People, Politics, Power Stations, Alternating Currents or Counter-Revolution: An Interpretation of Evidence of New Zealand's Electricity Reforms

Electricity reforms in New Zealand have been a topic of discussion and debate since their nominal introduction in 1987. Somewhat contrasting presentations have been made in two publications as to the influences and causes of electricity system development, both prior to and subsequently from the nominal reform date. The first focuses on the entire development of the New Zealand power industry since the 1880s. It conveys the major events that occurred and relates this to the influences of politics and powerful people. The second book interprets the developments from the viewpoint of competition theory, explaining what has occurred with reference to pricing, and supply and demand, the tenets of economic law. This paper is an interpretation of the graphical data presented in both books. There are sufficient long term patterns that show deregulation has had no effect in many ways. Generation capacity appears to be saturating while energy supplied increases linearly along with consumer numbers and their consumption. Real prices continue to decrease. Returns to government also are unchanged by deregulation. Deregulation has changed other factors. It has generated more profits to companies, added volatility to prices and rates of return, and removed cross-subsidisation between consumer sectors. Customers are less interested in changing retailers. Reliability statistics have improved, reflective of improvements in engineering operation and maintenance

Physical modelling of electroporation in close cell-to-cell proximity environments

Many applications of electroporation, especially those utilizing electrofusion and in-vivo electroporation, involve cell environments that include close cell-to-cell proximity and a wide range of target cell size. It is important to understand how this kind of environment may alter optimum electroporation electrical parameters for any given application. A physical, electrically equivalent model of biological cell electroporation, based on aqueous solution filled thin latex rubber membrane spheroids, was used to investigate membrane permeabilization behaviour where there is both close cell-to-cell proximity and different cell radii. Cell model arrangements were pulsed using either a 50 µs or 10 µs, 1/e decay time constant dc capacitive discharge electric field, with peak amplitudes of 160-500 kV m⁻¹. Results indicate that, compared to cells in isolation, electroporation initiates at substantially decreased applied electric field magnitudes in regions of close cell-to-cell proximity where the external media conductivity is lower than the cell interior conductivity, and the membrane is maximally polarized. Additionally, the use of shorter time constant, higher peak magnitude pulse parameters should reduce the relative difference in threshold membrane permeabilization in regions of close cell-to-cell proximity for cells of different size so that the degree of electroporation is more uniform for variable size and shape target cell populations

A Test Circuit for Long Distance Directional Plasma Discharge Using the Exploding Wire Technique

With the use of high voltage impulse equipment and the exploding wire technique, long distance directional plasma discharges have been achieved. The methods described in this paper allows for such discharges in a relatively safe and dependable fashion. This paper comprehensively describes the equipment and circuits required to repeat these experiments. Equipment design considerations are also given in the paper. Special considerations to earthing are required for this method to ensure operator safety and that measurement equipment is not damaged. Voltage waveforms and other data have been collected via the experiments; the results and procedures are quite different to those found in the short distance exploding wire literature. The research conducted at UoC has allowed for discharges up to 70 meters in length using only 60kV DC. In these discharges the various high voltage switching mechanisms and high energy impulse generators that have been used will be described in this paper. The measurement instrumentation which is able to measure the large currents and voltages is described

Volcanic Ash Contamination of High Voltage Insulators

Awarded Best Paper (Student) - Joint Winner - EEA Conference 2011Recent work in the University of Canterbury high voltage laboratory uncovered an interesting phenomenon. While studying the effect of volcanic ash contamination on high voltage insulator flashover levels, ash was seen ‘blowing’ off the insulator surface before flashover occurred. The goal of this project was to investigate and explain the observed phenomenon to provide a basis for potential development of self-cleaning insulators. Four different types of insulator and three different ash grain sizes were tested. The insulator electric fields were modelled; corona discharge waveforms and visual observations were obtained. Areas of ash removal coincided with areas of corona discharge. It was initially proposed that the ash was removed by an alternating current corona wind however the results do not support this theory. Instead, the observed results suggest that the ash acquires a negative charge and is removed by an electrostatic force. The electrostatic force is strongest during the negative half cycle of the applied voltage due to space charge and hence the ash pulses off the insulator at 50Hz. The amount of ash removed increased with the applied voltage however this led to a trade off between ash removal and flashover. The maximum amount of ash removed during this project was approximately 90% from the top weather shed and 30% from the middle and bottom weather sheds. This study focused on the removal of dry ash. It is unlikely that wet ash can be removed in this fashion, without flashover, due to the conductive and adhesive nature of wet ash

Partial Core Transformer for Energization of High Voltage Arc-Signs

paper T3-304A high voltage partial core resonating transformer has been designed and constructed such that its magnetising current reactance is matched to the reactive current drawn by the capacitance of an arc-sign. The supply only provides the real power losses of the transformer plus any reactive power mismatch between the magnetizing reactance and the capacitance of the arc-sign. A mathematical model of the transformer is developed using a reverse design modelling technique. The model is then used to design a 50Hz, 8kVA, 230V/80kV, partial core transformer to meet the required electrical demand of the load. The transformer was constructed and tested. The transformer successfully resonated with the load and provided 68VAr of compensation when operating at 10kV while being supplied from a domestic 230V, 10A, power outlet. The completed transformer has a finished weight of 69kg and has been successfully used for powering an arc-sign at an exhibition of electric sculptures

An Economic Comparison between Grid Based and Isolated Rural Electrification in Nepal

This paper presents a methodology for financial analysis that compares costs and benefits of rural electrification by grid expansion with isolated micro hydro schemes. Financial analysis of three existing isolated micro hydro schemes in different parts of Nepal are compared against the alternative option of grid expansion. Case study results are tabulated and discussed