Analysis of phasor measurement method in tracking the power frequency of distorted signals

This paper presents an analysis of phasor measurement method for tracking the fundamental power frequency to show if it has the performance necessary to cope with the requirements of power system protection and control. In this regard, several computer simulations presenting the conditions of a typical power system signal especially those highly distorted by harmonics, noise and offset, are provided to evaluate the response of the Phasor Measurement (PM) technique. A new method, which can shorten the delay of estimation, has also been proposed for the PM method to work for signals free of even-order harmonics.

Power management and power flow control with back-to-back converters in a utility connected microgrid

This paper proposes a method for power flow control between utility and microgrid through back-to-back converters, which facilitates desired real and reactive power flow between utility and microgrid. In the proposed control strategy, the system can run in two different modes depending on the power requirement in the microgrid. In mode-1, specified amount of real and reactive power are shared between the utility and the microgrid through the back-to-back converters. Mode-2 is invoked when the power that can be supplied by the DGs in the microgrid reaches its maximum limit. In such a case, the rest of the power demand of the microgrid has to be supplied by the utility. An arrangement between DGs in the microgrid is proposed to achieve load sharing in both grid connected and islanded modes. The back-to-back converters also provide total frequency isolation between the utility and the microgrid. It is shown that the voltage or frequency fluctuation in the utility side has no impact on voltage or power in microgrid side. Proper relay-breaker operation coordination is proposed during fault along with the blocking of the back-to-back converters for seamless resynchronization. Both impedance and motor type loads are considered to verify the system stability. The impact of dc side voltage fluctuation of the DGs and DG tripping on power sharing is also investigated. The efficacy of the proposed control ar-rangement has been validated through simulation for various operating conditions. The model of the microgrid power system is simulated in PSCAD.

Load sharing and power quality enhanced operation of a distributed microgrid

This paper describes control methods for proper load sharing between parallel converters connected in a microgrid and supplied by distributed generators (DGs). It is assumed that the microgrid spans a large area and it supplies loads in both in grid connected and islanded modes. A control strategy is proposed to improve power quality and proper load sharing in both islanded and grid connected modes. It is assumed that each of the DGs has a local load connected to it which can be unbalanced and/or nonlinear. The DGs compensate the effects of unbalance and nonlinearity of the local loads. Common loads are also connected to the microgrid, which are supplied by the utility grid under normal conditions. However during islanding, each of the DGs supplies its local load and shares the common load through droop characteristics. Both impedance and motor loads are considered to verify the system response. The efficacy of the controller has been validated through simulation for various operating conditions using PSCAD. It has been found through simulation that the total Harmonic Distortion (THD) of the of the microgrid voltage is about 10% and the negative and zero sequence component are around 20% of the positive sequence component before compensation. After compensation, the THD remain below 0.5%, whereas, negative and zero sequence components of the voltages remain below 0.02% of the positive sequence component.

Up the junction? Exploiting knowledge-based development through supply chain and SME cluster interactions

Maximisation of Knowledge-Based Development (KBD) benefits requires effective dissemination and utilisation mechanisms to accompany the initial knowledge creation process. This work highlights the potential for interactions between Supply Chains (SCs) and Small and Medium sized Enterprise Clusters (SMECs), (including via ‘junction’ firms which are members of both networks), to facilitate such effective dissemination and utilisation of knowledge. In both these network types there are firms that readily utilise their relationships and ties for ongoing business success through innovation. The following chapter highlights the potential for such beneficial interactions between SCs and SMECs in key elements of KBD, particularly knowledge management, innovation and technology transfer. Because there has been little focus on the interactions between SCs and SMECs, particularly when firms simultaneously belong to both, this chapter examines the conduits through which information and knowledge can be transferred and utilised. It shows that each network type has its own distinct advantages in the types of information searched for and transferred amongst network member firms. Comparing and contrasting these advantages shows opportunities for both networks to leverage the knowledge sharing strengths of each other, through these ‘junctions’ to address their own weaknesses, allowing implications to be drawn concerning new ways of utilising relationships for mutual network gains.

Approach to developing a 3D conceptual hydrogeology model, in a system with multiple bore logs, Howard East, Darwin, using in-house software (GVS)

The Howard East rural area has experienced a rapid growth of small block subdivisions and horticulture over the last 40 years, which has been based on groundwater supply. Early bores in the area provide part of the water supply for Darwin City and are maintained and monitored by NT Power & Water Corporation. The Territory government (NRETAS) has established a monitoring network, and now 48 bores are monitored. However, in the area there are over 2700 private bores that are unregulated.Although NRETAS has both FDM and FEM simulations for the region, community support for potential regulation is sought. To improve stakeholder understanding of the resource QUT was retained by the TRaCKconsortium to develop a 3D visualisation of the groundwater system.

Power system stability analysis based on descriptive study of electrical indices

In a power network, when a propagation energy wave caused by a disturbance hits a weak link, a reflection is appeared and some of energy is transferred across the link. In this work, an analytical descriptive methodology is proposed to study the dynamical stability of a large scale power system. For this purpose, the measured electrical indices (angle, or voltage/frequency) following a fault in different points among the network are used, and the behaviors of the propagated waves through the lines, nodes and buses are studied. This work addresses a new tool for power system stability analysis based on a descriptive study of electrical measurements. The proposed methodology is also useful to detect the contingency condition and synthesis of an effective emergency control scheme.

Evaluation of aerial remote sensing techniques for vegetation management in power line corridors

The following paper presents an evaluation of airborne sensors for use in vegetation management in powerline corridors. Three integral stages in the management process are addressed including, the detection of trees, relative positioning with respect to the nearest powerline and vegetation height estimation. Image data, including multi-spectral and high resolution, are analyzed along with LiDAR data captured from fixed wing aircraft. Ground truth data is then used to establish the accuracy and reliability of each sensor thus providing a quantitative comparison of sensor options. Tree detection was achieved through crown delineation using a Pulse-Coupled Neural Network (PCNN) and morphologic reconstruction applied to multi-spectral imagery. Through testing it was shown to achieve a detection rate of 96%, while the accuracy in segmenting groups of trees and single trees correctly was shown to be 75%. Relative positioning using LiDAR achieved a RMSE of 1.4m and 2.1m for cross track distance and along track position respectively, while Direct Georeferencing achieved RMSE of 3.1m in both instances. The estimation of pole and tree heights measured with LiDAR had a RMSE of 0.4m and 0.9m respectively, while Stereo Matching achieved 1.5m and 2.9m. Overall a small number of poles were missed with detection rates of 98% and 95% for LiDAR and Stereo Matching.

Cyber bullying in schools and the law : is there an effective means of addressing the power imbalance?

Cyber bullying – or bullying through the use of technology – is a growing phenomenon which is currently most commonly experienced by young people and the consequences manifested in schools. Cyber bullying shares many of the same attributes as face-to-face bullying such as a power imbalance and a sense of helplessness on the part of the target. Not surprisingly, targets of face-to-face bullying are increasingly turning to the law, and it is likely that targets of cyber bullying may also do so in an appropriate case. This article examines the various criminal, civil and vilification laws that may apply to cases of cyber bullying and assesses the likely effectiveness of these laws as a means of redressing that power imbalance between perpetrator and target.

A summary view of government cost recovery policies in Australia and New Zealand relating to the supply of public sector information

Researching administrative history is problematical. A trail of authoritative documents is often hard to find; and useful summaries can be difficult to organise, especially if source material is in paper formats in geographically dispersed locations. In the absence of documents, the reasons for particular decisions and the rationale underpinning particular policies can be confounded as key personnel advance in their professions and retire. The rationale for past decisions may be lost for practical purposes; and if an organisation’s memory of events is diminished, its learning through experience is also diminished. Publishing this document tries to avoid unnecessary duplication of effort by other researchers that need to venture into how policies of charging for public sector information have been justified. The author compiled this work within a somewhat limited time period and the work does not pretend to be a complete or comprehensive analysis of the issues.----- A significant part of the role of government is to provide a framework of legally-enforceable rights and obligations that can support individuals and non-government organisations in their lawful activities. Accordingly, claims that governments should be more ‘business-like’ need careful scrutiny. A significant supply of goods and services occurs as non-market activity where neither benefits nor costs are quantified within conventional accounting systems or in terms of money. Where a government decides to provide information as a service; and information from land registries is archetypical, the transactions occur as a political decision made under a direct or a clearly delegated authority of a parliament with the requisite constitutional powers. This is not a market transaction and the language of the market confuses attempts to describe a number of aspects of how governments allocate resources.----- Cost recovery can be construed as an aspect of taxation that is a sole prerogative of a parliament. The issues are fundamental to political constitutions; but they become more complicated where states cede some taxing powers to a central government as part of a federal system. Nor should the absence of markets be construed necessarily as ‘market failure’ or even ‘government failure’. The absence is often attributable to particular technical, economic and political constraints that preclude the operation of markets. Arguably, greater care is needed in distinguishing between the polity and markets in raising revenues and allocating resources; and that needs to start by removing unhelpful references to ‘business’ in the context of government decision-making.

Detection and Estimation of Nonstationary Power Transients

This chapter looks at issues of non-stationarity in determining when a transient has occurred and when it is possible to fit a linear model to a non-linear response. The first issue is associated with the detection of loss of damping of power system modes. When some control device such as an SVC fails, the operator needs to know whether the damping of key power system oscillation modes has deteriorated significantly. This question is posed here as an alarm detection problem rather than an identification problem to get a fast detection of a change. The second issue concerns when a significant disturbance has occurred and the operator is seeking to characterize the system oscillation. The disturbance initially is large giving a nonlinear response; this then decays and can then be smaller than the noise level ofnormal customer load changes. The difficulty is one of determining when a linear response can be reliably identified between the non-linear phase and the large noise phase of thesignal. The solution proposed in this chapter uses “Time-Frequency” analysis tools to assistthe extraction of the linear model.

Knowledge is not power, but it’s a start : young people and employment entitlements

This paper employs empirical evidence from a survey of Queensland secondary school students to examine their knowledge about their wages and working conditions. It does so within the theoretical lens of the Gagne (or Gagne-Briggs) theory of instruction, which centres on the content of learning and how learning is acquired (Gagne, Briggs & Wager, 1988). While Gagne articulates five categories of learning, our focus here is on two; verbal information or declarative knowledge (facts that people can declare), and procedural knowledge (the rules and procedures for achieving outcomes). We show that student workers know little about the instruments governing their employment, or their workplace entitlements. Of the total sample of year 9 and year 11 students surveyed (n=892), those students who worked, or who had worked in the past year (n=438), were asked to identify whether they were employed under an award, collective agreement or AWA. Eighty three per cent of students did not know which industrial instrument set their wages. We argue that if young workers do not have declarative knowledge of their entitlements, nor basic procedural knowledge about redress, then they are not in a position to deploy Gagne’s ‘cognitive strategies’ that would enable them to take action to ensure their working conditions meet legal minima. We advocate that young workers should be given summary information on their wages and other entitlements on appointment and that such summary information should be readily available on employers’ noticeboards and electronically on company websites, and that the information should include a brief summary of avenues for redressing issues of underpayment or sub-standard conditions.

To work or not to work? Child development and maternal labor supply

We estimate the effect of early child development on maternal labor force participation. Mothers of poorly developing children may remain at home to care for their children. Alternatively, mothers may enter the labor force to pay for additional educational and health resources. Which action dominates is the empirical question we answer in this paper. We control for the potential endogeneity of child development by using an instrumental variables approach, uniquely exploiting exogenous variation in child development associated with child handedness. We find that a one unit increase in poor child development decreases maternal labor force participation by approximately 10 percentage points.

A miniaturised wideband frequency synthesiser

Wideband frequency synthesisers have application in many areas, including test instrumentation and defence electronics. Miniaturisation of these devices provides many advantages to system designers, particularly in applications where extra space and weight are expensive. The purpose of this project was to miniaturise a wideband frequency synthesiser and package it for operation in several different environmental conditions while satisfying demanding technical specifications. The four primary and secondary goals to be achieved were: 1. an operating frequency range from low MHz to greater than 40 GHz, with resolution better than 1 MHz, 2. typical RF output power of +10 dBm, with maximum DC supply of 15 W, 3. synthesiser package of only 150  100  30 mm, and 4. operating temperatures from 20C to +71C, and vibration levels over 7 grms. This task was approached from multiple angles. Electrically, the system is designed to have as few functional blocks as possible. Off the shelf components are used for active functions instead of customised circuits. Mechanically, the synthesiser package is designed for efficient use of the available space. Two identical prototype synthesisers were manufactured to evaluate the design methodology and to show the repeatability of the design. Although further engineering development will improve the synthesiser’s performance, this project has successfully demonstrated a level of miniaturisation which sets a new benchmark for wideband synthesiser design. These synthesisers will meet the demands for smaller, lighter wideband sources. Potential applications include portable test equipment, radar and electronic surveillance systems on unmanned aerial vehicles. They are also useful for reducing the overall weight and power consumption of other systems, even if small dimensions are not essential.