Energy efficient electrical systems for buildings

513 Pages·2017·25.585 MB·English

by  Moncef Krarti

Energy-Efficient Electrical
Systems for Buildings
MECHANICAL AND AEROSPACE ENGINEERING
Frank Kreith
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Moncef Krarti

Energy-Efficient Electrical
Systems for Buildings
Moncef Krarti
CRC Press
Taylor & Francis Group
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Boca Raton, FL 33487-2742
© 2017 by Taylor & Francis Group, LLC
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Library of Congress Cataloging-in-Publication Data
Names: Krarti, Moncef, author.
Title: Energy-efficient electrical systems for buildings/Dr. Moncef Krarti.
Description: Boca Raton: Taylor & Francis, a CRC title, part of the Taylor & Francis
imprint, a member of the Taylor & Francis Group, the academic division of T&F Informa,
plc, [2017]
Identifiers: LCCN 2016039246| ISBN 9781482258332 (acid-free paper) | ISBN 9781315372297
(ebook)
Subjects: LCSH: Buildings--Electric equipment. | Buildings--Power supply. |
Electric apparatus and appliances--Energy consumption.
Classification: LCC TK4001 K73 2017 | DDC 621.319/24--dc23
LC record available at https://lccn.loc.gov/2016039246
Visit the Taylor & Francis Web site at
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Contents
Preface .............................................................................................................................................xv
Author ..........................................................................................................................................xvii
1. Introduction .............................................................................................................................1
1.1 Introduction ...................................................................................................................1
1.2 Overview of Building Electrical Distribution Systems ............................................2
1.2.1 Residential Buildings.......................................................................................2
1.2.1.1 Commercial Buildings .....................................................................3
1.2.2 Distribution Voltages .......................................................................................3
1.3 General Design Approach ............................................................................................6
1.3.1 Design Objectives .............................................................................................6
1.3.1.1 Safety ..................................................................................................6
1.3.1.2 Flexibility ...........................................................................................7
1.3.1.3 Accessibility ......................................................................................7
1.3.1.4 Reliability ...........................................................................................8
1.3.1.5 Energy Efficiency ..............................................................................8
1.3.2 Design Team .....................................................................................................9
1.3.3 General Design Procedure ............................................................................10
1.4 Summary ......................................................................................................................17
2. Overview of Electrical Circuits ..........................................................................................19
2.1 Introduction .................................................................................................................19
2.2 Review of DC and AC Circuits .................................................................................20
2.2.1 Direct Current .................................................................................................20
2.2.1.1 Ohm’s Law ......................................................................................23
2.2.1.2 Kirchhoff’s Laws ............................................................................24
2.2.2 Alternating Current .......................................................................................28
2.2.2.1 Instantaneous Voltage and Current .............................................29
2.2.2.2 Impedance of AC Systems ............................................................30
2.2.2.3 Power Triangle and Power Factor ................................................32
2.2.3 Advantages of AC Systems ..........................................................................35
2.3 Multiphase AC Systems .............................................................................................36
2.3.1 Two-Phase AC Systems .................................................................................36
2.3.2 Three-Phase AC Systems ..............................................................................38
2.3.2.1 Wye Systems ...................................................................................39
2.3.2.2 Delta Systems ..................................................................................41
2.3.2.3 Power in Three-Phase Systems .....................................................42
vii
viii Contents
2.4 Power Factor Correction ............................................................................................45
2.5 Summary ......................................................................................................................46
Problems ..................................................................................................................................47
3. Electrical Transformers ........................................................................................................51
3.1 Introduction .................................................................................................................51
3.2 Fundamentals of Transformers .................................................................................51
3.3 Types of Transformers ................................................................................................56
3.3.1 Power Transformers ......................................................................................56
3.3.2 Instrument Transformers ..............................................................................56
3.3.3 Autotransformers ...........................................................................................58
3.4 Transformer Connections ...........................................................................................60
3.5 Testing Methods for Transformers ............................................................................62
3.5.1 Transformer Efficiency ..................................................................................62
3.5.1.1 Transformer Regulation .................................................................64
3.5.1.2 Transformer Percent Impedance ..................................................65
3.6 Design Specifications for Transformers ...................................................................66
3.7 Summary ......................................................................................................................67
Problems ..................................................................................................................................67
4. Electrical Motors ...................................................................................................................69
4.1 Introduction .................................................................................................................69
4.2 Operation of Three-Phase Motors ............................................................................70
4.2.1 Rotating Magnetic Field ................................................................................70
4.2.2 Torque–Speed Relationship ..........................................................................77
4.2.3 Current–Speed Relationship ........................................................................79
4.3 Operation of One-Phase Motors ...............................................................................80
4.4 Performance Characteristics of Motors ....................................................................83
4.4.1 Energy Efficiency of Motors .........................................................................83
4.4.2 Power Factor for Motors ...............................................................................88
4.4.3 Effect of Voltage Variation ............................................................................89
4.4.4 Specifications of Motors ................................................................................91
4.5 Motor Energy Efficiency Improvements ..................................................................92
4.5.1 Adjustable Speed Drives (ASDs) .................................................................92
4.5.1.1 Energy-Efficient Motors ................................................................95
4.6 Summary ......................................................................................................................98
Problems ..................................................................................................................................98
5. Protection Systems ..............................................................................................................101
5.1 Introduction ...............................................................................................................101
5.2 Impact of Electricity on Humans ............................................................................104
5.2.1 Background ...................................................................................................104
5.2.2 Paths of Electrical Shock .............................................................................106
5.2.3 Blast Safe Distances .....................................................................................107
5.3 Basic Operation of Protection Devices ...................................................................108
5.4 Types of Protection Devices .....................................................................................110
5.4.1 Fuses ..............................................................................................................111
5.4.2 Circuit Breakers ............................................................................................117
Contents ix
5.5 Grounding and Bonding ..........................................................................................124
5.5.1 Definitions .....................................................................................................124
5.5.2 General Requirements for Grounding and Bonding ..............................125
5.5.2.1 Grounded Systems .......................................................................125
5.5.2.2 System Grounding Connections ................................................126
5.5.2.3 Basic Grounding Guidelines .......................................................127
5.5.3 Basic Analysis of Grounding ......................................................................127
5.5.4 Selection of Service Grounding Conductors ............................................131
5.5.5 Selection of Equipment Grounding ...........................................................133
5.5.6 Estimation of Potential Damages ..............................................................134
5.5.7 Ground-Fault Current Interrupters ...........................................................137
5.6 Summary ....................................................................................................................138
Problems ................................................................................................................................139
6. Branch Circuits and Feeders .............................................................................................141
6.1 Introduction ...............................................................................................................141
6.2 Size and Rating of Conductors ................................................................................143
6.3 Design of Conductors ...............................................................................................149
6.3.1 Continuous Current Rating ........................................................................149
6.3.2 Short-Circuit Current Rating ......................................................................151
6.3.3 Maximum Allowable Voltage Drop ..........................................................154
6.3.4 Design Approach for Conductors..............................................................158
6.4 Selection of Conduits ................................................................................................161
6.5 Branch Circuits and Feeders for Nonmotor Loads ..............................................166
6.5.1 Design of Branch Circuits ...........................................................................166
6.5.2 Design of Feeders .........................................................................................168
6.6 Branch Circuits and Feeders for Motors ................................................................169
6.6.1 Motor Branch Circuits .................................................................................170
6.6.2 Feeder for Several Motors ...........................................................................177
6.7 Summary ....................................................................................................................178
Problems ................................................................................................................................178
7. Electrical Systems for Dwellings .....................................................................................183
7.1 Introduction ...............................................................................................................183
7.2 General Design Approach ........................................................................................183
7.3 Main Service Entrance Design ................................................................................186
7.3.1 Standard Method for Sizing Service Entrance .........................................186
7.3.1.1 Estimation of the Demand Load for the Phases (A, B,
and, if Needed, C) ........................................................................187
7.3.1.2 Estimation of the Demand Load for the Neutral (N) ..............188
7.3.2 Optional Method for Sizing Service Entrance .........................................193
7.3.3 Sizing Service Entrance ...............................................................................195
7.4 Branch Circuits for Residential Buildings .............................................................198
7.4.1 General Guidelines for Receptacles ..........................................................198
7.4.2 General Guidelines for Lighting Outlets ..................................................201
7.4.3 General Sizing Procedure for Branch Circuits .........................................201
7.5 General Design Procedure .......................................................................................202
7.6 Electrical Systems for Apartment Buildings .........................................................207