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Bertenshaw D.R.,ENELEC Ltd | Smith A.C.,Singapore Institute of Manufacturing Technology | Ho C.W.,Singapore Institute of Manufacturing Technology | Chan T.,Aurecon Australia Pty Ltd | Sasic M.,Iris Power LP
IET Electric Power Applications | Year: 2012

Monitoring the health of large electrical machines, especially power station generators, is now an integral part of their operation to maintain and extend life. This work studies the use of electromagnetic sensors to detect inter-lamination insulation faults in the stator cores of large generators before they propagate to a level that can lead to catastrophic failure. The work develops a deeper understanding of the electromagnetic behaviour of core faults so that condition-monitoring sensors can be more specific about the location and severity of the fault. The study develops two new three-dimensional (3D) analytical models, one for predicting the fault current distribution in a stator core fault and the second for predicting the varying detection of such current by air-cored sensors. This further analysed the 3D detection efficiency of typical short fault lengths to compare with the two dimensional (2D) default of infinite-length faults. Different fault positions were modelled so that a clearer understanding of the location and severity of the fault is possible. These were validated on a specially constructed experimental test core that can impose controlled fault currents. The study also demonstrates how small core faults can escalate then self-limit radially, but may propagate axially into longer more damaging faults. © 2012 © The Institution of Engineering and Technology. Source

Mitchell P.W.,Aurecon Australia Pty Ltd | Mitchell P.W.,University of Adelaide
Australian Geomechanics Journal | Year: 2013

The problems of the stability of vertical or near vertical excavations in unsaturated fissured clay are discussed. A consideration of the stability of vertical excavations in non-fissured clay, in clay with tension cracks, and by considering the effects of lateral stress relief on excavation in clays without pre-existing fissures, gives greater excavation depths than would be regarded as acceptable in clays. The overall stability of the soil mass containing fissures is governed by the residual shear strength along the joints, particularly with polished slickensides. A common failure mechanism in vertical and near vertical excavations occurs when a slickenside intersects a vertical shrinkage crack. Using the residual shear strength parameters and a planar failure mechanism, the stability of vertical and steeply sided excavations, either supported or unsupported, in fissured clay is discussed. Three case examples are outlined, and recommendations for the successful construction of temporary batters in unsaturated fissured clay are given. Source

Hosseinzadeh N.,Swinburne University of Technology | Mayer J.E.,Aurecon Australia Pty Ltd | Wolfs P.J.,Curtin University Australia
International Journal of Electrical Power and Energy Systems | Year: 2011

Single Wire Earth Return (SWER) systems are used for supplying electricity at low cost, where electricity supply is required for small populations of people dispersed across wide geographical areas. It is principally used for rural electrification, but is also used for other isolated loads and light rail. The existing SWER distribution systems have been stretched with the sharp growth of their loads because of customers' change of lifestyle, which has introduced additional load of air conditioning equipment, motors driven by variable-speed drives and inverters. This paper proposes cost-effective solutions to address the problem of voltage regulation and compensation of the unbalancing effect of SWER lines on the three-phase feeder of these lines, which have been exacerbated by this load growth. To improve the voltage regulation problem, a LV switchable reactor has been designed, a prototype made and tested in the field. Also, an unbalance compensator has been designed to reduce the unbalancing effect of SWER lines. Two case networks have been used to perform simulation studies on the effectiveness of both proposed solutions. At first, a case study is used to demonstrate the impact of a switchable reactor on improving voltage regulation. Then, another case study shows that installation of a switchable reactor and an unbalance compensator simultaneously on a SWER distribution system effectively improves voltage regulation and reduces unbalancing effects. © 2010 Elsevier Inc. All rights reserved. Source

Peterseim J.H.,University of Technology, Sydney | White S.,University of Technology, Sydney | Tadros A.,Aurecon Australia Pty Ltd | Hellwig U.,ERK Eckrohrkessel GmbH
Renewable Energy | Year: 2013

This assessment aims to identify the most suitable concentrated solar power (CSP) technologies to hybridize with Rankine cycle power plants using conventional fuels, such as gas and coal, as well as non-conventional fuels, namely biomass and waste materials. The results derive from quantitative data, such as literature, industry information and own calculations, as well as qualitative data from an expert workshop. To incorporate the variety of technology criteria, quantitative and qualitative data the Analytical Hierarchy Process (AHP) is used as the multi-criteria decision making (MCDM) tool. Only CSP technologies able to directly or indirectly generate steam are compared in regards to feasibility, risk, environmental impact and Levelised Cost of Electricity (LCOE). Different sub-criteria are chosen to consider the most relevant aspects. The study focuses on the suitability of CSP technologies for hybridisation and results obtained are reality checked by comparison with plants already being built/under construction. The results of this assessment are time dependant and may change with new CSP technologies maturing and prices decreasing in the future.Key findings of this assessment show that Fresnel systems seem to be the best technology for feedwater preheating, cold reheat steam and <450 °C steam boost applications. Parabolic troughs using thermal oil rank second for all CSP integration scenarios with steam temperatures <380 °C. Generally, for steam temperatures above 450 °C the solar towers with direct steam generation score higher than solar towers using molten salt and the big dish technology. At and above 580 °C the big dish is the only alternative to directly provide high pressure steam.In addition to a general CSP technology selection for hybridisation the framework of this study could be used to identify the most suitable CSP technology for a specific CSP hybrid project but this requires detailed information for direct normal irradiance, climate conditions, space constraints etc to provide reliable results. © 2013 Elsevier Ltd. Source

Toombes L.,Aurecon Australia Pty Ltd
ISHS 2014 - Hydraulic Structures and Society - Engineering Challenges and Extremes: Proceedings of the 5th IAHR International Symposium on Hydraulic Structures | Year: 2014

Designed by 2007, built by 2010, limits pushed by 2011; the occurrence of an extreme flood event at the Nam Theun 2 hydropower dam system in Laos sparked a reassessment of the hydrology resulting in an increase of over 30% in design flows and leaving the flood release infrastructure well short of the required capacity. This increase and subsequent attempts to re-analyse the release structures, ranging from simplified HEC-RAS modelling to sophisticated CFD and physical modelling, serve as examples of the uncertainty and risks that can be encountered in the design of hydraulic structures. Source

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