1724e300Subestaciones

United StatesDepartment ofAgriculture

RuralUtilitiesService

RUS Bulletin1724E-300

IssuedJune 2001

Design Guide forRural Substations

(BLANK PAGE)

UNITED STATES DEPARTMENT OF AGRICULTURERural Utilities Service

RUS BULLETIN 1724E-300

SUBJECT: Design Guide for Rural Substations

TO: All RUS Borrowers RUS Electric Staff

EFFECTIVE DATE: Date of approval.

OFFICE OF PRIMARY INTEREST: Transmission Branch, Electric Staff Division.

INSTRUCTIONS: This bulletin is an update and revision of previous REA Bulletin 65-1, DesignGuide for Rural Substations (revised June 1978). Replace previous Bulletin 65-1 with this bulletinand file with 7 CFR Part 1724.

AVAILABILITY: This bulletin is available on the Rural Utilities Service website at:

http://www.usda.gov/rus/electric

PURPOSE: This bulletin provides a basic design guide and a reference tool for designing ruralsubstations.

GENERAL: This Bulletin has been revised to bring the publication up to date with latest industrystandards, current RUS format, and technical requirements.

Our thanks to Cooperative Research Network of the National Rural Electric Cooperative Association,(NRECA) which has supported this project, and it's consultant Burns & McDonnell EngineeringCompany for the work which has made it possible to put this revision of the design guide together.

The following current and former members of the Substation Subcommittee of the (NRECA),Transmission and Distribution (T&D) Engineering Committee provided invaluable assistance inpreparing this document.

1. Bardwell, Jim, SGS Witter, Inc., Albuquerque, New Mexico2. Chapman, George, Patterson & Dewar Engineers, Inc., Decatur, Georgia3. Eskandary, Mike, USDA-RUS-ESD-TB, Washington, DC4. Howard, Jerrod, Central Electric Power Co-op, Inc., Columbia, SC5. Kahanek, Bil, Lower Colorado River Authority, Austin, TX6. Myers, Tom, Berkeley Electric Co-op, Moncks Corner, SC7. Malone, Ken, Middle Tennessee EMC, Murfreesboro, TN8. Nicholson, Norris, USDA-RUS-ESD-TB, Washington, DC

Bulletin 1724E-300Page 5

TABLE OF CONTENTS

ABBREVIATIONS AND ACRONYMS.......................................................................................... 31CHAPTER 1 - INTRODUCTION.................................................................................................... 37

1.1 PREFACE........................................................................................................................ 371.2 PURPOSE AND SCOPE ................................................................................................. 371.3 RELATIONSHIP OF SUBSTATION TO OVERALL POWER SYSTEM......................... 371.4 IMPORTANCE OF ADEQUATE SUBSTATION PLANNING AND

ENGINEERING............................................................................................................... 381.5 TYPES OF SUBSTATIONS............................................................................................. 38

1.5.1 General.............................................................................................................. 381.5.2 Distribution Substations ....................................................................................... 391.5.3 Transmission Substations ..................................................................................... 391.5.4 Switching Substations .......................................................................................... 39

1.6 REFERENCES................................................................................................................. 40

CHAPTER 2 - GENERAL DESIGN CONSIDERATIONS............................................................... 412.1 INITIAL AND ULTIMATE REQUIREMENTS ............................................................... 412.2 SITE CONSIDERATIONS............................................................................................... 412.3 ENVIRONMENTAL CONSIDERATIONS...................................................................... 42

2.3.1 General.............................................................................................................. 422.3.2 Weather............................................................................................................. 462.3.3 Altitude .............................................................................................................. 462.3.4 Earthquakes ....................................................................................................... 472.3.5 Other Considerations........................................................................................... 50

2.4 INTERFACING CONSIDERATIONS.............................................................................. 512.4.1 Line Tension....................................................................................................... 51

2.5 RELIABILITY CONSIDERATIONS ............................................................................... 512.6 OPERATING CONSIDERATIONS ................................................................................. 522.7 SAFETY CONSIDERATIONS......................................................................................... 522.8 MAINTENANCE CONSIDERATIONS........................................................................... 522.9 REFERENCES................................................................................................................. 52

CHAPTER 3 - DOCUMENTS ......................................................................................................... 553.1 GENERAL....................................................................................................................... 55

3.1.1 Possible Documents or Studies Required of the Engineer....................................... 553.2 NEED FOR DOCUMENTATION.................................................................................... 553.3 PROCEDURES................................................................................................................ 563.4 PROCUREMENT ............................................................................................................ 563.5 DRAWINGS .................................................................................................................... 57

3.5.1 General.............................................................................................................. 573.5.2 Quality ............................................................................................................... 573.5.3 Types of Drawings ............................................................................................. 59

3.6 STUDIES......................................................................................................................... 713.7 REFERENCES................................................................................................................. 71


APPENDIX ATYPICAL SUBSTATION DRAWING CHECKLIST....................................... 73APPENDIX BU.S. DEPARTMENT OF AGRICULTURE RURAL UTILITIESSERVICE SUBSTATION DESIGN SUMMARY ....................................................................... 91

1 INTRODUCTION ................................................................................................... 942 DESIGN CONSIDERATIONS................................................................................. 953 DOCUMENTS ........................................................................................................ 984 PHYSICAL LAYOUT........................................................................................... 1005 MAJOR EQUIPMENT .......................................................................................... 1046 SITE .................................................................................................................. 1077 STRUCTURES...................................................................................................... 1088 FOUNDATIONS................................................................................................... 1099 GROUNDING....................................................................................................... 10910 INSULATED CABLES AND RACEWAYS.......................................................... 11111 CORROSION........................................................................................................ 11212 PROTECTIVE RELAYING................................................................................... 11213 INSTRUMENTS, TRANSDUCER, AND METERS ............................................... 11414 SUBSTATION AUTOMATION............................................................................ 11415 AC AND DC AUXILIARY SYSTEMS.................................................................. 11516 CONTROL HOUSE .............................................................................................. 11617 COMMUNICATIONS........................................................................................... 117

CHAPTER 4 - PHYSICAL LAYOUT ........................................................................................... 1194.1 INTRODUCTION.......................................................................................................... 1194.2 LAYOUT CONSIDERATIONS..................................................................................... 119

4.2.1 Initial Design Parameters .................................................................................. 1194.2.2 Selection of Switching Scheme .......................................................................... 1194.2.3 Substation Expansion......................................................................................... 1194.2.4 Substation Profile .............................................................................................. 1204.2.5 Underground Circuits ........................................................................................ 1204.2.6 Equipment Removal.......................................................................................... 120

4.3 DISTRIBUTION SUBSTATIONS.................................................................................. 1214.3.1 Basic Distribution Substation.............................................................................. 1214.3.2 Transformer Primary Protective Devices ........................................................... 1224.3.3 Voltage Regulation............................................................................................ 1224.3.4 Circuit Breaker/Recloser Bypass Facilities ......................................................... 1234.3.5 Surge Arresters ................................................................................................ 1244.3.6 Enclosed Equipment.......................................................................................... 124

4.4 TRANSMISSION SUBSTATIONS ................................................................................ 1254.4.1 Basic Transmission Substation ........................................................................... 1254.4.2 Circuit Breaker Bypass Facilities ....................................................................... 1264.4.3 Surge Arresters ................................................................................................ 1264.4.4 Carrier Equipment............................................................................................. 1274.4.5 Voltage Transformers ....................................................................................... 1274.4.6 Current Transformers ....................................................................................... 1274.4.7 Grounding Switches .......................................................................................... 127

4.5 SWITCHING STATIONS .............................................................................................. 1274.5.1 Basic Switching Substation ................................................................................ 128


4.5.2 Surge Arresters ................................................................................................ 1284.6 TYPICAL BUS CONFIGURATIONS............................................................................ 128

4.6.1 Single Bus ........................................................................................................ 1294.6.2 Sectionalized Bus .............................................................................................. 1324.6.3 Main and Transfer Bus ..................................................................................... 1334.6.4 Ring Bus .......................................................................................................... 1364.6.5 Breaker-and-a-Half .......................................................................................... 1394.6.6 Double BreakerDouble Bus ............................................................................. 1394.6.7 Relative Switching Scheme Costs ...................................................................... 141

4.7 PROTECTION OF SUBSTATION INSULATION......................................................... 1424.7.1 General............................................................................................................ 1424.7.2 Surge Protection ............................................................................................... 1424.7.3 Direct Stroke Protection.................................................................................... 142

4.8 SUBSTATION INSULATORS....................................................................................... 1464.8.1 Outdoor Apparatus Insulators ............................................................................ 1464.8.2 Suspension Insulators ........................................................................................ 151

4.9 ELECTRICAL CLEARANCES...................................................................................... 1534.10 BARE CONDUCTORS.................................................................................................. 157

4.10.1 Conductor Materials.......................................................................................... 1574.10.2 Rigid Conductors .............................................................................................. 1574.10.3 Flexible Conductors........................................................................................... 1594.10.4 Conductor Ampacity ......................................................................................... 1604.10.5 Bus Connections ............................................................................................... 160

4.11 RIGID BUS DESIGN ..................................................................................................... 1634.11.1 General Considerations...................................................................................... 1634.11.2 Procedure for Rigid Bus Design......................................................................... 1644.11.3 Bus Design Example ......................................................................................... 171

4.12 STRAIN BUS DESIGN.................................................................................................. 1764.12.1 General Considerations...................................................................................... 1764.12.2 Procedure for Strain Bus Design........................................................................ 177

4.13 APPLICATION OF MOBILE TRANSFORMERS AND SUBSTATIONS...................... 1844.13.1 Size and Maneuverability of the Equipment......................................................... 1854.13.2 Installation Location and Provisions .................................................................... 1854.13.3 Electrical Clearances ........................................................................................ 1854.13.4 Primary and Secondary Connections .................................................................. 1854.13.5 Grounding......................................................................................................... 1864.13.6 Auxiliary System Requirements ......................................................................... 1864.13.7 Safety................................................................................................................. 186

4.14 REFERENCES............................................................................................................... 1864.15 LEGEND FOR EQUATIONS......................................................................................... 188

CHAPTER 5 - MAJOR EQUIPMENT........................................................................................... 1915.1 GENERAL..................................................................................................................... 1915.2 POWER TRANSFORMERS .......................................................................................... 191

5.2.1 General............................................................................................................ 1915.2.2 Types............................................................................................................... 1925.2.3 Ratings............................................................................................................. 193


5.2.4 Taps ................................................................................................................ 2005.2.5 Impedance ....................................................................................................... 2015.2.6 Phase Relation.................................................................................................. 2015.2.7 Parallel Operation of Transformers .................................................................... 2025.2.8 Dielectric Requirements .................................................................................... 2045.2.9 Short-Circuit Requirements................................................................................ 2075.2.10 Cooling Equipment ............................................................................................ 2095.2.11 Oil and Oil Preservation Equipment.................................................................... 2105.2.12 Audible Sound .................................................................................................. 2105.2.13 Tank ................................................................................................................ 2145.2.14 Accessories...................................................................................................... 2145.2.15 Electrical Tests and Measurements.................................................................... 2145.2.16 Shipment .......................................................................................................... 2165.2.17 Warranty.......................................................................................................... 2165.2.18 Core and Coils .................................................................................................. 2165.2.19 Specifications ................................................................................................... 2175.2.20 References....................................................................................................... 217

5.3 POWER CIRCUIT BREAKERS .................................................................................... 2195.3.1 General............................................................................................................ 2195.3.2 Types of Circuit Breakers ................................................................................. 2215.3.3 Ratings............................................................................................................. 2265.3.4 Operating Mechanisms...................................................................................... 2385.3.5 Tests................................................................................................................ 2425.3.6 Control and Auxiliary Power Requirements ........................................................ 2445.3.7 Purchase Evaluation.......................................................................................... 2445.3.8 Shipment and Installation ................................................................................... 2445.3.9 References....................................................................................................... 244

5.4 METAL-CLAD SWITCHGEAR..................................................................................... 2455.4.1 General............................................................................................................ 2455.4.2 Types............................................................................................................... 2465.4.3 Ratings............................................................................................................. 2495.4.4 Purchase Considerations ................................................................................... 2505.4.5 References....................................................................................................... 252

5.5 SUBSTATION VOLTAGE REGULATORS................................................................... 2525.5.1 General............................................................................................................ 2525.5.2 Types............................................................................................................... 2535.5.3 Ratings............................................................................................................. 2545.5.4 Regulator Controls ............................................................................................ 2615.5.5 Lightning Protection .......................................................................................... 2625.5.6 References....................................................................................................... 262

5.6 SHUNT CAPACITOR EQUIPMENT ............................................................................ 2625.6.1 General............................................................................................................ 2625.6.2 System Considerations ...................................................................................... 2635.6.3 Types............................................................................................................... 2675.6.4 Bank Configuration ........................................................................................... 2685.6.5 Ratings............................................................................................................. 2695.6.6 Switching ......................................................................................................... 271


5.6.7 Protection......................................................................................................... 2805.6.8 Grounding and Short-Circuiting of Capacitor Banks ............................................. 2855.6.9 Mounting.......................................................................................................... 2855.6.10 Factory Tests ................................................................................................... 2885.6.11 Inspection and Maintenance .............................................................................. 2885.6.12 Typical Technical Specification.......................................................................... 2885.6.13 References....................................................................................................... 297

5.7 AIR SWITCHES ............................................................................................................ 2985.7.1 General............................................................................................................ 2985.7.2 Types of Air Switches....................................................................................... 2995.7.3 Various Constructions of Outdoor Air Switches .................................................. 3015.7.4 Usual Service Conditions ................................................................................... 3085.7.5 Ratings............................................................................................................. 3085.7.6 Other Requirements.......................................................................................... 3125.7.7 Mounting Considerations ................................................................................... 3225.7.8 References....................................................................................................... 323

5.8 SURGE ARRESTERS.................................................................................................... 3235.8.1 General............................................................................................................ 3235.8.2 Classification of Arresters ................................................................................. 3245.8.3 Ratings (Standard Definitions) ........................................................................... 3325.8.4 System Voltage ................................................................................................ 3335.8.5 Grounded vs. Ungrounded Systems .................................................................... 3335.8.6 Application Guide for Silicon-Carbide Valve Arresters ........................................ 3345.8.7 Application Guide for Metal Oxide Surge Arresters............................................. 3425.8.8 Location........................................................................................................... 3525.8.9 Protection at Line Entrances.............................................................................. 3565.8.10 References....................................................................................................... 357

5.9 AUTOMATIC CIRCUIT RECLOSERS.......................................................................... 3575.9.1 General............................................................................................................ 3575.9.2 Recloser Classifying Features............................................................................ 3615.9.3 Recloser Ratings............................................................................................... 3635.9.4 Construction ..................................................................................................... 3715.9.5 Recloser Operation ........................................................................................... 3735.9.6 Maintenance and Inspection .............................................................................. 3755.9.7 Mounting.......................................................................................................... 3765.9.8 References....................................................................................................... 376

5.10 INSTRUMENT TRANSFORMERS................................................................................ 3775.10.1 General............................................................................................................ 3775.10.2 Service Conditions ............................................................................................ 3775.10.3 Accuracy......................................................................................................... 3795.10.4 Secondary Burdens ........................................................................................... 3815.10.5 Construction ..................................................................................................... 3815.10.6 Current Transformers ....................................................................................... 3825.10.7 Voltage Transformers ....................................................................................... 3895.10.8 Combination Units............................................................................................. 3985.10.9 Tests................................................................................................................ 3995.10.10 References....................................................................................................... 399


5.11 COUPLING CAPACITORS AND COUPLING CAPACITOR VOLTAGETRANSFORMERS......................................................................................................... 4005.11.1 General............................................................................................................ 4005.11.2 Coupling Capacitors .......................................................................................... 4005.11.3 Coupling Capacitor Voltage Transformers .......................................................... 4015.11.4 Service Conditions ............................................................................................ 4045.11.5 Ratings............................................................................................................. 4045.11.6 Tests................................................................................................................ 4085.11.7 References....................................................................................................... 408

5.12 MOBILE UNITS............................................................................................................ 4095.12.1 Feasibility ......................................................................................................... 4095.12.2 Mobile Transformers......................................................................................... 4095.12.3 Mobile Substations ............................................................................................ 4105.12.4 Phase Rotation Indicators.................................................................................. 4105.12.5 Other Considerations......................................................................................... 4105.12.6 Accessories Included with the Mobile Unit ......................................................... 412

CHAPTER 6 - SITE DESIGN ........................................................................................................ 4136.1 GENERAL..................................................................................................................... 4136.2 TYPES OF GRADED YARDS....................................................................................... 413

6.2.1 Flat Yards ........................................................................................................ 4146.2.2 Sloped Yards .................................................................................................... 4146.2.3 Stepped Yards (Two or More Levels)................................................................ 414

6.3 PRELIMINARY REQUIREMENTS............................................................................... 4146.4 DRAINAGE CONSIDERATIONS................................................................................. 415

6.4.1 Stormwater Management .................................................................................. 4156.4.2 Surface Drainage System.................................................................................. 4156.4.3 Closed Drainage System................................................................................... 4156.4.4 Planning........................................................................................................... 4156.4.5 Design ............................................................................................................. 415

6.5 EARTHWORK CONSIDERATIONS AND DESIGN ..................................................... 4196.5.1 Borrow ............................................................................................................ 4196.5.2 Topsoil ............................................................................................................. 4196.5.3 Cut and Fill....................................................................................................... 4216.5.4 Compaction ...................................................................................................... 4216.5.5 Cleanup............................................................................................................ 422

6.6 ROADS AND OTHER ACCESS.................................................................................... 4226.6.1 General Access Roads ...................................................................................... 4226.6.2 Grade............................................................................................................... 4226.6.3 Curvature......................................................................................................... 4226.6.4 Design ............................................................................................................. 4226.6.5 Railroad Spur.................................................................................................... 4226.6.6 Roadways in the Substation Yard....................................................................... 423

6.7 EROSION PROTECTION ............................................................................................. 4236.7.1 General............................................................................................................ 4236.7.2 Legal Requirements .......................................................................................... 423

6.8 YARD SURFACING MATERIAL ................................................................................. 423


6.9 SECURITY FENCE ....................................................................................................... 4246.10 REFERENCES .............................................................................................................. 424APPENDIX CSAMPLE SUBSTATION SECURITY FENCE SPECIFICATION.................. 426

CHAPTER 7 - STRUCTURES....................................................................................................... 4317.1 MATERIALS................................................................................................................. 431

7.1.1 Steel................................................................................................................ 4317.1.2 Aluminum......................................................................................................... 4317.1.3 Concrete .......................................................................................................... 4327.1.4 Wood............................................................................................................... 432

7.2 FUNCTIONAL STRUCTURE TYPES........................................................................... 4327.2.1 Line Support Structures..................................................................................... 4327.2.2 Equipment Support Structures............................................................................ 4327.2.3 Distribution Substation Structure ........................................................................ 433

7.3 STRUCTURE MEMBER TYPES................................................................................... 4337.3.1 Lattice ............................................................................................................. 4337.3.2 Solid Profile ...................................................................................................... 4337.3.3 Semi-Solid Profile ............................................................................................. 4347.3.4 Summary.......................................................................................................... 434

7.4 DESIGN ........................................................................................................................ 4347.4.1 Design Loads ................................................................................................... 4347.4.2 Line Support Structures..................................................................................... 4347.4.3 Deflection Consideration ................................................................................... 4357.4.4 Lightning Masts ................................................................................................ 4367.4.5 Equipment Support Structures............................................................................ 4367.4.6 Base Condition ................................................................................................. 4367.4.7 Seismic Loads .................................................................................................. 4377.4.8 Wind Loads ...................................................................................................... 4397.4.9 Construction Loading ........................................................................................ 4407.4.10 Loading Combination for Design ........................................................................ 4417.4.11 Typical Design Approach.................................................................................. 441

7.5 FASTENERS ................................................................................................................. 4507.5.1 ASTM A394 .................................................................................................... 4507.5.2 ASTM A307 .................................................................................................... 4507.5.3 ASTM A325 .................................................................................................... 450

7.6 WELDING..................................................................................................................... 4527.7 FINISHES...................................................................................................................... 452

7.7.1 Galvanizing....................................................................................................... 4527.7.2 Painting............................................................................................................ 4527.7.3 Wood Preservatives.......................................................................................... 453

7.8 COMPUTER PROGRAMS ............................................................................................ 4537.8.1 Model Geometry............................................................................................... 4537.8.2 Load Input........................................................................................................ 4547.8.3 Computer Output .............................................................................................. 454

7.9 REFERENCES ................................................................................................................ 455APPENDIX DRISA-3D INPUT AND OUTPUT FOR A SIMPLE T STRUCTURE.......... 458


CHAPTER 8 - FOUNDATIONS.................................................................................................... 4658.1 GENERAL..................................................................................................................... 4658.2 SOIL INFORMATION................................................................................................... 465

8.2.1 General............................................................................................................ 4658.2.2 Soil Classification.............................................................................................. 4668.2.3 Bearing Values................................................................................................. 4668.2.4 Groundwater Level........................................................................................... 4678.2.5 Differential Settlement ...................................................................................... 4678.2.6 Chemical Tests................................................................................................. 4688.2.7 Seismic Evaluation ............................................................................................ 468

8.3 FOUNDATION TYPES................................................................................................. 4688.3.1 Drilled Shafts (Piers)......................................................................................... 4688.3.2 Drilled Shaft Design.......................................................................................... 4698.3.3 Drilled Shaft Design (Line Support Structure) ..................................................... 4758.3.4 Compression and Uplift Capacity (Drilled Shafts)................................................ 4788.3.5 Spread Footings ................................................................................................ 4828.3.6 Slabs on Grade ................................................................................................. 489

8.4 OIL POLLUTION.......................................................................................................... 4928.4.1 Basic Retention System..................................................................................... 4938.4.2 Oil Separator Tank............................................................................................ 4938.4.3 Summary.......................................................................................................... 494

8.5 REFERENCES ............................................................................................................... 494APPENDIX ESPECIFICATION FOR PROCURING GEOTECHNICALSUBSURFACE INVESTIGATION.......................................................................................... 497

CHAPTER 9 - GROUNDING........................................................................................................ 5019.1 GENERAL..................................................................................................................... 5019.2 DEFINITIONS............................................................................................................... 503

9.2.1 DC Offset........................................................................................................ 5039.2.2 Earth Current ................................................................................................... 5039.2.3 Ground Fault Current ........................................................................................ 5039.2.4 Ground Potential Rise (GPR)............................................................................. 5039.2.5 Mesh Voltage ................................................................................................... 5039.2.6 Soil Resistivity .................................................................................................. 5039.2.7 Step Voltage..................................................................................................... 5039.2.8 Touch Voltage .................................................................................................. 5039.2.9 Transferred Voltage.......................................................................................... 503

9.3 SOIL RESISTIVITY MEASUREMENTS ....................................................................... 5049.3.1 Analyzing Soil Resistivity Measurements ............................................................ 5059.3.2 Uniform Soil Assumption................................................................................... 506

9.4 AREA OF THE GROUND GRID................................................................................... 5069.5 GROUND FAULT CURRENTS..................................................................................... 506

9.5.1 Symmetrical Grid Current.................................................................................. 5109.5.2 Determine the Split Factor, Sf............................................................................. 5109.5.3 The Decrement Factor, Df................................................................................. 5339.5.4 Maximum Grid Current ..................................................................................... 5349.5.5 Asymmetrical Fault ........................................................................................... 534


9.6 GROUND CONDUCTOR.............................................................................................. 5359.6.1 Conductor Material........................................................................................... 5359.6.2 Ground Conductor Sizing................................................................................... 5359.6.3 Sizing Equipment Ground Conductor................................................................... 5369.6.4 Sizing Ground Grid Conductors .......................................................................... 5379.6.5 Additional Conductor Sizing Factors ................................................................... 5379.6.6 Connections from Equipment and Structures to Ground Grid ................................ 537

9.7 SAFETY CONSIDERATIONS....................................................................................... 5389.7.1 Tolerable Limits of Body Current....................................................................... 5399.7.2 Typical Shock Situations.................................................................................... 540

9.8 TOLERABLE TOUCH AND STEP VOLTAGES........................................................... 5409.9 PROTECTIVE SURFACE MATERIAL AND REDUCTION FACTOR CS .................... 545

9.9.1 Reduction Factor Cs.......................................................................................... 5469.10 DESIGN OF A SUBSTATION GROUNDING SYSTEM................................................ 548

9.10.1 General Concepts ............................................................................................. 5489.10.2 Design Procedures............................................................................................ 5489.10.3 Preliminary Design............................................................................................ 5509.10.4 Calculate Design Mesh Voltage ......................................................................... 5519.10.5 Step Voltage (Es).............................................................................................. 5539.10.6 Ground Potential Rise (GPR)............................................................................. 5549.10.7 Design Modifications......................................................................................... 5559.10.8 Application of Equations for Em and Es............................................................... 5579.10.9 Use of Computer Analysis in Grid Design........................................................... 5579.10.10 Special Danger Points ....................................................................................... 5579.10.11 Investigation of Transferred Voltage .................................................................. 5619.10.12 Effect of Sustained Ground Currents.................................................................. 562

9.11 REFERENCES............................................................................................................... 562

CHAPTER 10 - INSULATED CABLES AND RACEWAYS......................................................... 56310.1 GENERAL..................................................................................................................... 56310.2 600-VOLT CABLE ........................................................................................................ 563

10.2.1 Circuit Requirements......................................................................................... 56310.2.2 Conductors....................................................................................................... 56410.2.3 Conductor Configurations .................................................................................. 56410.2.4 Conductor Insulation and Jackets ....................................................................... 56610.2.5 Cable Sizing...................................................................................................... 56710.2.6 Segregation of Control Cables............................................................................ 56710.2.7 Installation Considerations ................................................................................. 569

10.3 POWER CABLE OVER 600 VOLTS............................................................................. 57010.3.1 Medium-Voltage Shielded Power Cable (2 kV up to 35 kV) ................................ 57010.3.2 Conductors....................................................................................................... 57010.3.3 Conductor Shield............................................................................................... 57010.3.4 Insulation.......................................................................................................... 57110.3.5 Insulation Shield................................................................................................ 57110.3.6 Jackets............................................................................................................. 57110.3.7 Cable Voltage Rating ........................................................................................ 57210.3.8 Conductor Sizing............................................................................................... 572


10.3.9 Terminations and Splices ................................................................................... 57310.3.10 Cable Segregation............................................................................................. 57310.3.11 Installation Considerations ................................................................................. 57310.3.12 High-Voltage Power Cable (69 kV up to 230 kV) ............................................... 574

10.4 SPECIALIZED CABLE ................................................................................................. 57410.5 RACEWAYS................................................................................................................. 575

10.5.1 Function........................................................................................................... 57510.5.2 Economics........................................................................................................ 575

10.6 UNDERGROUND RACEWAYS................................................................................... 57610.6.1 Direct-Buried Cable .......................................................................................... 57610.6.2 Direct-Buried Conduit ....................................................................................... 57710.6.3 Concrete-Encased Conduit (Duct Bank)............................................................. 57810.6.4 Cable Trenches ................................................................................................ 58210.6.5 Manholes ......................................................................................................... 58410.6.6 Handholes ........................................................................................................ 584

10.7 RACEWAY COMBINATION ....................................................................................... 58510.8 SUMMARYUNDERGROUND RACEWAYS............................................................ 58610.9 OVERHEAD RACEWAYS ........................................................................................... 586

10.9.1 Cable Trays...................................................................................................... 58710.9.2 Cable Duct....................................................................................................... 58710.9.3 Plastic Conduit.................................................................................................. 58710.9.4 Metal Conduit ................................................................................................... 58710.9.5 Above-Grade Cable Trench............................................................................... 588

10.10 SUMMARYOVERHEAD RACEWAYS .................................................................... 58810.11 RACEWAY MATERIALS............................................................................................. 588

10.11.1 Plastic .............................................................................................................. 58810.11.2 Fiber ................................................................................................................ 588

10.12 RACEWAY SIZING...................................................................................................... 58810.13 REFERENCES............................................................................................................... 589

CHAPTER 11 - CORROSION....................................................................................................... 59111.1 GENERAL..................................................................................................................... 591

11.1.1 Characteristics of Corrosion .............................................................................. 59111.1.2 Dissimilar Metals .............................................................................................. 59111.1.3 Dissimilar Environments .................................................................................... 592

11.2 PRELIMINARY PREVENTIVE MEASURES ............................................................... 59311.2.1 Surveys ............................................................................................................ 59311.2.2 Selection of Materials........................................................................................ 594

11.3 TESTING AND INSTALLATION ................................................................................. 59511.3.1 Earth Resistivity Measurements......................................................................... 59511.3.2 Soil Samples ..................................................................................................... 59511.3.3 Anode Locations............................................................................................... 59511.3.4 Underground Connections ................................................................................. 59511.3.5 Estimating Corrosion Conditions from DC Potential Measurements ...................... 595

11.4 REFERENCES............................................................................................................... 598


CHAPTER 12 - PROTECTIVE RELAYING.................................................................................. 60112.1 GENERAL..................................................................................................................... 601

12.1.1 Purpose of Protective Relays............................................................................. 60112.1.2 Design Objectives............................................................................................. 60112.1.3 Indications of Defective Equipment or Abnormal Conditions ................................ 601

12.2 FUNDAMENTAL CONSIDERATIONS........................................................................ 60312.2.1 Phasors............................................................................................................ 60312.2.2 Polarity ............................................................................................................ 60312.2.3 Faults............................................................................................................... 60312.2.4 Symmetrical Components .................................................................................. 60412.2.5 Relay Input Sources.......................................................................................... 604

12.3 BASIC RELAY TYPES ................................................................................................. 60412.3.1 General............................................................................................................ 60412.3.2 Relay Selection................................................................................................. 60712.3.3 Overcurrent Relay............................................................................................ 60912.3.4 Distance Relay................................................................................................. 60912.3.5 Differential Relay ............................................................................................. 61112.3.6 Overvoltage Relay............................................................................................ 61212.3.7 Undervoltage Relay .......................................................................................... 61212.3.8 Power Relay .................................................................................................... 61212.3.9 Directional Overcurrent Relay........................................................................... 61212.3.10 Frequency Relay............................................................................................... 61212.3.11 Thermal Relay.................................................................................................. 61312.3.12 Pressure Relay................................................................................................. 61312.3.13 Auxiliary Relay................................................................................................. 613

12.4 RELAY SCHEMES........................................................................................................ 61312.4.1 General............................................................................................................ 61312.4.2 Transmission Line Protection............................................................................. 61412.4.3 Distribution Feeder............................................................................................ 62412.4.4 Major Equipment .............................................................................................. 62612.4.5 Reclosing ......................................................................................................... 63112.4.6 Coordination..................................................................................................... 633

12.5 REFERENCES.............................................................................................................. 635APPENDIX FSTANDARD DEVICE FUNCTION NUMBERS............................................ 637APPENDIX GSUGGESTED SUFFIX LETTERS.................................................................. 646

CHAPTER 13 - INSTRUMENTS, TRANSDUCERS, AND METERS ............................................ 65113.1 INTRODUCTION.......................................................................................................... 65113.2 INSTRUMENTS AND TRANSDUCERS....................................................................... 651

13.2.1 Definitions........................................................................................................ 65113.2.2 Types of Instruments and Transducers............................................................... 65113.2.3 Classification of Instruments.............................................................................. 65113.2.4 Components of Instruments and Transducers...................................................... 65113.2.5 Analog Instrument Scales.................................................................................. 65213.2.6 Operating Procedures ....................................................................................... 653

13.3 METERS........................................................................................................................ 65413.3.1 Definition ......................................................................................................... 654


13.3.2 Types of Electric Meters................................................................................... 65413.3.3 Demand Meter ................................................................................................. 65413.3.4 Combination Watt-Hour and Demand Meters ..................................................... 65513.3.5 Types of Meter Indicating and Recording Devices .............................................. 65513.3.6 Connection of Watt-Hour and VAR-Hour Meters............................................... 656

13.4 MULTI-FUNCTION METERS....................................................................................... 65713.4.1 Definition ......................................................................................................... 65713.4.2 Input Quantities ................................................................................................ 65813.4.3 Measured and Calculated Values....................................................................... 65813.4.4 Communications ............................................................................................... 658

13.5 REFERENCES............................................................................................................... 658

CHAPTER 14 - SUBSTATION AUTOMATION........................................................................... 65914.1 INTRODUCTION.......................................................................................................... 65914.2 OPEN VS. PROPRIETARY SYSTEMS......................................................................... 65914.3 SUBSTATION AUTOMATION ARCHITECTURE....................................................... 66014.4 DATA ACQUISITION AND CONTROL ELEMENTS .................................................. 660

14.4.1 Substation Host Processor ................................................................................. 66114.4.2 Intelligent Electronic Devices............................................................................. 66314.4.3 Programmable Logic Controllers........................................................................ 66414.4.4 Data Concentrator ............................................................................................ 66514.4.5 Substation Local Area Network......................................................................... 66514.4.6 Communication Protocols .................................................................................. 666

14.5 REFERENCES............................................................................................................... 669APPENDIX HGLOSSARY OF TERMS............................................................................... 671

CHAPTER 15 - AC AND DC AUXILIARY SYSTEMS................................................................. 67315.1 AC AUXILIARY SYSTEM............................................................................................ 673

15.1.1 Typical Loads Supplied...................................................................................... 67315.1.2 Design Requirements ........................................................................................ 67315.1.3 Equipment ........................................................................................................ 67815.1.4 Summary.......................................................................................................... 680

15.2 DC AUXILIARY SYSTEM............................................................................................ 68015.2.1 Typical Loads Supplied...................................................................................... 68015.2.2 Design Requirements ........................................................................................ 68115.2.3 Types of Cells .................................................................................................. 68115.2.4 Typical Loads and Duty Cycle ........................................................................... 68215.2.5 Equipment ........................................................................................................ 683

15.3 REFERENCES............................................................................................................... 686

CHAPTER 16 - CONTROL HOUSES ........................................................................................... 68916.1 INTRODUCTION.......................................................................................................... 68916.2 CONTROL HOUSE CONSTRUCTION......................................................................... 689

16.2.1 Foundation........................................................................................................ 68916.2.2 Floor ................................................................................................................ 68916.2.3 Superstructure .................................................................................................. 690

16.3 CONTROL HOUSE LAYOUT ...................................................................................... 692


16.3.1 Control and Relay Panels .................................................................................. 69216.3.2 DC Equipment.................................................................................................. 69516.3.3 AC Equipment.................................................................................................. 69516.3.4 Cableways ....................................................................................................... 69516.3.5 Cable Entrance................................................................................................. 69616.3.6 Lighting............................................................................................................ 69716.3.7 Control House HVAC Systems ......................................................................... 69716.3.8 Control House Plumbing.................................................................................... 69816.3.9 Communications ............................................................................................... 698

16.4 REFERENCES............................................................................................................... 698

CHAPTER 17 - COMMUNICATIONS.......................................................................................... 69917.1 INTRODUCTION.......................................................................................................... 69917.2 APPLICATIONS........................................................................................................... 699

17.2.1 Relaying........................................................................................................... 69917.2.2 SCADA........................................................................................................... 69917.2.3 Telemetering .................................................................................................... 70017.2.4 Voice............................................................................................................... 700

17.3 METHODS.................................................................................................................... 70017.3.1 Power Line Carrier........................................................................................... 70017.3.2 Audio Tone ...................................................................................................... 70517.3.3 Carrier or Audio Tone on Shield Wire ................................................................ 70617.3.4 Microwave ....................................................................................................... 70617.3.5 Optical Fiber..................................................................................................... 70917.3.6 Wire Lines ....................................................................................................... 71117.3.7 Satellite Communications ................................................................................... 712

17.4 REFERENCES............................................................................................................... 714APPENDIX IGLOSSARY OF TERMS ................................................................................ 715

CHAPTER 18 - INSPECTION....................................................................................................... 71718.1 PURPOSE ..................................................................................................................... 71718.2 GENERAL..................................................................................................................... 717

18.2.1 Records ........................................................................................................... 71718.2.2 Safety .............................................................................................................. 717

18.3 PERIODIC INSPECTIONS............................................................................................ 71818.3.1 Visual Inspections ............................................................................................. 71918.3.2 Inspection with Diagnostic Online Test Equipment .............................................. 72318.3.3 Detailed Inspection of Major Equipment ............................................................. 72618.3.4 Internal Inspection of Transformers and Regulators ............................................ 728

18.4 NON-PERIODIC INSPECTIONS.................................................................................. 72918.4.1 Inspection of Porcelain ...................................................................................... 72918.4.2 Fuses, Disconnects, and Other Switches............................................................. 73018.4.3 Buses............................................................................................................... 73018.4.4 Transformers.................................................................................................... 73018.4.5 Transformer On-Load Tap Changers ................................................................. 73018.4.6 Regulators........................................................................................................ 73018.4.7 Oil Circuit Reclosers ......................................................................................... 730


18.4.8 Circuit Breakers ............................................................................................... 73018.4.9 Grounding System............................................................................................. 73018.4.10 Structures......................................................................................................... 730

18.5 REFERENCES............................................................................................................... 731

CHAPTER 19 - TESTS.................................................................................................................. 73319.1 GENERAL..................................................................................................................... 733

19.1.1 Records ........................................................................................................... 73319.1.2 Safety .............................................................................................................. 733

19.2 DETAILED REQUIREMENTS...................................................................................... 73419.2.1 Acceptance Tests............................................................................................. 73419.2.2 Periodic Tests................................................................................................... 73419.2.3 Tests After Failure............................................................................................ 734

19.3 DESCRIPTION OF TESTS ............................................................................................ 73419.3.1 Insulation Resistance Test ................................................................................. 73419.3.2 Power Factor Test............................................................................................ 73719.3.3 DC High Potential Test ..................................................................................... 73719.3.4 Dielectric Absorption Test................................................................................. 73919.3.5 AC Over-Potential Test .................................................................................... 74019.3.6 Contact Resistance Test.................................................................................... 74019.3.7 Winding Resistance Test ................................................................................... 74019.3.8 Insulating Oil Tests ........................................................................................... 74119.3.9 Combustible Gas Analysis ................................................................................. 74219.3.10 SF6 Gas Analyses ............................................................................................. 74219.3.11 Timing Test ...................................................................................................... 74219.3.12 Motion Analyzer Test........................................................................................ 74319.3.13 Series Overcurrent Test .................................................................................... 74319.3.14 Turns Ratio Test............................................................................................... 74319.3.15 Polarity Test..................................................................................................... 74319.3.16 Protective Relay System Tests .......................................................................... 74319.3.17 Meter Calibration Tests..................................................................................... 74419.3.18 Capacitance Test.............................................................................................. 74419.3.19 Pressure Test ................................................................................................... 74419.3.20 Ground Grid Resistance Measurement ............................................................... 745

19.4 REFERENCES............................................................................................................... 745

CHAPTER 20 - MAINTENANCE ................................................................................................. 74720.1 GENERAL..................................................................................................................... 747

20.1.1 Records ........................................................................................................... 74720.1.2 Safety .............................................................................................................. 747

20.2 PERIODIC MAINTENANCE ........................................................................................ 74720.2.1 Specific Requirements....................................................................................... 74820.2.2 Painting............................................................................................................ 749

20.3 UNSCHEDULED MAINTENANCE.............................................................................. 75020.4 RELIABILITY-CENTERED MAINTENANCE.............................................................. 751

20.4.1 Methods ........................................................................................................... 75120.4.2 Application....................................................................................................... 752


20.4.3 Conclusion........................................................................................................ 75420.5 REFERENCES............................................................................................................... 754

CHAPTER 21 - UPRATING AND EXPANDING EXISTING SUBSTATIONS.............................. 75521.1 APPLICABILITY.......................................................................................................... 75521.2 FEASIBILITY................................................................................................................ 75521.3 SUBSTATION UPRATING........................................................................................... 755

21.3.1 Major Equipment Uprating................................................................................. 75621.4 SUBSTATION EXPANSION......................................................................................... 758

21.4.1 General............................................................................................................ 75821.4.2 Site Work......................................................................................................... 76021.4.3 Grounding......................................................................................................... 76021.4.4 Raceway System.............................................................................................. 76021.4.5 Control House .................................................................................................. 76121.4.6 Equipment ........................................................................................................ 761

21.5 PLANNING FOR UPRATING OR EXPANSION .......................................................... 76221.6 COMPARISONSNEW VS. UPRATING OR EXPANSION........................................ 76321.7 SUBSTATION UPGRADING........................................................................................ 76321.8 REFERENCES............................................................................................................... 764


LIST OF FIGURES

These exhibits are available electronically as well as in hard copy.

FIGURE TITLE 2-1 Basic Wind Speed..................................................................................................... 482-2 Seismic Zone Map of the United States...................................................................... 50

3-1 Power Transformer .................................................................................................. 603-2 Three-Phase Transformer with Tertiary..................................................................... 603-3 Three-Phase Auto-Transformer................................................................................. 603-4 Step Voltage Regulator with Bypass Switch ............................................................... 613-5 Hook Stick-Operated Disconnecting Switch................................................................ 613-6 Three-Phase Gang-Operated Disconnecting Switch with Horn Gaps and

Grounding Switch...................................................................................................... 613-7 Three-Phase Double Side-Break Disconnecting Switch with Motor Operator ............... 623-8 Fused Disconnect ..................................................................................................... 623-9 Oil Circuit Recloser................................................................................................... 633-10 Circuit Breaker......................................................................................................... 633-11 Surge Arrester.......................................................................................................... 633-12 Voltage Transformer................................................................................................. 643-13 Current Transformer................................................................................................. 643-14 Coupling Capacitor with Voltage Transformer ............................................................ 643-15 Coupling Capacitor, Wave Trap, Tuning Unit, and Power Line Carrier

Transmitter/Receiver ................................................................................................ 643-16 Disconnecting Clamp ................................................................................................ 653-17 Shunt Capacitor ........................................................................................................ 653-18 One-Line Diagram Symbols....................................................................................... 663-19 Typical Relay and Meter Representation .................................................................... 673-20 Conceptual One-Line Diagram.................................................................................. 683-21 Partial Switching One-Line Diagram.......................................................................... 693-22 Partial Functional Relaying One-Line Diagram............................................................ 70

4-1 Substation Plan View Showing Space for Equipment Removal................................... 1214-2 Basic Distribution Substation.................................................................................... 1224-3 Voltage Regulator Bypass Arrangements ................................................................. 1234-4 Typical Circuit Breaker/Recloser Bypass Arrangement............................................. 1244-5 Use of Tandem Switches for Circuit Breaker/Recloser Bypassing ............................. 1244-6 Basic Transmission Substation ................................................................................. 1254-7 Typical Circuit Breaker Bypass Arrangement........................................................... 1264-8 Basic Switching Substation ...................................................................................... 1284-9 Single BusLow Profile ......................................................................................... 1304-10 Single BusHigh Profile ......................................................................................... 1314-11 Sectionalized Bus .................................................................................................... 1324-12 Main and Transfer BusLow Profile ...................................................................... 1344-13 Main and Transfer BusHigh Profile ...................................................................... 1354-14 Ring Bus ................................................................................................................ 1374-15 Breaker-and-a-Half ................................................................................................ 138


FIGURE TITLE 4-16 Double BreakerDouble Bus ................................................................................... 1404-17 Zones of Protection for Masts and Shield Wires Using Fixed Angle Method ............... 1434-18 Principle of Rolling Sphere....................................................................................... 1444-19 Station Post Insulator .............................................................................................. 1484-20 Suspension Insulator................................................................................................ 1524-21 Safety Clearance to Electric Supply Station Fences................................................... 1584-22 Drag Coefficients for Structural Shapes ................................................................... 1664-23 Typical Bus System Illustrating Provisions for Conductor Thermal Expansion ............. 1694-24 Coupler Location .................................................................................................... 1754-25 Bus Configuration for Example ................................................................................ 1764-26 Short Strain Bus Insulator Effect.............................................................................. 180

5-1 Methods of Oil Preservation .................................................................................... 2115-2 Dead Tank Breaker............................................................................................. 2225-3 Live Tank Breaker .............................................................................................. 2225-4 Three-Pole Single-Throw Breakers.......................................................................... 2235-5 SF6 Gas Circuit Breakers ........................................................................................ 2245-6 Type SDV Vacuum Circuit Breaker ........................................................................ 2255-7 Relation of Symmetrical Interrupting Capability, Closing Capability, Latching Capability, and Carrying Capability to Rated Short-Circuit Current ............................. 2355-8 Ratio of Circuit Breaker Asymmetrical to Symmetrical Interrupting Capabilities.......... 2365-9 Single-Aisle Metal-Clad Switchgear with Ancillaries ................................................. 2475-10 Typical Single-Aisle Switchgear Installation .............................................................. 2485-11 Single-Phase Voltage Regulator ............................................................................... 2555-12 Three-Phase Voltage Regulator ............................................................................... 2565-13 Typical Capacitor BankTwo Three-Phase Capacitor Racks Connected to

Form a Two-Step Bank, Floating Wye with a Common Neutral................................. 2645-14 A Y-Y Connected Capacitor Bank with One Series Section per Phase and

Neutrals Isolated..................................................................................................... 2705-15 Typical Capacitor Bank Grd Wye Connected............................................................ 2735-16 Typical Capacitor Bank Floating Wye ...................................................................... 2745-17 Typical Capacitor Bank Wye Wye Connecte

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