Dissertations / Theses on the topic 'Monitoring overhead'

Thermal limits of overhead transmission lines create network constraints that can result in curtailment of renewable energy generation. Thermal limits are conventionally static and based on worst-case, non-cooling ambient weather conditions, leading to under-utilization of overhead lines. Utilization can be increased and network constraints reduced by rating overhead lines dynamically, based on actual conductor temperature. Installation and maintenance of temperature and weather sensors along an overhead line is expensive and laborious. A more cost-effective solution is to derive average conductor temperature from overhead line impedance parameters, which can be calculated from measurements of electrical signals at each line end. Synchronized phasor measurement technology is becoming increasingly available in substations to capture voltage and current signals with high accuracy and reporting rates. It is known that the substation instrumentation channel can introduce significant systematic errors to the phasor measurements, which in turn cause inaccurate line impedance parameter and temperature values. This thesis presents novel methods for accurate, real-time monitoring of overhead line impedance parameters using synchronized phasor measurements that have systematic errors. In contrast to previous research, the time-variance and temperature dependence of line resistance as well as compensation of systematic errors is taken into account in the system model to increase parameter estimation accuracy. In addition, an algorithm for the selection of the best parameter estimates from different measurement sets is given. The effectiveness of the novel methods is demonstrated in several case studies on measurement data from simulations and an actual overhead line. The results show that the identified correction factors compensate systematic measurement errors, leading to a reduction in impedance parameter estimation errors of at least one order of magnitude compared to existing methods. Furthermore, the accuracy of real-time estimation of average conductor temperature was increased by at least one order of magnitude relative to previously proposed methods.

Overhead lines are the backbone of electrical power transmission. In most cases, the overhead line provides the best economic and practical solution for energy transmission. Nevertheless, overhead lines suffer more faults due to the vulnerability of the overhead lines to adverse weather condition, transient overvoltage and falling trees. An extensive literature review of existing condition monitoring and impulse a voltage measurement technique of overhead lines are covered in this work, and ultimately leads to the development of the proposed voltage transducer. Although conventional transducers such as voltage transformers and voltage dividers are widely used for monitoring and voltage measurement, yet they have several drawbacks in terms of their size and cost. These are the key factors that limit their widespread deployment for monitoring and measuring voltage on overhead lines and, in particular, rural areas. The proposed transducer is based on a non-contact capacitive voltage probe developed at Cardiff University. However, the proposed transducer uses a high voltage conductor rather than the ground as a measurement reference. The proposed transducer is based on a cylindrical-shaped in order to avoid sharp edges, which can initiate a partial discharge effect. Commercial numerical field computation software packages are used to assist in the development of the proposed transducer for simulation of the electric field distributions around the HV conductor and the transducer. The computed electric field magnitudes obtained on the sensing probe surface are then used for calibration of the proposed transducer. The proposed transducer is developed using low cost materials and tested in a laboratory environment with a low amplitude impulse supply using a surge generator and the corresponding output voltage amplitude obtained from the transducer was validated against a low ac voltage supply using variable output voltage source. The effects of variation in the input voltage, the integrating capacitor inserted between the HV conductor and the sensing probe and height of the transducer above ground on the output voltage amplitude are also investigated. The developed transducer is subsequently tested in field experiments using test overhead lines with low and high voltage supplies. Only a single-phase measurement setup was used in this test as there is only one voltage transducer fabricated in this work. Therefore, each phase of the overhead line was tested individually. Results obtained from the laboratory and field experiments have demonstrated the suitability of the developed transducer for measuring both ac and impulse voltages, which would be useful for fault monitoring on the high voltage overhead lines. However, the computed results obtained from the simulation demonstrated the presence of end-effects at the transducer sensing probe edges. Therefore, an improved design was proposed in this work by introducing a floating electrode between the sensing probe and the guard electrode, with the aim to reduce the fringing effects by preventing the sensing probe from sensing unwanted electric field. The physical development of this improved transducer design is yet to be initiated, and is thus proposed for future work.

With increasing design complexity, post-silicon validation has become a critical problem. In pre-silicon validation, coverage is the primary metric of validation effectiveness, but in post-silicon, the lack of observability makes coverage measurement problematic. On-chip coverage monitors are a possible solution, where a coverage monitor is a hardware circuit that sets to one when the coverage event of interest occurs. However, prior research has shown that the overhead is prohibitive for anything beyond a small number of coverage monitors. In this thesis, I explore techniques that reduce the number of instrumented coverage monitors, while still being able to imply full coverage with high probability. These techniques use a deterministic forward feature selection algorithm with the objective functions based on statistical information. For gathering the required statistical information, the method relies on emulation, where all coverage monitors of interest are instrumented on a version of the design. On this emulator, such as an FPGA, I stress the design with randomly generated tests to collect the data from the instrumented coverage monitors. I propose three objective functions for the feature selection algorithm: the first estimates the probability of a coverage monitor being set during a test; the next objective function builds a Bayesian Network (BN), then takes advantage of the relationship information between nodes (coverage monitors), which the network provides; the last objective function directly estimates the conditional probability of coverage from the gathered data. I demonstrate these techniques on a non-trivial system-on-chip, by measuring the code coverage achieved after executing randomly generated test programs. Depending on the objective function, results show a 67.7% to 95.5% reduction in the number of required coverage monitors. In the ASIC implementation, this would translate into an impact of 0.33-1.96% in silicon area overhead and 0.40-2.70% in static power overhead. These results show my technique works, by proving it is possible to track a smaller number of coverage events that statistically represent the whole set.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

As the demand for energy increases, as well as the demand for renewable energy, Vattenfall, as network owner, receives many requests to connect new wind power to the grid. The limiting factor for how much wind power that can be connected to the grid is in this case the maximum current capacity of the overhead lines that is based on a line temperature limit. The temperature limit is set to ensure a safety distance between the lines and the ground. This master thesis project is a part of a research project at Vattenfall Research and Development that is examining the possibilities of increasing the allowed current on overhead lines in order to be able to connect more wind power to the existing network. Measured data from two overhead lines in southern Sweden is analyzed and the internal relations between the measured parameters are examined. The measured parameters are overhead line sag, line temperature, ambient temperature, solar radiation, wind speed and line current. The results indicate that there is a big load margin that could be utilized to increase the maximum current as long as further work could show that low winds at line height correlates with low wind at nacelle height. The results show that the sag versus line temperature is approximately linear within the measured temperature range. This means that a real-time-monitoring system measuring the line temperature should give adequate knowledge of the line position to ensure the safety distance. A model for the line temperature as a function of insolation, current, ambient temperature and wind speed has been estimated for one of the lines. Simulations show that a sudden increase in current at a worst-case scenario would give the operators about ten minutes to react before the line reaches the temperature limit.

In this thesis, an integrated monitoring device for use on 11 kV overhead lines has been developed. Uniquely, the devices use an optimised form of Power Line Communication to enable a low latency communication network. It is shown that such a network is able to facilitate new and improved applications and offer tangible benefits to the network operator.

Le tecniche di monitoraggio possono estrarre dati accurati sul comportamento dei sistemi software. Se utilizzati nel campo, possono rivelare come le applicazioni si comportano in contesti del mondo reale e come i programmi sono effettivamente esercitati dai loro utenti. Tuttavia, la raccolta, l'elaborazione e la distribuzione dei dati sul campo devono essere eseguiti senza interruzioni e in modo non invasivo mentre gli utenti interagiscono con le loro applicazioni. Per limitare l'intrusività del monitoraggio sul campo, un approccio comune consiste nel ridurre la quantità di dati raccolti (ad esempio, in pochi eventi e in crash dump), che tuttavia possono influire gravemente sull'efficacia delle tecniche che sfruttano i dati sul campo. Questa tesi di dottorato indaga il trade-off tra il monitoraggio sul campo e il degrado dell'esperienza utente nelle applicazioni interattive, cioè le applicazioni che richiedono input dell'utente per continuare le sue operazioni. In particolare, abbiamo identificato due grandi sfide: capire come l'utente percepisce il sovraccarico del monitoraggio e studiare come raccogliere dati in modo non intrusivo senza perdere troppe informazioni. In breve, forniamo tre contributi principali. In primo luogo, presentiamo uno studio empirico volto a quantificare se e in che misura il sovraccarico di monitoraggio introdotto in un'applicazione interattiva è percepito dagli utenti. I risultati riportati possono essere sfruttati per progettare attentamente le procedure di analisi in esecuzione sul campo. In particolare, abbiamo scoperto che gli utenti non percepivano differenze significative per un overhead dell'80% e raramente percepivano un overhead del 140%. In secondo luogo, introduciamo un framework di monitoraggio per ricavare dati a runtime completi senza influire sulla qualità dell'esperienza utente. La tecnica produce un automa a stati finiti che mostra i possibili usi dell'applicazione dagli eventi osservati sul campo. Dal modello, è anche possibile estrarre tracce accurate e complete che potrebbero essere utilizzate per supportare varie attività, come il debugging, la riproduzione e la profilazione di errori di campo. Infine, presentiamo una strategia per ridurre ulteriormente l'impatto del monitoraggio limitando l'attività svolta in parallelo con le operazioni degli utenti: la strategia ritarda il salvataggio di eventi da archiviare in fasi di inattività dell'applicazione per ridurre l'impatto sull'esperienza utente. L'approccio riduce considerevolmente l'impatto del monitoraggio sulle operazioni degli utenti producendo tracce estremamente accurate. I risultati ottenuti in questo dottorato la tesi può abilitare una serie di soluzioni di test e analisi che sfruttano in modo estensivo i dati sul campo.
Monitoring techniques can extract accurate data about the behavior of software systems. When used in the field, they can reveal how applications behave in real-world contexts and how programs are actually exercised by their users. However, the collection, processing, and distribution of field data must be done seamlessly and unobtrusively while users interact with their applications. To limit the intrusiveness of field monitoring a common approach is to reduce the amount of collected data (e.g., to rare events and to crash dumps), which, however, may severely affect the effectiveness of the techniques that exploit field data. This Ph.D. thesis investigates the trade-off between field monitoring and the degradation of the user experience in interactive applications, that is, applications that require user inputs to continue its operations. In particular, we identified two big challenges: to understand how the user perceives monitoring overhead and, to study how to collect data in a non-intrusive way without losing too much information. In brief, we provide three main contributions. In the first place, we present an empirical study aimed at quantifying if and to what extent the monitoring overhead introduced in an interactive application is perceived by users. The reported results can be exploited to carefully design analysis procedures running in the field. In particular, we realized that users do not perceive significant differences for an overhead of 80\% and seldom perceived an overhead of 140\%. Secondly, we introduce a monitoring framework for deriving comprehensive runtime data without affecting the quality of the user experience. The technique produces a finite state automaton that shows possible usages of the application from the events observed in the field. From the model, it is also possible to extract accurate and comprehensive traces that could be used to support various tasks, such as debugging, field failures reproduction and profiling. Finally, we present a strategy to further reduce the impact of monitoring by limiting the activity performed in parallel with users' operations: the strategy delays the saving of events to file to idle phases of the application to reduce the impact on the user experience. The approach considerably decreases the impact of monitoring on user operations producing highly accurate traces. The results obtained in this Ph.D. thesis can enable a range of testing and analysis solutions that extensively exploit field data.

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.

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.

Tahle práce se zabývá monitorováním venkovních vysokonapěťových vedeních, což mohou být vedení od 70kV do 400kV. Senzory jsou umístěny na vodiči a hlavní myšlenkou je vyhodnotit mechanické chování vodičů, a to od nízkých frekvencí (zlomky Hz) až po vysoké frekvence (desítky Hz). Tahle práce se zabývala pohyby o nízkých frekvencích a vysokých amplitudách a popsala možnosti sestavení těchto pohybů na základě měření ze senzorů. Konkrétně se jedná o pohyby v případě silného větru, zkratu, opadávání ledu nebo dalších. Všechno tohle pomáhá operátorů dělat rozhodnutí ohledně provozování sítí. Vývoj zahrnuje přidání/kombinaci nových senzorů, popsání matematického algoritmu potřebného k sestavení pohybu na základě toho co bylo změřeno, ať už se jedná o hodnoty získané simulací, laboratorním testem nebo reálným měřením na vedení.

Розглянуто друге покоління систем моніторингу стану повітряних ліній електропередавання в умовах ожеледоутворення. Режимні заходи щодо захисту повітряних ліній від ожеледно-паморозевих відкладень та зменшення втрат на корону доцільно проводити з урахуванням поточної інформації про стан повітряних ліній.The second generation of the information monitoring system of overhead powerlines in the conditions of ice formation is considered. Regular measures to protect air lines from ice-frost deposits and reduction of the coronar losses are advisable to take into account current information on the state of the air lines.

Over the last several decades, electricity consumption and generation have continually grown. Investment in the Transmission and Distribution (T&D) infrastructure has been minimal and it has become increasingly difficult and expensive to permit and build new power lines. At the same time, a growing increase in the penetration of renewable energy resources is causing an unprecedented level of dynamics on the grid. Consequently, the power grid is congested and under stress. To compound the situation, the utilities do not possess detailed information on the status and operating margins on their assets in order to use them optimally. The task of monitoring asset status and optimizing asset utilization for the electric power industry seems particularly challenging, given millions of assets and hundreds of thousands of miles of power lines distributed geographically over millions of square miles. The lack of situational awareness compromises system reliability, and raises the possibility of power outages and even cascading blackouts. To address this problem, a conceptual Power Line Sensor Network (PLSN) is proposed in this research. The main objective of this research is to develop a distributed PLSN to provide continuous on-line monitoring of the geographically dispersed power grid by using hundreds of thousands of low-cost, autonomous, smart, and communication-enabled Power Line Sensor (PLS) modules thus to improve the utilization and reliability of the existing power system. The proposed PLSN specifically targets the use of passive sensing techniques, focusing on monitoring the real-time dynamic capacity of a specific span of a power line under present weather conditions by using computational intelligence technologies. An ancillary function is to detect the presence of incipient failures along overhead power lines via monitoring and characterizing the electromagnetic fields around overhead conductors. This research integrates detailed modeling of the power lines and the physical manifestations of the parameters being sensed, with pattern recognition technologies. Key issues of this research also include design of a prototype PLS module with integrated sensing, power and communication functions, and validation of the Wireless Sensor Network (WSN) technology integrated to this proposed PLSN.

This thesis concerns monitoring in Middle- and Low-Voltage distribution systems penetrated by distributed generation. Monitoring itself means measuring voltages and power flows and sending relevant data to the supervisory system. The first part of the thesis describes distribution systems with differences between individual voltage levels. The following chapter is focused on consequences of high share of renewable energy sources in distribution systems. Most of the problems are partially resolved by technical conditions for connection of the new power sources. However, difficulties with voltage regulation and uncontrolled power flows to higher voltage levels remain. These are the reasons for measuring voltages and currents in medium voltage networks. Second to last subhead of this chapter is dedicated to possible benefits of monitoring. The fourth part of the thesis deals with voltage and current sensors with their advantages and disadvantages. The best suitable devices are chosen in the end of the chapter. It is crucial to mention that sensors are only part of measuring system. Analog outputs from current or voltage transformers need to be converted to digital signal and further processed. After that required quantities are finally sent. Properties of these circuit cards are described in the sixth chapter. Following part aims to define a certain key that will determine the suitable locations for installation of the measurement. The final part of the thesis compares measured voltages and power flows from real 22 kV network with calculated values from computer program PAS DAISY Bizon.

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.14.02 – електричні станції, мережі і системи. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2017. Дисертація присвячена дослідженню проблемних питань, пов'язаних із розробкою інформаційних систем моніторингу стану повітряних ліній в умовах ожеледоутворення, що забезпечують зниження відмов у електропостачанні шляхом надання електротехнічному персоналу завчасної інформації про момент ожеледоутворення. У роботі представлено критичний аналіз існуючих систем моніторингу ожеледоутворення. З метою усунення їх недоліків, запропоновано нові первинний інформативний параметр і вимірювальний перетворювач ожеледоутворення. Для цього вдосконалено нестаціонарну теплову модель ділянки проводу, на основі якої, для заданих умов, досліджено інформативний параметр. Розроблено модель прогнозування динамічного ряду інформативного параметра, що дозволяє оцінити надійність отриманого прогнозу. Проведено необхідні експериментальні дослідження. Обґрунтовано архітектуру системи моніторингу стану повітряних ліній електропередавання. Для технічної реалізації системи моніторингу стану обґрунтовано структуру та будову вимірювального перетворювача блоку збору даних. Розроблено чисельну модель вимірювального перетворювача у програмному комплексі SolidWorks, що поєднує в собі розв'язок гідродинамічної та теплової задач. Також розроблено макет пристрою блоку збору даних системи моніторингу.
Thesis for getting scientific degree of the Candidate of technical science on the specialty 05.14.02 – electric power stations, network and system. – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2017. The thesis is devoted to the study of problematic issues related to the development of information systems for monitoring the state of overhead power lines in icing conditions, ensuring reduction of failures in the power supply, through the provision of electrical engineering personnel advance information about the icing point. The work presents a critical analysis of existing ice formation monitoring systems. In order to correct their deficiencies, proposed a new primary informative parameter and an ice accretion measuring transducer. To this end, the transient thermal model of the wire section of overhead power lines was improved. And based on this improved model, for the given conditions, an informative parameter was researched. The developed model for forecasting the time series of the informative parameter let to estimate the reliability of the obtained forecast. The necessary experimental studies were carried out. Architecture of the monitoring system of overhead power lines was justified. For the technical implementation of information monitoring system is justified the structure and a design of the measurement transducer of data collection unit. In this work were developed the numerical model in the SolidWorks software package, which combines the solution of the hydrodynamic and thermal problems. Also, was developed the device layout for the data acquisition unit of the monitoring system.

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.14.02 – електричні станції, мережі і системи. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2017. Дисертація присвячена дослідженню проблемних питань, пов'язаних із розробкою інформаційних систем моніторингу стану повітряних ліній в умовах ожеледоутворення, що забезпечують зниження відмов у електропостачанні шляхом надання електротехнічному персоналу завчасної інформації про момент ожеледоутворення. У роботі представлено критичний аналіз існуючих систем моніторингу ожеледоутворення. З метою усунення їх недоліків, запропоновано нові первинний інформативний параметр і вимірювальний перетворювач ожеледоутворення. Для цього вдосконалено нестаціонарну теплову модель ділянки проводу, на основі якої, для заданих умов, досліджено інформативний параметр. Розроблено модель прогнозування динамічного ряду інформативного параметра, що дозволяє оцінити надійність отриманого прогнозу. Проведено необхідні експериментальні дослідження. Обґрунтовано архітектуру системи моніторингу стану повітряних ліній електропередавання. Для технічної реалізації системи моніторингу стану обґрунтовано структуру та будову вимірювального перетворювача блоку збору даних. Розроблено чисельну модель вимірювального перетворювача у програмному комплексі SolidWorks, що поєднує в собі розв'язок гідродинамічної та теплової задач. Також розроблено макет пристрою блоку збору даних системи моніторингу.
Thesis for getting scientific degree of the Candidate of technical science on the specialty 05.14.02 – electric power stations, network and system. – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2017. The thesis is devoted to the study of problematic issues related to the development of information systems for monitoring the state of overhead power lines in icing conditions, ensuring reduction of failures in the power supply, through the provision of electrical engineering personnel advance information about the icing point. The work presents a critical analysis of existing ice formation monitoring systems. In order to correct their deficiencies, proposed a new primary informative parameter and an ice accretion measuring transducer. To this end, the transient thermal model of the wire section of overhead power lines was improved. And based on this improved model, for the given conditions, an informative parameter was researched. The developed model for forecasting the time series of the informative parameter let to estimate the reliability of the obtained forecast. The necessary experimental studies were carried out. Architecture of the monitoring system of overhead power lines was justified. For the technical implementation of information monitoring system is justified the structure and a design of the measurement transducer of data collection unit. In this work were developed the numerical model in the SolidWorks software package, which combines the solution of the hydrodynamic and thermal problems. Also, was developed the device layout for the data acquisition unit of the monitoring system.

The thesis aims to examine the impact of climate change on line rating and to investigate the possibility of a potential increase of capacity of an overhead line. The line rating of an overhead line determines how much current can be transmitted in the line. The weather parameters which affect the line rating are ambient temperature, solar radiation, wind speed, and wind direction. If the line rating is adapted to weather conditions, it is important to be able to predict how the weather will change in the future. Therefore, the impact of climate change on weather parameters is investigated. The ambient temperature and solar radiation are expected to change between different scenarios. However, it is unclear how wind speed and wind direction will be affected. Climate scenarios are designed that take these findings into account. The results show that wind speed has, by a large margin from other weather parameters, the largest impact on the dynamic line rating. This is followed by the wind's angle of attack to the conductor, ambient temperature, and finally solar radiation. For the designed climate scenarios, the dynamic line rating is almost the same in each case, which means that the calculated change in ambient temperature and solar radiation has no significant effect on the line rating. To further increase the capacity of the overhead line, the line could be upgraded with a conductor with a larger cross-sectional area.

Multi functional health monitoring wearable devices are quite prominent these days. Usually these devices are battery-operated and consequently are limited by their battery life (from few hours to a few weeks depending on the application). Of late, it was realized that these devices, which are currently being operated at fixed voltage and frequency, are capable of operating at multiple voltages and frequencies. By switching these voltages and frequencies to lower values based upon power requirements, these devices can achieve tremendous benefits in the form of energy savings. Dynamic Voltage and Frequency Scaling (DVFS) techniques have proven to be handy in this situation for an efficient trade-off between energy and timely behavior. Within imec, wearable devices make use of the indigenously developed MUSEIC v2 (Multi Sensor Integrated circuit version 2.0). This system is optimized for efficient and accurate collection, processing, and transfer of data from multiple (health) sensors. MUSEIC v2 has limited means in controlling the voltage and frequency dynamically. In this thesis we explore how traditional DVFS techniques can be applied to the MUSEIC v2. Experiments were conducted to find out the optimum power modes to efficiently operate and also to scale up-down the supply voltage and frequency. Considering the overhead caused when switching voltage and frequency, transition analysis was also done. Real-time and non real-time benchmarks were implemented based on these techniques and their performance results were obtained and analyzed. In this process, several state of the art scheduling algorithms and scaling techniques were reviewed in identifying a suitable technique. Using our proposed scaling technique implementation, we have achieved 86.95% power reduction in average, in contrast to the conventional way of the MUSEIC v2 chip’s processor operating at a fixed voltage and frequency. Techniques that include light sleep and deep sleep mode were also studied and implemented, which tested the system’s capability in accommodating Dynamic Power Management (DPM) techniques that can achieve greater benefits. A novel approach for implementing the deep sleep mechanism was also proposed and found that it can obtain up to 71.54% power savings, when compared to a traditional way of executing deep sleep mode.
Nuförtiden så har multifunktionella bärbara hälsoenheter fått en betydande roll. Dessa enheter drivs vanligtvis av batterier och är därför begränsade av batteritiden (från ett par timmar till ett par veckor beroende på tillämpningen). På senaste tiden har det framkommit att dessa enheter som används vid en fast spänning och frekvens kan användas vid flera spänningar och frekvenser. Genom att byta till lägre spänning och frekvens på grund av effektbehov så kan enheterna få enorma fördelar när det kommer till energibesparing. Dynamisk skalning av spänning och frekvens-tekniker (såkallad Dynamic Voltage and Frequency Scaling, DVFS) har visat sig vara användbara i detta sammanhang för en effektiv avvägning mellan energi och beteende. Hos Imec så använder sig bärbara enheter av den internt utvecklade MUSEIC v2 (Multi Sensor Integrated circuit version 2.0). Systemet är optimerat för effektiv och korrekt insamling, bearbetning och överföring av data från flera (hälso) sensorer. MUSEIC v2 har begränsad möjlighet att styra spänningen och frekvensen dynamiskt. I detta examensarbete undersöker vi hur traditionella DVFS-tekniker kan appliceras på MUSEIC v2. Experiment utfördes för att ta reda på de optimala effektlägena och för att effektivt kunna styra och även skala upp matningsspänningen och frekvensen. Eftersom att ”overhead” skapades vid växling av spänning och frekvens gjordes också en övergångsanalys. Realtidsoch icke-realtidskalkyler genomfördes baserat på dessa tekniker och resultaten sammanställdes och analyserades. I denna process granskades flera toppmoderna schemaläggningsalgoritmer och skalningstekniker för att hitta en lämplig teknik. Genom att använda vår föreslagna skalningsteknikimplementering har vi uppnått 86,95% effektreduktion i jämförelse med det konventionella sättet att MUSEIC v2-chipets processor arbetar med en fast spänning och frekvens. Tekniker som inkluderar lätt sömn och djupt sömnläge studerades och implementerades, vilket testade systemets förmåga att tillgodose DPM-tekniker (Dynamic Power Management) som kan uppnå ännu större fördelar. En ny metod för att genomföra den djupa sömnmekanismen föreslogs också och enligt erhållna resultat så kan den ge upp till 71,54% lägre energiförbrukning jämfört med det traditionella sättet att implementera djupt sömnläge.

Runtime verification is a lightweight technique that serves to complement existing approaches, such as formal methods and testing, to ensure system correctness. In runtime verification, monitors are synthesized to check a system at run time against a set of properties the system is expected to satisfy. Runtime verification may be used to determine software faults before and after system deployment. The monitor(s) can be synthesized to notify, steer and/or perform system recovery from detected software faults at run time. The research and proposed methods presented in this thesis aim to reduce the monitoring overhead of runtime verification in terms of memory and execution time by leveraging time-triggered techniques for monitoring system events. Traditionally, runtime verification frameworks employ event-triggered monitors, where the invocation of the monitor occurs after every system event. Because systems events can be sporadic or bursty in nature, event-triggered monitoring behaviour is difficult to predict. Time-triggered monitors, on the other hand, periodically preempt and process system events, making monitoring behaviour predictable. However, software system state reconstruction is not guaranteed (i.e., missed state changes/events between samples). The first part of this thesis analyzes three heuristics that efficiently solve the NP-complete problem of minimizing the amount of memory required to store system state changes to guarantee accurate state reconstruction. The experimental results demonstrate that adopting near-optimal algorithms do not greatly change the memory consumption and execution time of monitored programs; hence, NP-completeness is likely not an obstacle for time-triggered runtime verification. The second part of this thesis introduces a novel runtime verification technique called hybrid runtime verification. Hybrid runtime verification enables the monitor to toggle between event- and time-triggered modes of operation. The aim of this approach is to reduce the overall runtime monitoring overhead with respect to execution time. Minimizing the execution time overhead by employing hybrid runtime verification is not in NP. An integer linear programming heuristic is formulated to determine near-optimal hybrid monitoring schemes. Experimental results show that the heuristic typically selects monitoring schemes that are equal to or better than naively selecting exclusively one operation mode for monitoring.

碩士
國立臺灣科技大學
資訊工程系
107
With the growing of network services on the internet, quality of service and perfor-mance evaluation are critical issues for service provider. With regard to service runningnormally that need to monitor the network status. Network monitoring is an importantpart of network management, which collects flow statistics on the network for traffic en-gineering, flow re-routing, and attack detection. However, network monitoring may causelarge bandwidth overhead and long processing delay on switches. With monitoring de-mand, we need to have more efficiency and lower cost solution. Software-defined networking(SDN) splits network to control plane and data planeand relies on the central controller to control the whole network. Flow monitoring inSDN is more flexible than traditional networking. Network monitoring in SDN onlyneeds to install a monitoring module into the controller. Without configuring the specifichardware devices and software for high costs on operation and maintenance. In SDN,the controller collects all switches information and statistic on the control channel. SDNcontroller communicates with switches to dynamically manage the entire network. Tomake scalability and reliability on network, central controller has the global traffic viewof the whole network. The flow statistics can be collected from each switch which ispart of the flow passing path. However, many papers are using per-flow and per-switchmechanisms to get the flow statistics from switch. It may make huge bandwidth cost inthe control plane channel and collect much redundant flow information from switch. Inthis paper, we propose two algorithms to reduce the monitoring cost in SDN. We re-routenetwork traffic to minimize the monitoring node and bandwidth cost. With compare toother algorithms, we have reduced the monitoring node than other algorithms over 62%.Also, we improve monitoring bandwidth overhead than other algorithms over 41% .iv

碩士
國立臺灣大學
生物產業機電工程學研究所
106
For power companies around the world, transmission efficiency and power grid safety are two of the most important issues. The importance of the power grid safety goes without saying, after witnessing the impacts of a few power outages, such as the Northeast blackout of 2003, the 729 and 815 blackouts in Taiwan, and the 2012 India blackouts. The safety, efficiency and flexibility of high/extra-high voltage transmission lines can be improved by conducting real-time analyses on the parameters relating to the directly monitored transmission lines and their surrounding areas. The real-time information is criterial to power companies in power grid safety monitoring and power dispatch decision making. To monitor the safety of large scaled power grids, the best solution is to introduce “Internet of Things (IoT)” to power grids and use an IoT-based safety monitoring system on power grids. “IoT” has been one of the hottest terms in technology industries. An IoT monitoring system employs a wireless sensor network at the front-end sensing module to collect required local parameters for further analysis, and the analysis results can be used to improve various services. Nevertheless, the strong electromagnetic field around high/extra-high voltage lines is quite a technical barrier for electronic devices, which is much more challenging compared to other IoT applications. But the technical barrier has been removed and a reliable monitoring system for power grids that directly measures parameters on and around high voltage transmission lines in real time has been developed. In this research, a transmission line sag system is proposed. In this system, a three-axis accelerometer is used to measure transmission line sags, preventing the monitored transmission line from touching objects beneath it, which might lead to ground fault and even large-scale power failures. This study analyzes measured sag values collected during a seven-month stable operation and compares the measured values with theoretical values. The correlation coefficient of the two types of the sag values is 0.8603, and the mean absolute percent error (MAPE) is only 0.44%. Moreover, the accuracy of the measured sag values has been verified by comparing the values with field measurements. These results confirm the high accuracy, reliability and durability of the proposed sag monitoring system. In addition, this study examines the measurement results obtained from the devices placed on the three phases of a transmission line to verify the feasibility of applying the IoT technology to EHV transmission systems. The results show that this proposed sag monitoring system has overcome the challenge of the strong electromagnetic field around a transmission line with high/extra-high voltage. It reduces excessive construction costs when using other power grids monitoring systems. By adopting the IoT technology, the proposed system is able to be widely implemented in large-scale power grid monitoring. And, the line sag information can be used as power dispatch suggestions. The research results and conclusion provide criterial information not only to improve the flexibility of power dispatch but also to ensure the safety of power grids.

碩士
國立中興大學
電機工程學系所
101
Because of economic growth and incremental power demand, the construction of transmission lines needs to keep up with electricity growth except increasing power generation. In rising public opinion period, it is not easy to construct new overhead transmission line. Therefore, the best solution is to increase original transmission line''s capacity. Following the rapid development of information and internet technology, a way to increase transmission capacity both economically and rapidly has been developed. By installing real-time monitoring system into the overhead transmission line, the power system can monitor meteorological parameters and then calculate real-time transmission capacity through real-time communicating and calculating. Therefore, the real-time transmit power capacity can be greater than rated transmission capacity. As it takes a lot of parameters to calculate real-time transmission capacity, in this paper, we analyze the formula of calculating real-time transmission capacity with both the IEEE-738 and the JCS-374 standards. Taylor series method is employed to find each parameter''s influence in real-time transmission capacity. This paper proposes a real-time monitoring simulating system to yield a safe distance under the conductor. The simulating system also calculates the real-time transmission capacity to be compared with the rated transmission capacity. Taiwan power company has installed the first real-time monitoring system on Shanshang - Longqi line. Comparison of the calculated result of the real-time monitoring simulating system with the real-time monitoring system is conducted. The difference between the simulated results and real-time monitoring system is then analyzed.