Electric Power distribution handbook

1 Fundamentals of Distribution Systems

1.1 Primary Distribution Configurations

1.2 Urban Networks

1.3 Primary Voltage Levels

1.4 Distribution Substations

1.5 Subtransmission Systems

1.6 Differences between European and North American Systems

1.7 Loads

1.8 The Past and the Future

References

2 Overhead Lines

2.1 Typical Constructions

2.2 Conductor Data

2.3 Line Impedances

2.4 Simplified Line Impedance Calculations

2.5 Line Impedance Tables

2.6 Conductor Sizing

2.7 Ampacities

2.7.1 Neutral Conductor Sizing

2.8 Secondaries

2.9 Fault Withstand Capability

2.9.1 Conductor Annealing

2.9.2 Burndowns

2.10 Other Overhead Issues

2.10.1 Connectors and Splices

2.10.2 Radio Frequency Interference

References

3 Underground Distribution

3.1 Applications

3.1.1 Underground Residential Distribution (URD)

3.1.2 Main Feeders

3.1.3 Urban Systems

3.1.4 Overhead vs. Underground

3.2 Cables

3.2.1 Cable Insulation

3.2.2 Conductors

3.2.3 Neutral or Shield

3.2.4 Semiconducting Shields

3.2.5 Jacket

3.3 Installations and Configurations

3.4 Impedances

3.4.1 Resistance

3.4.2 Impedance Formulas

3.4.3 Impedance Tables

3.4.4 Capacitance

3.5 Ampacity

3.6 Fault Withstand Capability

3.7 Cable Reliability

3.7.1 Water Trees

3.7.2 Other Failure Modes

3.7.3 Failure Statistics

3.8 Cable Testing

3.9 Fault Location

References

4 Transformers

4.1 Basics

4.2 Distribution Transformers

4.3 Single-Phase Transformers

4.4 Three-Phase Transformers

4.4.1 Grounded Wye – Grounded Wye

4.4.2 Delta – Grounded Wye

4.4.3 Floating Wye – Delta

4.4.4 Other Common Connections

4.4.4.1 Delta – Delta

4.4.4.2 Open Wye – Open Delta

4.4.4.3 Other Suitable Connections

4.4.5 Neutral Stability with a Floating Wye

4.4.6 Sequence Connections of Three-Phase Transformers

4.5 Loadings

4.6 Losses

4.7 Network Transformers

4.8 Substation Transformers

4.9 Special Transformers

4.9.1 Autotransformers

4.9.2 Grounding Transformers

4.10 Special Problems

4.10.1 Paralleling

4.10.2 Ferroresonance

4.10.3 Switching Floating Wye – Delta Banks

4.10.4 Backfeeds

4.10.5 Inrush

References

5 Voltage Regulation

5.1 Voltage Standards

5.2 Voltage Drop

5.3 Regulation Techniques

5.3.1 Voltage Drop Allocation and Primary Voltage Limits

5.3.2 Load Flow Models

5.3.3 Voltage Problems

5.3.4 Voltage Reduction

5.4 Regulators

5.4.1 Line-Drop Compensation

5.4.1.1 Load-Center Compensation

5.4.1.2 Voltage-Spread Compensation

5.4.1.3 Effects of Regulator Connections

5.4.2 Voltage Override

5.4.3 Regulator Placement

5.4.4 Other Regulator Issues

5.5 Station Regulation

5.5.1 Parallel Operation

5.5.2 Bus Regulation Settings

5.6 Line Loss and Voltage Drop Relationships

References

6 Capacitor Application

6.1 Capacitor Ratings

6.2 Released Capacity

6.3 Voltage Support

6.4 Reducing Line Losses

6.4.1 Energy Losses

6.5 Switched Banks

6.6 Local Controls

6.7 Automated Controls

6.8 Reliability

6.9 Failure Modes and Case Ruptures

6.10 Fusing and Protection

6.11 Grounding

References

7 Faults

7.1 General Fault Characteristics

7.2 Fault Calculations

7.2.1 Transformer Connections

7.2.2 Fault Profiles

7.2.3 Effect of X/R Ratio

7.2.4 Secondary Faults

7.2.5 Primary-to-Secondary Faults

7.2.6 Underbuilt Fault to a Transmission Circuit

7.2.7 Fault Location Calculations

7.3 Limiting Fault Currents

7.4 Arc Characteristics

7.5 High-Impedance Faults

7.6 External Fault Causes

7.6.1 Trees

7.6.2 Weather and Lightning

7.6.3 Animals

7.6.4 Other External Causes

7.7 Equipment Faults

7.8 Faults in Equipment

7.9 Targeted Reduction of Faults

References

8 Short-Circuit Protection

8.1 Basics of Distribution Protection

8.1.1 Reach

8.1.2 Inrush and Cold-Load Pickup

8.2 Protection Equipment

8.2.1 Circuit Interrupters

8.2.2 Circuit Breakers

8.2.3 Circuit Breaker Relays

8.2.4 Reclosers

8.2.5 Expulsion Fuses

8.2.5.1 Fuse Cutouts

8.2.6 Current-Limiting Fuses

8.3 Transformer Fusing

8.4 Lateral Tap Fusing and Fuse Coordination

8.5 Station Relay and Recloser Settings

8.6 Coordinating Devices

8.6.1 Expulsion Fuse–Expulsion Fuse Coordination

8.6.2 Current-Limiting Fuse Coordination

8.6.3 Recloser–Expulsion Fuse Coordination

8.6.4 Recloser–Recloser Coordination

8.6.5 Coordinating Instantaneous Elements

8.7 Fuse Saving vs. Fuse Blowing

8.7.1 Industry Usage

8.7.2 Effects on Momentary and Sustained Interruptions

8.7.3 Coordination Limits of Fuse Saving

8.7.4 Long-Duration Faults and Damage with Fuse Blowing

8.7.5 Long-Duration Voltage Sags with Fuse Blowing

8.7.6 Optimal Implementation of Fuse Saving

8.7.7 Optimal Implementation of Fuse Blowing

8.8 Other Protection Schemes

8.8.1 Time Delay on the Instantaneous Element (Fuse Blowing)

8.8.2 High-Low Combination Scheme

8.3.3 SCADA Control of the Protection Scheme

8.8.4 Adaptive Control by Phases

8.9 Reclosing Practices

8.9.1 Reclose Attempts and Dead Times

8.9.2 Immediate Reclose

8.9.2.1 Effect on Sensitive Residential Devices

8.9.2.2 Delay Necessary to Avoid Retriggering Faults

8.9.2.3 Reclose Impacts on Motors

8.10 Single-Phase Protective Devices

8.10.1 Single-Phase Reclosers with Three-Phase Lockout

References

9 Reliability

9.1 Reliability Indices

9.1.1 Customer-Based Indices

9.1.2 Load-Based Indices

9.2 Storms and Weather

9.3 Variables Affecting Reliability Indices

9.3.1 Circuit Exposure and Load Density

9.3.2 Supply Configuration

9.3.3 Voltage

9.3.4 Long-Term Reliability Trends

9.4 Modeling Radial Distribution Circuits

9.5 Parallel Distribution Systems

9.6 Improving Reliability

9.6.1 Identify and Target Fault Causes

9.6.2 Identify and Target Circuits

9.6.3 Switching and Protection Equipment

9.6.4 Automation

9.6.5 Maintenance and Inspections

9.6.6 Restoration

9.6.7 Fault Reduction

9.7 Interruption Costs

References

10 Voltage Sags and Momentary Interruptions

10.1 Location

10.2 Momentary Interruptions

10.3 Voltage Sags

10.3.1 Effect of Phases

10.3.2 Load Response

10.3.3 Analysis of Voltage Sags

10.4 Characterizing Sags and Momentaries

10.4.1 Industry Standards

10.4.2 Characterization Details

10.5 Occurrences of Voltage Sags

10.5.1 Site Power Quality Variations

10.5.2 Transmission-Level Power Quality

10.6 Correlations of Sags and Momentaries

10.7 Factors That Influence Sag and Momentary Rates

10.7.1 Location

10.7.2 Load Density

10.7.3 Voltage Class

10.7.4 Comparison and Ranking of Factors

10.8 Prediction of Quality Indicators Based on Site Characteristics

10.9 Equipment Sensitivities

10.9.1 Computers and Electronic Power Supplies

10.9.2 Industrial Processes and Equipment

10.9.2.1 Relays and Contactors

10.9.2.2 Adjustable-Speed Drives

10.9.2.3 Programmable-Logic Controllers

10.9.3 Residential Equipment

10.10 Solution Options

10.10.1 Utility Options for Momentary Interruptions

10.10.2 Utility Options for Voltage Sags

10.10.2.1 Raising the Nominal Voltage

10.10.2.2 Line Reactors

10.10.3.2 Neutral Reactors

10.10.2.4 Current-Limiting Fuses

10.10.3 Utility Options with Nontraditional Equipment

10.10.3.1 Fast Transfer Switches

10.10.3.2 DVRs and Other Custom-Power Devices

10.10.4 Customer/Equipment Solutions

10.11 Power Quality Monitoring

References

11 Other Power Quality Issues

11.1 Overvoltages and Customer Equipment Failures

11.1.1 Secondary/Facility Grounding

11.1.2 Reclose Transients

11.2 Switching Surges

11.2.1 Voltage Magnification

11.2.2 Tripping of Adjustable-Speed Drives

11.2.3 Prevention of Capacitor Transients

11.3 Harmonics

11.3.1 Resonances

11.3.2 Telephone Interference

11.4 Flicker

11.4.1 Flicker Solutions

11.4.1.1 Load Changes

11.4.1.2 Series Capacitor

11.4.1.3 Static Var Compensator

11.4.1.4 Other Solutions

11.5 Voltage Unbalance

References

12 Lightning Protection

12.1 Characteristics

12.2 Incidence of Lightning

12.3 Traveling Waves

12.4 Surge Arresters

12.4.1 Ratings and Selection

12.4.2 Housings

12.4.3 Other Technologies

12.4.4 Isolators

12.4.5 Arrester Reliability and Failures

12.5 Equipment Protection

12.5.1 Equipment Insulation

12.5.2 Protective Margin

12.5.3 Secondary-Side Transformer Failures

12.6 Underground Equipment Protection

12.6.1 Open Point Arrester

12.6.2 Scout Arresters

12.6.3 Tapped Cables

12.6.4 Other Cable Failure Modes

12.7 Line Protection

12.7.1 Induced Voltages

12.7.2 Insulation

12.7.2.1 Practical Considerations

12.7.3 Shield Wires

12.7.4 Line Protection Arresters

12.8 Other Considerations

12.8.1 Role of Grounding

12.8.2 Burndowns

12.8.3 Crossarm and Pole Damage and Bonding

12.8.4 Arc Quenching of Wood

References

13 Grounding and Safety

13.1 System Grounding Configurations

13.1.1 Four-Wire Multigrounded Systems

13.1.2 Other Grounding Configurations

13.2 System Grounding and Neutral Shifts During Ground Faults

13.2.1 Neutral Shifts on Multigrounded Systems

13.2.2 Neutral Reactor

13.2.3 Overvoltages on Ungrounded Systems

13.3 Equipment/Customer Grounding

13.3.1 Special Considerations on Ungrounded Systems

13.3.2 Secondary Grounding Problems

13.4 Ground Rods and Other Grounding Electrodes

13.4.1 Soil Characteristics

13.4.2 Corrosion and Grounding Electrodes

13.4.3 Resistance Measurements

13.5 Shocks and Stray Voltages

13.5.1 Biological Models

13.5.2 Step and Touch Potentials

13.5.3 Stray Voltage

13.5.4 Tree Contacts

13.6 Protective Grounding

References

14 Distributed Generation

14.1 Characteristics of Distributed Generators

14.1.1 Energy Sources

14.1.2 Synchronous Generators

14.1.3 Induction Generators

14.1.4 Inverters

14.1.5 Modeling Small Generators

14.2 Islanding Issues

14.2.1 Effect of Transformer Connections on Overvoltages

14.2.1.1 Overvoltage Relays and 59G Ground Fault Detection

14.2.1.2 Effectively Grounding a Grounded-Wye – Grounded-Wye Transformer Connection

14.2.1.3 Sizing a Neutral Grounding Reactor on a Grounded-Wye – Delta Connection to Maintain Effective Grounding

14.2.2 Anti-Islanding Protection

14.2.3 Active Anti-Islanding

14.2.4 Relaying Issues

14.2.5 Self-Excitation

14.2.6 Ferroresonance

14.2.7 Backfeed to a Downed Conductor and Backfeed Voltages

14.3 Protection Issues

14.3.1 Tradeoff Between Overvoltages and Ground Fault Current

14.3.2 Fuse Saving Coordination

14.4 Power Quality Impacts

14.4.1 Voltage Regulation

14.4.2 Harmonics

14.4.3 Flicker

14.4.4 Other Impacts on Power Quality

14.4.5 High Quality Power Configurations

14.5 Generator Reliability

References


 

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