Assessing of circuit breaker restrike risks using computer simulation and wavelet analysis

A breaker restrike is an abnormal arcing phenomenon, leading to a possible breaker failure. Eventually, this failure leads to interruption of the transmission and distribution of the electricity supply system until the breaker is replaced. Before 2008, there was little evidence in the literature of monitoring techniques based on restrike measurement and interpretation produced during switching of capacitor banks and shunt reactor banks in power systems. In 2008 a non-intrusive radiometric restrike measurement method and a restrike hardware detection algorithm were developed by M.S. Ramli and B. Kasztenny. However, the limitations of the radiometric measurement method are a band limited frequency response as well as limitations in amplitude determination. Current restrike detection methods and algorithms require the use of wide bandwidth current transformers and high voltage dividers. A restrike switch model using Alternative Transient Program (ATP) and Wavelet Transforms which support diagnostics are proposed. Restrike phenomena become a new diagnostic process using measurements, ATP and Wavelet Transforms for online interrupter monitoring. This research project investigates the restrike switch model Parameter „A. dielectric voltage gradient related to a normal and slowed case of the contact opening velocity and the escalation voltages, which can be used as a diagnostic tool for a vacuum circuit-breaker (CB) at service voltages between 11 kV and 63 kV. During current interruption of an inductive load at current quenching or chopping, a transient voltage is developed across the contact gap. The dielectric strength of the gap should rise to a point to withstand this transient voltage. If it does not, the gap will flash over, resulting in a restrike. A straight line is fitted through the voltage points at flashover of the contact gap. This is the point at which the gap voltage has reached a value that exceeds the dielectric strength of the gap. This research shows that a change in opening contact velocity of the vacuum CB produces a corresponding change in the slope of the gap escalation voltage envelope. To investigate the diagnostic process, an ATP restrike switch model was modified with contact opening velocity computation for restrike waveform signature analyses along with experimental investigations. This also enhanced a mathematical CB model with the empirical dielectric model for SF6 (sulphur hexa-fluoride) CBs at service voltages above 63 kV and a generalised dielectric curve model for 12 kV CBs. A CB restrike can be predicted if there is a similar type of restrike waveform signatures for measured and simulated waveforms. The restrike switch model applications are used for: computer simulations as virtual experiments, including predicting breaker restrikes; estimating the interrupter remaining life of SF6 puffer CBs; checking system stresses; assessing point-on-wave (POW) operations; and for a restrike detection algorithm development using Wavelet Transforms. A simulated high frequency nozzle current magnitude was applied to an Equation (derived from the literature) which can calculate the life extension of the interrupter of a SF6 high voltage CB. The restrike waveform signatures for a medium and high voltage CB identify its possible failure mechanism such as delayed opening, degraded dielectric strength and improper contact travel. The simulated and measured restrike waveform signatures are analysed using Matlab software for automatic detection. Experimental investigation of a 12 kV vacuum CB diagnostic was carried out for the parameter determination and a passive antenna calibration was also successfully developed with applications for field implementation. The degradation features were also evaluated with a predictive interpretation technique from the experiments, and the subsequent simulation indicates that the drop in voltage related to the slow opening velocity mechanism measurement to give a degree of contact degradation. A predictive interpretation technique is a computer modeling for assessing switching device performance, which allows one to vary a single parameter at a time; this is often difficult to do experimentally because of the variable contact opening velocity. The significance of this thesis outcome is that it is a non-intrusive method developed using measurements, ATP and Wavelet Transforms to predict and interpret a breaker restrike risk. The measurements on high voltage circuit-breakers can identify degradation that can interrupt the distribution and transmission of an electricity supply system. It is hoped that the techniques for the monitoring of restrike phenomena developed by this research will form part of a diagnostic process that will be valuable for detecting breaker stresses relating to the interrupter lifetime. Suggestions for future research, including a field implementation proposal to validate the restrike switch model for ATP system studies and the hot dielectric strength curve model for SF6 CBs, are given in Appendix A.

Supply chain management systems benefits : the expectation-confirmation theory perspective

Organizations adopt a Supply Chain Management System (SCMS) expecting benefits to the organization and its functions. However, organizations are facing mounting challenges to realizing benefits through SCMS. Studies suggest a growing dissatisfaction among client organizations due to an increasing gap between expectations and realization of SCMS benefits. Further, reflecting the Enterprise System studies such as Seddon et al. (2010), SCMS benefits are also expected to flow to the organization throughout its lifecycle rather than being realized all at once. This research therefore proposes to derive a lifecycle-wide understanding of SCMS benefits and realization to derive a benefit expectation management framework to attain the full potential of an SCMS. The primary research question of this study is: How can client organizations better manage their benefit expectations of SCM systems? The specific research goals of the current study include: (1) to better understand the misalignment of received and expected benefits of SCM systems; (2) to identify the key factors influencing SCM system expectations and to develop a framework to manage SCMS benefits; (3) to explore how organizational satisfaction is influenced by the lack of SCMS benefit confirmation; and (4) to explore how to improve the realization of SCM system benefits. Expectation-Confirmation Theory (ECT) provides the theoretical underpinning for this study. ECT has been widely used in the consumer behavior literature to study customer satisfaction, post-purchase behavior and service marketing in general. Recently, ECT has been extended into Information Systems (IS) research focusing on individual user satisfaction and IS continuance. However, only a handful of studies have employed ECT to study organizational satisfaction on large-scale IS. The current study will enrich the research stream by extending ECT into organizational-level analysis and verifying the preliminary findings of relevant works by Staples et al. (2002), Nevo and Chan (2007) and Nevo and Wade (2007). Moreover, this study will go further trying to operationalize the constructs of ECT into the context of SCMS. The empirical findings of the study commence with a content analysis, through which 41 vendor reports and academic reports are analyzed yielding sixty expected benefits of SCMS. Then, the expected benefits are compared with the benefits realized at a case organization in the Fast Moving Consumer Goods industry sector that had implemented a SAP Supply Chain Management System seven years earlier. The study develops an SCMS Benefit Expectation Management (SCMS-BEM) Framework. The comparison of benefit expectations and confirmations highlights that, while certain benefits are realized earlier in the lifecycle, other benefits could take almost a decade to realize. Further analysis and discussion on how the developed SCMS-BEM Framework influences ECT when applied in SCMS was also conducted. It is recommended that when establishing their expectations of the SCMS, clients should remember that confirmation of these expectations will have a long lifecycle, as shown in the different time periods in the SCMS-BEM Framework. Moreover, the SCMS-BEM Framework will allow organizations to maintain high levels of satisfaction through careful mitigation and confirming expectations based on the lifecycle phase. In addition, the study reveals that different stakeholder groups have different expectations of the same SCMS. The perspective of multiple stakeholders has significant implications for the application of ECT in the SCMS context. When forming expectations of the SCMS, the collection of organizational benefits of SCMS should represent the perceptions of all stakeholder groups. The same mechanism should be employed in the measurements of received SCMS benefits. Moreover, for SCMS, there exists interdependence of the satisfaction among the various stakeholders. The satisfaction of decision-makers or the authorized staff is not only driven by their own expectation confirmation level, it is also influenced by the confirmation level of other stakeholders‘ expectations in the organization. Satisfaction from any one particular stakeholder group can not reflect the true satisfaction of the client organization. Furthermore, it is inferred from the SCMS-BEM Framework that organizations should place emphasis on the viewpoints of the operational and management staff when evaluating the benefits of SCMS in the short and middle term. At the same time, organizations should be placing more attention on the perspectives of strategic staff when evaluating the performance of the SCMS in the long term.

Modelling resilience in a water supply system : contrasting conditions of drought and flood

This paper presents an approach to modelling the resilience of a generic (potable) water supply system. The system is contextualized as a meta-system consisting of three subsystems to represent the natural catchment, the water treatment plant and the water distribution infrastructure for urban use. An abstract mathematical model of the meta-system is disaggregated progressively to form a cascade of equations forming a relational matrix of models. This allows the investigation of commonly implicit relationships between various operational components within the meta system, the in-depth understanding of specific system components and influential factors and the incorporation of explicit disturbances to explore system behaviour. Consequently, this will facilitate long-term decision making to achieve sustainable solutions for issues such as, meeting a growing demand or managing supply-side influences in the meta-system under diverse water availability regimes. This approach is based on the hypothesis that the means to achieve resilient supply of water may be better managed by modelling the effects of changes at specific levels that have a direct or in some cases indirect impact on higher-order outcomes. Additionally, the proposed strategy allows the definition of approaches to combine disparate data sets to synthesise previously missing or incomplete higher-order information, a scientifically robust means to define and carry out meta-analyses using knowledge from diverse yet relatable disciplines relevant to different levels of the system and for enhancing the understanding of dependencies and inter-dependencies of variable factors at various levels across the meta-system. The proposed concept introduces an approach for modelling a complex infrastructure system as a meta system which consists of a combination of bio-ecological, technical and socio-technical subsystems.

Evaluation of implementation of a healthy food and drink supply strategy throughout the whole school environment in Queensland state schools, Australia

BACKGROUND/OBJECTIVES: This paper reports on the evaluation of the Smart Choices healthy food and drink supply strategy for Queensland schools (Smart Choices) implementation across the whole school environment in state government primary and secondary schools in Queensland, Australia. SUBJECTS/METHODS: Three concurrent surveys using different methods for each group of stakeholders that targeted all 1275 school Principals, all 1258 Parent and Citizens’ Associations (P&Cs) and a random sample of 526 tuckshop convenors throughout Queensland. Nine hundred and seventy-three Principals, 598 P&Cs and 513 tuckshop convenors participated with response rates of 78%, 48% and 98%, respectively. RESULTS: Nearly all Principals (97%), P&Cs (99%) and tuckshop convenors (97%) reported that their school tuckshop had implemented Smart Choices. The majority of Principals and P&Cs reported implementation, respectively, in: school breakfast programs (98 and 92%); vending machine stock (94 and 83%); vending machine advertising (85 and 84%); school events (87 and 88%); school sporting events (81 and 80%); sponsorship and advertising (93 and 84%); fundraising events (80 and 84%); and sporting clubs (73 and 75%). Implementation in curriculum activities, classroom rewards and class parties was reported, respectively, by 97%, 86% and 75% of Principals. Respondents also reported very high levels of understanding of Smart Choices and engagement of the school community. CONCLUSIONS: The results demonstrated that food supply interventions to promote nutrition across all domains of the school environment can be implemented successfully.

Managing older workers during a period of tight labour supply

This article reports on a recent survey of employer attitudes and policies towards older workers in Australia at a time of sustained economic growth and ongoing concerns about labour shortages. Findings from a survey of 590 employers with more than 50 employees in the State of Queensland point to an unusually strong orientation towards the recruitment of older workers among respondents, although the retraining of older workers is not prioritised by the majority. The issue of workforce ageing is viewed as being of medium-term importance by the majority of respondents, although for a substantial number the issue is of immediate concern. Both sector and organisation size are predictive of the application of a broad range of policies targeting older workers, with public-sector and larger organisations more likely to be active. Concerns about workforce ageing and labour supply are predictive of employer behaviours regarding older workers, suggesting that sustained policy making may be emerging in response to population ageing over and above more immediate concerns about labour shortages and that this broad thrust of organisational policy making may be immune to the point in the economic cycle. This study found no evidence that the flexible firm will not countenance an ageing workforce.

Smarten up! applying market design theory to greyfields housing supply : a background paper

This paper examines whether recent innovation in market design can address persistent problems of housing choice and affordability in the inner and middle suburbs of Australian cities. Australia's ageing middle suburbs are the result of a low density and highly car-dependent garden city greenfield approach to planning that failed to consider possible future resource or environmental constraints on urban development (Newton et al., 2011). Described as 'greyfield' sites in contrast to greenfield (signalling the change from rural to urban land use) and 'brownfield' (being the transformation of former industrial use to mixed use, including housing), intensification of development in such areas is expected to deliver positive social, economic and environmental outcomes (Trubka et al., 2008; Gurran et al., 2006; Newton et al., 2011; Goodman et al., 2010). Yet despite broad policy consensus progress remains elusive (Major Cities Unit, 2010). In this paper we argue that the application of market design theory, specifically through the internet-based coordination of market information, offers a new policy approach and practical measures to address these problems.

Applying market design theory to 'greyfields' housing supply

This paper examines whether innovation in market design can address persistent problems of housing choice and affordability in the ageing inner and middle suburbs of Australian cities. Despite policy consensus that urban intensification of these low density, ‘greyfield’ areas should be able to deliver positive social, economic and environmental outcomes, existing models of development have not increased housing stock or delivered adequate gains in sustainability, affordability or diversity of dwellings in greyfield localities. We argue that application of smart market and matching market principles to the supply of multi-unit housing can unlock land, reduce development costs and improve design.

Application of Resilience concept for enhanced management of water supply systems

This paper presents an approach to developing indicators for expressing resilience of a generic water supply system. The system is contextualised as a meta-system consisting of three subsystems to represent the water catchment and reservoir, treatment plant and the distribution system supplying the end-users. The level of final service delivery to end-users is considered as a surrogate measure of systemic resilience. A set of modelled relationships are used to explore relationships between system components when placed under simulated stress. Conceptual system behaviour of specific types of simulated pressure is created for illustration of parameters for indicator development. The approach is based on the hypothesis that an in-depth knowledge of resilience would enable development of decision support system capability which in turn will contribute towards enhanced management of a water supply system. In contrast to conventional water supply system management approaches, a resilience approach facilitates improvement in system efficiency by emphasising awareness of points-of-intervention where system managers can adjust operational control measures across the meta-system (and within subsystems) rather than expansion of the system in entirety in the form of new infrastructure development.

Consumer guarantees and the supply of educational services by higher education providers

The higher education sector is undergoing a number of significant changes, the implications of which have yet to emerge. One such change is the increasing reliance by higher education providers on the revenue generated by full fee paying international students to fund their operating expenses. The report by the Victorian Ombudsman, Investigation into how Universities Deal with International Students ('Victorian Ombudsman's Report') tabled in the Victorian Parliament on 27 October 2011, provides evidence that Australian higher education providers may be failing to meet their legal obligations to international students. The Victorian Ombudsman's Report is the result of an investigation into four Victorian universities teaching international students with a focus on accounting and nursing schools. The report contains evidence that the universities were admitting students with scores below, or at the lower end of, the International English Language Testing System ('IELTS') score considered acceptable. Alternatively, they were relying upon their own language testing admission standards and not on an independent test like the IELTS test. While the universities provided English language support services for their international students after they had been admitted, the Ombudsman was concerned that the universities 'have not dedicated sufficient resources to meet the level of need amongst international students'.

Supply chain benefits expectation management framework

Organizations invest heavily in Supply Chain Management Systems expecting the benefits promised by the software vendors and the implementation partners. However, both academic and industry reports suggest that there is growing dissatisfaction among client organizations due to an increasing gap in benefits purported by the software vendors and benefits realised by the client. In order to better manage expectations of the client organization, this study proposes a Benefit Expectation Management Framework for Supply Chain Management Systems, based on Expectation-Confirmation Theory. This study derives 60 expected benefits of Supply Chain Management Systems through 41 vendor-reported customer stories and academic papers. Through comparing those benefits with the received benefits by a case organization that has implemented SAP Supply Chain Management Systems for seven years, two salient factors – long timetable and multiple stakeholders – have been identified as the controlling factors affecting the confirmation level of Supply Chain Management System expectations and further impacting the satisfaction of a client organization. The case study also highlights the likely causes for realized benefits and enduring issues in relation to the Supply Chain Management Systems.

Harmonic elimination technique for a single-phase multilevel converter with unequal DC link voltage levels

Multilevel converters, because of the benefits they attract in generating high quality output voltage, are used in several applications. Various modulation and control techniques are introduced by several researchers to control the output voltage of the multilevel converters like space vector modulation and harmonic elimination (HE) methods. Multilevel converters may have a DC link with equal or unequal DC voltages. In this study a new HE technique based on the HE method is proposed for multilevel converters with unequal DC link voltage. The DC link voltage levels are considered as additional variables for the HE method and the voltage levels are defined based on the HE results. Increasing the number of voltage levels can reduce lower order harmonic content because of the fact that more variables are created. In comparison to previous methods, this new technique has a positive effect on the output voltage quality by reducing its total harmonic distortion, which must take into consideration for some applications such as uninterruptable power supply, motor drive systems and piezoelectric transducer excitation. In order to verify the proposed modulation technique, MATLAB simulations and experimental tests are carried out for a single-phase four-level diode-clamped converter.

Climate change-related corporate governance information : an explanation of the difference between the supply of and demand for such information

This study investigates the gap between the climate change-related corporate governance information being disclosed by companies, and the information sought by stakeholders. To accomplish this objective we utilised previous research on stakeholder demand for information, and we conducted in-depth interviews with six corporate representatives from major Australian emission-intensive companies. Having gained and documented a rich insight into the potential factors responsible for the current gap in disclosure we find that the existence of an expectations gap; the perceived cost of providing commercially sensitive information; the limited accountability being accepted by the corporate managers; and, a lack of stakeholder pressure together contribute to the lack of disclosure. In highlighting the gap in disclosure, this study suggests strategies to reduce the gap in climate change-related corporate governance disclosures.

Safety culture in supply chains : 'Customer is king'

Despite the presence of many regulations governing the operation of heavy vehicles and supply chains in Australia, the truck driving sector continues to have the highest incidence of fatal injuries compared to all other industries. The working environment has been the focus of attention by safety researchers during the past few decades, with particular consideration been given to the concept ‘safety culture’ and how to maintain, modify and advance responses to occupational risk. One important aspect of the heavy industry which sets it apart is the existence of cultural or sub-cultural influences at an industry wide and occupation-specific level rather than organisational level. This paper reports on the findings of stakeholder’s perceptions of the influences of power and control, and culture on industry safety. In-depth structured interviews were conducted during 2011 with Australian industry stakeholders (n=31). The questioning surrounded decision-making processes with regards to identifying risks, self-monitoring and reducing risky activities; as well as how power-affected relationships may influence the operational performance of supply chains and impacts on driver safety. One of the most significant findings from these interviews relates to the notion of power. The perception that the ‘Customer is King’ was widely viewed, with the majority of stakeholders believing that there exists a ‘master slave mentality’ in the industry. There appears to be great frustration in the industry as to the apparent immunity of customers (particularly retail supply chains) to their responsibilities. There was also a strong perception that the customer holds the balance of power by covertly employing remuneration-related incentives and pressures. Smaller trucking companies are perceived as being more vulnerable to the pressure of customer expectations.

Sample selection in a model of female labour supply : an alternative approach

Suggests an alternative and computationally simpler approach of non-random sampling of labour economics and represents an observed outcome of an individual female′s choice of whether or not to participate in the labour market. Concludes that there is an alternative to the Heckman two-step estimator.

Analysing DBD plasma lamp intensity versus power consumption using a push-pull pulsed power supply

In this paper characteristic of a DBD (Dielectric Barrier Discharge) plasma lamp is investigated based on the lamp intensity and power consumption. A pulsed power supply with controllable parameters based on a push-pull converter is developed for lamp excitation at different voltage levels and repetition rate. The experimentations were conducted for 28 different operating points with the frequency range of 2 kHz to 15 Khz at output voltage levels of between 7.4 kV up to 13 kV. The obtained results show the feasibility of finding an optimum operation point due to nonlinear behaviour of the DBD lamp.