Electrical Safety Engineering of Renewable Energy Systems E-Book

Rodolfo Araneo

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Serie: Wiley - IEEE
• Sprache: Englisch

Seitenzahl: 420

Veröffentlichungsjahr: 2021

Beschreibung

Electrical Safety Engineering of Renewable Energy Systems

A reference to designing and developing electrical systems connected to renewable energies

Electrical Safety Engineering of Renewable Energy Systems is an authoritative text that offers an in-depth exploration to the safety challenges of renewable systems. The authors—noted experts on the topic—cover a wide-range of renewable systems including photovoltaic, wind, and cogeneration and propose a safety-by-design approach. The book clearly illustrates safe behavior in complex real-world renewable energy systems using practical approaches.

The book contains a review of the foundational electrical engineering topics and highlights how safety engineering links to the renewable energies. Designed as an accessible resource, the text discusses the most relevant and current topics supported by rigorous analytical, theoretical and numerical analyses. The authors also provide guidelines for readers interested in practical applications. This important book:

• Reviews of the major electrical engineering topics
• Shows how safety engineering links to the renewable energies
• Discusses the most relevant current topics in the field
• Provides solid theoretical and numerical explanations

Written for students and professional electrical engineers, Electrical Safety Engineering of Renewable Energy Systems explores the safety challenges of renewable systems and proposes a safety-by-design approach, which is currently missing in current literature.

Leseprobe

Electrical Safety Engineering of Renewable Energy Systems

Rodolfo Araneo

University of RomeRome, Italy

Massimo Mitolo

Irvine Valley CollegeIrvine, California

This edition first published 2022

© 2021 John Wiley & Sons, Ltd.

© 2022 by The Institute of Electrical and Electronics Engineers, Inc. All rights reserved.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey.

Published simultaneously in Canada.

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Library of Congress Cataloging-in-Publication Data

Names: Araneo, Rodolfo, author. | Mitolo, Massimo A. G., author. | JohnWiley & Sons, publisher.Title: Electrical safety engineering of renewable energy systems / RodolfoAraneo, Massimo Mitolo.Description: Hoboken : John Wiley & Sons, 2022. | Includes bibliographicalreferences and index.Identifiers: LCCN 2021025391 (print) | LCCN 2021025392 (ebook) | ISBN9781119624981 (hardback) | ISBN 9781119624998 (pdf) | ISBN 9781119625018 (epub)| ISBN 9781119625056 (ebook)Subjects: LCSH: Electric apparatus and appliances--Safety measures. |Renewable energy sources--Safety measures.Classification: LCC TK152 .A73 2022 (print) | LCC TK152 (ebook) |DDC 621.3028/9--dc23LC record available at https://lccn.loc.gov/2021025391LC ebook record available at https://lccn.loc.gov/2021025392

Cover image: © oxygen/Getty

Cover design by Wiley

Set in 9.5/12.5pt STIXTwoText by Integra Software Services, Pondicherry, India.

Contents

Cover

Title page

Copyright

Preface

Acknowledgments

1 Fundamental Concepts of Electrical Safety Engineering

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

1.10 Identification of Extraneous-Conductive-Parts

1.11 Measuring Touch Voltages

2 Safety-by-Design Approach in AC/DC Systems

2.1 Introduction

2.2 Class I PV Equipment

2.3 Class II PV Equipment

2.4 Ground Faults and Ground Fault Protection

2.5 Functionally Grounded PV Systems

2.6 Non-Ground-Referenced PV Systems

2.7 Ground-Referenced PV Systems

2.8 Fire Hazard in Ground-Referenced PV Systems

2.9 Faults at Loads Downstream the PV Inverter in Ground-Referenced
PV Systems

2.10 Non-Electrically Separated PV System

2.11 PV Systems Wiring Methods and Safety

2.12 d.c. Currents and Safety

2.13 Electrical Safety of PV Systems

2.14 Rapid-Shutdown of PV Arrays on Buildings

2.15 Hazard and Risk

3 Grounding and Bonding

3.1 Introduction

3.2 Basic Concepts of Grounding Systems: The Ground Rod

3.3 The Maxwell Method

3.4 Multiple Rods: Mutual Resistance

3.5 Ground Rings and Ground Grid

3.6 Complex Arrangements: Rings and Ground Grids Combined with Rods and Horizontal Electrodes

4 Lightning Protection Systems

4.1 Review of Natural Lightning Physics, Modeling and Protection

4.2 Lightning Protection of PV Systems

4.2.1 Ground-Mounted PV Systems

4.2.2 Rooftop Mounted PV Systems

4.2.3 Protection against Overvoltage

4.2.4 Surge Protective Devices (SPDs)

4.3 Lighting Protection of Wind Turbines

4.3.1 Lightning Protection System (LPS)

4.3.2 Step and Touch Voltages

4.3.3 Lightning Exposure Assessment

4.3.4 Assessment of the Average Annual Number of Dangerous Events N

L

Due to Flashes Directly to and near Service Cables

4.3.5 Lightning Protection Zones

4.4 High-Frequency Grounding Systems

4.4.1 Arrangement of Ground Electrodes

4.4.2 Effective Length of a Ground Electrode

4.4.3 Frequency-dependent Soil and Ionization

5 Renewable Energy System Protection and Coordination

5.1 Introduction

5.2 Power Collection Systems

5.3 Cable Connections

5.4 Offshore Wind Farm

5.5 Distributed Energy Resources: Battery Energy Storage Systems and Electric Vehicles

6 Soil Resistivity Measurements and Ground Resistance

6.1 Soil Resistivity Measurements

6.2 Wenner Method

6.3 Schlumberger Method

6.4 Multi-layer Soils

6.4.1 Ground Grid in Multi-layer Soil

6.4.2 Ground Rod in Multi-layer Soil

6.5 Fall-of-Potential Method for Ground Resistance Measurement

6.6 Slope Method for Grounding Resistance Measurement

6.7 Star-delta Method for Grounding Resistance Measurement

6.8 Four Potential Method for Grounding Resistance Measurement

6.9 Potentiometer Method for Grounding Resistance Measurement

Appendix 1: Performance of Grounding Systems in Transient Conditions

1 Grounding System Analysis

2 Mathematical Model

3 Computation of Impedances

4 Green’s Function

4.1 Static Formulation

4.1.1 One-Layer Ground

4.1.2 Two-Layer Ground

4.2 Dynamic Formulation

4.2.1 Equivalent Transmission Line Approach

5 Numerical Integration Aspects

5.1 Singular Term

5.2 Sommerfeld Integrals

Appendix 2: Cable Failures in Renewable Energy Systems

1 Cable Failures in Renewable Energy Systems: Introduction

2 Possible Solutions

2.1 Optimal Solutions

2.2 Termite Attacks Prevention

3 Non-destructive Methods for Cable Testing and Fault-locating

3.1 Insulation Resistance (IR) Test

3.1.1 IR Measurement of the Cable Insulation (XLPE)

3.1.2 IR Measurement of the Polyethylene (PE) Cable Jacket

3.2 High-Potential Test

3.3 LCR Test

3.3.1 Insulation Resistance (IR)

3.3.2 Dielectric Absorption Ratio (DAR)

3.3.3 Polarization Index (PI)

3.3.4 Quality Factor (Q)

3.3.5 Dissipation Factor (DF)

3.3.6 Time Domain Reflectometry (TDR) Test

3.3.7 Arc Reflection (ARC) Test

3.3.8 Bridge Methods

3.4 Cable Fault Analysis

3.4.1 Prelocation

3.4.2 Pinpointing

4 Sheath and Jacket Repairs

5 Termite Baiting Stations and Monitoring

6 Termite-proof Cables

Index

End User License Agreement

List of Illustrations

Chapter 1

Figure 1.1 Electric conduction of the heart.

Figure 1.2 A normal electrocardiogram (EKG).

Figure 1.3 Impedances of the human body.

Figure 1.4 Current response of human body to d.c. voltage.

Figure 1.5 Internal partial impedances of the human body (no skin contribution).

Figure 1.6 Body impedances at 1250 V for a path hand-to-hand vs. the area of contact.

Figure 1.7 Temperature–Time Relationship for burns.

Figure 1.8 Hemispherical ground-electrode.

Figure 1.9 Hyperbolic distribution of the ground-potential....

Figure 1.10 Electrode ground-resistance as an equivalent one-port...

Figure 1.11 Ground-electrodes in parallel...

Figure 1.12 Hemispherical electrodes connected in series.

Figure 1.13 Equivalent circuit for the computation of body currents due to a touch voltage.

Figure 1.14 Person standing in a region at zero...

Figure 1.15 Distribution of the ground-potential with a person standing...

Figure 1.16 Distribution of the ground-potential with person standing in a...

Figure 1.17 Equivalent circuit for the computation of body currents in the...

Figure 1.18 Touch voltage measurement with the current...

Chapter 2

Figure 2.1 Single-phase inverter.

Figure 2.2 (a) Metal frames and mounting racks of PV arrays and...

Figure 2.3 Sun-tracking PV arrays.

Figure 2.4 Mounting racks are equipotential to metal frames of...

Figure 2.5 Protective devices in combiner box.

Figure 2.6 Functionally grounded PV system.

Figure 2.7 Functionally grounded system with faulty positive conductor.

Figure 2.8 Functionally grounded system with faulty functionally grounded conductor.

Figure 2.9 Non-ground-referenced PV system.

Figure 2.10 Second Fault in non-ground-referenced PV systems.

Figure 2.11 Ground Fault in PV systems.

Figure 2.12 Ground Fault Detection Interruption in TN PV systems.

Figure 2.13 Defect in the insulation of the grounded conductor.

Figure 2.14 GFDI installed in combiner box.

Figure 2.15 Faults downstream the PV inverter in ground-referenced PV systems.

Figure 2.16 Faults within the inverter.

Figure 2.17 Fault occurring at load between inverter and point of common coupling.

Figure 2.18 Non- electrically-separated PV system.

Figure 2.19 Transformerless PV inverter and ground fault on the a.c. side.

Figure 2.20 Transformerless PV inverter and ground fault on the d.c. side.

Figure 2.21 Conventional time/current curves describing the effects of d.c. currents.

Figure 2.22 Comparison between a.c. and d.c. fibrillation curves.

Figure 2.23 Comparison between a.c. and d.c. maximum permissible touch voltages.

Figure 2.24 Putting in safety PV generators.

Figure 2.25 Array boundary and d.c. voltage requirements.

Figure 2.26 Iso-risk curves.

Chapter 3

Figure 3.1 Schematics of the grounding system of a PV installation.

Figure 3.2 (a) Copper rod manufactured in solid steel and electrolytically copper-plated,...

Figure 3.3 Potential distribution of a rod...

Figure 3.4 (a) galvanized steel driven-pile connected to the earth system;...

Figure 3.5 General representation of a discretized electrode structure (a)...

Figure 3.6 Current density distribution over a rod....

Figure 3.7 Earth resistance of a ground rod....

Figure 3.8 Earth resistance of a ground rod...

Figure 3.9 Soil ground potential distribution....

Figure 3.10 Two dimensional map of the potential V and the current...

Figure 3.11 Comparison between numerical and analytical...

Figure 3.12 Ground resistance of different grounding systems...

Figure 3.13 Graphs of the ground resistance of a system composed...

Figure 3.14 Typical grounding systems of megawatt-sized PV...

Figure 3.15 Ground systems of megawatt-sized PV central inverter substations:...

Figure 3.16 Ground-grid of a wind farm substation...

Figure 3.17 Construction details of a grounding system of a wind farm substation.

Figure 3.18 Surface ground potential...

Figure 3.19 Definitions of fundamental voltages.

Figure 3.20 Sketch of the earthing-systems for circular wind tower foundation slab.

Figure 3.21 Grounding system for a square foundation (a) with additional rods (b)...

Figure 3.22 Views of the construction of a wind tower.

Figure 3.23 General view of an onshore wind farm site.

Figure 3.24 Ground resistance of a rectangular ring of shorter side a,...

Figure 3.25 Ground resistance (a), prospective touch voltage...

Figure 3.26 Ground resistance of a rectangular ring of shorter side a,...

Figure 3.27 Prospective touch....

Chapter 4

Figure 4.1 Types of lightning flashes comprising (a) cloud-to-ground,...

Figure 4.2 Evolution of cloud-to-ground lightning with schematic...

Figure 4.3 Types of lightning flashes.112

Figure 4.4 Current of a multiple stroke negative downward lightning....

Figure 4.5 Short return-stroke current waveform.

Figure 4.6 Current (a) and voltage (b) waveforms.

Figure 4.7 Rolling sphere method (a) and protective angle method (a-b).

Figure 4.8 Main coupling mechanisms: galvanic, inductive and capacitive.

Figure 4.9 Main sources of damages.

Figure 4.10 Risk components for ground-mounted PV generators.

Figure 4.11 Isolated and non-isolated LPS.

Figure 4.12 Risk components for rooftop-mounted PV generators.

Figure 4.13 Minimum induction loop area.

Figure 4.14 SPD in combiner boxes.

Figure 4.15 SPD in a central inverter station.

Figure 4.16 Three-blade, horizontal axis wind turbine.

Figure 4.17 Pictures taken during the construction of a wind tower.

Figure 4.18 Lightning protection system over the nacelle.

Figure 4.19 LPS of a WT: (a) Lightning path from the blade to the nacelle...

Figure 4.20 Equivalent circuit in the case of contact with the down conductor...

Figure 4.21 Equivalent collection area of WT.

Figure 4.22 Rolling sphere method and Lightning Protection Zones.151

Figure 4.23 Equivalent circuit of a horizontal ground electrode.152

Figure 4.24 Transient potential rise at the top of a vertical rod under a...

Figure 4.25 Frequency behavior of the normalized harmonic impedance...

Figure 4.26 Grounding impedance as a function of time.

Figure 4.27 Ground-termination system of a WT.

Chapter 5

Figure 5.1 Typical MV central collection point.

Figure 5.2 Examples of RMU in a wind farm (a) and RMU and CCP in a PV plant (b).

Figure 5.3 Radial collection configuration.

Figure 5.4 Single-sided ring collection configuration.

Figure 5.5 Double-sided ring collection configuration.

Figure 5.6 Multi ring collection configuration.

Figure 5.7 Star collection configuration.

Figure 5.8 RMU (a) and CCP (b) switchgear with trapped-key interlocks.

Figure 5.9 Examples of regular PV cluster (a) and irregular wind farm cluster (b).

Figure 5.10 Examples of connection with directly buried cables.

Figure 5.11 Connection infrastructure of a wind farm: MV connection to the HV/MV...

Figure 5.12 Access tracks used for the construction of a wind farm.

Figure 5.13 Cable tray with brackets secured to an existing bridge.

Figure 5.14 Twisted three-core cable, or triplex.

Figure 5.15 General layouts for offshore wind farms: (a)...

Figure 5.16 Configurations for the d.c. grid of an offshore...

Figure 5.17 Charging modes.

Figure 5.18 Plugs: (a) Type 01, (b) Type 2, (c) Type CCS-1, (d) Type CCS-2, (e) CHAdeMO.

Figure 5.19 Coordinated LPS and SPD system for EV charging stations.

Chapter 6

Figure 6.1 Wenner electrode arrangement. A and B denote the current electrodes,....

Figure 6.2 IRIS Syscal Pro equipment. .

Figure 6.3 Establishment of a 2D electrical resistivity pseudo-section with the Wenner method.

Figure 6.4 CVES data obtained through commercial software Surfer (a) and RES2DINV (b) .

Figure 6.5 Point electrode source and its infinite images in a two-layered soil model....

Figure 6.6 Resistivity measured at a utility-scale PV system in Abruzzo region (Italy).

Figure 6.7 Establishment of a 2D electrical resistivity pseudo-section with...

Figure 6.8 Ground resistance and mesh voltage of a groundi grid with four meshes...

Figure 6.9 Ground rod intwo-layer soil....

Figure 6.10 Fall-of-potential method....

Figure 6.11 Ground resistance measurements of utility-scale PV plants.

Figure 6.12 Overlapping and non-overlapping shells of grounding resistance....

Figure 6.13 Star-delta configuration....

Figure 6.14 Measuring RG with the potentiometer method.

Appendix 1

Figure 1 Typical grounding system arrangement:...

Figure 2 Section of the discretized model:...

Figure 3 Stratified ground...

Appendix 2

Figure 1 MV cable damaged by termites.

Figure 2 Circuit diagram for Murray bridge method.

Figure 3 Connection of three-point voltage drop measurement for dc systems.

Figure 4 Voltage-drop method connection diagram for jacket fault locating.

Figure 5 Nylon Cable.

Figure 6 Anti-termite resistant cable equipped with aluminum screen.

List of Tables

Chapter 1

Table 1.1 Heart-current factor

F

for different current paths

Table 1.2 Body impedances and resistances for a current path hand-to-hand

Table 1.3 Electrical conductivity σ of biological tissues

Table 1.4 Standard contact durations

Table 1.8 Temperature limits in normal service for accessible parts of equipment

Chapter 2

Table 2.1 Maximum disconnection times.

Table 2.2 Residual or ground current thresholds and response time.

Table 2.3 Rated current of overcurrent protection in the...

Table 2.4 Description of the time/current zones for d.c. currents.

Chapter 3

Table 3.1 Formulae for the ground resistance of basic horizontal ground electrodes.

Chapter 4

Table 4.1 Main lightning stroke parameters for different IEC protection levels.

Table 4.2 Sources of damage.

Table 4.3 Types of damage.

Table 4.4 Types of loss.

Table 4.5 Risk components.

Table 4.6 Location factor...

Table 4.7 Environmental factor...

Chapter 6

Table 6.1 Typical soil resistivity of various types of soil.

Table 6.2 Some of the most common used electrode configurations...

Guide

Cover

Title page

Copyright

Table of Contents

Preface

Acknowledgments

Begin Reading

Appendix 1: Performance of Grounding Systems in Transient Conditions

Appendix 2: Cable Failures in Renewable Energy Systems

Index

End User License Agreement

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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 AraneoRoma, Italy, March 28, 2021

Prof. Massimo MitoloIrvine, California, March 28, 2021