This thesis details the design and development of a solid-state, high power modulator for driving plasma ion implantation systems. A plurality of modulators can be stacked in a Marx geometry to allow complete voltage (implantation energy) scalability. Unlike a classic Marx modulator, the design employs actively controlled charging and discharging paths. This allows maximum modulation flexibility and efficiency. A hybrid Marx bank - pulse transformer configuration was commissioned in a 20keV 12A plasma ion implantation system for the purpose of photonics research. <p>The design portion of this work is accompanied by an investigation, extension and discretization of the Lieberman analytical model of plasma ion implantation dynamics. The model predicts final implantation concentrations as well as system operational limits in specific plasma conditions. A new extension to the model accounts for subtle time-of-flight effects on accelerating ions. Agreement between modeled and measured ion currents is good.<p>Finally, a collection of material processing experiments conducted with the plasma ion implantation system since its inauguration in February 2006 is briefly presented. In it, a new silicon-based light emitting diode is introduced.

During the three decades, the torsional impact on turbine-generator sets due to power system disturbances has been extensively discussed in many research works. However, most of them are focused on the fatigue damage of turbine shafts due to large-signal disturbances. For example, network faults occur. Obviously, the torsional effect subject to small-signal disturbances has not received much attention. In fact, although the small disturbances would not immediately damage the turbine mechanism, the cumulative long-term damaging effects may not be negligible under certain circumstances. Many operating conditions in power systems may lead to small disturbances on blades; for examples, shedding loads, switching transmission line, resetting control system parameters, and harmonics etc. Nevertheless, others only cause short-term or transient non-resonant disturbances occasionally except the power system subharmonics which could results in electro-mechanical resonance. Therefore, two types of subharmonics in power systems are proposed so as to investigate the toque impact and long-term fatigue life expenditure in turbine shafts and blades. Firstly, from the steady-state disturbance viewpoint, the long-term cumulative fatigue estimation based on the three-year project of the GE Co. shows that there are potential damages for both the shafts and the blades of the nearby generators caused by the subharmonic excitations of the HVDC link. The fatigue life sensitivity works are also carried out to provide the recommendations for the safety operation. The optimal damper type and disposition scheme for depressing the resonant torque and prolonging the turbine lifetime is consequently motivated, which is based on participation factor of linear systems with the electromechanical analogy. The effectiveness of this scheme on suppressing vibration torque arising from network faults is also satisfying. In addition, the authors propose the new electromechanical supersynchronous resonance phenomenon for the turbine-generators near the inverter station owing to asymmetric line faults near the rectifier station. Secondly, the dramatic real and reactive power consumption during the melting period of an electrical arc furnace load. The voltage flicker pollution is mainly caused by the reactive power fluctuation while the stochastic subsynchronous oscillation in turbine mechanism is excited by the electromagnetic torque of the subsynchronous frequency which is induced by the real power fluctuation. Such a small stress imposed on the low-pressure long turbine blade combined with its evitable corrosive environment contributing to the corrosion fatigue effect. Although the voltage flicker severity at the point of common coupling is still within the limit, the blade may have been damaged from the long-term corrosion fatigue life expenditure estimation. In other words, the conventional voltage flicker limit established to make human-eye comfortable might not protect the blade from damaging risk. The long-term influence resulted from the electric arc furnace loads cannot always be neglected. It is necessary to take care of the blade material intensity and operating environment. If there is the potential of blade damage, one has to strengthen the output capacity at the power plant or separate the peak load durations among the steel plants to limit the over-fluctuation real power of the generator.

The interest in the utilization of offshore wind power is increasing significantly. Due to the shortage of in-land locations for wind farm and the wind speed offshore is potentially higher than that of onshore, which leads to a much higher power production. In this thesis a large offshore wind farm is modeled using Matlab simulation package. In the simulations active stall regulated wind turbines driving fixed speed asynchronous generators are used. Two different types of interconnections are modeled and compared, one is the Voltage Source Converter (VSC) based HVDC link and the other one uses high voltage AC (HVAC) cable interconnection. Transmission faults are simulated in each system and the transient response are examined. Three phase fault and single line to ground fault are used to compare the performance of the VSC based HVDC interconnection system and HVAC interconnection. It is found that compared to the traditional HVAC transmission, the VSC based HVDC transmission would have better performance under various system disturbances.

Developments in automotive (particularly hybrid electric vehicles), aerospace, and energy production industries over the recent years have led to expanding research interest in integrated circuit (IC) design toward high-temperature applications. A high-voltage, high-temperature SOI process allows for circuit design to expand into these extreme environment applications. Nearly all electronic devices require a reliable supply voltage capable of operating under various input voltages and load currents. These input voltages and load currents can be either DC or time-varying signals. In this work, a stable supply voltage for embedded circuit functions is generated on chip via a voltage regulator circuit producing a stable 5-V output voltage. Although applications of this voltage regulator are not limited to gate driver circuits, this regulator was developed to meet the demands of a gate driver IC. The voltage regulator must provide reliable output voltage over an input range from 10 V to 30 V, a temperature range of −50 ºC to 200 ºC, and output loads from 0 mA to 200 mA. Additionally, low power stand-by operation is provided to help reduce heat generation and thus lower operating junction temperature. This regulator is based on the LM723 Zener reference voltage regulator which allows stable performance over temperature (provided proper design of the temperature compensation scheme). This circuit topology and the SOI silicon process allow for reliable operation under all application demands. The designed voltage regulator has been successfully tested from −50 ºC to 200 ºC while demonstrating an output voltage variation of less than 25 mV under the full range of input voltage. Line regulation tests from 10 V to 35 V show a 3.7-ppm/V supply sensitivity. With the use of a high-temperature ceramic output capacitor, a 5-nsec edge, 0 to 220 mA, 1-µsec pulse width load current induced only a 55 mV drop in regulator output voltage. In the targeted application, load current pulse widths will be much shorter, thereby improving the load transient performance. Full temperature and input voltage range tests reveal the no-load supply current draw is within 330 µA while still providing an excess of 200 mA of load current upon demand.

Microbial colonization on the surface of silicone rubber high voltage outdoor insulators often results in the formation of highly hydrated biofilm that influence the surface properties, such as surface hydrophobicity. The loss of hydrophobicity might lead to dry band formation, and, in the worst cases, flashover and failure of the insulator. In this work, the biocidal effects of various antimicrobial compounds in silicone rubber materials were determined. These materials were evaluated according to an ISO standard for the antimicrobial activity against the growth of aggressive fungal strains, and microorganisms that have been found colonizing the surfaces of outdoor insulators in several areas in the world. Several compounds suppressed microbial growth on the surfaces of the materials without compromising the material properties of the silicone rubber. A commercial biocide and thymol were very effective against fungal growth, and sodium benzoate could suppress the fungal growth to some extent. Thymol could also inhibit algal growth. However, methods for preservation of the antimicrobial agents in the bulk of the material need to be further developed to prevent the loss of the compounds during manufacturing. Biofilm formation affected the surface hydrophobicity and complete removal of the biofilm was not achieved through cleaning. Surface analysis confirmed that traces of microorganisms were still present after cleaning. Further, surface modification of the silicone rubber was carried out to study how the texture and roughness of the surface affect biofilm formation. Silicone rubber surfaces with regular geometrical patterns were evaluated to determine the influence of the surface texture on the extent of microbial growth in comparison with plane silicone rubber surfaces. Silicone rubber nanocomposite surfaces, prepared using a spray-deposition method that applied hydrophilic and hydrophobic nanoparticles to obtain hierarchical structures, were studied to determine the effects of the surface roughness and improved hydrophobicity on the microbial attachment. Microenvironment chambers were used for the determination of microbial growth on different modified surfaces under conditions that mimic those of the insulators in their outdoor environments. Different parts of the insulators were represented by placing the samples vertically and inclined. The microbial growth on the surfaces of the textured samples was evenly distributed throughout the surfaces because of the uniform distribution of the water between the gaps of the regular structures on the surfaces. Microbial growth was not observed on the inclined and vertical nanocomposite surfaces due to the higher surface roughness and improved surface hydrophobicity, whereas non-coated samples were colonized by microorganisms. / <p>QC 20151002</p>

Στόχος της παρούσας διπλωματικής εργασίας είναι η αξιολόγηση της προστασίας του δικτύου Υψηλής Τάσης της Αρχής Ηλεκτρισμού Κύπρου, ΑΗΚ, ενάντια στα πλήγματα κεραυνών. Γίνεται μια παρουσίαση των διαφόρων τύπων κεραυνικών υπερτάσεων που μπορούν να εμφανιστούν σε ένα εναέριο δίκτυο μεταφοράς ηλεκτρικής ενέργειας, των σφαλμάτων που αυτά μπορεί να προκαλέσουν και εξετάζεται η αντοχή του δικτύου έναντι αυτών. Αρχικά γίνεται μία ιστορική αναδρομή της πορείας της ηλεκτρικής ενέργειας στην Κύπρο και του κεντρικού φορέα διαχείρισης του ηλεκτρικού ρεύματος στο νησί, της ΑΗΚ. Εν συνεχεία παρατίθενται λεπτομερώς τα στοιχεία που συνθέτουν σήμερα το δίκτυο της Αρχής Ηλεκτρισμού Κύπρου, το σύστημα παραγωγής, μεταφοράς και διανομής της ηλεκτρικής ενέργειας. Επίσης γίνεται σύντομη αναφορά στα σημαντικότερα στοιχεία που χαρακτηρίζουν το κλίμα της Κύπρου με ιδιαίτερη αναφορά στις καταιγίδες. Στο επόμενο κεφάλαιο παρουσιάζονται οι καταπονήσεις τις οποίες υφίστανται οι γραμμές μεταφοράς ενός δικτύου ηλεκτρικής ενέργειας με ιδιαίτερη έμφαση στις Ατμοσφαιρικές Υπερτάσεις. Γίνεται μια ενδελεχής παρουσίαση της βασικής αιτίας πρόκλησης αυτών, του Κεραυνού, και παρουσιάζονται αναλυτικά οι μηχανισμοί δημιουργίας υπερτάσεων στις γραμμές από κεραυνούς. Το επόμενο κεφάλαιο πραγματεύεται την παρουσίαση και επεξεργασία του συνόλου των σφαλμάτων που εμφανίστηκαν στο δίκτυο της ΑΗΚ σε μια περίοδο επτά ετών. Διαχωρίζονται σε κατηγορίες, παρουσιάζονται οι διάφορες αιτίες σφαλμάτων και αποτιμάται η βαρύτητα που έχουν τα πλήγματα από κεραυνούς στη πρόκληση σφαλμάτων στο δίκτυο. Τέλος, επιχειρείται να εκτιμηθεί ο πιθανός αριθμός σφαλμάτων από ανάστροφα βραχυκυκλώματα του δικτύου Υψηλής Τάσης της ΑΗΚ. Για το σκοπό αυτό, παρατίθενται δύο μεθόδοι, η αρχική και βελτιωμένη μέθοδος ANACOM. Εν κατακλείδι, γίνεται παρουσίαση των αποτελεσμάτων μας και διατυπώνονται τα συμπεράσματα μας αναφορικά με τα πραγματικά και αναμενόμενα σφάλματα στο δίκτυο Υ.Τ. της ΑΗΚ. / The aim of this degree paper is to evaluate the level of protection of the H.V. network of the EAC against lightning strokes. The various types of lightning overvoltages which could appear in an overhead electrical network are presented, as well as the faults that these could cause and finally the endurance of the network against them. Initially, a historical reference of electricity in Cyprus and of the EAC, which is the sole authority of electricity on the island, is given. Next, all the elements concerning the network of the EAC are presented in detail, namely the production, transmission and distribution systems. There is also a brief reference to the climatic conditions prevailing in Cyprus with a special reference to storms. In the next chapter the stresses of the lines are referred to with a special reference to the atmospheric overvoltages. A thorough presentation of the main cause of these overvoltage stresses is made, i.e. lightning, and their creation mechanisms is presented in detail. The following chapter deals with the presentation and processing of the total number of faults which appeared in EAC’s network over a period of seven years. These are then divided into categories, their causes are listed and an evaluation is made concerning the role of lightning strokes in the creation of faults in the network. Finally, an effort is made to estimate the number of faults caused by back-flashovers in the H.V. network of the EAC. In order to do this, two methods are presented, the basic and improved ANACOM methods. In the end the results are given and our conclusions are presented relating to the real and expected faults due to lightning strokes in the EAC’s H.V. network.

Τα Σύνθετα Υλικά χρησιμοποιούνται από την αρχαιότητα αλλά η ουσιαστική τους ανάπτυξη άρχισε από τον 20ο αιώνα. Είναι πολυφασικά υλικά τα οποία μπορούν να οριστούν ως ένας συνδυασμός από δύο ή περισσότερα υλικά που είναι ευδιάκριτα με φυσικό τρόπο και εύκολα διαχωρίσιμα με μηχανικό τρόπο. Ο συνδυασμός αυτός οδηγεί στη δημιουργία ενός υλικού με ανώτερες ιδιότητες από αυτές των διακριτών συστατικών. Τα επιμέρους συστατικά δεν είναι διαλυτά το ένα στο άλλο και μπορούν να αναμιχθούν μεταξύ τους με ελεγχόμενο τρόπο και με καθορισμένες αναλογίες. Τα σύνθετα υλικά αποτελούνται από δυο φάσεις: τη μήτρα και τη φάση ενίσχυσης ή φάση διασποράς ή έγκλεισμα. Η μήτρα είναι αυτή που δίνει στο υλικό την ακαμψία και το σχήμα του. Μεταφέρει, επίσης, τις μηχανικές τάσεις μέσα στο σύνθετο υλικό, διατηρεί τον προσανατολισμό των συστατικών και προστατεύει τα εγκλείσματα από τις περιβαλλοντικές συνθήκες. Τα εγκλείσματα διαφέρουν σε μέγεθος, γεωμετρία και σύσταση. Βρίσκονται σφηνωμένα στη μήτρα και είναι αυτά που προσδίδουν τις ιδιαίτερες ιδιότητες στο Σύνθετο Υλικό. Στη παρούσα εργασία γίνεται μια πειραματική διερεύνηση με ηλεκτρικές μεθόδους της επίδρασης νανοενισχύσεων στη μήτρα πολυμερών ινωδών σύνθετων υλικών συνεχούς ενίσχυσης. Για το σκοπό αυτό χρησιμοποιήθηκαν πολυμερή ινώδη σύνθετα υλικά με ενίσχυση υαλονημάτων, στη μήτρα των οποίων προσμίχθηκαν σε δύο περιπτώσεις πολυφλοιικοί νανοσωλήνες άνθρακα και πολύστρωτο γραφένιο σε συγκεντρώσεις της τάξης του 1%. Και τα δύο υλικά φημίζονται για τις εξαιρετικές ηλεκτρικές τους ιδιότητες. Στη συνέχεια διενεργήθηκαν τρεις τύποι ηλεκτρικών μετρήσεων. Αρχικά διενεργήθηκαν μετρήσεις της ηλεκτρικής αγωγιμότητας των υλικών υπό συνεχές ρεύμα, έπειτα διενεργήθηκαν μετρήσεις ηλεκτρικής αγωγιμότητας υπό την επίδραση εναλλασσόμενου ρεύματος και τέλος πραγματοποιήθηκαν μετρήσεις κρουστικής υψηλής τάσης προκειμένου να ελεγχθεί η ικανότητα των πολυλειτουργικών νανοσύνθετων υλικών να φέρουν κεραυνικά ηλεκτρικά φορτία τα οποία επιφέρουν μεγάλα πλήγματα στη δομή των αεροπορικών κατασκευών. Για τις μετρήσεις της ηλεκτρικής αγωγιμότητας συνεχούς ρεύματος DC χρησιμοποιήθηκε ένα ψηφιακό πολύμετρο “Keithley DMM 2002”. Για τις μετρήσεις ηλεκτρικής αγωγιμότητας υπό εναλλασσόμενο ρεύμα χρησιμοποιήθηκε η μέθοδος της διηλεκτρικής φασματοσκοπίας. Ο ηλεκτρικός χαρακτηρισμός των δειγμάτων πραγματοποιήθηκε σε εύρος συχνοτήτων από 10-1Hz έως 107Hz, με χρήση της ηλεκτρικής γέφυρας Alpha-N Analyser (High resolution dielectric analyzer) της εταιρείας Novocontrol. Όλα τα εξετασθέντα δείγματα υποβλήθηκαν σε ισόθερμες σαρώσεις συχνοτήτων. Η κυψελίδα μετρήσεων που χρησιμοποιήθηκε ήταν η BDS 1200 της ίδιας εταιρείας. Τέλος, οι μετρήσεις κρουστικής υψηλής τάσης πραγματοποιήθηκαν στο Εργαστήριο Υψηλών Τάσεων με χρήση της διβάθμιας κρουστικής γεννήτριας HAEFELY. Από την πειραματική διαδικασία και τα αντίστοιχα αποτελέσματα, που παρουσιάζονται αναλυτικά στα κεφάλαια 8 και 9 προέκυψαν τα συμπεράσματα που περιγράφονται στο κεφάλαιο 10. Συνοπτικά σημειώνεται ότι σε τρεις διαφορετικές πειραματικές διαδικασίες και σε καθεστώς διαφορετικών συνθηκών (στατική φόρτιση, εναλλασσόμενη φόρτιση και επιβολή κρουστικών τάσεων) το υλικό 1% CNT παρουσίασε σε όλες τις περιπτώσεις αισθητά καλύτερη αγώγιμη συμπεριφορά. / The Composite materials have been used since ancient times but their actual development did not start till the 20th century. These are polyphase materials which can be identified as a combination of two or more components which are distinguishable in a natural way and easily separable in a mechanical way. This combination leads to the development of a material with superior qualifies to those of distinct components. The particular components are not dissolvable but they can mix with each other when under control and in specific proportions. The composite materials are composed by two phases. The matrix and the reinforcement phase. The matrix is the one responsible for the rigidness and the shape of the material. It also transfers the mechanical stretches within the composite material, it sustains orientation of the components and protects the reinforcement phase from environmental conditions. Particulates of the reinforcement phase differ in size, geometry and composition. They are firmly located in the matrix and they are the ones to add specific qualities to the Composite. This work aims to survey experimentally through electric methods the impact of the nano-reinforcements in the matrix of fiber polymers. For this purpose fibre polymer composites with fiberglass reinforcement were used. In the matrix of these materials multi-walled carbon nanotubes και multi-layer graphene in concentration of about 1% were blended. Both materials are known for their exceptional electrical properties. Then, three types of electric conductivity measurements were carried out. Initially measurements of electric conductivity of the material was performed under dc, then measurements of electric conductivity under ac and finally there were measurements of impulse high voltage in order to check the ability of multifunctional nano-composite material to conduct thunder electric charges which may gravely afflict aeroplanes. For the specific measurements of the electric conductivity under dc, a digital polymeter “Keithley DMM 2002” was used. For the measurements under ac the method of dielectric spectroscopy was used. The electric characterization of the materials was carried out in frequency range of 10-1Hz έως 107Hz, using the Alpha-N Analyser (high resolution dielectric analyzer) of Novocontrol company. All the materials were subjected to frequency scanning of constant temperature. For this experiment the BDS 1200 device of the same company was used. Finally, the impulse high voltage measurements were performed in High Voltage Lab using the HAEFELY two stage impulse generator. The results which occurred from the experimental procedure and the respective results and which are presented in chapters 8 & 9 are described in chapter 10. In summary, it is noted that in three different experimental procedures and different status conditions (DC, AC and impulse high voltage) the material 1% CNT showed in all cases significantly better conductive behavior.

Σκοπός της παρούσας διπλωματικής εργασίας είναι η μελέτη της λειτουργίας των καθοδικών αλεξικεραύνων κατά την προστασία γραμμών μεταφοράς υψηλής τάσης. Ειδικότερα, λόγω της ιδιαίτερης φύσης των κεραυνών και των πληγμάτων που αυτοί επιφέρουν, γίνεται μελέτη μοντέλων που έχουν προταθεί για την προσομείωση των αλεξικεραύνων κατά την λειτουργία τους. / The purpose of this paper is to study the function of surge arresters protecting high voltage transmission lines. Specifically, given the particular nature of lightning strikes and the blows they bring, models that have been proposed for the simulation of surge arrestes during operation are being studied.

Στην διπλωματική αυτή μελετάται η επίδραση των ηλεκτρικών εκκενώσεων (κεραυνών) σε επιφάνειες ηλεκτροδίων, που αποτελούν μέρος συστήματος αντικεραυνικής προστασίας (ΣΑΠ). Στο Κεφάλαιο 1 αναλύεται το φαινόμενο των υπερτάσεων και των κεραυνικών εκκενώσεων. Το φαινόμενο των ηλεκτρικών εκκενώσεων, μελετάται σε εργαστήρια υψηλής τάσης, με διάκενα αέρος, ενώ στην συγκεκριμένη περίπτωση, το φαινόμενο των κεραυνών προσομοιώνεται με την διάταξη Ακίδα-Πλάκα. Μετά από μια σύντομη αναφορά στα διάκενα αέρος και τις εκκενώσεις, στο Κεφάλαιο 2 αναλύονται οι συνθήκες που επηρεάζουν τις εκκενώσεις, οπως διαστάσεις, αποστάσεις, ατμοσφαιρικές συνθήκες (υγρασία, θερμοκρασία, ατμοσφαιρική πίεση). Στο Εργαστήριο Υψηλών Τάσεων χρησιμοποιούνται γεννήτριες υψηλών τάσεων που μας παρέχουν τάσεις σε επιθυμητό επίπεδο και επιθυμητή μορφή (στην συγκεκριμένη περίπτωση κρουστικά κύματα). Περιγράφεται σύντομα η κατασκευή της γεννήτριας του εργαστηρίου, τα κύρια χαρακτηριστικά της καθώς και ο τρόπος λειτουργίας που την διέπει. Στην συνέχεια (Κεφάλαιο 3), παρατίθενται οι συνήθεις τρόποι για προστασία κτιρίων, υποδομών και μηχανημάτων από ηλεκτρικές εκκενώσεις, ο τρόπος σχεδίασης του ΣΑΠ δηλαδή. Παρατίθενται οι μέθοδοι τοποθέτησης συλλεκτήριων αγωγών των ΣΑΠ, καθώς και οι τρόποι γείωσης που συναντώνται πιο συχνά και η επίδραση του περιβάλλοντος πάνω τους. Στην συνέχεια (Κεφάλαιο 4), μελετάται το αλουμίνιο (Al ) σαν υλικό χρησιμοποιούμενο σε ΣΑΠ. Αναλύονται τα βασικά χαρακτηριστικά του, συμπεριφορά του και οξείδωση του. Στο Κεφάλαιο 5 αναλύεται η διαδικασία επεξεργασίας των πλακών αλουμινίου, και οι μέθοδοι τεχνητής γήρανσης που ακολουθήθηκαν, ενώ στο Κεφάλαιο 6 περιγράφεται η πειραματική διαδικασία και ο τρόπος συλλογής και επεξεργασίας των μετρήσεων. Στο Κεφάλαιο 7 καταγράφονται οι μετρήσεις που ελήφθησαν σε διάφορες πλάκες αλουμινίου, με διαφορετικές διαδικασίες τεχνητής γήρανσης,για διαφορετικά διάκενα (αποστάσεις), καθώς και για διαφορετικές ατμοσφαιρικές συνθήκες, που δείχνουν την συμπεριφορά των πλακών , υπό διαφορετικές συνθήκες γήρανσης και λειτουργίας. Τέλος, στο Κεφάλαιο 8 γίνεται η σύνοψη της πειραματικής διαδικασίας και η παράθεση των αποτελεσμάτων της μελέτης. / The main subject this project is the effect of electric discharge (lightning) on the surfaces of electrodes, that are part of a Lightning protection System (LPS). In Chapter 1, we study the phenomenon of electric-surge (hyper-voltage) and lightning discharge. Lightning Discharges are studied in High-Voltage Laboratories with the help of test air-gaps and in this particular situation, lightning is simulated by a spike-plate setup. After a short report on air-gaps and discharges, the conditions that effect discharges are analyzed in Chapter 2 (i.e moisture, temperature, air pressure). In our High-Voltage Lab we use high-voltage generators that provide voltages of desired level and form (here, shock-waved voltages). The lab's generator is shortly described, its main characteristics and its operation. In Chapter 3, we meet the most often used ways of protecting buildings, infrastructures and machinery against electric discharges and the way an LPS is designed. The methods of mounting lightning collectors (lighting protection components - LPCs) are listed, as well as the methods of grounding the LPS and the environmental effect on them. In Chapter 4 Aluminium (Al) is studied, as a material used in LPS. Its basic characteristics, behavior and oxidation are analyzed. In Chapter 5, the plates processing procedures are described, as well as the artificial-ageing methods used in the experiment, whereas in Chapter 6 the experimental procedure and the collection and processing of measurements is analyzed. The measurements of discharges on different aluminium plates are recorded in Chapter 7, with different artificial-ageing processes used, different gaps (distance), and different atmospheric conditions, showing the behavior of the plates under various operating conditions and ageing. Finally, in Chapter 8 there is the summary of the experimental procedure and the presentation of the study results.

This dissertation presents circuit techniques for designing high performance amplifiers. In low power design, the range of common mode input signal shrinks due to reduced power supply voltage. In addition, due to reduced bias current, noise density rises. The reduced input signal range and raised noise floor severely degrade system dynamic range. A novel rail to rail input circuit is presented. The proposed circuit has advantages over conventional circuits in term of noise and power consumption. Moreover, due to reduced bias current, low power amplifiers typically have lower bandwidth and slew rate, which limits their dynamic performance. The bandwidth is further reduced at high gain settings because of the constant gain bandwidth product. A novel self-adaptive compensation technique to extend small signal bandwidth and improve slew behavior is presented. If an amplifier needs to drive various capacitive and/or resistive loads, parallel Miller compensation is the most power efficient frequency compensation scheme. However, the frequency response of parallel Miller compensation is complicated and no thorough analysis on frequency response has been given in literatures. To illustrate the connection between poles/zeros and each individual circuit component, we use a design oriented approach to derive transfer functions for various load conditions. With these transfer functions, circuit designers can optimize their design accordingly. As a case study, a low power precision instrumentation amplifier is designed. Compared to low power instrumentation amplifiers on the market or reported in literature, it can save at least 40% power, meanwhile offer higher bandwidth and faster slew rate at typical gain settings. Many challenges also exist in designing high voltage amplifiers. To achieve low cost and high performance, a novel topology of a high voltage current sensing amplifier is proposed. With this topology, major portion of amplifiers can be designed with low voltage, for instance, 5 V, devices, and only a limited amount of LDMOS are required to stand off high voltage. This topology does not have high noise gain as conventional solutions have. The same principle can be used for other high voltage amplifiers. A prototype chip is fabricated. The amplifier functions as expected. Test results are presented.