This third edition comprises 23 chapters covering high-voltage engineering and testing themes – with many valuable references describing CIGRE work. Table 1 is set out at the end of this introduction to assist in understanding the range and scope of individual CIGRE Study Committees (SCs) and associated terminology, while Table 2 provides an abridged summary of recent strategic work in the transformer sector by CIGRE (SC A2), which we will return to later.
Chapter 1 provides an authoritative coverage of ‘Electric power transmission and distribution systems’ by Dr Arslan Erinmez. In this, ‘The progressive devel-opment from 1880s to date is described mainly with reference to the UK system, as most systems around the world have gone through the same stages of development at and around the same time following technological, political and organisational developments which reflected the trends current at the time’. Global developments are also reviewed together with several key factors, for example technical, orga-nisational structures that heavily influence the development and operation of these networks. Design, security and operational and planning aspects are also con-sidered. Future developments and challenges: organisational, security, technical and technological are discussed, including a large detailed list of conventional and non conventional power electronic thyristor-controlled voltage regulators and other devices (also touched on in Chapters 4, 5 and briefly in Chapter 23 – relating to use with offshore-wind farms). The author also points out that ‘although three phase overhead lines is still the usual method of interconnection, in cases where long transmission distances and/or sea crossings are involved, HVDC transmission is economic despite the relatively higher costs of converter and terminal equipment’.
Erinmez comments on HVDC transmission that is also used for inter-connecting utilities with different supply frequencies (e.g. 50/60 Hz) and in cases where an asynchronous link between systems is required. ‘Back-to-back’ HVDC interconnections have also been used with both ‘converter stations’ situated in the same site. Erinmez (Chapter 1) also reports that the rapid development of com-puting and communication systems has accelerated development strategies often referred to as the so-called ‘smart-grid initiatives’.1
The author comments that smart-grid initiatives tend to focus on consumer demand control, remote switching and metering aspects but considers that they currently suffer from inadequately defined objectives as well as protocols and
1 These are discussed further in Chapter 11 and in greater detail in Chapter 23 (section 23.13 and Tables 23.9–23.14).
standards (this editor endorses these remarks). Further, Erinmez considers smart-grid initiatives, at transmission level, are more appropriate for special protection and system control applications, whereas in distribution systems their application will be subject to consumer approval and placement of privacy safeguards. He also warns that the use of Internet-based communications also exposes transmission and distribution utilities to malicious attacks and cyber-hacking activity. These issues, which are likely to require increasing efforts to ensure robustness of systems to such threats, are considered further in Chapter 23, Appendix A.2
Erinmez in Chapter 1 points out that NGC is the first and largest fully priva-tised independent transmission utility in the world that has been subjected to organisational and electricity market driven changes. As a result, it has been ‘able to utilise every available technology to address the challenges of facilitating com-petition and responding to the electricity market place’. He outlines the leading role of NGC in ‘FACTS and HVDC development/applications and provides a brief summary of both traditional and the new technology portfolio readily available to utilities’ (see section 1.6.2).
The important concept of insulation co-ordination (IC) of high-voltage and EHV AC systems is thoroughly covered in Chapter 2 (Irwin and Ryan), while Chapter 3 (Ryan) touches on a few important aspects of IC for UHV AC systems recently covered in CIGRE TBs 546 (2011) and 542 (2O13).* The more recent study, reproduced in a summarised form in Table 3.2, takes into account the state-of-the-art technology, with special reference to higher performance surge arresters.
*This review takes into account: the accumulated knowledge of various CIGRE working bodies; recent measured data of very fast temporary overvoltages (VFTO); and air gap dielectric characteristics in collaboration with CIGRE SC A3 and B3.
The emphasis in Chapter 3 relates to the application of gaseous insulants to switchgear, mainly SF6 in GIS/GIL, and outlines criteria for EHV/UHV testing laboratories, dielectric modelling studies enabling optimal dielectric design of circuit-breaker units etc. to be produced and minimum breakdown voltages to be predicted, often without recourse to extensive and costly development testing. Ryan (Chapter 3) also considers that the subtle nuances of the complex fundamental arc-physics measurements in SF6, systematic interrupter high-current performance assessments and development, and effective dielectric design of practical interrupter layouts fully justified the effective use of the complementary skills of a group of experts in this sector when making decisions regarding the final commercial SF6
GIS and circuit-breaker designs that subsequently achieved outstanding interruption and dielectric and in-service performance. These were systematically developed from a four-break interrupter design to a two-break design, and eventually to the design of one-break interrupter in a remarkably short timescale (see Chapter 8).3
2 The reader is encouraged to use Chapter 1 as a major ‘reference point’ source when considering smart grids of the future and cyber-crime, cyber hacking/malicious attacks.
3 The supporting R&D for these developments, carried out towards the end of the twentieth century, has been extensively reported in the literature, by S.M.G. Ali, G.R. Jones, D. Lightle, H.M. Ryan, et al.
(see also Chapters 7, 8, 21–23).
Chapters 2, 3 and 8 also discuss strategic aspects relating to UHV substation design; it should be recognised that, because only a few UHV AC transmission networks exist and have only recently entered service worldwide, at 1.1 MV or 1.2 MV (e.g. in China and in India respectively):
1. The background of the technical specifications for substation equipment exceeding 800 kV AC [CIGRE TB 546 (2011)] is less well defined than at lower system voltage levels, where robust standards already exist.
2. Only limited experimental/technical/specification information exists for UHV substation equipment, and two recent CIGRE Technical Brochures TB 546 and TB 542 are currently of strategic importance and will remain so till the time more robust full IEC specifications are developed for UHV systems:
– TB 546: This study has collated the limited available background UHV information and has presented interim recommendations for the interna-tional specification and standardisation of UHV equipment [in CIGRE Technical Brochure TB 456-WG A3.22 (2011)];
– TB 542: This study discusses the insulation co-ordination practices in three UHV AC Systems [TB 542-WG A4.306 (2013)] at:
[a] the 1100 kV Jindongnan Substation (China),
[b] the 1100 kV Shin-Haruna Testing Station (Japan) and [c] the 1200 kV Bina Testing Station (India).
TB 542, a follow-on study from the work of TB 546 (2011), has described further useful measures and simulation studies. It considers that overvoltage miti-gation techniques such as higher performance arresters can drastically reduce lightning overvoltage levels. The CIGRE review (WG A4.306) intimated that it will prepare recommendations, ‘such as recent practices of insulation coordination based on the higher performance surge arresters, estimation of overvoltage and air clearance, and these will be proposed for future revisions of the application guide IEC 60071-2 (1996) and IEC apparatus standards’.
Insulation co-ordination (IC) is a very complex subject area and one of immense strategic technical/economic importance to the network design and effective operation. Consequently, here again it is always strongly recommended to use the complementary skills of a group of experts in this sector when making final design decisions. Aspects such as IC (including the use made of surge arresters at UHV levels), switching phenomena for circuit-breakers, dis-connectors and earthing switches and testing are also considered in Chapters 2 and 8. In situations such as this, refinements and knowledge updates will continue as service experience with UHV systems increases – and until full robust IEC Standards are produced. Again, CIGRE technical activities are considered in many chapters of this book and in Table 1 at the end of this introduction section, the reader is provided with useful backgroud to the wide range of CIGRE tech-nical activities: ‘CIGRE key: SC, Study Committee; WG, Working Group and JWG, Joint Working Group; TF, Task Force; TB, Technical Brochure; TR, Technical Report; SC, Scientific Paper’.
Introduction 3
Chapter 3 [CIGRE TB 546] informs the reader that, at present, UHV tech-nology is ‘characterised by a need to minimise the sizes, weights, costs and environmental impacts of the overhead lines and substations and hence to develop projects which are feasible from economic, societal and technical points of view’.
This interim utility/CIGRE strategy is discussed together with a brief explanation of how, by means of ‘the application of a number of new technologies and new ana-lysis techniques, utilities are able to reduce the dielectric requirements to values that lead to much smaller structures’.
This results in insulation voltage levels at UHV that are not far from the levels applied at the 800 kV class. For example, in Japan the towers of the UHV OH lines are only 77% of the size that would be necessary if insulation levels would have been extrapolated directly from lower voltage class. Chapter 3 goes on to detail other strategic aspects considered in CIGRE TBs 546 or 542. Three important aspects included in this list, which are also touched on in Chapters 2, 8 and Table 3.2 of Chapter 3, are:
1. the use of closing resistors to control slow front overvoltages (SFO) 2. the use of opening resistors to reduce opening SFO
3. damping resistors to be used in GIS disconnectors to reduce the amplitude of VFTO (very fast transient overvoltage) phenomena which otherwise may exceed the lightning impulse withstand voltage of the switchgear
4. mitigation techniques such as higher performance arresters can dramatically reduce the lightning overvoltage levels [TB 542-WG A4.306 (2013)].
Further, the reader should note that, while some experts are concerned with the present IC situation, everyone should be at least partly reassured that another CIGRE expert Working Group [TB 542-WG A4.306] has had deliberations cerning the vital issue of field testing techniques on UHV substations during con-struction and operation. An updated CIGRE TB provisionally entitled ‘Field Testing Technology on UHV Substation Construction and Operation’ was due to be issued by CIGRE by late 2012. However, the work on this proposed document might well have been incorportated into TB 452-WG A4.306 (2013).
Chapter 4 by Gearo´id o´ hEidhin considers HVDC4 and power electronic systems that are now widely used in modern networks and will certainly find increased application as the industry moves towards smart grids and enhanced transmission and distribution networks of the future, that is within the next one or two decades. This chapter provides comprehensive material and informs the reader how modern HVDC converter stations are designed, general principles (including basic components); details of main components of HVDC links including converter transformer, McNeill HVDC station designs; control systems and AC filters and reactive power control; smoothing reactor and DC filters;
switchgear; valve cooling techniques; surge arrester equipment; typical layouts of control building and valve hall; development of voltage-sourced converters (VSCs) and other devices; environmental aspects; adherence to standard
4The term gas circuit-breakers (GCBs) has recently been used when discussing HVDC systems in the literature.
specifications and more. Power electronic support for AC systems is also briefly covered in Chapter 4.
Note: A generous list of valuable reference sources is provided for further reading and current/
future CIGRE publications are available from IET/IEEE/CIGRE and can be regularly monitored, simi-larly IET/IEEE/IEC Standards, etc. In particular, CIGRE sources (see Table 1 for details of Study Committees) provide many regular strategic Technical Brochures (TBs) on important worldwide issues in the sector (e.g. see appendices to Chapters 8, 9, 10 and elsewhere in this book).
The theme of ‘back-to-back’ HVDC interconnections being used, with both converter stations situated in the same site, has already been touched on in Chapter 1. This is considered further in Chapter 4, by the author of ‘HVDC and power electronic systems’, who points out:
1. If the function of a HVDC transmission scheme is to transfer power over a long distance, then it will invariably use a high direct voltage. Most ‘modern’
schemes use voltages up to 800 kV for overhead lines, while cables have been approaching voltages up to600 kV progressively over the past 20 years.
2. Converter stations can be roughly characterised into two groups:
(i) back-to-back converters using low direct voltage and high current typically 20–250 kV and 2.5–5 kA
(ii) long-distance transmission schemes using higher direct voltages and more moderate current typically 300–800 kV and 1–4 kA.
Notes:
1. For back-to-back schemes, the author points out that the pressure to use HV disappears and the voltage used is the lowest voltage at which the required power can be transferred (within the limitations of the converter valves).
2. Economic HVDC power transfer, for example from a remote power source to an urban area: a DC line is significantly cheaper to build than an AC line to carry the same power and additionally, if the distance is great enough, this economy is sufficient to pay for costs of the converter stations at both ends of the line. Chapter 4 quotes the break-even distance as approximately 800 km for an overhead line and 50 km for a cable.
Chapter 5 by Adrian Wilson discusses the implications of renewable energy on grid networks and provides a valuable overview of the subject. The reader should also be aware that:
1. Another recent IET book – Power and Energy Series 63, entitled Energy Storage for Power Systems, 2nd edn, 2011, by A. G. Ter-Gazarian provides a valuable additional resource and contains 144 references.
2. Chapter 23 of the present book provides several interesting UK press/public perceptions as to the recent effectiveness of renewable energy wind farm sup-plies in the UK, the high UK energy costs to the British Public, customer fuel poverty and several other strategic aspects relating to the future energy strategy of the UK government including those for new-build nuclear, following on from the aftermath of the Fukushima nuclear accident of 2011.
Introduction 5
Basic cable designs and theory are covered in Chapter 6, by A. Barclay, with some brief supplementary offshore wind farm material touching on EU North Sea Energy grid aspirations and other recent applications that plan to use modern low-loss superconducting cable designs being briefly touched on in Chapter 23. Interest-ingly, CIGRE Table 2, in this introduction, indicates that Japanese R&D has targeted 2020 for the commercial deployment of high-temperature superconducting transformers in power systems.
Chapters 7–10 cover circuit-breaking aspects. Chapter 7, by G.R. Jones, M. Seeger and J. Spencer, provides an excellent comprehensive fundamental treatment of gas-filled interrupters and this is followed, respectively, by thorough treatment and reviews of high-power SF6 switchgear design development and service (Chapter 8, by S.M. Ghufran Ali, Distribution switchgear; Chapter 9, by B.M. Pryor, Differences in performance between SF6and vacuum circuit-breakers;
Chapter 10, by S.M. Ghufran Ali).
The subtle nuances of the complex fundamental arc-physics measurements in SF6(for example by Professor G.R. Jones and his group at CIMS, Department of Electrical and Electronics, University of Liverpool and by Reyrolle switchgear staff towards the end of the twentieth century), the systematic interrupter high-current performance assessments and development, and effective dielectric design of practical interrupter layouts fully justified the effective use by Reyrolle of the complementary skills of a group of experts in this sector, when making a late decision regarding the final ‘worldclass’ commercial SF6 designs that subsequently achieved outstanding circuit-breaker interruption, dielectric and in-service performance. High-power com-mercial interrupter designs were speedily and systematically developed from four-break interrupter/phase to two-four-break interrupter/phase and quickly to one-four-break/phase commercial interrupter design, as reported by S.M. Ghufran Ali, G.R. Jones et al.
These collaborative developments are considered further in Chapter 3.
It must be stressed that vital partnerships, such as mentioned above, between universities and the power industry, are of even more strategic importance now in the twenty-first century, and in the case of the University of Liverpool it was very pleasing for this writer to note that a major Chinese electrical engineering firm, the Pinggao Group (a direct subsidiary of the Chinese State Grid) is to invest
£1.5 million in research at the University of Liverpool over the next five years.
Pinggao is one of China’s major manufacturers, engaged in the design and produc-tion of switchgear and power plant equipment at HV, EHV and UHV voltage levels.
It appears that the framework agreement will see the university build on the existing provision of technological support for the development and optimisation of Pinggao’s electrical apparatus, in order to supply reliable electrical equipment as China moves towards developing ‘smart grids’ and enhanced energy networks of the future.
Welcoming this agreement while on a visit to University of Liverpool, Quingping Pang, Pinggao, Vice General Manager, ended his statement by stating: ‘We hope the technologies developed here will be successfully used for the benefit of all society’.5
5Without doubt this agreement ‘provides further robust evidence’ of the high quality of expertise available at some UK universities – in this case at the University of Liverpool, UK, Electrical Engineering and Electronics Department/Centre for Intelligent Monitoring Systems.
Much valuable supplementary strategic CIGRE ‘switchgear-related’ material is also included in the appendices of Chapters 8–10, mostly from appropriate CIGRE (TB) sources, thanks to its effective and wide-ranging worldwide working group activities infrastructure as set in Table 1, at the end of this introduction section. The reader is provided with further strategic CIGRE information in Chapter 23.
Chapter 11, by John Steed, considers ‘Life management of electrical plant: a distribution perspective’. Overall Steed presents an interesting distribution per-spective of life management of electrical plant. He points out that the effective management of assets to ensure that the user obtains the optimum life for the plant is becoming more vital as electricity distribution systems are worked harder and all equipment need to be reliable. He considers several strategic aspects to substantiate his viewpoints. Steed also discusses the impact of smart grids on asset management; he comments that in the early part of twenty-first century much has been talked about smart grids, i.e. the use of new technologies that will:
1. facilitate the transition to a low-carbon electricity supply system 2. enable an increase in security of supply.
Steed is of the view that as far as (2) is concerned, this relates the challenges of being able to integrate inflexible and/or intermittent generation into the system.
He considers the essential elements for this will include:
● a wider use of automation and intelligent systems
● distributed and centralised intelligence, real-time monitoring and diagnostics
● an integrated ‘cyber-security’ data protection and data privacy safeguards.
Consequently, Steed considers that condition monitoring systems will become increasingly important and are likely to be applied to more equipment especially those identified as system-critical, informing the users of impending failures in the system. (Note: Three aspects of condition monitoring are discussed exclusively and sequentially in Chapters 20–22.)
Note: At this point, the attention of the reader is again directed towards the fact that frequent reference in this book will be made to CIGRE technical publications. In anticipation of future developments in the power sector CIGRE totally reformed its specialist professional Technical Study Committees in 2002 –
Note: At this point, the attention of the reader is again directed towards the fact that frequent reference in this book will be made to CIGRE technical publications. In anticipation of future developments in the power sector CIGRE totally reformed its specialist professional Technical Study Committees in 2002 –