No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

In this thesis, high-voltage nitrile-based electrolytes for lithium ion batteries were investigated. The electrolytes were composed of nitrile, dinitrile, and vinylene carbonate (VC) as an additive. Scanning electron microscopy showed the change of surface morphology of electrodes. The chemical compositions of the solid electrolyte interface were characterized by high resolution X-ray photo electron spectroscopy (HR-XPS). We found that the optimal ratio of dinitrile to nitrile is 6 to 4 by volume in terms of electrochemical performances. 5wt% VC as the additive has the enhanced electrochemical performances. The oxidation potential of the nitrile-based electrolytes can reach to 5.7 V. The discharge capacity of the Li||LiFePO4 cell with the nitrile-based electrolyte is about 80 mAhg-1 at a charge/discharge rate of 5 C under 30 oC, and its discharge efficiency after 100 cycles still keeps 94.35%.

No description available.

High voltage direct current. (hvdc) transmission of electrical paver has been made possible with the recent advent of multi-anode mercury arc valves with grading electrodes. However, mercury are valves do suffer from random phenomena such as arcback, which requires special bracing for the converter transformer. In addition, mercury arc valves need considerable auxiliaries, including cooling and vacuum plants. Research and development directed towards the improvement in the voltage and current capabilities of thyristors are yielding encouraging results. In contrast to mercury arc valves, thyristors do not suffer from random phenomena and require minim auxiliaries. Considering these advantages, thyristors offer a viable alternative to mercury arc valves for hvdc converters. The comparatively low ratings of thyristors necessitate series and parallel connection of thyristors in order to construct a valve of sufficient rating for hvdc operation. The design of thyristor valve should ensure even distribution of voltage and current among all thyristors of the valve, during all operating conditions. To achieve this objective transmission of the firing signal to the gate of each thyristors should have good coherence. The thesis examines design aspects, and considers the different methods of firing both theoretically and practically. Finally, the design and subsequent experimental results of the prototype thyristors valve rated at 10kv and 10A are also included.

Society has an every increasing thirst for electrical energy; this is only set to increase as the 21st Century progresses. In order to sustain this increasing demand, the power industry needs to consider a number of factors; adding generation capacity and maintaining the transmission and distribution networks that connect the producers to the consumers. This work focuses on the development of systems to aid maintenance operations. Parts of the transmission network in the UK date back to the 1950's and 60's, consisting of over 22,500 circuit km of overhead lines. The monitoring of this network is a significant ongoing task and needs to locate potential problems prior to failure. Numerous assessment techniques are presented in literature which discuss the examination of line components from the air or ground using the visual, infra-red or ultra-violet spectrums. Of particular interest in this work is the live-line inspection of composite insulators; thereby aligning with other ongoing work at The University of Manchester. While existing techniques have proved adequate to date, not all insulator surfaces can be appropriately seen. The ideal solution would be a device capable of photographing all insulator surfaces from a camera mounted on the insulator itself. While a number of live-line robotic systems are both in development and use around the world, operation and performance information is lacking; possibly due to commercial sensitivity issues. This work aims to clarify this situation, in particular focusing on the nature of broadband communication from, and survivability of complex electronics in areas of intense electric field strength and partial discharges. These areas are explored through the development of a technology demonstrator, a robot capable of imaging composite insulator surfaces in real-time and transmitting them to a ground station. Knowledge gained can then be adapted to create systems for other high-voltage monitoring situations. A systems level approach is taken whereby the technology demonstrator is divided into its constituent functional components. The requirements of each are assessed and research and development needs are detailed. Literature is reviewed to collate existing knowledge and enable comparison with the envisaged requirements. Prototype systems are developed to test the selected communication mechanism under high voltage conditions, while designs are created and fabricated for imaging and mechanical needs. The separate systems are then combined into the technology demonstrator and examined as a single unit under energised conditions. The author presents extensive results on the capability and nature of broadband radio frequency communication from areas of high electric field strength and partial discharges. They show that high data rates from such environments is possible up to a certain point at which high enhanced shield and antenna protection needs to be considered. They additionally demonstrate the transmission of live video from an energised composite insulator. This knowledge can be used to both improve the current system and as a basis to create additional monitoring solutions for high voltage situations. As such a new method of electric field distribution assessment is proposed.