Practical Grounding, Bonding, Shielding and Surge Protection

249 Pages·2004·12.651 MB·English

by  G Vijayaraghavan

Practical Grounding, Bonding, Shielding and Surge
Protection
ii Contents
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Contents iii
Practical Grounding, Bonding,
Shielding and Surge
Protection
G. Vijayaraghavan,
B.Eng (Hons) Consulting Engineer, Chennai, India
Mark Brown,
Pr.Eng, DipEE, B.Sc (Elec.Eng), Senior Staff Engineer,

IDC Technologies, Perth, Australia.
Malcolm Barnes,
CPEng, BSc (ElecEng), MSEE, Alliance Automation, Perth,
Western Australia
Series editor: Steve Mackay
AMSTERDAM (cid:127) BOSTON (cid:127) HEIDELBERG (cid:127) LONDON
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iv Contents
Newnes
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First published 2004

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British Library Cataloguing in Publication Data
Vijayaraghavan, G.
Practical grounding, bonding, shielding and surge
protection. – (Practical professional)
1. Electric apparatus and appliances – Protection 2. Electric currents – Grounding
I. Title
621. 3’17

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A catalogue record for this book is available from the Library of Congress

ISBN 0 7506 6399 5

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Contents v
Contents
Preface............................................................................................................................ix

1 Introduction and basics.........................................................................................1
1.1 Introduction...............................................................................................1
1.2 Basics of grounding..................................................................................2
1.3 Bonding....................................................................................................4
1.4 Lightning and its effect on electrical systems............................................4
1.5 Static charges and the need for bonding..................................................5
1.6 Ground electrodes and factors affecting their efficacy..............................6
1.7 Noise in signaling circuits and protective measures such as shielding.....8
1.8 Surge protection of electronic equipment .................................................9
1.9 UPS systems and their role in power quality improvement.....................10
1.10 Case studies...........................................................................................11
1.11 Importance of local codes.......................................................................11
1.12 Summary................................................................................................11

2 Grounding of power supply system neutral..........................................................13
2.1 Introduction.............................................................................................13
2.2 Ungrounded systems..............................................................................15
2.3 Solidly grounded systems.......................................................................16
2.4 Impedance grounding using neutral reactor ...........................................18
2.5 Resonant grounding using neutral reactor..............................................18
2.6 Impedance grounding through neutral resistance...................................19
2.7 Point of grounding..................................................................................20
2.8 Other challenges....................................................................................21
2.9 Summary................................................................................................23

3 Equipment grounding..........................................................................................24
3.1 Introduction.............................................................................................24
3.2 Shock hazard .........................................................................................24
3.3 Grounding of equipment.........................................................................27
3.4 Operation of protective devices..............................................................28
3.5 Thermal capability..................................................................................29
3.6 Touch Potential during ground faults......................................................30
3.7 Induced voltage problem........................................................................30
3.8 Mitigation by multiple ground connection................................................31
3.9 Mitigation by reduction of conductor spacing..........................................31
vi Contents
3.10 EMI suppression....................................................................................32
3.11 Metal enclosures for grounding conductors...........................................32
3.12 Grounding connections for surge protection equipment.........................34
3.13 Sensing of ground faults........................................................................34
3.14 Equipotential bonding............................................................................35
3.15 Summary...............................................................................................37
4 Lightning, its effect on buildings and electrical systems and protection
against lightning..................................................................................................38
4.1 Introduction............................................................................................38
4.2 Incidence of lightning.............................................................................41
4.3 Probability of lightning strike..................................................................45
4.4 Method of lightning protection................................................................47
4.5 Planning for lightning protection.............................................................50
4.6 Improvements to lightning protection.....................................................51
4.7 Factors governing decision whether or not to protect.............................52
4.8 Effect of lightning strike on electrical lines..............................................53
4.9 Summary...............................................................................................54
5 Static electricity and protection...........................................................................55
5.1 Introduction............................................................................................55
5.2 What is static electricity?........................................................................55
5.3 Generation of charge.............................................................................56
5.4 Some common examples of static buildup.............................................56
5.5 Energy of spark and its ignition capability..............................................57
5.6 Dangers of static electricity buildup........................................................58
5.7 Control of static electricity......................................................................58
5.8 Assessment of static risks and planning prevention...............................61
5.9 Summary...............................................................................................61
6 Ground electrode system....................................................................................62
6.1 Introduction............................................................................................62
6.2 Grounding electrodes.............................................................................62
6.3 Soil resistance .......................................................................................63
6.4 Measurement of soil resistivity...............................................................64
6.5 Resistance of a single rod electrode......................................................68
6.6 Current-carrying capacity of an electrode..............................................70
6.7 Use of multiple ground rods in parallel...................................................71
6.8 Measurement of ground resistance of an electrode...............................71
6.9 Concrete-encased electrodes................................................................73
6.10 Corrosion problems in electrical grounding systems..............................75
6.11 Maintenance of grounding system.........................................................76
6.12 Chemical electrodes..............................................................................76
6.13 Summary...............................................................................................78
7 Surge protection of electronic equipment............................................................79
7.1 Introduction............................................................................................79
7.2 What is a surge?....................................................................................79
Contents vii
7.3 Bonding of different ground systems as a means of surge proofing.......80
7.4 Surges and surge protection...................................................................82
7.5 Principle of surge protection...................................................................85
7.6 Surge protection of electronic equipment ...............................................86
7.7 Achieving graded surge protection.........................................................88
7.8 Positioning and selection of lightning/surge arrestor...............................89
7.9 A practical view of surge protection for sensitive equipment...................92
7.10 Summary..............................................................................................101
8 Electrical noise and mitigation...........................................................................102
8.1 Introduction...........................................................................................102
8.2 Definition of electrical noise and measures for noise reduction............102
8.3 How are sensitive circuits affected by noise?.......................................105
8.4 Frequency analysis of noise.................................................................106
8.5 Categories of noise...............................................................................109
8.6 Disturbances from other equipment in the same distribution system....110
8.7 Earth loop as a cause of noise.............................................................111
8.8 The ways in which noise can enter a signal cable and its control.........113
8.9 More about shielding ...........................................................................117
8.10 Shielded isolation transformer..............................................................121
8.11 Avoidance of earth loop........................................................................123
8.12 Use of insulated ground (IG) receptacle ..............................................125
8.13 Zero signal reference grid and signal transport ground plane...............126
8.14 Harmonics in electrical systems ..........................................................128
8.15 Summary..............................................................................................131
9 UPS systems and their grounding practices......................................................132
9.1 Introduction...........................................................................................132
9.2 Power quality issues.............................................................................132
9.3 Definitions of abnormal voltage conditions ...........................................134
9.4 Susceptibility and measures to handle voltage abnormalities...............137
9.5 Regulating transformer.........................................................................137
9.6 Standby sources...................................................................................138
9.7 Electromechanical UPS systems..........................................................142
9.8 Solid-state UPS systems......................................................................144
9.9 Multiple units for redundancy................................................................146
9.10 Considerations in selection of UPS systems for ADP facilities..............147
9.11 Grounding issues in static UPS configurations.....................................149
9.12 UPS configurations and recommended grounding practices................149
9.13 Summary..............................................................................................153
10 Case studies......................................................................................................154
10.1 Introduction...........................................................................................154
10.2 Case study 1........................................................................................154
10.3 Case study 2........................................................................................155
10.4 Case study 3........................................................................................158
viii Contents
10.5 Case study 4........................................................................................159
10.6 Case study 5........................................................................................160
10.7 Case study 6........................................................................................160
10.8 Case study 7........................................................................................162
10.9 Case study 8........................................................................................162
Appendix A: Grounding regulations from various national codes ................................165
Appendix B: IEE system classification based on grounding practices .........................182
Appendix C: IEEE exposure classifications .................................................................191
Appendix D: Glossary of terms related to grounding ...................................................193
Appendix E: Steps to ensure effective substation grounding .......................................201
Appendix F: Course exercises ....................................................................................207
Appendix G: Answer schemes ....................................................................................210
Appendix H: Group activities .......................................................................................221
Index.. .........................................................................................................................233
Preface

Few topics generate as much controversy and argument as that of grounding and the associated topics
of surge protection, shielding and lightning protection of electrical and electronic systems. Poor
grounding practice can be the cause of continual and intermittent difficult-to-diagnose problems in a
facility. This book looks at these issues from a fresh yet practical perspective and enables you to
reduce expensive downtime on your plant and equipment to a minimum by correct application of these
principles. This book is designed to demystify the subject of grounding and presents the subject in a
clear, straightforward manner. Installation, testing and inspection procedures for industrial and
commercial power systems will be examined in detail. Essentially the discussion in this book is broken
down into grounding, shielding and surge protection for both power and electronics systems.
Grounding and surge protection for Telecommunications and IT systems are examined in detail.
Finally, the impact of lightning is examined and simple techniques for minimizing its impact are
described. The terms grounding and earthing are understood to be interchangeable in this book but due
to the larger readership the term grounding has been the preferred usage. Our apologies to our
European readers for this unfortunate compromise.
Typical people who will find this book useful include:
• Instrumentation and Control Engineers
• Consulting Engineers
• Electrical Engineers
• Project Engineers
• Maintenance Engineers
• Electrical Contractors
• Safety Professionals
• Consulting Engineers
• Electricians
• Electrical Inspectors
• Power System Protection and Control Engineers
• Building Service Designers
• Data Systems Planners and Managers
• Electrical and Instrumentation Technicians.
We would hope that you will gain the following from this book:
• Knowledge of the various methods of grounding electrical systems
• Details of the applicable national Standards
• The purposes of grounding and bonding
• A list of the types of systems that cannot be grounded
• Details on how to correctly shield sensitive communications cables from noise and
interference
• Know-how on surge and transient protection