Acknowledgments ............................................... xxv
Shoaib A. Khan .............................................. xxvii
Chapter 1 Introduction ......................................... 1
Chapter 2 System Planning ...................................... 3
2.1 Introduction ............................................... 3
2.2 Basic Design Considerations ................................ 3
2.2.1 Safety of Life ...................................... 3
2.2.2 Reliability of Utility Power Supply ................. 4
2.2.3 Reliability of Plant Distribution System ............ 4
2.2.4 Simplicity of Operation and Maintenance ............. 5
2.2.5 Voltage Regulation and Flicker ...................... 5
2.2.6 Cost (Last Priority) ................................ 5
2.3 Plant Distribution Systems ................................. 5
2.3.1 An Overview ......................................... 5
2.3.2 Plant Main Substation ............................... 5
2.3.3 Primary Distribution System ......................... 6
2.3.4 Secondary Distribution System ....................... 7
2.3.5 In-Plant Generation ................................. 7
2.3.6 Emergency Power Supply .............................. 7
2.3.7 Power Supply for Monitoring and Control Systems ..... 8
2.3.8 DC Power Supply for Protection and Control .......... 9
2.4 Distribution Types ......................................... 9
2.4.1 Simple Radial ....................................... 9
2.4.2 Expanded Radial ..................................... 9
2.4.3 Primary Selective .................................. 10
2.4.4 Secondary Selective ................................ 10
2.4.5 Sparing Transformer ................................ 10
2.5 Plant Power Demand and Load Estimate ...................... 11
2.5.1 Estimate of Power Demand and Energy Cost ........... 11
2.5.2 Factors Used for Load Estimate and Power Demand .... 15
2.6 Voltage Considerations .................................... 15
2.6.1 Voltages Used in North America ..................... 15
2.6.2 Voltages Used in Europe ............................ 16
2.6.1 Voltage and Frequency Used in Other Countries ...... 16
2.6.4 Voltage Drop and Flicker ........................... 17
2.6.5 Voltage Sag and Threshold Voltage .................. 24
References ................................................ 25
Bibliography .............................................. 26
Chapter 3 Power System Studies ................................ 27
3.1 Introduction and Overview ................................. 27
3.2 Useful Formulae ........................................... 27
3.3 Load Flow ................................................. 28
3.3.1 Overview ........................................... 28
3.3.2 Load-Flow Runs ..................................... 29
3.4 Short Circuits ............................................ 29
3.4.1 Contribution from Different Sources ................ 29
3.4.2 Steps Required for a Short-Circuit Study ........... 31
3.4.3 Medium- and High-Voltage Circuit Breakers .......... 31
3.4.4 Interrupting Duty of Low-Voltage Circuit Breakers
(<1000 V) .......................................... 35
3.4.5 Interrupting Duty of Medium- and High-Voltage
Fuses [S5] ......................................... 36
3.4.6 For Time-Delayed Relaying Devices .................. 36
3.4.7 Rotating Machine Impedance Multipliers [S9] ........ 36
3.4.8 Short-Circuit Current Multiplying Factors for
Higher X/R Ratio ................................... 37
3.4.9 X/R Ratio of System Component ...................... 38
3.4.10 System and Equipment Data .......................... 39
3.4.11 Example: Short-Circuit Calculation for Equipment
Rating ............................................. 45
3.5 Protective Device Coordination ............................ 53
3.5.1 Introduction ....................................... 53
3.5.2 Data Required for a Study .......................... 54
3.5.3 Time Interval for Coordination of Overcurrent
Elements ........................................... 54
3.5.4 Computer Programs for Overcurrent Coordination ..... 55
3.6 Arc-Flash Hazard Calculations ............................. 55
3.6.1 Introduction ....................................... 55
3.6.2 Steps Required for the Analysis ..................... 57
3.7 Harmonic Analysis ......................................... 57
3.7.1 Introduction ....................................... 57
3.7.2 Methods and Techniques ............................. 57
3.7.3 Necessary Steps for the Study ...................... 58
3.8 Power System Stability .................................... 59
3.8.1 An Overview ........................................ 59
3.8.2 Transient Behavior of Synchronous Generators and
Motors ............................................. 59
3.8.3 Stability Study for an Ammonia Plant ............... 60
3.9 Other Common Studies and Calculations ..................... 62
3.9.1 Switching Transients ............................... 62
3.9.2 Cable Ampacity Calculations ........................ 63
3.9.3 DC Power Supply .................................... 63
3.9.4 Motor Starting ..................................... 63
3.9.5 Ground Grid ........................................ 64
References ................................................ 64
Bibliography .............................................. 64
Chapter 4 System Neutral Grounding ............................ 67
4.1 Introduction and Overview ................................. 67
4.2 Ungrounded System ......................................... 68
4.2.1 Normal Operation ................................... 68
4.2.2 Ground Fault on Phase "a" .......................... 68
4.2.3 Derivation of Equivalent Circuit ................... 69
4.2.4 Overvoltage Due to Ground Fault through an
Impedance .......................................... 69
4.2.5 Conclusion and Recommendation ...................... 70
4.3 High-Resistance Grounded System ........................... 71
4.3.1 Normal Operation ................................... 71
4.3.2 Ground Fault on Phase "a" .......................... 71
4.3.3 Example of a High-Resistance Grounding
Calculation ........................................ 72
4.3.4 HR Grounding for Delta-Connected Systems (System
Neutral not Available) ............................. 74
4.3.5 HR Grounding for Low-Voltage (480 and 600 V)
Systems ............................................ 75
4.3.6 Measurement of System Charging Current ............. 75
4.3.7 Conclusions ........................................ 75
4.3.8 Recommendations .................................... 76
4.4 Low-Resistance (LR) Grounded System ....................... 76
4.4.1 LR Grounding for Wye-Connected System .............. 76
4.4.2 LR Grounding for Delta-Connected System ............ 77
4.4.3 Conclusions ........................................ 77
4.4.4 Recommendations .................................... 78
4.5 Solidly Grounded Neutral System ........................... 79
4.5.1 Solidly Grounded Neutral ........................... 79
4.5.2 Power System Considerations ........................ 79
4.5.3 Conclusions ........................................ 79
4.5.4 Recommendations ..................................... 80
4.6 Generator Neutral Grounding ............................... 80
4.6.1 Solidly Grounded Neutral ........................... 80
4.6.2 High-Resistance Grounding .......................... 81
4.6.3 Low-Resistance Grounding ........................... 84
4.6.4 Generator HR Grounded and System LR Grounded ....... 85
4.6.5 Hybrid High-Resistance Grounding ................... 85
4.6.6 Low-Reactance Grounding ............................ 85
4.6.7 Resonant Grounding ................................. 85
4.7 Grounding of Mine Power System ............................ 86
4.7.1 An Overview ........................................ 86
4.7.2 Safety Considerations in HV Substation ............. 86
4.7.3 Factors Involved in Shock Hazard ................... 86
4.7.4 Neutral Grounding Resistor ......................... 87
4.7.5 Ground-Fault Relaying and Ground-Conductor
Monitoring ......................................... 88
4.7.6 Low-Voltage (600 V and 480 V) Systems .............. 88
4.8 Neutral Grounding Equipment ............................... 89
4.8.1 HR Grounding for Wye-Connected MV Systems .......... 89
4.8.2 HR Grounding for Wye-Connected LV Systems .......... 89
4.8.3 LR Grounding for Wye-Connected MV Systems .......... 90
4.8.4 HR Grounding for Wye-Connected Generator Neutral ... 90
4.8.5 Grounding Transformer .............................. 90
4.8.6 Zig-Zag Grounding Transformer ...................... 91
4.8.7 Wye-Delta Grounding Transformer .................... 92
4.9 System Capacitance Data ................................... 93
4.9.1 Surge Capacitors for Rotating Machines ............. 93
4.9.2 Overhead Transmission/Distribution Lines ........... 93
4.9.3 Power Cable ........................................ 94
4.9.4 Power Transformers ................................. 95
4.9.5 Outdoor Apparatus Bushings ......................... 95
4.9.6 Isolated Phase, Segregated, and Nonsegregated Bus .. 95
4.9.7 Synchronous Motors with Class В Insulation System .. 95
4.9.8 Air-Cooled Generators .............................. 96
4.9.9 Induction Motors ................................... 96
References ................................................ 97
Bibliography .............................................. 97
Chapter 5 Power Transformers and Reactors ..................... 99
5.1 General ................................................... 99
5.1.1 Basic Construction ................................. 99
5.1.2 Normal (Usual) Service Conditions .................. 99
5.1.3 Unusual Service Conditions ........................ 100
5.1.4 Transformer Categories and Short-Circuit
Withstand ......................................... 102
5.1.5 Short-Circuit Impedance or Impedance Voltage
(ZT) .............................................. 103
5.1.6 Vector Group, Angular Displacement, and Terminal
Markings .......................................... 103
5.1.7 Taps or Tap Changer ............................... 105
5.1.8 Parallel Operation ................................ 106
5.2 Oil-Filled (Immersed) Transformers ....................... 107
5.2.1 Classification of Mineral-Oil-Immersed
Transformers ...................................... 107
5.2.2 Voltage, Power Rating, and Temperature Rise ....... 107
5.2.3 Impedance ......................................... 108
5.2.4 Cooling Designation ............................... 108
5.2.5 Oil or Liquid Preservation System ................. 110
5.2.6 Winding Insulation Levels ......................... 112
5.2.7 Tap Changers ...................................... 113
5.2.8 Transformer Bushings .............................. 114
5.2.9 Bushing Current Transformers ...................... 114
5.2.10 Accessories ....................................... 115
5.2.11 Cooling Equipment ................................. 116
5.2.12 Nameplate Information ............................. 117
5.2.13 Core Grounding .................................... 117
5.2.14 Transformer Gas Analysis: Dissolved Gases in
Transformers ...................................... 117
5.3 Nonflammable Liquid-Filled Transformers .................. 118
5.3.1 Overview .......................................... 118
5.3.2 Askeral-Immersed Transformers ..................... 118
5.3.3 Silicone-Immersed Transformers .................... 119
5.3.4 Other Available Transformer Types ................. 119
5.4 Dry-Type Transformers .................................... 119
5.4.1 Type and Rating ................................... 119
5.4.2 Insulation Class and Temperature Rise ............. 120
5.4.3 Primary System Fault Level for Short-Circuit
Withstand ......................................... 120
5.4.4 Insulation Level .................................. 121
5.4.5 Impedance ......................................... 121
5.4.6 Tap Changer or Taps ............................... 121
5.4.7 Accessories ....................................... 122
5.4.8 Surge Arresters for Dry-Type Transformers ......... 122
5.5 Transformers for Nonlinear Loads ......................... 122
5.5.1 Standard Design ................................... 122
5.5.2 Transformer Losses ................................ 122
5.5.3 K-Rated Transformers .............................. 123
5.6 Generator Step-Up and Other Special Transformers ......... 124
5.7 Installation of Oil-Filled Transformers and Reactors ..... 126
5.7.1 General ........................................... 126
5.7.2 Indoor (Inside Buildings) ......................... 126
5.7.3 Outdoor Installation .............................. 127
5.8 Reactors ................................................. 127
5.9 Inspection and Testing ................................... 128
5.9.1 Factory Routine and Type Tests .................... 128
5.9.2 Test of Transformer ............................... 130
5.9.3 Routine Power Transformer Inspection .............. 131
5.9.4 Internal Inspection of Transformer ................ 132
References ............................................... 132
Bibliography ............................................. 133
Chapter 6 Instrument Transformers ............................ 135
6.1 Introduction and Overview ................................ 135
6.2 Current Transformers ..................................... 135
6.2.1 Bushing Type ...................................... 135
6.2.2 Equivalent Circuit ................................ 137
6.2.3 Excitation Characteristics ........................ 138
6.2.4 Accuracy Class and Burden ......................... 139
6.2.5 Current Transformers Saturation ................... 141
6.2.6 Remnant Flux ...................................... 144
6.2.7 Accuracy Voltage of Bushing Current Transformers .. 144
6.2.8 Accuracy Voltage of Current Transformers Used in
Switchgear ........................................ 144
6.2.9 Current Transformers in Series .................... 145
6.2.10 Polarity of CT: Polarity Marking .................. 145
6.2.11 Auxiliary Current Transformers .................... 146
6.2.12 Metering Current Transformers ..................... 146
6.3 Voltage Transformers ..................................... 146
6.3.1 Inductive Voltage Transformer ..................... 146
6.3.2 Capacitor Voltage Transformers .................... 147
6.3.3 Standard Accuracy Class and Burden ................ 148
6.3.4 Ratings and Characteristics ....................... 148
6.3.5 Protection of Voltage Transformers ................ 149
6.3.6 Ferro-Resonance in Voltage Transformer ............ 150
6.4 Grounding of Secondary ................................... 150
6.5 European Standards ....................................... 151
6.5.1 Current Transformers .............................. 152
References ............................................... 153
Bibliography ............................................. 154
Cbapter 7 Switchgear, Circuit Breakers, and Motor Control
Center ........................................................ 155
7.1 Low Voltage .............................................. 155
7.1.1 Short Circuit ..................................... 155
7.1.2 Important Features to Be Specified ................ 155
7.2 Medium Voltage ........................................... 156
7.3 Load-Interrupter Switchgear .............................. 157
7.4 Power Fuse ............................................... 166
7.4.1 Advantages ........................................ 166
7.4.2 Disadvantages ..................................... 166
7.4.3 Fuse Size for Motor Branch Circuit ................ 167
7.4.4 Application of Fuse Let-Through Charts ............ 167
7.5 Medium- and High-Voltage Circuit Breaker ................. 167
7.5.1 Overview of Medium-and High-Voltage Circuit-
Breaker Standards ................................. 168
7.5.2 Basic Performance Requirements: Medium- and
High-Voltage Circuit-Breaker Standards ............ 169
7.5.3 Circuit-Breaker Types ............................. 170
7.5.4 Circuit-Breaker Short-Circuit Rating and E/X
Method ............................................ 173
7.6 SF6 Gas-Insulated Switchgear ............................. 174
7.6.1 Main Features ..................................... 175
7.6.2 Design Concepts ................................... 175
7.6.3 Specifications .................................... 176
7.7 Low- and Medium-Voltage Motor Control Centers ............ 177
7.7.1 Low-Voltage Motor Control Center .................. 177
7.7.2 Medium-Voltage Motor Control Center ............... 178
7.7.3 Short-Circuit Capacity ............................ 178
7.7.4 Coordinated Protection in Medium-Voltage Fused
Starters .......................................... 179
7.7.5 Main and Vertical Bus Bars ........................ 179
7.7.6 Minimum Size ...................................... 179
7.7.7 IEC-Rated Contactors .............................. 179
References ............................................... 180
Chapter 8 Station Battery .................................... 181
8.1 Introduction ............................................. 181
8.2 System Types ............................................. 181
8.3 DC Distribution Systems .................................. 182
8.4 Types of Battery ......................................... 185
8.5 Battery Chargers ......................................... 188
8.6 Application Criteria ..................................... 189
8.6.1 Application Voltage Levels ........................ 189
8.6.2 Rating ............................................ 190
8.6.3 Load Classification ............................... 190
8.7 Battery Sizing ........................................... 191
8.7.1 System Voltage .................................... 191
8.7.2 Correction Factor ................................. 193
8.7.3 Duty Cycle ........................................ 193
References ............................................... 193
Bibliography ............................................. 194
Chapter 9 Application and Protection of Medium-Voltage
Motors ........................................................ 195
9.1 Introduction and Overview ................................ 195
9.2 Load Characteristics ..................................... 195
9.2.1 Load Categories ................................... 195
9.2.2 Steady-State Power ................................ 196
9.2.3 Average Starting Torque and Acceleration .......... 197
9.3 Squirrel-Cage Induction Motors ........................... 199
9.3.1 Torque Characteristics ............................ 199
9.3.2 NEMA Design Letters ............................... 200
9.3.3 NEMA Code Letter .................................. 201
9.3.4 Inertia ........................................... 201
9.3.5 Service Factor .................................... 202
9.3.6 Insulation Systems and Temperature Rise ........... 203
9.3.7 Surge-Withstand Capability ........................ 203
9.3.8 Power Supply Voltage and Frequency ................ 203
9.3.9 Starting or Locked-Rotor Power Factor ............. 204
9.3.10 Enclosures ........................................ 204
9.3.11 Motors for Classified (Hazardous) Areas ........... 205
9.3.12 Bearing and Shaft Currents ........................ 206
9.3.13 Accessories ....................................... 208
9.3.14 Motor Terminal Box ................................ 208
9.4 Wound Rotor (Slip Ring) Induction Motors ................. 209
9.5 Synchronous Motors ....................................... 211
9.5.1 An Overview ....................................... 211
9.5.2 Power Supply Voltage and Frequency ................ 211
9.5.3 Insulation System and Temperature Rise ............ 212
9.5.4 Torque Characteristics ............................ 212
9.5.5 Inertia (Wk2) ..................................... 213
9.5.6 Excitation System ................................. 213
9.5.7 Rotor Protection and Monitoring ................... 214
9.5.8 System Power Factor Improvement ................... 214
9.5.9 Torque Pulsations during Acceleration ............. 215
9.5.10 Current Pulsations ................................ 216
9.5.11 Application ....................................... 217
9.6 Electric Motors for Variable Frequency Drives ............ 217
9.7 Voltage Drop and Acceleration Time ....................... 218
9.7.1 Guidelines ........................................ 218
9.7.2 Voltage Drop Using Hand Calculations .............. 220
9.7.3 Voltage Dip When a Sudden Load Is Applied to
a Small Generator ................................. 224
9.7.4 Voltage Drop and Acceleration Time Using
Computer Software ................................. 225
9.7.5 Estimate of Acceleration Time Using Hand
Calculations ...................................... 226
9.7.6 Estimate of Deceleration Time ..................... 227
9.7.7 Simplified Method for Estimating the
Acceleration Time of Centrifugal Drives (Fans,
Blowers) .......................................... 227
9.8 Motor Controllers and Starting Methods ................... 228
9.8.1 Fused Starter ..................................... 228
9.8.2 Switchgear-Type Controllers ....................... 230
9.8.3 Starting Methods .................................. 234
References ............................................... 234
Bibliography ............................................. 234
Chapter 10 Power and Control Cables ........................... 237
10.1 Introduction and Overview ................................ 237
10.2 Cable Selection Criteria ................................. 237
10.2.1 Load Current Criteria ............................. 238
10.2.2 Voltage-Drop Limitations .......................... 238
10.2.3 Fault-Current Criteria ............................ 239
10.2.4 Insulation Levels and System Grounding ............ 239
10.3 Cable Shielding .......................................... 239
10.3.1 Inner Shield ...................................... 239
10.3.2 Outer Shield ...................................... 240
10.3.3 Outer or Overall Shield Size ...................... 240
10.3.4 Shield and Outer Sheath Grounding ................. 241
10.3.5 Recommended Practice for Industrial Cable System .. 241
10.4 Additional Application Considerations .................... 243
10.4.1 Short-Circuit Conductor Heating ................... 243
10.4.2 Application of Power Cables for Variable-
Frequency Drives .................................. 244
10.5 Cable Insulation ......................................... 246
10.5.1 Standards ......................................... 246
10.5.2 Insulation Characteristics ........................ 247
10.5.3 Insulation Levels ................................. 247
10.5.4 Insulation Reliability ............................ 248
10.6 Testing .................................................. 249
10.6.1 High-Voltage DC Testing (DC Hi Pot) of Medium-
Voltage Cable Insulation .......................... 249
10.6.2 EPR Insulation Testing ............................ 249
10.7 Control Cables ........................................... 250
References ............................................... 251
Bibliography ............................................. 252
Chapter 11 Protection ......................................... 253
11.1 Introduction ............................................. 253
11.2 Protection and Coordination Principles ................... 254
11.2.1 Protection Schemes and Relay Selection ............ 254
11.2.2 Necessary Steps to Carry Out Relay-Setting and
Time-Current Coordination ......................... 255
11.3 Transformer Protection ................................... 257
11.3.1 Protective Devices and Features ................... 257
11.3.2 Transformer Protection with a Primary Fuse ........ 260
11.3.3 Protection of Low-Voltage Unit Substation
Transformers ...................................... 263
11.3.4 Electrical Code Rules for Transformer Protection .. 264
11.3.5 Transformer Through-Fault Current Damage Curves ... 266
11.3.6 Differential Protection of Transformers ........... 268
11.3.6.1 Phase Differential Scheme ....................... 268
11.3.7 Protection of Grounding Transformers .............. 271
11.3.8 Overexcitation Protection ......................... 272
11.3.9 Surge Protection .................................. 273
11.4 Motor Protection ......................................... 274
11.4.1 Data Required for Relay Selection and Setting ..... 274
11.4.2 Motor-Protection Schemes .......................... 276
11.4.3 Recommended Protection ............................ 279
11.4.4 Protective Devices and Suggested Settings ......... 281
11.4.5 Electrical Code Requirements ...................... 292
11.4.6 Typical Coordination Curves ....................... 295
11.5 Generator Protection ..................................... 296
11.5.1 Data Required for Relay Selection and Settings .... 297
11.5.2 Recommended Protection Schemes .................... 298
11.5.3 Protective Devices and Suggested Settings ......... 301
11.5.4 Diesel Generator Connected to a Low-Voltage Bus ... 312
11.5.5 Generator Tripping Schemes ........................ 312
11.6 Feeder Protection ........................................ 313
11.7 Capacitor Protection ..................................... 314
11.7.1 Fuse for Individual Capacitor Unit Protection ..... 314
11.7.2 Relaying for Capacitor-Bank Protection ............ 315
11.8 Reactor Protection ....................................... 317
11.9 Bus Protection ........................................... 317
11.9.1 Current-Transformer Saturation .................... 317
11.9.2 Bus-Differential Schemes .......................... 318
References ............................................... 321
Bibliography ............................................. 322
Chapter 12 High-Voltage Substation Design Considerations ...... 325
12.1 Introduction ............................................. 325
12.2 Necessary Information for the Design of Substations ...... 325
12.2.1 Considerations for the Location of the
Substations ....................................... 325
12.2.2 Basic Information Required ........................ 327
12.3 Standards and Design Principles for Substation Design .... 327
12.3.1 System of Units ................................... 327
12.3.2 Applicable Standards .............................. 328
12.3.3 Standard Transformer Connections and System
Phasing ........................................... 328
12.4 Substation Electrical Configuration ...................... 330
12.4.1 Switching Configuration ........................... 330
12.4.2 Commonly Used Substation Configurations ........... 331
12.4.3 Recommended Configurations ........................ 334
12.5 Secondary System Aspects of Substation Design ............ 335
12.5.1 Substation Protection ............................. 335
12.5.2 Local and Remote Control and Metering and
Indication Requirements ........................... 336
12.5.3 Relay Building Location ........................... 338
12.5.4 Utility Telecommunication Requirements ............ 338
12.5.5 Current and Voltage Transformers Requirements ..... 339
12.6 High-Altitude Considerations ............................. 340
12.6.1 Effect of Altitude on Insulation Levels ........... 340
12.6.2 Effect of Altitude on Conductor Size .............. 340
12.6.3 Definition of Altitude Zones for Substation
Design ............................................ 341
12.7 Substation Design Considerations ......................... 342
12.7.1 Layout and Conductor Spacing ...................... 342
12.7.2 General Considerations for Bus Design ............. 342
12.7.3 Rigid Bus Design .................................. 345
12.7.4 Strain Bus Design ................................. 346
12.8 Grounding Design and Lightning Protection ................ 347
12.8.1 Introduction ...................................... 347
12.8.2 Substation Area ................................... 347
12.8.3 General Surge Protection .......................... 348
12.8.4 Equipment Surge Protection ........................ 349
12.8.5 Direct-Stroke Shielding Principles ................ 349
12.8.6 Lightning Protection Shielding Calculation
Methods ........................................... 351
12.9 Medium- and Low-Voltage Substations and Switchgear ....... 352
12.10 Site Testing and Commissioning .......................... 352
12.10.1 Scope of Work .................................... 352
12.10.2 Objectives ....................................... 353
12.10.3 Responsibilities ................................. 353
12.10.4 Safety Procedures ................................ 353
12.10.5 Training of the Employer's Staff ................. 354
12.10.6 Maintenance Aspects .............................. 354
References ............................................... 354
Bibliography ............................................. 355
Chapter 13 Substation Grounding Design Considerations ......... 361
13.1 Introduction and Overview ................................ 361
13.2 Soil-Resistivity Measurements ............................ 361
13.2.1 Soil Resistivity .................................. 361
13.2.2 Soil Model and Its Impact on Grid Design .......... 362
13.2.3 Measurement Techniques ............................ 364
13.3 Permissible Potential Difference ......................... 365
13.3.1 Step Voltage ...................................... 365
13.3.2 Touch Voltage ..................................... 366
13.3.3 Mesh Voltage ...................................... 367
13.3.4 Transferred Voltage ............................... 367
13.3.5 Typical Shock Situation for Gas-Insulated
Switchgear ........................................ 367
13.4 Maximum Ground Current ................................... 368
13.4.1 Worst-Case Symmetrical Fault Current (Lor 3L,) .... 368
13.4.2 Symmetrical Grid Current .......................... 369
13.4.3 Maximum Grid Current for Design ................... 370
13.4.4 Effect of Station Ground Resistance ............... 370
13.4.5 Effect of Overhead Ground Wires and Neutral
Conductors ........................................ 371
13.4.6 Effect of Direct Buried Pipes and Cables .......... 371
13.4.7 Computation of Current Division Factor ............ 371
13.4.8 Grid Current Returning through the Earth .......... 372
13.4.9 Decrement Factor .................................. 373
13.5 Selection of Conductors and Joints ....................... 373
13.5.1 Basic Requirement ................................. 373
13.5.2 Data Required to Design ........................... 373
13.5.3 Minimum Size (for Hard-Drawn Copper Wire) ......... 374
13.6 Design of Grounding System ............................... 374
13.6.1 Evaluation of Ground Resistance ................... 375
13.6.2 Design Procedure .................................. 376
13.6.3 Maximum Mesh and Step Voltage ..................... 378
13.7 Treatment of Substation Fence ............................ 380
13.7.1 Fence-Grounding System Design ..................... 381
13.7.2 Station Fence-Grounding Details ................... 382
13.8 Case Study (Ground Grid Design) .......................... 382
13.8.1 Design Parameters ................................. 382
13.8.2 Grid Design ....................................... 384
13.9 Conclusion ............................................... 386
References ............................................... 386
Bibliography ............................................. 386
Chapter 14 Electrical Aspects of Power Generation ............. 387
14.1 Introduction and Overview ................................ 387
14.2 Generator Rating and Parameters .......................... 387
14.3 Excitation System ........................................ 390
14.3.1 Brushless Excitation System ....................... 391
14.3.2 Static Excitation System .......................... 392
14.3.3 Voltage-Regulating System ......................... 392
14.3.4 Power System Stabilizer ........................... 393
14.4 Synchronizing ............................................ 393
14.5 Integration into the Power System ........................ 395
14.5.1 General ........................................... 395
14.5.2 Higher Reactance .................................. 396
14.5.3 Current-Limiting Reactor .......................... 396
14.5.4 Duplex Reactor .................................... 396
14.5.5 Unit-Connected System ............................. 396
14.5.6 Fault-Current Limiters ............................ 397
14.6 Plant Power System and Utility Interface ................. 398
14.7 System Disturbances and Islanding ........................ 399
14.7.1 Faults on HV (Utility) System ..................... 399
14.7.2 Performance Criteria for Plant Electrical System
and Equipment ..................................... 400
14.7.3 Steps to Improve Plant Electrical System
Ride-Through Capability ........................... 401
14.8 Induction Generator ...................................... 403
14.8.1 General ........................................... 403
14.8.2 Characteristics ................................... 403
14.8.3 Terminal Voltage .................................. 403
14.8.4 Excitation ........................................ 404
14.8.5 Protection ........................................ 404
14.8.6 Controls .......................................... 405
14.8.7 Advantages and Disadvantages ...................... 405
14.8.8 Differences with an Induction Motor ............... 406
14.9 Station Auxiliaries ...................................... 406
14.9.1 Auxiliary System Load ............................. 406
14.9.2 Power Supply Arrangement .......................... 406
14.9.3 Design Criteria ................................... 408
References ............................................... 410
Bibliography ............................................. 411
Chapter 15 Application of Capacitors .......................... 413
15.1 Introduction ............................................. 413
15.2 Capacitor Application .................................... 413
15.2.1 Capacitor Construction ............................ 413
15.2.2 Individual Capacitors ............................. 414
15.2.3 Motor Capacitors .................................. 414
15.2.4 Switched Capacitors ............................... 415
15.2.5 Switching Device Rating ........................... 416
15.3 Large-Bank Construction .................................. 417
15.3.1 Bank Construction ................................. 417
15.3.2 Capacitor Unit Rating ............................. 418
15.3.3 Bank Monitoring Criteria .......................... 419
15.3.4 Bus Insulation Systems ............................ 420
15.3.5 Interlocking and Safety ........................... 420
15.4 Control and Monitoring Systems ........................... 420
15.5 Capacitor Protection and Monitoring ...................... 421
15.5.1 Capacitor Fusing .................................. 421
15.5.2 Protective Control and Monitoring ................. 424
15.6 Capacitor-Bank Resonances ................................ 426
15.6.1 Introduction ...................................... 426
15.6.2 Example of a Resonance Risk Calculation ........... 427
References ............................................... 428
Bibliography ............................................. 428
Chapter 16 Impact of Nonlinear Loads on Power System and
Equipment ..................................................... 429
16.1 Introduction ............................................. 429
16.2 Harmonics and Resonance .................................. 429
16.2.1 What are Harmonics? ............................... 429
16.2.2 Harmonic Current Generated by Nonlinear Loads ..... 431
16.2.3 Effects of Harmonics .............................. 431
16.2.4 Harmonic Resonance ................................ 435
16.2.5 IEEE Standards for Harmonic Distribution Levels ... 438
16.3 Variable-Frequency Drives ................................ 440
16.4 System Neutral Grounding ................................. 441
16.5 Design Recommendations for Mitigation of Harmonics ....... 442
16.5.1 Capacitor Bank Applications ....................... 442
16.5.2 Variable-Frequency-Drive Application .............. 443
References ............................................... 445
Bibliography .................................................. 445
Index ......................................................... 447
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