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Foreword to second edition
Foreword to second edition
In the past, one of the main issues in power system planning and operation that needed regular attention depending on the generation dispatch was to be sure that short circuit fault currents would be within the capability of equipment, particularly circuit breakers. Such a key dependency on safety of course means that the analysis of system faults is something every power engineer should know about. However, the ever-increasing need for breadth in a modern electrical engineer’s education, not least, at the time of writing this Foreword, the ‘smarter’ grid’s need for knowledge of communications, the latest monitoring and control techniques, power electronics, software engineering, optimisation and data analytics squeezes the depth with which ‘traditional’ topics can be treated. Thus, many of the critical details in accurate representation of real power system equipment and the practical assessment of system behaviour are often omitted from degree courses. The first edition of this book was therefore extremely welcome in filling that gap. The process had already started in 2007 when the first edition was published, but, since then, the pace of change on power systems around the world has accelerated. In my own home country, the United Kingdom, nearly 30% of electricity produced in 2017 came from renewable sources, something that would have been unthinkable just 10 years earlier when the figure was only 5%. This has meant a squeezing out of the market of fossil-fuelled generation, much of which has now closed, with a lot of the rest running only when wind and solar conditions are unfavourable. While the reduction in carbon emissions associated with electricity generation is essential, the change in energy sources has profound consequences for operation of the system with wind turbines and inverter-connected infeeds increasingly prevalent. Thus, just as, at certain times and in certain places, fault levels can still be too high, there are periods and locations when the worry is that they are too low, for example, the intended operation of protection or avoidance of commutation failure on line-commutated high voltage direct current (HVDC). However, the fault current contributions from equipment other than directly connected synchronous machines cannot be neglected. They must therefore be calculated accurately. Moreover, given both their increasing significance and the broad pallet available in respect of the control of power electronics, grid codes need to be clear in what performance is required under a variety of system conditions, including unbalanced faults. Indeed, in 2019, a subject of research is the cost and potential benefits of changes to short-term current ratings and control of voltage source converters to
xxvi
Foreword to second edition
provide more reliable operation under short-circuit conditions, lessen the depth of voltage dips and provide a ‘grid-forming’ capability so aiding system stability. Against the background outlined above, the second edition of Nasser’s book is extremely timely. He has enriched it to include analysis of both Type 3 and Type 4 wind turbines and all inverter-connected sources and has described their behaviour under short-circuit conditions and the nature of extant international grid codes. He has also addressed the emerging technology of grid-forming inverters, both virtual synchronous machines and droop-controlled inverters. Other enhancements include new material on superconducting fault current limiters and environmental influences on earth return currents and rise of earth potential. In the Preface to the first edition, Nasser noted that, since liberalisation of electricity supply industries around the world, ‘many new engineers entering industry are neither adequately equipped academically nor are they finding many experienced engineers to train them.’ A number of the companies with which I have contacts do now succeed in recruiting bright, motivated young people. When I’m interviewing prospective undergraduates and teaching them before they leave, I am encouraged by how many of them show an acute awareness of challenges faced by a globally warming planet and an active desire to do their bit to address them. However, it appears to me to be increasingly the case that senior managers in companies with a strong cost-reduction focus are losing sight of the need for both solid educational foundations and experienced, patient mentoring. I see little problem with the fundamental calibre of young people other than the ability of those of us established in the sector to attract them to dedicate their careers to electrical energy and to give them the knowledge they need. I worry that the sector, certainly where I live, is not taking seriously enough the need for technical excellence to keep ahead of the curve of change. The lights might not yet be going out much more often, but for how long will that continue? More broadly, how do we most costeffectively provide access to low-carbon electricity, not just for those already on the grid but also the millions around the world currently lacking it, and whose lives would be improved by it? Nasser’s career has been notable from when he was an outstanding PhD student at the University of Manchester at a time when there were many good students through to when he had senior positions with National Grid in England and, now, with the Dubai Electricity and Water Authority. He shows a rare combination of academic rigour, breadth, clarity and industrial know-how with a sense of the importance of detail and which details matter in practical analysis and decision making. He is also unfailingly polite and generous with his knowledge. In my own career, I have reached a position of responsibility with respect to education of the next generation of professional engineers and, potentially, sector leaders. I also find myself being regularly asked for advice by utilities, regulators and government officials, and yet I am all too conscious of the limits to my own knowledge and understanding. However, I know how much I learned from working alongside Nasser and others when we were in National Grid in England, and how much I could still learn
Foreword to second edition
xxvii
from him. It is, sadly, many years since I had a desk across the partition from his, but at least I, and many others, can benefit from this new edition of his excellent and important book. Keith Bell Professor of Smart Grids, University of Strathclyde, Glasgow, United Kingdom
January 2019
In the past, one of the main issues in power system planning and operation that needed regular attention depending on the generation dispatch was to be sure that short circuit fault currents would be within the capability of equipment, particularly circuit breakers. Such a key dependency on safety of course means that the analysis of system faults is something every power engineer should know about. However, the ever-increasing need for breadth in a modern electrical engineer’s education, not least, at the time of writing this Foreword, the ‘smarter’ grid’s need for knowledge of communications, the latest monitoring and control techniques, power electronics, software engineering, optimisation and data analytics squeezes the depth with which ‘traditional’ topics can be treated. Thus, many of the critical details in accurate representation of real power system equipment and the practical assessment of system behaviour are often omitted from degree courses. The first edition of this book was therefore extremely welcome in filling that gap. The process had already started in 2007 when the first edition was published, but, since then, the pace of change on power systems around the world has accelerated. In my own home country, the United Kingdom, nearly 30% of electricity produced in 2017 came from renewable sources, something that would have been unthinkable just 10 years earlier when the figure was only 5%. This has meant a squeezing out of the market of fossil-fuelled generation, much of which has now closed, with a lot of the rest running only when wind and solar conditions are unfavourable. While the reduction in carbon emissions associated with electricity generation is essential, the change in energy sources has profound consequences for operation of the system with wind turbines and inverter-connected infeeds increasingly prevalent. Thus, just as, at certain times and in certain places, fault levels can still be too high, there are periods and locations when the worry is that they are too low, for example, the intended operation of protection or avoidance of commutation failure on line-commutated high voltage direct current (HVDC). However, the fault current contributions from equipment other than directly connected synchronous machines cannot be neglected. They must therefore be calculated accurately. Moreover, given both their increasing significance and the broad pallet available in respect of the control of power electronics, grid codes need to be clear in what performance is required under a variety of system conditions, including unbalanced faults. Indeed, in 2019, a subject of research is the cost and potential benefits of changes to short-term current ratings and control of voltage source converters to
xxvi
Foreword to second edition
provide more reliable operation under short-circuit conditions, lessen the depth of voltage dips and provide a ‘grid-forming’ capability so aiding system stability. Against the background outlined above, the second edition of Nasser’s book is extremely timely. He has enriched it to include analysis of both Type 3 and Type 4 wind turbines and all inverter-connected sources and has described their behaviour under short-circuit conditions and the nature of extant international grid codes. He has also addressed the emerging technology of grid-forming inverters, both virtual synchronous machines and droop-controlled inverters. Other enhancements include new material on superconducting fault current limiters and environmental influences on earth return currents and rise of earth potential. In the Preface to the first edition, Nasser noted that, since liberalisation of electricity supply industries around the world, ‘many new engineers entering industry are neither adequately equipped academically nor are they finding many experienced engineers to train them.’ A number of the companies with which I have contacts do now succeed in recruiting bright, motivated young people. When I’m interviewing prospective undergraduates and teaching them before they leave, I am encouraged by how many of them show an acute awareness of challenges faced by a globally warming planet and an active desire to do their bit to address them. However, it appears to me to be increasingly the case that senior managers in companies with a strong cost-reduction focus are losing sight of the need for both solid educational foundations and experienced, patient mentoring. I see little problem with the fundamental calibre of young people other than the ability of those of us established in the sector to attract them to dedicate their careers to electrical energy and to give them the knowledge they need. I worry that the sector, certainly where I live, is not taking seriously enough the need for technical excellence to keep ahead of the curve of change. The lights might not yet be going out much more often, but for how long will that continue? More broadly, how do we most costeffectively provide access to low-carbon electricity, not just for those already on the grid but also the millions around the world currently lacking it, and whose lives would be improved by it? Nasser’s career has been notable from when he was an outstanding PhD student at the University of Manchester at a time when there were many good students through to when he had senior positions with National Grid in England and, now, with the Dubai Electricity and Water Authority. He shows a rare combination of academic rigour, breadth, clarity and industrial know-how with a sense of the importance of detail and which details matter in practical analysis and decision making. He is also unfailingly polite and generous with his knowledge. In my own career, I have reached a position of responsibility with respect to education of the next generation of professional engineers and, potentially, sector leaders. I also find myself being regularly asked for advice by utilities, regulators and government officials, and yet I am all too conscious of the limits to my own knowledge and understanding. However, I know how much I learned from working alongside Nasser and others when we were in National Grid in England, and how much I could still learn
Foreword to second edition
xxvii
from him. It is, sadly, many years since I had a desk across the partition from his, but at least I, and many others, can benefit from this new edition of his excellent and important book. Keith Bell Professor of Smart Grids, University of Strathclyde, Glasgow, United Kingdom
January 2019