Supporting transient stability in future highly distributed power systems

Incorporating a substantial volume of microgeneration (consumer-led rather than centrally planed) within a system that is not designed for such a paradigm could lead to conflicts in the operating strategies of the new and existing centralised generation technologies. So it becomes vital for such substantial amounts of microgeneration among other decentralised resources to be controlled in the way that the aggregated response will support the wider system. In addition, the characteristic behaviour of such populations requires to be understood under different system conditions to ascertain measures of risk and resilience. Therefore, this paper provides two main contributions: firstly, conceptual control for a system incorporating a high penetration of microgeneration and dynamic load, termed a Highly Distributed Power System (HDPS), is proposed. Secondly, a technical solution that can support enhanced transient stability in such a system is evaluated and demonstrated

A dynamic modelling environment for the evaluation of wide area protection systems

This paper introduces the concept of dynamic modelling for wide area and adaptive power system protection. Although not limited to these types of protection schemes, these were chosen due to their potential role in solving a multitude of protection challenges facing future power systems. The dynamic modelling will be implemented using a bespoke simulation environment. This tool allows for a fully integrated testing methodology which enables the validation of protection solutions prior to their operational deployment. Furthermore the paper suggests a distributed protection architecture, which when applied to existing and future protection schemes, has the potential to enhance their functionality and avoid mal-operation given that safety and reliability of power systems are paramount. This architecture also provides a means to better understand the underlying dynamics of the aforementioned protection schemes and will be rigorously validated using the modelling environment

Applying series braking resistors to improve the stability of low inertia synchronous generators

Widely held concerns over the environmental impact of emissions from large fossil fuelled generating plants are serving to promote the connection of renewable or sustainable generation onto distribution networks. Many such generators are synchronous machines with low values of inertia, and thus possess short critical clearance times to avoid the onset of transient instability. With fault clearance times of up to 1s occurring in distribution networks, there is the potential for a growing problem as distributed generation makes up a larger proportion of installed capacity. This paper proposes the use of series braking resistors that are switched into circuit at the generator terminals as a means of improving transient stability, and thus avoid, or at least defer major upgrades to distribution system protectio

Modelling the impact of micro generation on the electrical distribution system

In the UK and elsewhere there is considerable debate as to the future form of the electricity distribution system. The coming years will see a rise in the amount of micro-generation connected to the network at low voltages and the emergence of highly-distributed power systems (HDPS). However, there is considerable uncertainty as to the impact that this micro-generation will have on the quality of power supplied to our homes or to the stability of the electricity system as a whole. To address these engineering challenges the UK Engineering and Physical Sciences Research Council (EPSRC) is funding a three year research programme featuring a multi-disciplinary team from a variety of UK Universities: Supergen HDPS. This paper documents one piece of work emerging from the consortium, where a multi-tool approach is used to analyse the impact of micro-generation on the electricity system. This used a building simulation tool to produce electrical generation profiles for domestic cogeneration device models. These, along with profiles produced for other micro-generation technology models and electrical load profiles are then replicated and aggregated using a customised statistical approach. The profiles were then used as boundary conditions for a set of electrical load flow simulations on a model of a section of real network, where the number of microgenerators was varied according to different scenarios for the future of the UK electricity grid. The results indicate that a significant number of micro-generation devices can be accommodated before any power quality problems arise, however this is dependent upon maintaining a robust central grid

Electricity network scenarios for 2020

This report presents a set of scenarios for the development of the electricity supply industry in Great Britain in the years to 2020. These scenarios illustrate the varied sets of background circumstances which may influence the industry over the coming years – including political and regulatory factors, the strength of the economy and the level to which environmentally-driven restrictions and opportunities influence policy and investment decisions. Previous work by the authors (Elders et al, 2006) has resulted in a set of six scenarios illustrating possible developments in the electricity industry in the period up to 2050. While such scenarios are valuable in gauging the long-term direction of the electricity industry and its economic and environmental consequences, shorter-range scenarios are useful in assessing the steps necessary to achieve these long-range destinations, and to determine their relationship to current trends, policies and targets. In this chapter, a set of medium-range scenarios focused on the year 2020 is developed and described. These scenarios are designed to be consistent both with the current state of the electricity supply industry in Great Britain, and with the achievement of the ultimate electricity generation, supply and utilisation infrastructure and patterns described in each of the 2050 scenarios. The consequences of these scenarios in terms of the emissions of carbon dioxide are evaluated and compared with other predictions. The SuperGen 2020 scenarios described in this report were developed as a collaborative effort between the SuperGen project team and the ITI-Energy Networks Project team both based at the University of Strathclyde

Diamond based nanostructures for electronic applications

Research in the area of CVD diamond thin films has increased significantly during the last decades to the point where single crystal diamond is now commercially available. The remarkable properties of diamond including its extreme hardness, low coefficient of friction, chemical inertness, high thermal conductivity, transparency and semiconducting properties make it attractive for a number of applications, among which electronic devices is one of the key areas. A detailed knowledge of electrical properties of diamond films is therefore critical. This thesis describes (1) a Hall effect study of highly boron-doped (111) diamond films (2) a Hall effect and impedance spectroscopic study of boron δ-doped diamond structures and (3) the synthesis of carbon nanotubes on single crystal diamond. Systematic investigations have been carried out on single crystal, boron-doped (111) diamond films. The influence of ultra pure gases, doping concentration and temperature on carrier transport are discussed in detail. A comprehensive study on boron δ-doped diamond films is also performed; Hall effect and impedance spectroscopy are used to evaluate these films, providing valuable insight into the complex carrier transport mechanisms occurring in these structures. The influence of temperature on carrier mobility and the free carrier density are discussed. This is allied with valuable information gained from impedance spectroscopy, where the presence of multiple semicircular responses (conduction pathways), modelled using a RC parallel circuit, yields data which leads to a greater understanding on the influence of the interface between the boron δ-doped layer and the surrounding intrinsic diamond layers. These semicircular responses are thus attributed to different crystalline regions in these structures, namely the boron δ -doped layer and the interfacial regions surrounding δ-layer. The influence of this interface region on the structures overall conductivity is discussed. Finally the synthesis of carbon nanotubes (CNTs) on single crystal diamond is reported for the first time. Scanning electron microscopy combined with Raman spectroscopy is used to understand the influence of temperature and differing growth gas mixtures on the yield and crystallinity of these as-grown CNTs

The sacramental worship of the reformed tradition and its music

Thesis (M.A.)--Boston University PLEASE NOTE: page 111 appears to be missing from the thesis. Our determination is that this is the result of misnumbering by the author, and no substantive content is actually missing. If you are able to determine otherwise, please contact us.From every quarter which is advocating serious reform there is a general concensus of opinion that there must be a re-examination of worship: sacramental worship must be central and it must be recognized as such. It alone fully expresses the mystery of the Incarnation, from which every Christian doctrine stems, and which, therefore, must receive primary expression in Christian worship. The closest element connected with sacramental worship is the observance of the Church Year. The place of lectionaries and the proper use of fixed forms of prayer and extemporaneous prayer must be given proper consideration. The richer forms which are being provided by the Churches give much more opportunity for congregational singing. A new field for a distinctive contribution to music is opened up by the emphasis on sacramental worship now developing. The "congregational service" and the prose Psalm provide two important fields for development. One of the most significant potentialities of the entire Church's renewed interest in sacramental worship is its relation to the Ecumenical Movement. The so-called liturgical Churches are evidencing just as vital a concern as the others in the matter of reforms in worship. It appears that the reforms being called for from all sides have something in common. It is probable that a fuller unity of Christendom shall again reveal the great Christian Sacrament in the wholeness of its many-sided glory

Mathematical analysis of the equivalent impedance at the harmonic frequency for the proposed aircraft power system

The proposals for the `More Electric Aircraft' place a significant, increased demand on the electrical power distribution system. To increase safety and reduce aircraft maintenance times on the ground, there is a greater need to quickly identify and locate electrical faults within the electrical distribution system. The work presented in this study provides the mathematical basis for the use of power system harmonic impedance measurement for identifying and locating faults within power cables. The method is passive - that is, it does not require the injection of any test signals - and can potentially be embedded into a centralised equipment controller to provide intelligent, real time diagnostics. The method monitors the harmonic line-line self-impedance at strategic points in the distribution system; this is obtained by measuring load voltage and current. Faults can be identified and located within a few fundamental cycles, and therefore provides a `backup protection' system which does not require measurement of the line current. It also can provide details of the fault location and could therefore be a significant aid to aircraft maintenance. This study derives the theoretical basis of the scheme and provides simulation results for a proposed aircraft power system to demonstrate the validity of this approach to detect and locate faults within the system