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This thesis presents a unique design for an infrared spectrometer based on a MEMS Binary Fresnel Zone Plate for the purpose of assessing the health of oil-impregnated high voltage (HV) equipment. It does so by measuring dissolved gases within it. These gases include carbon monoxide, carbon dioxide, methane, ethane, ethylene, and acetylene. These gases are currently measured using numerous technologies such as gas combustion, gas chromatography, photoacoustic spectroscopy, and FTIR spectroscopy. Each of these technologies have their advantages and disadvantages. The design presented in this thesis consists of an analysis of how the various Binary Zone Plate parameters affect its spectral resolution and transmission efficiency. Simulations show that increasing the number of zones and the focal length, as well as decreasing the aperture diameter, increases the spectral resolution of the spectrometer. Simulations also show that transmission efficiency is proportional to the number of zones and the aperture diameter. This thesis presents a theoretical argument for how one zone plate lens can be used to measure all dissolved gases present in HV equipment. Lenses for the visible and infrared ranges were fabricated in the University of Manitoba NSFL Cleanroom. The lenses were then tested in an optical setup. The results show that the visible light experiments were successful in achieving appropriate spectral discrimination by changing the distance between the aperture and the lens. The results from the infrared experiment show that a detector was able to discriminate between full and no incident radiation. / May 2017

Outdoor electrical insulator is one of the important components of a power system which directly influences the system reliability. Traditionally ceramic insulators have been used for close to a century in both transmission and distribution lines. In the last few decades, polymer based outdoor insulators are being increasingly used in the above application. Polymeric insulators offer attractive advantages such as light weight, resistance to vandalism and they also outperform conventional ceramic insulators under contaminated wet conditions at least in the initial stages of their usage. However, there are certain disadvantages with polymeric insulators which have made the utilities hesitant to replace readily the ceramic insulators with polymeric insulators. One of the major concerns with the polymeric insulators is the aging w.r.t time due to the presence of multiple environmental stresses (fog, humidity, temperature, rain as well as contamination due to industrial, sea and agricultural pollution) along with electrical stress. The manifestations of the aging of insulators include tracking or/and erosion of the weathersheds. Polymers in pure form (unfilled) can not perform satisfactorily all the required functions (electrical, mechanical, thermal etc.) of an insulator used in such high voltage transmission lines. Polymers have inherently poor thermal stability. Thermal stability directly influences the tracking and erosion resistance of the weathershed. Without adequate tracking and erosion resistance, polymeric insulators can not perform satisfactorily under contaminated wet conditions. Hence the common practice to improve the tracking and erosion resistance (and other properties such as mechanical, thermal) is by filling the base polymer with large loadings (> 30 wt %) of micron sized fillers. This makes the processing of the polymer composite difficult as the viscosity of the material rises substantially at such large loadings. Due to the large filler loadings beyond a certain limit, the flexibility of the end product also suffers. Though tracking and erosion resistance of the polymer has been improved substantially at these large filler loadings, the recent failures in the field suggest the need for an alternate material with higher tracking and erosion resistance than what is achieved at these large loadings of micron sized fillers. Of late nanocomposites are emerging as promising alternatives which can offer the above mentioned functionalities at low filler loadings itself without sacrificing the flexibility in the end product as well as ease of processing. There are even indications suggesting that the tracking and erosion resistance performance is better than what is obtained using micronsized fillers. As the development of nanocomposite dielectrics/insulation is still at its infancy, it is required to investigate their specific properties needed for outdoor applications and to understand the various mechanisms responsible for the interesting behaviour of the nanocomposites. Also, it is known that dc pollution performance of ceramic insulators is much inferior to the performance under ac stress. With the introduction of higher ac/dc transmission voltages in many countries including India, it is required to design insulators with better performing materials so as to get a reliable performance under polluted wet conditions. Due to the hydrophobic nature of the polymers, it is believed that polymers especially silicone rubber insulators can perform better as compared to the ceramic insulators under polluted conditions under ac and dc. As the dc tracking and erosion (T&E) resistance of polymer is poor compared to the ac tracking and erosion resistance, it is required to investigate the T&E resistance characteristics of the nanocomposites under dc stress. In addition, due to the enhanced electric fields at the line end of the insulators in extra and ultra high voltage transmission lines, there is always a possibility of corona generation on the hardware at the metal-sheath junction and at the water droplet tips on the weathersheds of the polymeric insulators especially under foul weather conditions. It is reported that the long-term exposure to such corona has the potential to degrade the polymeric material. The effects include reduction of the hydrophobicity, surface oxidation of the weathersheds and development of microcracks on the surface of the polymeric material. These cracks (corona cutting) can worsen the wet pollution performance of the insulator. If the cracks grow deeper, then FRP rod would get exposed to the atmospheric conditions leading to brittle fracture of the FRP rod and finally resulting in the line drop. Hence, the corona aging resistance of nanocomposites has also been studied especially at low filler concentrations to see its performance under the above mentioned adverse conditions. Therefore, the research work presented here deals with three aspects of the aging (1) Study the ac and dc tracking and erosion resistance performance of silicone rubber nanocomposites with low concentrations of fillers and their suitability for outdoor applications (2) Study the corona aging performance of silicone rubber nanocomposites with low concentrations of fillers and (3) To develop a model to explain the unusual behaviour of nanocomposites observed in the above studies. The thesis also reports results of the accelerated multistress weathering studies conducted on normal polymeric outdoor insulators under prolonged dry conditions. The major challenge in case of the polymer nanocomposite processing is getting uniform distribution of the fillers. A protocol has been standardised for the processing which comprises high shear mechanical mixing followed by sonication to get good dispersion of the fillers. Room Temperature Vulcanised (RTV) silicone rubber was successfully processed with different micron and nanosized fillers and with different weight (wt.) percentages in the present work. For carrying out the T & E resistance, corona aging and multistress aging studies, facilities (such as Inclined Plane T & E Resistance Test Apparatus in line with IEC/ASTM standards and aging chambers) have been designed and developed in house as a part of the thesis work. The ac tracking and erosion resistance performance of the unfilled, microcomposite (filled with alumina trihydrate filler of 5, 10, 15, 20 and 30 % by wt) and nanocomposite (filled with alumina, silica and magnesium hydroxide fillers of 2.5 and 4 % by wt) have been compared in inclined plane (IP) tracking and erosion resistance test facility specifically developed for the work. It was very interesting to observe that nanocomposites at 4 % performed on par with the microcomposites at 30 % filler loadings. Leakage current was also measured during the IP test and it was found that the form factor (ratio of r.m.s to average leakage current) was in good agreement with the variation in the erosion resistance of the silicone rubber composites and hence it can be used as a diagnostic tool for assessing the aging state of the polymeric materials. It was also observed that the performance under positive dc stress was much inferior to the performance under ac stress. The dissipation of power under dc stress was estimated by measuring the leakage current through the sample and is found to be about four times (towards the end of the test) higher as compared to the power dissipation under ac stress. Intense electrolytic corrosion has been observed (under positive dc) on the grounded electrode and on the sample and chemical studies of the same have been carried out. The poor performance under dc is due to the absence of the voltage zero crossing, more accumulation of the contaminant (scaling) and electrolytic corrosion. It was also observed that to get the same tracking and erosion resistance under dc as in the case of ac during IP test, dc stress levels have to be reduced to about 60 % of the ac stress. This information would be helpful to the design engineer of the outdoor insulators for the HVDC transmission lines. To understand the different mechanisms responsible in improving the tracking and erosion resistance of the micro and nanocomposites, thermal, SEM and FTIR studies have been carried out. Thermal stability of the samples was measured using thermogravimetric analysis (TGA) and differential thermo gravimetric (DTG) studies. It was observed that thermal stability of nanocomposites even at low filler loadings (4 wt %) was comparable with the microcomposites at higher filler loadings (30 wt %). SEM studies indicate that the barrier resistance (against discharges) offered by the fillers in the nanocomposites even at low filler loadings (4 %) could be comparable with the microcomposites at higher filler loadings (30 %). The interaction between the fillers and the host matrix has been studied using various techniques. SEM studies done on the eroded regions of the composites revealed that a honey comb type formation had taken place on the nanocomposites during the IP test which was believed to be due to the interaction of the filler and the polymer. This honey comb structure formation at the eroded site in the nanocomposites greatly helps to protect the sample from further damage due to the discharges. The interaction at the interface between the polymer and fillers could also lead to further improvement in the thermal stability of the nanocomposite. A model was proposed which considers barrier resistance and a single-layer interaction around the fillers to explain the improvements offered by the nanocomposites. Corona aging studies have been carried out on unfilled silicone rubber, micro and nanocomposites for 25 h and 50 h of aging using a needle-plane electrode arrangement. Different parameters such as hydrophobicity, surface roughness, microcracks width on the aged surface, FTIR and SEM studies were carried out to study the corona aging resistance of the new and aged samples. The studies indicate that silicone rubber samples containing nanofillers at 3 wt % are able to impart significantly enough corona resistance compared to the unfilled and microcomposite samples. It is known that the discharge resistance offered by the fillers and the interaction/bonding between the fillers and polymers directly influences the corona aging resistance. Hence, the model proposed (discussed above) is valid for understanding the corona aging performance of the nanocomposites which is better than the unfilled and ATH filled silicone rubber. In addition to the tracking and erosion resistance and corona aging studies, multistress aging of commercially available polymeric insulators containing micron sized fillers has been carried out. The aging behaviour of the polymeric insulators under tropical and subtropical conditions (in the absence of discharges under wet conditions) has not been explored. Further, the long-term influence of the UV radiation on silicone rubber in the presence of temperature and electric stress is also not explored. Hence, to understand the aging phenomena (weathering characteristics) under multistress (electric, thermal and UV), distribution class composite polymeric insulators were aged for 30,000 h in a multistress aging chamber developed specifically for the studies. Insulators were continuously subjected to the accelerated electric and thermal stresses as well as UV radiation. Different studies like leakage current, SEM, hydrophobicity, surface roughness and low molecular weight (LMW) molecules content in the samples before and after the aging have been investigated. It is interesting to observe that even in the absence of electrical discharges on the surface of the material, significant monotonous reduction in LMW molecules has been observed w.r.t weathering time. Appreciable increase in the surface roughness (at least 200 % as that of the new material) as well as increased oxygen levels on the surface has also been observed. The results indicate that surface hydrophobicity is dynamic in nature and may not reflect the slow and permanent changes taking place in the bulk of the material. The results obtained for the nanocomposites enable us to design a better material with improved tracking, erosion and corona resistance without sacrificing the flexibility in the end product as well as ease of processing. The silicone rubber nanocomposites also open up the possibility for economically designing a smart material possibly with a higher reliability for outdoor insulator application.

It is anticipated that massive amounts of energy will be transferred long distances via High-Voltage Direct Current (HVDC) links in the future and the prospect of having meshed HVDC grids is envisioned, for example the European super grid. Such a power system would benefit greatly if HVDC circuit breakers could reliably clear faults within the HVDC network. Different ways to break large direct currents have been proposed throughout the years and one distinguished concept is based on generating an artificial zero-crossing of the current and pass it through a mechanical interrupter as it opens. This concept is implemented in the Voltage-Source Converter Assisted Resonant Current (VARC) circuit breakers developed at Scibreak which require auxiliary power from an off-line supply unit to energize their electronic equipment. This thesis continuous and builds on research previously carried out at Scibreak on a special Auxiliary Power Supply (APS) concept for 525 kV HVDC applications. In essence, it is a unique modularized high-frequency transformer whose power transfer and voltage withstand capabilities are the cornerstones of its design. The APS must supply an adequate amount of power to drive the VARC circuit breakers with preferably high efficiency while also fulfilling the considerable insulation demands of HVDC grids. A feasibility study of this APS concept was carried out by building a parametric 3D model in the Finite Element Analysis (FEA) software Ansys Maxwell which includes all parts that affect both its magnetic and electrical properties. The initial model reproduced experimental results from a magnetic APS prototype and was then used to explore a plethora of different geometries and materials with regards to its magnetic and dielectric designs. Specific design candidates were selected for more in-depth analysis and experimental work. All obtained results together with knowledge of commercially available materials show that the APS holds great promise to meet the necessary design criteria for its HVDC applications. Its dielectric design is well suited to continuously handle an operating voltage of 525 kV DC, meet the required impulse voltage levels of the grid and properly shield the magnetic structure. It is expected to have a long life time where the design criterion was always 30 years in this work. Moreover, its magnetic design is anticipated to supply a few kW of active power with efficiencies between 80 to 95 percent and manage a continuous operating time of 5 min. Both design aspects are interchangeable to a decent extent in order to cope with one another and produce a compromised design. / Det förväntas att enorma mängder energi kommer överföras långa sträckor med Högspänd Likström (HVDC) i framtiden och blivande HVDC-nät håller på att föreställas, till exempel det europeiska superelnätet. Ett sådant kraftsystem skulle ha stor nytta av HVDC-brytare som tillförlitligt kan bryta felströmmar inom HVDC-nätet. Olika sätt att bryta stora likströmmar har föreslagits med åren och ett distinkt koncept bygger på att generera en artificiell nollgenomgång av strömmen och föra den genom en mekanisk brytarkammare när den öppnas. Detta koncept är implementerat i de så kallade VARC-strömbrytarna som utvecklas hos Scibreak, vilka kräver hjälpmatning av effekt från en extern försörjningsenhet för att driva deras elektroniska utrustning. Denna avhandling fortsätter och bygger vidare på forskning som tidigare utförts hos Scibreak på ett speciellt Hjälpmatningskoncept (APS) för 525 kV HVDC-tillämpningar. I huvudsak är det en unik modulariserad högfrekvenstransformator vars kraftöverföring och spänningståligheter är huvudfokusen i dess design. Hjälpmatningen måste kunna leverera en tillräcklig mängd effekt för att driva VARC-brytarna med företrädesvis hög verkningsgrad, samtidigt som den ska uppfylla de betydande isolationskraven för HVDC-nät. En genomförbarhetsstudie av detta APS-koncept gjordes genom att bygga en parametrisk 3D modell i Finita Elementmetodsprogramvaran (FEM) Ansys Maxwell som inkluderar alla delar som påverkar både dess magnetiska och elektriska egenskaper. Den initiala modellen reproducerade experimentella resultat från en magnetisk APS-prototyp och användes sedan för att utforska en uppsjö av olika geometrier och material med avseende på dess magnetiska och dielektriska konstruktioner. Specifika designkandidater valdes ut för mer djupgående analys och experimentiellt arbete. Alla erhållna resultat tillsammans med kunskap om kommersiellt tillgängliga material visar att APS:n har stora möjligheter att uppfylla alla nödvändiga kriterier för sina HVDC-tillämpningar. Dess dielektriska design är väl lämpad för att kontinuerligt hantera en driftspänning på 525 kV DC, möta de erforderliga stötspänningståligheterna i nätet och ordentligt skydda den magnetiska strukturen. Den förväntas ha en lång livstid där designkriteriet alltid var 30 år i detta arbete. Dessutom förväntas dess magnetiska design leverera några kW aktiv effekt med verkningsgrader mellan 80 till 95 procent och klara en kontinuerlig drifttid på 5 min. Båda designaspekterna kan justeras i en någorlunda utsträckning för möta de krav som ställs från varandra och producera en kompromissad design.