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Odorous gases such as hydrogen sulfide have long been associated with wastewater treatment plants, especially those with long forced mains which allow septic conditions to develop. With the encroachment of urban and suburban populations, many wastewater treatment plants are no longer located far enough from residential areas to prevent odor problems. This has lead to renewed efforts to develop odor control techniques. The application of high energy coronas as a means to oxidize odorous gases has been limited by the relatively small size of the corona region around a given charged wire, approximately 1 centimeter at an applied voltage of 35 kilovolts. Attempts to enlarge the effective corona region by spacing wires such that their coronas would overlap have failed due to corona extinction, the destructive interference of the electric fields surrounding adjacent charged wires. This study demonstrates that corona extinction can be avoided in a system of closely spaced wires flanked by grounded plates if the wires are energized individually instead of' simultaneously. By employing a rapid load-switching technique an essentially continuous corona sheet can be produced. A bench-scale device utilizing the rapid switching principle was constructed and its ability to remove odorous gases, including hydrogen sulfide, was demonstrated. The influence of parameters such as flowrate, inlet concentration, switching frequency, temperature, and humidity on removal efficiency was evaluated. / Ph. D. / incomplete_metadata

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2007. / Electrical energy is continuously transported across the world by high voltage transmission lines. These transmission lines are however subject to losses beside the inherent resistive and dielectric losses. This additional loss phenomenon is described as corona. The CSIR has developed an optical system to detect the radiation caused by the corona so that preventive measures can be taken to reduce these losses. The corona mechanism and how it results in measurable radiation is explored and the structure of the optical system is analyzed. The optical emissions detected by the present optical system offer no indication of the severity of the corona discharge. This issue is addressed in this thesis as correlations are sought between the illuminated pixels displayed on the camera’s display and physical quantities. A blackbody is employed to find a correlation between these illuminated pixels and radiation. Deviations from the correlation drawn is explored regarding the saturation mechanisms of the optical system and the distance from the blackbody. A corona cage is next employed to find a correlation between the illuminated pixels and electrical corona loss, a quantity indicative of the severity of corona losses on a transmission line. Further tests are also performed at a reduced gain as it was discovered that the optical system’s response is more linear at reduced gain than at full gain. It is also indicated that this usage of reduced gain does not have a detrimental effect on the sensitivity of the optical system. The corona cage measurement employs a small spheric source which is taken as a base measurement against which all other measurements can be compared. The deviation of this base analogy is explored against deviations in the corona discharge geometry used, the prevalent weather condition, and the saturation of the optical system itself. Both the corona cage and blackbodies used are quite bulky pieces of laboratory equipment. The use of a smaller, more portable calibration source is therefore also explored. A literature study is made of lasers, lamp sources, and laser diodes that can be employed as a more portable calibration source. The final choice of calibration source is shown to be a lamp source. Tungsten calibration lamps are explored in depth and a circuit is designed to keep the radiation from a lamp source constant in order to improve on its ability as a calibration source.

Chung, Chor Fung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 95-97). / Abstracts in English and Chinese. / Acknowledgements --- p.iv / Table of Contents --- p.v / List of Figures --- p.viii / List of Tables --- p.xiii / Nomenclature --- p.xiv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Development of Micro Indoor Surveillance Flyers --- p.1 / Chapter 1.1.1 --- Overview --- p.1 / Chapter 1.1.2 --- Intrinsic Problem of Surveillance Helicopters --- p.2 / Chapter 1.2 --- Proposed Non-moving Parts and Noiseless Flyers --- p.2 / Chapter 1.3 --- Organization of the remaining dissertation --- p.5 / Chapter Chapter 2 --- The Basic Structure of the Ionic Flyers --- p.7 / Chapter 2.1 --- The Components and the Structural Parameters of the Ionic Flyers --- p.7 / Chapter 2.2 --- Proposed Operational Principles --- p.8 / Chapter 2.2.1 --- The Electrohydrodynamic Effect --- p.9 / Chapter 2.2.2 --- The Biefeld-Brown Effect --- p.10 / Chapter Chapter 3 --- Overview of Corona Discharge --- p.11 / Chapter 3.1 --- The Gaseous Discharge --- p.11 / Chapter 3.2 --- "Uniform Fields, Electrical Breakdown" --- p.12 / Chapter 3.3 --- "Non-uniform Fields, Corona Discharge" --- p.12 / Chapter 3.3.1 --- Positive Corona Discharge --- p.13 / Chapter 3.3.2 --- Negative Corona Discharge --- p.14 / Chapter 3.4 --- Conclusion --- p.15 / Chapter Chapter 4 --- Electrical Current-Voltage Model --- p.16 / Chapter 4.1 --- Experimental Setup and Measurement --- p.17 / Chapter 4.2 --- Basic Current to Voltage Relationship --- p.18 / Chapter 4.2.1 --- The Three Electrical Stages of the Ionic Flyers --- p.20 / Chapter 4.2.2 --- Proposed Quadratic Equation for the Current to Voltage Relationship --- p.22 / Chapter 4.3 --- Determination of the Current Gain C and the Onset Voltage V0 by the Structural Parameters of the Ionic Flyers --- p.22 / Chapter 4.3.1 --- The Electrode Length (L) --- p.24 / Chapter 4.3.2 --- The Gap Distance between the Wire-emitter and the Plate-collector (d) --- p.27 / Chapter 4.3.3 --- The Wire-emitter Radius (rw) --- p.31 / Chapter 4.3.4 --- The Plate-collector Height (h) --- p.36 / Chapter 4.3.5 --- The Electrode Enclosed Area (A) --- p.38 / Chapter 4.3.6 --- The Electrical Environmental Constant (Ke) --- p.43 / Chapter 4.4 --- Summary of the Experimental Derived Current-Voltage Model --- p.45 / Chapter Chapter 5 --- Mechanical Lift-force Models --- p.46 / Chapter 5.1 --- Experimental Setup and Measurement --- p.47 / Chapter 5.2 --- Basic Lift-force to Voltage Relationship --- p.49 / Chapter 5.2.1 --- The Initial Power Dissipation (IPD) --- p.50 / Chapter 5.2.2 --- The Maximum Lift-force --- p.51 / Chapter 5.2.3 --- Proposed Third-order Equation for the Lift-force to Power Relationship --- p.52 / Chapter 5.3 --- Determination of the Voltage Gain J and the Barrier Voltage Vfby the Structural Parameters of the Ionic Flyers --- p.54 / Chapter 5.3.1 --- The Electrical Length (L) --- p.55 / Chapter 5.3.2 --- The Gap Distance between the Wire-emitter and the Plate-collector (d) --- p.59 / Chapter 5.3.3 --- The Wire-emitter Radius (rw) --- p.63 / Chapter 5.3.4 --- The Plate-collector Height (h) --- p.66 / Chapter 5.3.5 --- The Electrode Enclosed Area (A) --- p.67 / Chapter 5.3.6 --- The Lift-force Environmental Constant (Kf) --- p.71 / Chapter 5.4 --- Summary of the Experimental Derived Lift-force Model --- p.73 / Chapter 5.5 --- Analysis on the Force/Power Ratio of the Ionic Flyers --- p.74 / Chapter Chapter 6 --- Further development of the Ionic Flyers --- p.76 / Chapter 6.1 --- Multi-directional Force Generation --- p.76 / Chapter 6.1.1 --- Linear Motion --- p.77 / Chapter 6.1.2 --- Rotation Motion --- p.78 / Chapter 6.2 --- Application of MEMS Motion Sensors and Wireless Signal Transmission --- p.80 / Chapter Chapter 7 --- Future Work --- p.84 / Chapter 7.1 --- Single-Emitter-Multiple-Collector Ionic Flyers --- p.84 / Chapter 7.2 --- Development of Miniaturized High-voltage Power Supply --- p.88 / Chapter Chapter 8 --- Conclusion --- p.90 / Chapter 8.1 --- The Electrical Current to Voltage Model --- p.90 / Chapter 8.2 --- The Mechanical Lift-force to Power Model --- p.91 / Chapter 8.3 --- The Force/Power Ratio Model --- p.91 / Appendix A --- p.92

Even minimal improvements in particle collection efficiency of electrostatic precipitators significantly reduce dust emission from fossil-fuelled power stations and reduce pollution. Yet current designs rely on the Deutsch collection theory, which was developed for tubular precipitators and has been applied to wire-plate precipitators on the assumption that the inter-electrode electric fields at the same discharge distance in both were similar. Differences in geometry and associated collector electric fields and current density non-uniformity have not been taken into account, although the collector electric field and current density of the wire-plate precipitator are not uniform. And observations show that precipitated dust patterns and the distribution of collector current density are interrelated. Investigations revealed a simple square law relationship between the collector electric field and the collector current density in the space charge dominated coronas. Applying this relationship to the Deutsch collection theory led to a current-density-based collection formula that takes into account the non-uniform collector current density distribution. The current-density-based collection formula is then used to assess the impact of collector current density on collection efficiency, the results closely following published measurements. Applying the current-density-based collection formula to estimate the dust accumulation shows that most of the dust accumulates at collector locations facing the corona wires. The effect of the non-uniform precipitated dust layer on collection performance is assessed using the distributed corona impedance - the ratio of the inter-electrode voltage and the non-uniform collector current. Re-distribution of the collector current profile as dust builds up is also compatible with published measurements. Finally this is applied to optimize the wire-plate precipitator collection performance. This shows that optimal collection performance is obtained with the wire-wire spacing less than the wire-plate distance, once again confirming published experimental results. This is the first analytical approach to show better collection performance can be achieved at the ratio of wire-wire spacing/wire-plate distance not equal to unity, which has been the standard industry practice since 1960.

The main objective of this research was to study DC conductor corona loss (CL) and audible noise (AN) in the context of local climatic conditions, through corona cage measurements, and do a comparative analysis of the measured data with results available in literature and EPRI TLW software simulation results. The ultimate aim was to assess the applicability of the software to our local conditions and hence determine, if necessary, appropriate correction factors for application in HYDC transmission line designs. For this study, short term measurements of corona AN and currents were carried out in an indoor meshed cylindrical corona cage, under DC and AC voltages. The cage was later converted into a short test line and some of the measurements repeated. The DC supply was obtained from a two stage ±500 kV Walton-Cockroft generator. The AC voltages were obtained from a 2x 100 kV, 50 Hz, AC test transformer set. The tests were performed using single solid and stranded aluminum conductors with three different diameters (1.6 cm, 2.8 cm, and 3.5 cm). All the measurements were carried out at low altitude. A CoroCAM I camera was used to determine the corona inception gradients and to observe the corona activity at different surface gradients and under different voltages and polarities. AN measurements at different conductor surface gradients were done using the Rohde&Schwarz and the Bruel&Kjaer sound level meters. To obtain the frequency spectra, a Bruel&Kjaer octave-band filter set attached to the sound level meter was used. The measured data was corrected for both height and length effects, and then compared with simulations from the EPRI-TLW software through curve fitting. A digital micro-ammeter connected to the centre of the cage through a 560 .Q measuring resistor was used to measure the corona current. Current pulses were viewed using a digital storage oscilloscope. To verify the corona current results obtained from the cage measurements, current measurements were also done for a point-plane spark gap. The corona current data was, later on, used to evaluate the total corona power loss for DC. The results obtained from test line measurements were used to compare the CL and AN for different configurations. The effect of the space charge under DC voltages was assessed through current measurements. The measurements were done with the cage covered with an aluminum foil to trap the charge and then repeated with the cage uncovered. On the test line, the space charge effect was investigated using a high power fan blowing along the conductor, to simulate the wind factor. The results of this study have shown the characteristics of corona discharges under different system voltages. The results also give an understanding of how factors such as conductor surface conditions and size, polarity and system voltage affect CL and AN. Both CL and AN were found to increase with conductor size for the same conductor surface gradient and to be higher for stranded conductors. Positive polarity DC and AC noise levels were higher than the negative polarity levels. CL under positive polarity DC was lower than the negative polarity loss. The effects of space of space charge were noted to some extend. The comparison of test line results and cage results showed that CL depends more on the gap size and the shorter the gap the higher the loss. Hence CL results were not compared with the software simulations. The comparison between the corrected AN results and the software simulations showed a very good agreement. The comparison was done for the 3.5 cm and the 2.8 cm diameter conductors under both positive and negative polarities. The trends compared through curve fitting were quite similar and the trend line equations were of the same order of magnitude. The magnitudes of the corrected noise levels were higher than the CRIEPI and BPA predictions but closer to the EPRl prediction. Generally there is a very good and encouraging agreement between the available literature, simulation results and the results obtained from the laboratory measurements. It is proposed, as part of further studies, to extend this work to high altitude regions and use bundled conductors as well. Consideration of different and larger test configurations will provide an understanding of the effects of geometry on corona discharges. Space charge analysis will also assist in determining the effect of space charge on different configurations. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007.

In order to improve efficiency and reliability of the world's power grids, sensors are being deployed for constant status monitoring. Placing inexpensive wireless sensors on high-voltage power lines presents a new challenge to the RF engineer. Large electric field intensities can exist around a wireless sensor antenna on a high-voltage power line, leading to the formation of a corona plasma. A corona plasma is a partially ionized volume of air formed through energetic electron-molecule collisions mediated by a strong electric field. This corona can contain large densities of free electrons which act as a conducting medium, absorbing RF energy and detuning the sensor's antenna. Through the use of low-profile antennas and rounded geometries, the possibility for corona formation on the antenna surface is greatly reduced, as compared with wire antennas. This study looks at the effects of a corona plasma on a patch antenna, which could be used in a power line sensor. The corona's behavior in the presence of an electromagnetic plane wave is analyzed mathematically to understand the dependence of attenuation on frequency and electron density. A Drude model is used to convert plasma parameters such as electron density and collision frequency to a complex permittivity that can be incorporated in antenna simulations. Using CST Microwave Studio, a 5.8 GHz patch antenna is simulated with a plasma material on its surface, of varying densities and thicknesses. Power absorption by the plasma dominates the power loss, as opposed to detuning. A wideband patch is simulated to show that the detuning effects by the plasma can be further reduced. Power absorption by the plasma is significant for electron densities greater than 10¹⁸ m⁻³. However, small point corona are found to have little effect on antenna radiation.

Mémoire (Sc.A.)--Université du Québec à Chicoutimi, 1986. / Document électronique également accessible en format PDF. CaQCU

Mémoire (M.Sc.A.)-- Université du Québec à Chicoutimi, 1991. / Bibliogr.: f. 86-91. Document électronique également accessible en format PDF. CaQCU

Mémoire (M.Eng.)--Université du Québec à Chicoutimi, 2000. / Document électronique également accessible en format PDF. CaQCU