CONTENIDO
Introduction to Distribution Systems 1
The Distribution System 2
Distribution Substations 2
Radial Feeders 5
Distribution Feeder Map 6
Distribution Feeder Electrical Characteristics 8
Summary 9
The Nature of Loads 11
Definitions 11
Individual Customer Load 13
Demand 13
Maximum Demand 13
Average Demand 14
Load Factor 14
Distribution Transformer Loading 15
Diversified Demand 16
Maximum Diversified Demand 17
Load Duration Curve 17
Maximum Noncoincident Demand 17
Diversity Factor 18
Demand Factor 19
Utilization Factor 19
Load Diversity 20
Feeder Load 20
Load Allocation 20
Application of Diversity Factors 21
Load Survey 21
Transformer Load Management 25
Metered Feeder Maximum Demand 25
What Method to Use? 27
Voltage-Drop Calculations Using Allocated Loads 27
Application of Diversity Factors 27
Load Allocation Based upon Transformer Ratings 31
Summary 32
Problems 33
Approximate Methods of Analysis 39
Voltage Drop 39
Line Impedance 41
"K" Factors 43
The Kdrop Factor 43
The Krise Factor 46
Uniformly Distributed Loads 47
Voltage Drop 48
Power Loss 50
The Exact Lumped Load Model 52
Lumping Loads in Geometric Configurations 55
The Rectangle 55
The Triangle 60
The Trapezoid 65
Summary 71
References 71
Problems 71
Series Impedance of Overhead and Underground Lines 77
Series Impedance of Overhead Lines 77
Transposed Three-Phase Lines 78
Untransposed Distribution Lines 79
Carson's Equations 81
Modified Carson's Equations 83
Primitive Impedance Matrix for Overhead Lines 85
Phase Impedance Matrix for Overhead Lines 86
Sequence Impedances 89
Series Impedance of Underground Lines 95
Concentric Neutral Cable 96
Tape-Shielded Cables 101
Summary 105
References 105
Problems 105
Shunt Admittance of Overhead and Underground Lines 109
The General Voltage-Drop Equation 110
Overhead Lines 111
Concentric Neutral Cable Underground Lines 115
Tape-Shielded Cable Underground Lines 119
Sequence Admittance 121
Summary 122
References 122
Problems 122
Distribution System Line Models 125
Exact Line Segment Model 125
The Modified Line Model 132
The Approximate Line Segment Model 136
Summary 141
References 141
Problems 141
Regulation of Voltages 145
Standard Voltage Ratings 145
Two-Winding Transformer Theory 147
The Two-Winding Autotransformer 152
Autotransformer Ratings 156
Per-Unit Impedance 158
Step-Voltage Regulators 162
Single-Phase Step-Voltage Regulators 163
Type A Step-Voltage Regulator 163
Type B Step-Voltage Regulator 164
Generalized Constants 167
The Line Drop Compensator 168
Three-Phase Step-Voltage Regulators 174
Wye-Connected Regulators 175
Closed Delta-Connected Regulators 180
Open Delta-Connected Regulators 183
Summary 193
References 194
Problems 194
Three-Phase Transformer Models 199
Introduction 199
Generalized Matrices 200
The Delta--Grounded Wye Step-Down Connection 201
Voltages 202
Currents 206
The Ungrounded Wye-Delta Step-Down Connection 212
The Grounded Wye--Grounded Wye Connection 222
The Delta--Delta Connection 224
The Open Wye--Open Delta Connection 236
The Thevenin Equivalent Circuit 242
Summary 245
Problems 245
Load Models 251
Wye-Connected Loads 252
Constant Real and Reactive Power Loads 252
Constant Impedance Loads 253
Constant Current Loads 253
Combination Loads 254
Delta-Connected Loads 257
Constant Real and Reactive Power Loads 257
Constant Impedance Loads 258
Constant Current Loads 258
Combination Loads 258
Line Currents Serving a Delta-Connected Load 259
Two-Phase and Single-Phase Loads 259
Shunt Capacitors 259
Wye-Connected Capacitor Bank 259
Delta-Connected Capacitor Bank 260
The Three-Phase Induction Motor 261
References 266
Problems 266
Distribution Feeder Analysis 269
Power-Flow Analysis 269
The Ladder Iterative Technique 270
Linear Network 270
Nonlinear Network 271
The General Feeder 274
The Unbalanced Three-Phase Distribution Feeder 276
Series Components 276
Shunt Components 278
Applying the Ladder Iterative Technique 279
Putting It All Together 279
Load Allocation 289
Summary of Power-Flow Studies 289
Short-Circuit Studies 290
General Theory 290
Specific Short Circuits 293
Summary 298
References 299
Problems 299
Appendix A 303
Appendix B 307
Index 309