Electrical Safety Engineering of Renewable Energy Systems. Rodolfo Araneo

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Preface

      To my wife Stefania, for her unfailing love, patience, and encouragement,

      and to my blessed sons Leonardo and Giulio, who give me the tremendous energy of the youth.

      To my wife Jennifer and my daughters Alessandra and Giorgia,

      who are the true renewable energy source in the heart of their father.

      It was the year 2004 when Prof. Araneo began his journey through renewable energies. And it was the year 1990 when Prof. Mitolo started his in electrical safety engineering.

      Prof. Araneo was asked by a high school and college mate to jointly work on the design of one of the first 1 MWp utility-scale photovoltaic plants in Italy to be built in Sardinia. He was an inexperienced, fresh PhD graduate in electrical engineering, but driven by an innate curiosity and interest in all that was electrical engineering. He did accept the challenge, and in the years to come, he worked on the design and construction of almost 1 GW of renewable energy plants. In the early 2010s, he started teaching a university graduate course on renewable energies.

      Prof. Mitolo, a fresh PhD graduate in electrical engineering, read the EU Directive 89/391/EEC, also known as the Framework Directive, which indicated that the risk assessment was to be the cornerstone in the prevention of accidents. This, right then, confirmed in his mind the idea that electrical safety could not only be implemented through a list of prudent actions near energized parts but mainly via the proper design: the safety-by-design approach to anticipate and design out hazards. Since then, Prof. Mitolo has accordingly designed, researched, taught, and authored.

These authors met during the Christmas Holidays of 2018 in beautiful California and spent time enjoying with their families the beautiful scenery of the Pacific Ocean, and, at the same time, discussing the typical academic issues (i.e., conferences, papers, research, and grants – topics that their families found boring, especially during those sunny days). It was then that Prof. Araneo forwarded the idea to write a book on renewable energies and safety. Some may decide to write engineering books after long and erudite meditations; others (i.e., these authors) did it under California’s blue skies, surrounded by family.

      An amazing (and demanding) period of two years of work and dedication started, whose results the authors hope the readers will enjoy.

      The authors believe that a book is the ideal means to make it possible to share the results of experience and research with the readers. Many books on renewable energies have been written, yet this book introduces a different view on the topic: it teaches the practitioner (student or engineer) how to ensure electrical safety in renewable energy systems (e.g., when the sun shines, a PV array cannot be turned off).

      This book does not want to be the classic academic book for a university course, but it has been written with the intent to marry the experience of the professional engineer with the scientific rigor of the university professor: two ugly beasts that together may have produced an interesting result.

      Nowadays, there is a great and unsatisfied demand for electrical engineers, especially in power systems, which now do include renewable energies. This is especially true in light of the global energy transition that we are experiencing: we are walking along a pathway toward a transformation of the global energy sector from fossil-based to zero-carbon footprint. The electric engineer will play a major role since safe electrification is expected to be a critical milestone for decarbonization. There should be no shortage of challenging problems in renewables in the foreseeable future. There will be a clear need for engineers to have both an understanding of the fundamentals of electric safety as applicable to renewables and the creativity to apply this knowledge to problems of practical interest.

      This book is for those engineers.

Acknowledgments

      It is a pleasure to acknowledge the role of many students in helpful discussions. Prof. Araneo would like to thank Giorgio Mingoli for the phone call in 2004. The authors would like to thank the following persons for providing materials and being available: Giuseppe Mastropieri, Fabio Amico and Massimiliano D’Angelo of REA Advisors, Raffaella De Cupis and Gianfranco De Simone of Ghella, Massimilano Donati of VEI Green, Saverio Spampanato of Secundm Naturam, and Riccardo Cecere of Enel Global Power Generation. Finally, Prof. Araneo finds it difficult to express in words his gratefulness to Prof. Salvatore Celozzi, who provided him with guidance, support, and encouragement during his career.

      Prof. Rodolfo Araneo

      Roma, Italy, March 28, 2021

      Prof. Massimo Mitolo

Irvine, California, March 28, 2021

1 Fundamental Concepts of Electrical Safety Engineering

       CONTENTS

      1.1 Introduction

      1.2 Electric Shock

      1.2.1 Ventricular Fibrillation

      1.2.2 The Heart-current Factor

      1.3 The Electrical Impedance of the Human Body

      1.3.1 The Internal Resistance of the Human Body

      1.4 Thermal Shock

      1.5 Heated Surfaces of Electrical Equipment and Contact Burn Injuries

      1.6 Ground-Potential and Ground-Resistance

      1.6.1 Area of Influence of a Ground-electrode

      1.7 Hemispherical Electrodes in Parallel

      1.8 Hemispherical Electrodes in Series

      1.9 Person’s Body Resistance-to-ground and Touch Voltages

       Example 1.1

      1.10 Identification of Extraneous-Conductive-Parts

      1.11 Measuring Touch Voltages

      References

      I shall be telling this with a sigh Somewhere ages and ages hence: Two roads diverged in a wood, and I- I took the one less traveled by, And that has made all the difference.

      Robert Frost

      1.1 Introduction

The renewable energy sector has been rapidly growing in the past decade [1–3], and so has been the number of accidents involving workers in “green”