Powerline technology (PL T) employs the electrical distribution network to transmit data in addition to supplying power. PL T is currently employed to provide data networking in many domestic environments, and is expected to play a major part in the development of the forthcoming Smart Grid. Given that the electrical distribution network was not designed with data transmission in mind, electromagnetic radiation from the network can give rise to interference. Regulators and researchers have considered the impact of such widespread radiation, and investigations of the various aspects of powerline have been conducted over the last decade. Despite this prolonged period, however, there remains a lack of agreement on the typical performance of such networks or the implications for regulation policy. An accurate model of the radio frequency (RF) properties of the typical electrical distribution network would be extremely valuable in developing standards and informing policy. The aim of this thesis is to provide a cohesive approach to determining the RF characteristics of a typical domestic property and applying such parameters to model the performance of PL T. The thesis reviews the recent development of broadband PL T, the progress made by the more prominent regulators, and the trials undertaken to define the key parameters affecting propagation. A detailed experimental programme carried out both in the laboratory and at typical sites is described.

New generation technology, small scale generation and storage, advances in power electronics, communication and computer technologies create different possibilities and opportunities for radical changes in the power system architecture. The increasing utilization of distributed generation and islanding operation practice becomes a hot topic around the world. Power system reliability is one of the most important factors in power system planning and operation. Distributed generation and microgrid have many issues, which directly and indirectly affect distribution system reliability. The basic objective of the research described in this thesis is to investigate the reliability benefits of utilizing distributed energy resources (DERs) and microgrid operation, and give some recommendations for planning and designing microgrids.

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Jn today's distribution system, voltage regulation is a big challenge. In fact, with more, inclusion of DG (Distributed Generation), managing Voltage to customer becomes more of a concern. Failure to maintain system voltage can result in unsatisfactory performance of customer's devices or complete failure resulting in damage.

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No description available.

Earthing systems are designed to perform satisfactorily under normal system voltage conditions as well as power frequency faults. The performance of most earth electrode geometries is now fairly well understood under these conditions. However, the response of earthing systems under high frequency and transient conditions is yet to be fully clarified, and there are several aspects of earthing systems that require further investigations. In this thesis, both modelling and experimental studies were carried out using high frequency and impulse current injection. Generic earth electrodes as well as the full earthing grid of an operating substation were investigated. The studies carried out in this work have confirmed some of the previous findings published in the open literature, and have clarified some aspects of conduction in earthing systems. The literature review on injuries due to lightning currents has highlighted the importance of good earthing systems. A comprehensive parametric simulation study was conducted on vertical rods, horizontal electrodes as well as earth grids under variable frequency and impulse currents. The effects of geometry and soil characteristics were also studied. It was demonstrated that significant inductive effects appear at high frequency, and the size of the earthing systems was found to reach an "effective dimension" beyond which negligible performance benefit is obtained. For horizontal electrodes the concept of effective length is investigated and for grids the effective area was used instead. The Simulation techniques developed for these simple electrodes were applied to an operating transmission substation, and similar trends were seen under high frequency and impulse current conditions. The safety voltages were calculated but no conclusion could be drawn as there are no recommended safety guidelines for safety at high frequency and impulse current. These Generic studies have led to a new proposal for earthing systems so that the short fall of poor performance due to inductive effects and "effective dimensions" are minimized. It was shown that this proposal is a major improvement on the existing enhancement techniques currently used in practice. Parallel to the simulation programme, an experimental set up was used to study the performance of laboratory earth electrode models under fast impulse current. It was found that highly non-linear conduction phenomena take place in such configurations. These complex conduction processes were explained by thermal effects and soil ionisation.

This thesis presents investigations of field-aged composite silicone rubber insulators, which have been deployed for 15 years on a 400 k V transmission line in a coastal region of the UK. Extensive measurements of their hydrophobicity, as detennined by contact angle, are given along with a description of their appearance. The hydrophobicity change varies from the low voltage end to the high voltage end with the lowest contact angles being found in the middle of the string. The sheds also aged differently around their circumference and this was reflected in discoloration differences on different sides of the insulator, in addition to hydrophobicity changes. Leakage current and surface discharge measurements carried out in the laboratory are also presented. Material analysis shows cracking and oxidation of the surface. Ageing effects were far from uniform over each shed, the greatest oxidation being on the top surfaces of the sheds on the south side: Microscopy, EDX and FTIR were found to be the most useful and effective tools for analysis of these polymeric insulators. The measurements of the various parameters over the whole surface of the insulators are found to be consistent with each other and can be interpreted in tenns of the chemistry of ageing and the longer term performance of the specific insulators in question. Two distinct types of ageing are identified. The role of solar radiation appears critical. It is suggested that wind direction, which is very consistent in the region concerned, may also be an important consideration. It is concluded that a possibility exists of an accelerated reduction in performance because of the non-uniformities observed. The asymmetry adds to the complexity of any model generated, and must be considered if the longer term operation of the insulator is to be forecast.

Liquid based insulation systems in the Electrical Power Industry will suffer a reduction in their dielectric performance over time because of ageing. Changes due to ageing effects include reduction in breakdown strength and increases in the conductivity of the liquid leading to larger losses in the system. In recent years, adding nanoparticles have been discovered to be a possible way of improving the properties of the liquid insulating material by increasing breakdown strength and thermal conductivity. It is therefore important to investigate whether the presence of nanoparticles can affect the mechanisms or rates at which ageing occurs. The research presented in this thesis focuses on the influence of ageing on the conductivity of Shell Diala S3 ZX-IG mineral insulation oil and the number and mobility of charge carriers present in the system. The conductivity and mobility have been derived from current transients produced under bipolar conditions at relatively low electric fields (0.3 to 0.7 kV/cm). Background material on ageing processes and reaction kinetics and possible diagnostic measurements; conductivity, mobility and how they can be measured and the nature properties of nanoparticles are provided. The techniques used to accelerate the ageing of the insulating liquids are then discussed with some broad estimates of the degree of acceleration. The development of the measurement system used to record the current transients and the interpretation of these transients in terms of mobility and conductivity is then described. Three sets of aged samples have been considered: samples that were thermally aged without nanoparticles (to act as a reference); samples that were thermally aged then had EFH1 magnetite nanoparticles added and samples that had Sigma magnetite nanoparticles added prior to thermal ageing. Current transients were measured for each sample over a range of voltages and these measurements were repeated over 5 successive days. Changes were observed in the current transients over this 5 day period. Possible reasons for these changes are discussed and the fitting techniques developed to determine the initial values and the equilibrium values of the parameters are described. For oil samples without nanoparticles added, thermal ageing resulted in a monotonic increase of the conductivity. Changes were also observed in the mobility of charge carriers. The mobility of charge carriers initially decreases in the first 48 hours of ageing and then increases with further ageing time. Increase of the density of charge carriers was observed as a result of thermal ageing. The samples with EFH with ageing time. The higher conductivities appear to be due to a higher mobility of charge carriers in the samples with EFH1 nanoparticles added. Again there is no simple relationship between mobility and ageing time. The study using the Sigma nanoparticles indicates that adding a relatively low concentration of nanoparticles to an unaged sample or to a sample after ageing does not change the conductivity of the liquid and the mobility of charge carriers significantly. However if the same concentration is added prior to thermal ageing significant changes in both the conductivity and the mobility of charge carriers is observed. This suggests that the rate of ageing or the ageing mechanism is affected by the presence of the nanoparticles. Although the addition of nanoparticles provides an approach of improving the dielectric properties of insulating oil, special attention needs to be paid on the drawbacks caused by the presence of nanoparticles. Using the insulating oil modified by nanoparticles can lead to an increase of the energy losses. In addition, the thermal ageing rate of the insulating oil could also be increased by the presence of nanoparticles. Further investigation of the effect of nanoparticles on ageing is required before the nanofluid can be used as alternative of the traditional insulating oil. Key words: Aging, liquid insulating material, nanoparticles, time-of-flight measurement, conductivity, mobility.