and operating conditions of the press as it relates to various print quality issues. Even though paper is in competition with electronic media, high quality printed products are still in demand. The results should provide useful information for this segment of the industry.

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The most outstanding conceptual challenge of modern crisis management is the principle of consent. It is not a problem only at the operational level - it challenges the entire decision-making structures of crisis management operations. In post-cold war times and especially in the 21st century, there has been a transition from peacekeeping with limited size and scope towards large and complex peace operations. This shift has presented peace operations with a dilemma. How to balance between maintaining consent for peace operations, whilst being able to use military force to coerce those attempting to wreck peace processes? To address such a dilemma, this research aims to promote understanding, on what can be achieved by military crisis management operations (peace support operations) in the next decade. The research concentrates on the focal research question: Should military components induce consent or rely on the compliance of conflicting parties in crisis management operations of the next decade (2020 – 2030)? The focus is on military – political strategic level considerations, and especially on the time before political decisions to commit to a crisis management operation. This study does not focus on which actor or organisation should intervene. The framework of this thesis derives from the so called ‘peacebuilding space’, the scope of peace operations and spoiler theory. Feasibility of both peace enforcement and peacekeeping in countering future risk conditions are analysed in this framework. This future-orientated qualitative research uses the Delphi-method with a panel of national and international experts. Citation analysis supports identification of relevant reference material, which consists of contemporary literature, the Delphi-questionnaires and interviews. The research process followed three main stages. In the first stage, plausible future scenarios and risk conditions were identified with the Delphi-panel. In the second stage, operating environments for peace support operations were described and consequent hypotheses formulated. In the third stage, these hypotheses were tested on the Delphi-panel. The Delphi-panel is sufficiently wide and diverse to produce plausible yet different insights. The research design utilised specifically military crisis management and peace operations theories. This produced various and relevant normative considerations. Therefore, one may argue that this research; which is based on accepted contemporary theory, hypotheses derived thereof and utilising an expert panel, contributes to the realm of peace support operations. This research finds that some degree of peace enforcement will be feasible and necessary in at least the following risk conditions: failed governance; potential spillover of ethnic, religious, ideological conflict; vulnerability of strategic chokepoints and infrastructures in ungoverned spaces; as well as in territorial and extra-territorial border disputes. In addition, some form of peace enforcement is probably necessary in risk conditions pertaining to: extremism of marginalised groups; potential disputes over previously uninhabited and resource-rich territories; and interstate rivalry. Furthermore, this research finds that peacekeeping measures will be feasible and necessary in at least risk conditions pertaining to: potential spillover of ethnic, religious, ideological conflict; uncontrolled migration; consequences from environmental catastrophes or changes; territorial and extra-territorial border disputes; and potential disputes over previously uninhabited and resource-rich territories. These findings are all subject to both generic and case specific preconditions that must exist for a peace support operation. Some deductions could be derived from the research findings. Although some risk conditions may appear illogical, understanding the underlying logic of a conflict is fundamental to understanding transition in crisis management. Practitioners of crisis management should possess cognizance of such transition. They must understand how transition should occur from threat to safety, from conflict to stability – and so forth. Understanding transition is imperative for managing the dynamic evolution of preconditions, which begins at the outset of a peace support operation. Furthermore, it is pertinent that spoilers are defined from a peace process point of view. If spoilers are defined otherwise, it changes the nature of an operation towards war, where the logic is breaking the will of an enemy - and surrender. In peace support operations, the logic is different: actions towards spoilers are intended to cause transition towards consent - not defeat. Notwithstanding future developments, history continues to provide strategic education. However, the distinction is that the risk conditions occur in novel futures. Hence, lessons learned from the past should be fitted to the case at hand. This research shows compelling evidence that swaying between intervention optimism and pessimism is not substantiated. Both peace enforcement and peacekeeping are sine qua non for successful military crisis management in the next decade.

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Operation Musketeer, a combined joint Anglo-French operation aimed at regaining control of the Suez Canal in 1956, has received much attention from scholars. The most common approach to the crisis has been to examine the political dimension. The political events that led Prime Minister Anthony Eden’s cabinet to decide to use military force against the wishes of their superior American ally and in the face of American economic pressure and a Soviet threat to attack Paris and London with rockets have been analysed thoroughly. This is particularly the case because the ceasefire and eventual withdrawal were an indisputable defeat of British policy in the Middle East. The military operation not only ruined Prime Minister Eden’s career, but it also diminished the prestige of Britain. It was the beginning of the end, some claim. The British Empire would never be the same. As the consequences of using force are generally considered more important than the military operations themselves, very little attention has been paid to the military planning of Operation Musketeer. The difference between the number of publications on Operation Corporate of the Falklands War and Operation Musketeer is striking. Not only has there been little previous research on the military aspects of Musketeer, the conclusions drawn in the existing works have not reached a consensus. Some historians, such as Correlli Barnett, compare Musketeer to the utter failures of the Tudor landings and Gallipoli. Among significant politicians, Winston Churchill, who had retired from the prime ministership only a year before the Suez Crisis, described the operation as “the most ill-conceived and ill-executed imaginable”. Colin McInnes, a well-known author on British defence policy, represents the middle view when he describes the execution as “far from failure”. Finally, some, like Julian Thompson, the Commander of 3 Commando Brigade during the Falklands War, rate the military action itself as being successful. The interpretation of how successful the handling of the Suez Crisis was from the military point of view depends very much on the approach taken and the areas emphasised in the subject. Frequently, military operations are analysed in isolation from other events. The action of a country’s armed forces is separated from the wider context and evaluated without a solid point of comparison. Political consequences are often used as validated criteria, and complicated factors contributing to military performance are ignored. The lack of comprehensive research on the military action has left room for an analysis concentrating on the military side of the crisis.

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Among the alternatives to meet the increasing of world demand for energy, the use of biomass as energy source is one of the most promising as it contributes to reducing emissions of carbon dioxide in the atmosphere. Gasification is a technological process of biomass energy production of a gaseous biofuel. The fuel gas has a low calorific value that can be used in Diesel engine in dual mode for power generation in isolated communities. This study aimed to evaluate the reduction in the consumption of oil Diesel an engine generator, using gas from gasification of wood. The engine generator brand used was a BRANCO, with direct injection power of 7.36 kW (10 HP) coupled to an electric generator 5.5 kW. Diesel oil mixed with intake air was injected, as the oil was injected via an injector of the engine (dual mode). The fuel gas was produced in a downdraft gasifier. The engine generator was put on load system from 0.5 kW to 3.5 kW through a set of electrical resistances. Diesel oil consumption was measured with a precision scale. It was concluded that the engine converted to dual mode when using the gas for the gasification of wood decreased Diesel consumption by up to 57%.

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ABSTRACT This paper studied the effect of adding an enzyme (ellulose) on anaerobic digestion of maize silage. We compared materials at chopping lengths of 8 mm (MSL), 4mm (MSS) and natural size (Ms) under a mesophilic and discontinuous operation (batch process). Hence, we found the process to be significantly influenced by particle size. Moreover, the ellulose addition did not significantly impact biogas production after a 35-day digestion period. Ms and MSS displayed an improved response to all variables when compared with MSL and MSL+C, with significant differences. Studies on the refractory fraction at infinite time (R0) have demonstrated that the lowest values correspond to Ms and MSS (0.122 and 0.155, respectively). The Kinetic approach and the Ultimate Biodegradability test are useful tools to evaluate the effect of the addition of an enzyme to the anaerobic process.

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Tämä työ on tehty Fingrid Oyj:lle. Työn tavoitteena oli tutkia, miten reaaliaikaista PMU-mittaustietoa voidaan hyödyntää voimajärjestelmän valvonnassa. Voimajärjestelmän dynaamisia ilmiöitä ovat jännite- ja kulmastabiilius. Työssä tutkittiin voimajärjestelmän kulmastabiiliutta PSS/E-ohjelmalla simuloitujen mittaustulosten perusteella. Fouriermuunnoksen tulokset osoittavat, että huonoiten vaimeneva taajuuskomponentti on 0,3 Hz taajuus. Lisäksi tiedetään, että huonosti vaimeneva taajuuskomponentti rajoittaa siirtokapasiteettia. Voimajärjestelmän stabiiliutta voidaan esittää Wide Area Monitoring -järjestelmien (WAMS) avulla. WAMS perustuu Phasor Measurement -laitteen (PMU) reaaliaikaiseen mittaustekniikkaan. Jännitteen vaihekulman mittaaminen mahdollistaa voimajärjestelmän tilan määrittämisen reaaliajassa. Työssä on esitelty Fingridin käytössä oleva WAMS ja lisäksi esitelty kolmen eri laitetoimittajan WAMS:n rakennetta ja operaattorin käyttöön tarkoitettuja käyttöliittymiä. WAMS:n rakenteet ovat pääpiirteittäin samanlaisia, mutta stabiiliuden visuaalisessa esittämisessä on eroja. PMU -mittaustietoja on mahdollista tuoda käytönvalvontajärjestelmään erillisellä tiedonsiirtoprotokollalla. PMU-mittaustiedon hyödyntäminen käytönvalvontajärjestelmän toimintaaluenäytöllä mahdollistaa verkon tilan esittämisen reaaliajassa. Roottorin kulmastabiilius esitetään Fingridin käytönvalvontajärjestelmässä vaihekulmaerojen avulla ja työssä on esitetty, kuinka vaihekulmaeron arvolla on vaikutus tehonsiirtoon. Vaihekulmaeron arvo kuvaa vian jälkeisen tehoheilahtelun voimakkuutta. PMU-mittaustiedon esittäminen antaa operaattorille selkeämmän kuvan ylläpitää tehonsiirto turvallisella tasolla ja epästabiilin heilahtelun havainnoiminen vähentää suurhäiriön riskiä. Tulevaisuudessa siirtoverkon kehittyessä tarvitaan operaattorin käyttöön myös nopeita stabiilisuutta esittäviä työkaluja.