Alternative exciter supply for use on synchronous alternators in micro-hydroelectric applications

University of Technology, Sydney. Faculty of Engineering.This thesis develops an understanding of the context, and operating nexus linking synchronous machine excitation requirements and ballast load frequency controllers in remote area power supplies in developing communities in the Pacific. A framework has been developed to serve as a guide for this study as well as future technology transfer projects. Remaining chapters in the thesis coalesce to offer confidence in the hardware solutions presented: an alternative, simpler exciter supply circuit; and a novel method for drying alternator windings. The thesis stems from an ongoing need for the APACE-VFEG technical team to develop dedicated systems and hardware solutions for micro-hydroelectric systems. The close relationship between system designer and rural community users has afforded a wealth of valuable ‘technical’ experience and knowledge. Much of this ‘intellectual property’ remains in-house. We have evidence to show there is merit in the models and community partnership approach adopted; this study affords an appropriate vehicle to research this ‘contextual’ material with more rigour. A void between two standpoints is apparent: one where researchers identify barriers to technology transfer at a systems or sociology level - and lack depth in technical design aspects; the other standpoint where electronic systems designers typically remain focussed on component level analysis of their equipment - and hence fail to consider the broader contextual issues. The study promotes the thesis that, beyond the barriers to technological diffusion at institutional, social, and political level (which appear to dominate the issues normally considered), problems remain in providing sustainable technical solutions for this small Pacific island context. The framework is developed to provide guidance for this study and for future technology transfer projects. Soft Systems Methodology, STEEP analysis, the concepts of Actor Network Theory, and technology compatibility, readiness, and maturity afford pertinent insights to the framework at the institutional, actor, and technical levels. A review of literature pertinent to this study has been completed and gaps identified in the general body of knowledge associated with micro-hydroelectric systems for consideration in this study. Focus areas include the assumption that an Automatic Voltage Regulator (AVR) is the only solution, the requirements for flywheels, and the various explanations for what causes the unsatisfactory operation of (AVR excited) ballast load controlled micro-hydroelectric systems. This thesis shows that despite the complexity of interconnections and time constants involved, a complete and verified control systems model developed from first principles is achievable. Relationships between the system steady state operating points and the equations describing the system parameters (accelerating torque, moment of inertia, armature current, alternator rotor speed) are modelled, simulated, and verified with measured responses on a full scale micro-hydroelectric test rig. Further system testing shows an alternative solution to the AVR exists, flywheels may not be a necessity, and the cause of the unsatisfactory operation (with AVR excitation) stems from the similar time constants of the two feedback control systems (the frequency controller and voltage regulator) as well as the Under Frequency Roll-Off characteristic of the AVR. Two hardware solutions are specified, designed, simulated, implemented, and verified: the alternative exciter field supply; and a novel method for drying alternator windings. The specifications prepared have sufficient detail to afford confidence in the hardware solutions developed - they address the technical requirements and broader contextual requirements of a technology to be transferred into a developing community. Two feedback control circuits have been completed: one to replicate the constant field current design of the existing APACE constant current exciter supply; the other to incorporate voltage regulation attributes (which address the constraints of the existing APACE solution). Experiments have been conducted to verify the predicted (simulated) operating characteristics. Although designed for the Renewable Energy Laboratory alternator, the alternative exciter supply is based on the specifications for a range of AVRs and hence the solution is expected to be transferable to a broad range of machines, as well as applications beyond those described in this study. A review of the new technology developed has been completed, with a view to verifying the designs against the specifications as well as the framework guidelines. Moisture is the prime cause of machine winding insulation deterioration and corrosion of metallic parts, and this is certainly the case in humid or rainy conditions, such as those prevalent in the wet tropics. Moreover, moisture can demonstrably have catastrophic impacts if it is allowed to expand in the confined space of the windings during start-up. Given that the mechanism for moisture ingress (and egress) is not perceptible to users in this context, the existing remedy has been counter-intuitive and difficult to transfer. A novel method for drying machine windings has been developed and implemented to address this essential requirement. The method is safer and more intuitive for the system operators and reduces risks of damage to equipment. Finally, this study is considered an incremental step towards improved system sustainability. That is, rather than being seen as an exit point, the outcomes from this study have proven the concept at component level. The recommendation is therefore to commence planning on the next phase, which may be to consider combining all the various control system components together into a single package. Consideration of such a design integration will benefit from the contextual framework suggested here

Transformer Oil Passivation and Impact of Corrosive Sulphur

In recent years a significant volume of research has been undertaken in order to understand the recent failures in oil insulated power apparatus due to deposition of copper sulphide on the conductors and in the insulation paper. Dibenzyl Disulfide (DBDS) has been found to be the leading corrosive sulphur compound in the insulation oil [1]. The process of copper sulphide formation and the deposition in the paper is still being investigated, but a recently proposed method seems to be gaining some confidence [1]. This method suggests a two-step process; initially the DBDS and some oil soluble copper complexes are formed. Secondly the copper complexes are absorbed in the paper insulation, where they then decompose into copper sulphide [2]. The most commonly used mitigating technique for corrosive sulphur contaminated oil is passivation, normally using Irgamet 39 or 1, 2, 3-benzotriazole (BTA). The passivator is diluted into the oil to a concentration of around 100ppm, where it then reacts with the copper conductors to form a complex layer around the copper, preventing it from interacting with DBDS compounds and forming copper sulphide. This research project will investigate the electrical properties of HV transformers which have tested positive for corrosive sulphur, and the evolution of those properties as the asset degrades due to sulphur corrosion. Parallel to this the long term properties of transformers with passivated insulation oil will be analysed in order to understand the passivator stability and whether it is necessary to keep adding the passivator to sustain its performance. Condition monitoring techniques under investigation will include dielectric spectroscopy, frequency response analysis, recovery voltage method (aka interfacial polarisation) amongst others. Partial discharge techniques will not be investigated, as the voltage between the coil plates is low and therefore it will not contribute significantly to the overall insulation breakdown, in corrosive oil related faults [3]. The goal of this research is to establish key electrical properties in both passivated and non-passivated power transformers that demonstrate detectable changes as the equipment degrades due to the insulation oil being corrosive

Foliage insect diversity in dry eucalypt forests in eastern Tasmania

Species numbers and composition of the insect fauna occurring on trees and shrubs were studied in dry eucalypt forests in eastern Tasmania over nine years. In all, 1164 named and putative species representing 17 orders and 157 families were collected. The bulk of the species belonged to the orders Coleoptera (28%), Hymenoptera (25%), Hemiptera (18%), Lepidoptera (14%) and Diptera (10%). Of the species collected, 388 -- about one-third -- were identified at least to genus or species level. These included 21 named species not previously listed in the Tasmanian insect fauna and 90 undescribed species. A list of 22 host plants for 171 insect species was compiled from records of 132 insect species observed feeding during the study and from previous records ofinsect/host plant associations for 39 insect species found on the study plots. Most insects were feeding on eucalypts (127 insect species) and acacias (38 species). The most widely distributed and commonly collected species were several well-known pests of eucalypts: Gonipterus scutellatus (Coleoptera: Curculionidae), Uraba lugens (Lepidoptera: N octuidae), Amorbus obscuricornis (Hemiptera: Coreidae), Chaetophyes compacta (Hemiptera: Machaerotidae) and Eriococcus coriaceous(Hemiptera: Eriococcidae). Host plants supporting the richest insect fauna were Eucalyptus amygdalina (74 species), E. obliqua (64), E. viminalis (46), Acacia dealbata (35), E. dalrympleana (33), E. sieberi (31), E. delegatensis (30), E. pulchella (24) and E. globulus (19). The broad-striped ghost moth, Fraus latistria Walker (Lepidoptera: Hepialidae), was collected during the study. This species is classified as 'rare' on the list of Tasmania's threatened fauna and the collection established a new locality record

Kappa Opioid Regulation of Depressive-Like Behavior During Acute Withdrawal and Protracted Abstinence from Ethanol

The dynorphin/kappa opioid receptor (DYN/KOR) system appears to be a key mediator of the behavioral effects of chronic exposure to alcohol. Although KOR opioid receptor antagonists have been shown to decrease stress-related behaviors in animal models during acute ethanol withdrawal, the role of the DYN/KOR system in regulating long-term behavioral changes following protracted abstinence from ethanol is not well understood. The objective of the current study was to further explore the role of the DYN/KOR system in regulating stress-related behavioral changes associated with acute withdrawal and protracted abstinence from ethanol. More specifically, the present experiments sought to examine the ability of the KOR antagonist norbinaltorphimine (nor-BNI) to reverse depressive-like behavior in the forced swim test in rats exposed to chronic ethanol. In the first experiment, rats were fed an ethanol or control liquid diet for 28–30 days, and then 24 hours after removal of the diet, were exposed to inescapable swim stress. Immediately following this procedure, rats were injected with nor-BNI (20 mg/kg) or saline and then tested 24 hours later in the forced swim test. A second experiment used a similar procedure to examine the effects of nor-BNI on behavioral changes during protracted abstinence in rats tested in the forced swim test 3 weeks after exposure to the ethanol liquid diet procedure. Ethanol-dependent rats showed increased immobility, which is thought to indicate a depressive-like state, when examined during acute withdrawal and protracted abstinence compared to controls, an effect attenuated by nor-BNI. These results suggest that the DYN/KOR system plays role in mediating both short- and long-term behavioral changes associated with depression following chronic alcohol exposure

Enhancing Industry Exposure, Discovery-Based and Cooperative Learning in Mechanics of Solids

BACKGROUND Mechanics of Solids is a second year undergraduate subject, undertaken by both Civil and Mechanical engineering students at the University of Technology, Sydney (UTS). Mechanics of Solids has been delivered for many years in a traditional format with lectures and problem solving tutorials. As part of a national Australian project “Enhancing Industry Exposure in Engineering Degrees”, UTS in partnership with other universities and industry partners in Australia has sought industry involvement to engage students with the real-world challenges of engineering practice. PURPOSE The main objective of this project is to design, develop and implement learning modules in Mechanis of Solids that integrate industry exposure to provide context for the concepts included in this subject. DESIGN The project consisted of six guest lectures by industry representatives on topics related to typical Mechanics of Solids subject matter and two seminars on using MDSolids software. Students completed a collaborative assignment aligned with one of the industry presentations. Their reports and presentations were assessed on assessment criteria which included contextual understanding, judgement, effective collaboration and creativity, and their perceptions were captured to evaluate the impact of industry engagement in this subject. RESULTS One of the major benefits of this project was students’ better understanding of engineering practice. There were also positive effects on students’ motivation for learning engineering. CONCLUSIONS This paper reports the major findings, outcomes and challenges for implementing enhancing industry exposure approach in Mechanics of Solids subject at UTS. The main finding of this research concluded that this project is very valuable to both students as it promotes exposure to real-world engineering challenges. The students’ exposure to real and substantive challenges improves their contextual understanding, plus their judgement, practice based planning, teamwork, and initiative learning skills

Developing a decision support tool for the positioning and sizing of vortex flow controls in existing sewer systems

12th International Conference on Computing and Control for the Water Industry, CCWI2013This is the final version of the article. Available from Elsevier via the DOI in this record.This paper describes the development of a decision support tool for the positioning and sizing of vortex flow controls in existing sewer systems. The tool aims to prioritise the placement of vortex flow controls primarily within subcatchments with the greatest flood consequence rating and maximise the use of unused inpipe volumes during critical rainfall events. The decision support tool is intended for use in catchments where opportunities to implement SuDS and rainwater harvesting to defend against flooding are limited. The decision support tool is envisaged to identify potential strategies which could enhance flood resistance of sewer systems in a cost effective manner. © 2013 The Authors

Getting it right: The case for supervisors assessing process in capstone projects

© 2015 TEMPUS Publications. Capstone projects represent the culmination of an undergraduate engineering degree and are typically the last checkpoint measure before students graduate and enter the engineering profession. In Australia there is a longstanding interest in and commitment to developing quality capstone experiences.Anational study into the supervision and assessment of capstone projects has determined that whilst there is relative consistency in terms of what project tasks are set and assessed, there is not comparable consistency in how these tasks or assignments are marked. Two interconnected areas of assessing process and the role of the supervisor in marking are identified as contentious. This paper presents some findings of a national case study and concludes that whilst further investigation is warranted, assessing process as well as project products is valuable as is the need for greater acceptance of project supervisors as capable of making informed, professional judgments when marking significant project work

ENVIROSAT-2000 report: Federal agency satellite requirements

The requirement of Federal agencies, other than NOAA, for the data and services of civil operational environmental satellites (both polar orbiting and geostationary) are summarized. Agency plans for taking advantage of proposed future Earth sensing space systems, domestic and foreign, are cited also. Current data uses and future requirements are addressed as identified by each agency

Current Models of Investor State Dispute Settlement Are Bad for Health: The European Union Could Offer an Alternative Comment on "The Trans-Pacific Partnership: Is It Everything We Feared for Health?"

In this commentary, we endorse concerns about the health impact of the trans-pacific partnership (TPP), paying particular attention to its mechanisms for investor state dispute settlement. We then describe the different, judge-led approach being advocated by the European Commission team negotiating the Trans-Atlantic Trade and Investment Partnership, arguing that, while not perfect, it offers significant advantages