Three-phase electrical power PDF
Preview Three-phase electrical power
Engineering – Electrical FF ll ee cc kk ee nn ss tt ee ii nn T h r e e - P h a s e Three-Phase Electrical Power addresses all aspects of three-phase power circuits. The book treats the transmission of electrical power from the common sources where it is generated to locations where it is E l e c t r i c a l consumed. At typical facilities where electrical power is used, the T book covers the important topics of grounding, currents, power, h demand, metering, circuit protection, motors, motor protection, r power factor correction, tariffs, electrical drawings, and relays. e Included in the text are the necessary methods of computing e currents and power in all possible types of circuit applications as P o w e r - those that are balanced, unbalanced, leading, lagging, three-wire, P and four-wire. h Focusing on electrical gear, programs, and issues related to a the generation and use of three-phase electrical power, this contem- s porary educational guide: e • Uses simple, straightforward language to explain key E concepts and their underlying theory l e • Introduces numerous examples, illustrations, and photographs to aid in comprehension c • Employs phasor concepts throughout the text to aid t r in the analysis of three-phase circuits • Encourages applied learning by supplying practical i c problems at the end of each chapter a • Provides extensive references and a glossary of symbols, acronyms, and equations l P Three-Phase Electrical Power delivers a much-needed mod- ern-day treatment of three-phase electrical power for electrical o engineering students and practitioners alike. w e r K26554 ISBN: 978-1-4987-3777-7 Joseph E. Fleckenstein 90000 9 781498 737777 Three-Phase Electrical Power Three-Phase Electrical Power Joseph E. Fleckenstein Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Group, an informa business CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2016 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Version Date: 20150626 International Standard Book Number-13: 978-1-4987-3778-4 (eBook - PDF) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. 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CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com Contents Preface ...................................................................................................................xiii Author ...................................................................................................................xix 1. Alternating Current .......................................................................................1 1.1 Single-Phase Alternating Current ......................................................2 1.1.1 Instantaneous Voltage and Instantaneous Current ............2 1.1.2 RMS Voltage and RMS Current .............................................5 1.1.3 Single-Phase Circuits ...............................................................7 1.1.3.1 Resistive Loads .........................................................7 1.1.3.2 Leading and Lagging Power Factor .......................9 1.1.4 Phasor Diagrams of Single-Phase Circuits ........................11 1.1.5 Parallel Single-Phase Loads .................................................14 1.1.6 Polar Notation ........................................................................17 1.2 Three-Phase Alternating Current: Basic Concepts ........................18 1.2.1 Three-Phase Alternating Current Source ...........................18 1.2.2 Delta and Wye Circuits Defined ..........................................19 1.2.3 Common Service Voltages ....................................................20 1.2.3.1 240/120 VAC Three-Phase Four-Wire Delta .......20 1.2.3.2 480 VAC Three-Phase Two-Wire Delta or Three-Phase Three-Wire Delta .............................21 1.2.3.3 208/120 VAC Wye (Three-Phase Four-Wire) ......22 1.2.3.4 480 VAC Wye (Three-Phase Four-Wire) ..............23 1.2.3.5 480 VAC Wye (Three-Phase Three-Wire) ............24 1.2.4 Phases and Lines ....................................................................24 1.2.5 Balanced and Unbalanced Three-Phase Circuits ..............25 1.2.6 Lead, Lag, and Power Factor in a Balanced Three-Phase Circuit ...............................................................25 1.2.7 Phasor Diagrams of Three-Phase Circuits .........................27 1.2.8 Advantage of Three-Phase Electricity over Single-Phase Electricity .........................................................30 1.3 ac Impedance and Admittance .........................................................33 1.3.1 Impedance ...............................................................................33 1.3.2 Admittance .............................................................................49 Problems ..........................................................................................................53 v vi Contents 2. Generation, Transmission, and Distribution ..........................................57 2.1 Generation ............................................................................................57 2.1.1 Fossil-Fired Steam Power Plants ..........................................58 2.1.2 Biofuel-Fired Steam Power Plant .........................................61 2.1.3 Nuclear Power Plant ..............................................................61 2.1.4 Gas Turbine Generators ........................................................61 2.1.5 Wind Turbines ........................................................................62 2.1.6 Solar .........................................................................................62 2.1.7 Hydro .......................................................................................63 2.1.8 Geothermal .............................................................................63 2.2 Transmission ........................................................................................63 2.3 Distribution ..........................................................................................65 2.4 Electrical Gear .....................................................................................66 2.4.1 Generators ...............................................................................66 2.4.2 Transformers ...........................................................................72 2.4.2.1 Power Transformers ...............................................73 2.4.2.2 Instrument Transformers ......................................79 2.5 Per Unit Calculations ..........................................................................81 2.5.1 Systems with Transformers ..................................................88 2.6 Cybersecurity ......................................................................................90 Problems ..........................................................................................................92 3. Grounding ......................................................................................................95 3.1 Definitions ............................................................................................95 3.1.1 Ground ....................................................................................96 3.1.2 Equipment Grounding Conductor ......................................96 3.1.3 Neutral Conductor .................................................................96 3.1.4 Bonding ...................................................................................96 3.1.5 Ground Loops ........................................................................97 3.2 Reasons for Grounding ......................................................................97 3.2.1 Non-Current-Carrying Ground ...........................................99 3.2.2 Current-Carrying Ground ....................................................99 3.2.3 Lightning Grounds ................................................................99 3.2.4 Grounding of LV, MV, and HV Cable Screens .................100 3.3 Single-Phase Grounding ..................................................................101 3.4 Three-Phase Grounding...................................................................103 3.4.1 Utility Three-Phase Grounding Practices ........................103 3.4.2 User Three-Phase Grounding Practices ...........................103 3.4.3 Grounding Resistors ............................................................104 3.4.3.1 Low-Resistance NGR ...........................................105 3.4.3.2 High-Resistance NGR ..........................................106 3.4.4 Ground Fault Detector ........................................................106 3.4.5 Neutral Grounding Reactor................................................107 Problems ........................................................................................................108 Contents vii 4. Calculating Currents in Three-Phase Circuits .....................................109 4.1 Calculating Currents in Balanced Three-Phase Circuits ............109 4.1.1 Calculating Currents in a Balanced Three-Phase Delta Circuit: General ..........................................................109 4.1.1.1 Resistive Loads .....................................................110 4.1.1.2 Capacitive Loads ..................................................115 4.1.1.3 Inductive Loads ....................................................116 4.1.1.4 Two or More Loads ..............................................119 4.1.2 Calculating Currents in a Balanced Three-Phase Wye Circuit: General ...........................................................127 4.1.2.1 Resistive Loads .....................................................128 4.1.2.2 Capacitive Loads ..................................................130 4.1.2.3 Inductive Loads ....................................................130 4.1.2.4 Two or More Loads ..............................................130 4.2 Calculating Currents in Unbalanced Three-Phase Circuits: General ................................................................................130 4.2.1 Unbalanced Three-Phase Delta Circuits ..........................131 4.2.1.1 Unbalanced Three-Phase Delta Circuits with Resistive, Inductive, or Capacitive Loads ............131 4.2.1.2 Unbalanced Three-Phase Delta Circuit with Only Resistive Loads ...........................................142 4.2.2 Unbalanced Three-Phase Wye Circuit ..............................145 4.3 Combined Balanced or Unbalanced Three-Phase Circuits ........147 Problems ........................................................................................................158 5. Calculating Three-Phase Power ..............................................................161 5.1 Units ....................................................................................................161 5.2 Calculating Power of a Single-Phase Circuit ................................162 5.3 Calculating Power in Balanced Three-Phase Circuits .................166 5.3.1 Calculating Power in Balanced Three-Phase Wye Circuits .........................................................................169 5.3.1.1 Calculating Power in Balanced Three-Phase Wye Circuits: Resistive Loads ............................170 5.3.1.2 Calculating Power in Balanced Three-Phase Wye Circuits: Inductive or Capacitive Loads ...172 5.3.2 Calculating Power in Balanced Delta Three-Phase Circuits ..................................................................................172 5.3.2.1 Calculating Power in Balanced Three-Phase Delta Circuits: Resistive Loads ...........................173 5.3.2.2 Calculating Power in Balanced Three-Phase Delta Circuits: Inductive or Capacitive .............174 5.4 Calculating Power in Unbalanced Three-Phase Circuits ............174 5.4.1 Calculating Power in Unbalanced Three-Phase Wye Circuits .........................................................................174 viii Contents 5.4.1.1 Calculating Power in Unbalanced Three-Phase Wye Circuits: Resistive Loads .....175 5.4.1.2 Calculating Power in Unbalanced Three-Phase Wye Circuits: Inductive or Capacitive Loads ..............................................178 5.4.2 Calculating Power in Unbalanced Three-Phase Delta Circuits ........................................................................180 5.4.2.1 Calculating Power in Unbalanced Three-Phase Delta Circuits: Resistive Loads ....181 5.4.2.2 Calculating Power in Unbalanced Three-Phase Delta Circuits: Inductive or Capacitive .........................................................182 5.5 Calculating Power in a Three-Phase Circuit with Mixed Wye and Delta Loads ........................................................................188 5.5.1 Using Phase Parameters .....................................................188 5.5.2 Using Line Parameters ........................................................189 5.6 Nonlinear Electrical Circuits ...........................................................189 5.6.1 Linear Circuits and Power Factor ......................................191 5.6.2 Root Mean Square ................................................................193 5.6.3 Nonlinear Circuits and Power Factor ...............................194 5.7 Conclusion ..........................................................................................196 Problems ........................................................................................................197 6. Demand and Demand Response .............................................................201 6.1 Demand Defined ...............................................................................201 6.1.1 Why Demand? ......................................................................202 6.1.2 Decreasing Demand ............................................................202 6.2 Demand Response ............................................................................203 6.2.1 Definitions.............................................................................203 6.2.2 Implementation Examples of Demand Response ...........205 6.2.2.1 NYISO (New York–Based Utility) ......................205 6.2.2.2 TXU Energy (Texas-Based Utility) .....................206 6.2.2.3 EnerNOC (Boston-Based Utility) .......................206 6.3 Smart Grid ..........................................................................................207 6.3.1 Definition ..............................................................................207 6.3.2 Implementation Examples of Smart Grid .........................207 6.3.2.1 Florida Power and Light ......................................208 Problems ........................................................................................................208 7. Instruments and Meters ............................................................................209 7.1 Power Measurements .......................................................................209 7.1.1 Single-Phase Power Measurements ..................................210 7.1.2 Three-Phase Power Measurements ...................................211 Contents ix 7.2 Measuring Power in Three-Phase, Three-Wire Circuits .............212 7.2.1 Using One Single-Phase Wattmeter to Measure Power in a Three-Phase, Three-Wire Circuit ...................213 7.2.2 Using Two Single-Phase Wattmeters to Measure Power in a Three-Phase, Three-Wire Circuit ...................214 7.2.3 Using Three Single-Phase Wattmeters to Measure Power in a Three-Phase, Three-Wire Circuit ...................216 7.2.4 Using a Three-Phase Wattmeter to Measure Power in a Three-Wire, Three-Phase Circuit ...............................219 7.3 Measuring Power in a Three-Phase, Four-Wire Circuit ..............220 7.3.1 Using One Single-Phase Wattmeter to Measure Power in a Three-Phase, Four-Wire Circuit .....................220 7.3.2 Using Three Single-Phase Wattmeters to Measure Power in a Three-Phase, Four-Wire Circuit .....................220 7.3.3 Using a Three-Phase Wattmeter to Measure Power in a Three-Phase, Four-Wire Circuit .................................220 7.4 Power Analyzers and Power Quality Meters ................................222 7.5 Watt-Hour Meters .............................................................................222 7.6 Demand Meters .................................................................................224 7.7 Smart Meters ......................................................................................226 7.7.1 Definitions.............................................................................226 7.7.2 Operation ..............................................................................227 7.7.3 Implementation Examples ..................................................228 7.7.3.1 Ontario Power Authority, Canada .....................229 7.7.3.2 State of Pennsylvania ...........................................229 7.8 Submeters ...........................................................................................229 7.9 Phase Sequence Meters ....................................................................230 7.10 Earth Resistance ................................................................................231 7.11 Megohmmeter ...................................................................................232 7.12 High-Potential Tester ........................................................................233 7.13 Multimeters ........................................................................................234 Problems ........................................................................................................235 8. Circuit Protection .......................................................................................237 8.1 General Requirements ......................................................................237 8.2 Ungrounded Systems .......................................................................240 8.3 Overcurrent ........................................................................................240 8.4 Faults ...................................................................................................241 8.5 Circuit Breakers .................................................................................243 8.5.1 Molded Case Circuit Breakers ...........................................243 8.5.1.1 Thermal-Magnetic Circuit Breakers ..................244 8.5.1.2 Magnetic-Only Circuit Breaker ..........................246 8.5.1.3 Electronic Circuit Breakers .................................246 8.5.1.4 Sizing MCCBs .......................................................248
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