United StatesDepartment ofAgricultureRural                Design Guide forUtilitiesServiceRUS Bulletin                Rura...
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UNITED STATES DEPARTMENT OF AGRICULTURE                                  Rural Utilities Service                          ...
Bulletin 1724E-300                                                                                                        ...
Bulletin 1724E-300Page 6     APPENDIX A—TYPICAL SUBSTATION DRAWING CHECKLIST....................................... 73    ...
Bulletin 1724E-300                                                                                                        ...
Bulletin 1724E-300Page 8         5.2.4  Taps ................................................................................
Bulletin 1724E-300                                                                                                        ...
Bulletin 1724E-300Page 10     5.11 COUPLING CAPACITORS AND COUPLING CAPACITOR VOLTAGE          TRANSFORMERS..................
Bulletin 1724E-300                                                                                                        ...
Bulletin 1724E-300Page 12CHAPTER 8 - FOUNDATIONS.............................................................................
Bulletin 1724E-300                                                                                                        ...
Bulletin 1724E-300Page 14             10.3.9 Terminations and Splices .......................................................
Bulletin 1724E-300                                                                                                        ...
Bulletin 1724E-300Page 16          13.3.2 Types of Electric Meters...........................................................
Bulletin 1724E-300                                                                                                        ...
Bulletin 1724E-300Page 18          18.4.8 Circuit Breakers ..................................................................
Bulletin 1724E-300                                                                                                        ...
Bulletin 1724E-300Page 20                                                   LIST OF FIGURESThese exhibits are available el...
Bulletin 1724E-300                                                                                                        ...
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Design Guide for Rural Substations

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Design Guide for Rural Substations

  1. 1. United StatesDepartment ofAgricultureRural Design Guide forUtilitiesServiceRUS Bulletin Rural Substations1724E-300IssuedJune 2001
  2. 2. (BLANK PAGE)
  3. 3. UNITED STATES DEPARTMENT OF AGRICULTURE Rural Utilities Service RUS BULLETIN 1724E-300SUBJECT: Design Guide for Rural SubstationsTO: All RUS Borrowers RUS Electric StaffEFFECTIVE 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/electricPURPOSE: 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 its 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
  4. 4. Bulletin 1724E-300 Page 5 TABLE OF CONTENTSABBREVIATIONS AND ACRONYMS.......................................................................................... 31CHAPTER 1 - INTRODUCTION.................................................................................................... 37 1.1 PREFACE........................................................................................................................ 37 1.2 PURPOSE AND SCOPE ................................................................................................. 37 1.3 RELATIONSHIP OF SUBSTATION TO OVERALL POWER SYSTEM......................... 37 1.4 IMPORTANCE OF ADEQUATE SUBSTATION PLANNING AND ENGINEERING............................................................................................................... 38 1.5 TYPES OF SUBSTATIONS............................................................................................. 38 1.5.1 General.............................................................................................................. 38 1.5.2 Distribution Substations ....................................................................................... 39 1.5.3 Transmission Substations ..................................................................................... 39 1.5.4 Switching Substations .......................................................................................... 39 1.6 REFERENCES................................................................................................................. 40CHAPTER 2 - GENERAL DESIGN CONSIDERATIONS............................................................... 41 2.1 INITIAL AND ULTIMATE REQUIREMENTS ............................................................... 41 2.2 SITE CONSIDERATIONS............................................................................................... 41 2.3 ENVIRONMENTAL CONSIDERATIONS...................................................................... 42 2.3.1 General.............................................................................................................. 42 2.3.2 Weather............................................................................................................. 46 2.3.3 Altitude .............................................................................................................. 46 2.3.4 Earthquakes ....................................................................................................... 47 2.3.5 Other Considerations........................................................................................... 50 2.4 INTERFACING CONSIDERATIONS.............................................................................. 51 2.4.1 Line Tension....................................................................................................... 51 2.5 RELIABILITY CONSIDERATIONS ............................................................................... 51 2.6 OPERATING CONSIDERATIONS ................................................................................. 52 2.7 SAFETY CONSIDERATIONS......................................................................................... 52 2.8 MAINTENANCE CONSIDERATIONS........................................................................... 52 2.9 REFERENCES................................................................................................................. 52CHAPTER 3 - DOCUMENTS ......................................................................................................... 55 3.1 GENERAL....................................................................................................................... 55 3.1.1 Possible Documents or Studies Required of the Engineer....................................... 55 3.2 NEED FOR DOCUMENTATION.................................................................................... 55 3.3 PROCEDURES................................................................................................................ 56 3.4 PROCUREMENT ............................................................................................................ 56 3.5 DRAWINGS .................................................................................................................... 57 3.5.1 General.............................................................................................................. 57 3.5.2 Quality ............................................................................................................... 57 3.5.3 Types of Drawings ............................................................................................. 59 3.6 STUDIES......................................................................................................................... 71 3.7 REFERENCES................................................................................................................. 71
  5. 5. Bulletin 1724E-300Page 6 APPENDIX A—TYPICAL SUBSTATION DRAWING CHECKLIST....................................... 73 APPENDIX B—U.S. DEPARTMENT OF AGRICULTURE RURAL UTILITIES SERVICE SUBSTATION DESIGN SUMMARY ....................................................................... 91 1 INTRODUCTION ................................................................................................... 94 2 DESIGN CONSIDERATIONS................................................................................. 95 3 DOCUMENTS ........................................................................................................ 98 4 PHYSICAL LAYOUT........................................................................................... 100 5 MAJOR EQUIPMENT .......................................................................................... 104 6 SITE .................................................................................................................. 107 7 STRUCTURES...................................................................................................... 108 8 FOUNDATIONS................................................................................................... 109 9 GROUNDING....................................................................................................... 109 10 INSULATED CABLES AND RACEWAYS.......................................................... 111 11 CORROSION........................................................................................................ 112 12 PROTECTIVE RELAYING................................................................................... 112 13 INSTRUMENTS, TRANSDUCER, AND METERS ............................................... 114 14 SUBSTATION AUTOMATION............................................................................ 114 15 AC AND DC AUXILIARY SYSTEMS.................................................................. 115 16 CONTROL HOUSE .............................................................................................. 116 17 COMMUNICATIONS........................................................................................... 117CHAPTER 4 - PHYSICAL LAYOUT ........................................................................................... 119 4.1 INTRODUCTION.......................................................................................................... 119 4.2 LAYOUT CONSIDERATIONS..................................................................................... 119 4.2.1 Initial Design Parameters .................................................................................. 119 4.2.2 Selection of Switching Scheme .......................................................................... 119 4.2.3 Substation Expansion......................................................................................... 119 4.2.4 Substation Profile .............................................................................................. 120 4.2.5 Underground Circuits ........................................................................................ 120 4.2.6 Equipment Removal.......................................................................................... 120 4.3 DISTRIBUTION SUBSTATIONS.................................................................................. 121 4.3.1 Basic Distribution Substation.............................................................................. 121 4.3.2 Transformer Primary Protective Devices ........................................................... 122 4.3.3 Voltage Regulation............................................................................................ 122 4.3.4 Circuit Breaker/Recloser Bypass Facilities ......................................................... 123 4.3.5 Surge Arresters ................................................................................................ 124 4.3.6 Enclosed Equipment.......................................................................................... 124 4.4 TRANSMISSION SUBSTATIONS ................................................................................ 125 4.4.1 Basic Transmission Substation ........................................................................... 125 4.4.2 Circuit Breaker Bypass Facilities ....................................................................... 126 4.4.3 Surge Arresters ................................................................................................ 126 4.4.4 Carrier Equipment............................................................................................. 127 4.4.5 Voltage Transformers ....................................................................................... 127 4.4.6 Current Transformers ....................................................................................... 127 4.4.7 Grounding Switches .......................................................................................... 127 4.5 SWITCHING STATIONS .............................................................................................. 127 4.5.1 Basic Switching Substation ................................................................................ 128
  6. 6. Bulletin 1724E-300 Page 7 4.5.2 Surge Arresters ................................................................................................ 128 4.6 TYPICAL BUS CONFIGURATIONS............................................................................ 128 4.6.1 Single Bus ........................................................................................................ 129 4.6.2 Sectionalized Bus .............................................................................................. 132 4.6.3 Main and Transfer Bus ..................................................................................... 133 4.6.4 Ring Bus .......................................................................................................... 136 4.6.5 Breaker-and-a-Half .......................................................................................... 139 4.6.6 Double Breaker–Double Bus ............................................................................. 139 4.6.7 Relative Switching Scheme Costs ...................................................................... 141 4.7 PROTECTION OF SUBSTATION INSULATION......................................................... 142 4.7.1 General............................................................................................................ 142 4.7.2 Surge Protection ............................................................................................... 142 4.7.3 Direct Stroke Protection.................................................................................... 142 4.8 SUBSTATION INSULATORS....................................................................................... 146 4.8.1 Outdoor Apparatus Insulators ............................................................................ 146 4.8.2 Suspension Insulators ........................................................................................ 151 4.9 ELECTRICAL CLEARANCES...................................................................................... 153 4.10 BARE CONDUCTORS.................................................................................................. 157 4.10.1 Conductor Materials.......................................................................................... 157 4.10.2 Rigid Conductors .............................................................................................. 157 4.10.3 Flexible Conductors........................................................................................... 159 4.10.4 Conductor Ampacity ......................................................................................... 160 4.10.5 Bus Connections ............................................................................................... 160 4.11 RIGID BUS DESIGN ..................................................................................................... 163 4.11.1 General Considerations...................................................................................... 163 4.11.2 Procedure for Rigid Bus Design......................................................................... 164 4.11.3 Bus Design Example ......................................................................................... 171 4.12 STRAIN BUS DESIGN .................................................................................................. 176 4.12.1 General Considerations...................................................................................... 176 4.12.2 Procedure for Strain Bus Design........................................................................ 177 4.13 APPLICATION OF MOBILE TRANSFORMERS AND SUBSTATIONS...................... 184 4.13.1 Size and Maneuverability of the Equipment......................................................... 185 4.13.2 Installation Location and Provisions .................................................................... 185 4.13.3 Electrical Clearances ........................................................................................ 185 4.13.4 Primary and Secondary Connections .................................................................. 185 4.13.5 Grounding......................................................................................................... 186 4.13.6 Auxiliary System Requirements ......................................................................... 186 4.13.7 Safety................................................................................................................. 186 4.14 REFERENCES............................................................................................................... 186 4.15 LEGEND FOR EQUATIONS......................................................................................... 188CHAPTER 5 - MAJOR EQUIPMENT........................................................................................... 191 5.1 GENERAL..................................................................................................................... 191 5.2 POWER TRANSFORMERS .......................................................................................... 191 5.2.1 General............................................................................................................ 191 5.2.2 Types............................................................................................................... 192 5.2.3 Ratings............................................................................................................. 193
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Bulletin 1724E-300Page 8 5.2.4 Taps ................................................................................................................ 200 5.2.5 Impedance ....................................................................................................... 201 5.2.6 Phase Relation.................................................................................................. 201 5.2.7 Parallel Operation of Transformers .................................................................... 202 5.2.8 Dielectric Requirements .................................................................................... 204 5.2.9 Short-Circuit Requirements................................................................................ 207 5.2.10 Cooling Equipment............................................................................................ 209 5.2.11 Oil and Oil Preservation Equipment.................................................................... 210 5.2.12 Audible Sound .................................................................................................. 210 5.2.13 Tank ................................................................................................................ 214 5.2.14 Accessories...................................................................................................... 214 5.2.15 Electrical Tests and Measurements.................................................................... 214 5.2.16 Shipment .......................................................................................................... 216 5.2.17 Warranty.......................................................................................................... 216 5.2.18 Core and Coils .................................................................................................. 216 5.2.19 Specifications ................................................................................................... 217 5.2.20 References....................................................................................................... 217 5.3 POWER CIRCUIT BREAKERS .................................................................................... 219 5.3.1 General............................................................................................................ 219 5.3.2 Types of Circuit Breakers ................................................................................. 221 5.3.3 Ratings............................................................................................................. 226 5.3.4 Operating Mechanisms...................................................................................... 238 5.3.5 Tests................................................................................................................ 242 5.3.6 Control and Auxiliary Power Requirements ........................................................ 244 5.3.7 Purchase Evaluation.......................................................................................... 244 5.3.8 Shipment and Installation ................................................................................... 244 5.3.9 References....................................................................................................... 244 5.4 METAL-CLAD SWITCHGEAR..................................................................................... 245 5.4.1 General............................................................................................................ 245 5.4.2 Types............................................................................................................... 246 5.4.3 Ratings............................................................................................................. 249 5.4.4 Purchase Considerations ................................................................................... 250 5.4.5 References....................................................................................................... 252 5.5 SUBSTATION VOLTAGE REGULATORS................................................................... 252 5.5.1 General............................................................................................................ 252 5.5.2 Types............................................................................................................... 253 5.5.3 Ratings............................................................................................................. 254 5.5.4 Regulator Controls ............................................................................................ 261 5.5.5 Lightning Protection .......................................................................................... 262 5.5.6 References....................................................................................................... 262 5.6 SHUNT CAPACITOR EQUIPMENT ............................................................................ 262 5.6.1 General............................................................................................................ 262 5.6.2 System Considerations ...................................................................................... 263 5.6.3 Types............................................................................................................... 267 5.6.4 Bank Configuration ........................................................................................... 268 5.6.5 Ratings............................................................................................................. 269 5.6.6 Switching ......................................................................................................... 271
  8. 8. Bulletin 1724E-300 Page 9 5.6.7 Protection......................................................................................................... 280 5.6.8 Grounding and Short-Circuiting of Capacitor Banks ............................................. 285 5.6.9 Mounting.......................................................................................................... 285 5.6.10 Factory Tests ................................................................................................... 288 5.6.11 Inspection and Maintenance .............................................................................. 288 5.6.12 Typical Technical Specification.......................................................................... 288 5.6.13 References....................................................................................................... 2975.7 AIR SWITCHES ............................................................................................................ 298 5.7.1 General............................................................................................................ 298 5.7.2 Types of Air Switches....................................................................................... 299 5.7.3 Various Constructions of Outdoor Air Switches .................................................. 301 5.7.4 Usual Service Conditions ................................................................................... 308 5.7.5 Ratings............................................................................................................. 308 5.7.6 Other Requirements.......................................................................................... 312 5.7.7 Mounting Considerations ................................................................................... 322 5.7.8 References....................................................................................................... 3235.8 SURGE ARRESTERS .................................................................................................... 323 5.8.1 General............................................................................................................ 323 5.8.2 Classification of Arresters ................................................................................. 324 5.8.3 Ratings (Standard Definitions) ........................................................................... 332 5.8.4 System Voltage ................................................................................................ 333 5.8.5 Grounded vs. Ungrounded Systems .................................................................... 333 5.8.6 Application Guide for Silicon-Carbide Valve Arresters ........................................ 334 5.8.7 Application Guide for Metal Oxide Surge Arresters............................................. 342 5.8.8 Location........................................................................................................... 352 5.8.9 Protection at Line Entrances.............................................................................. 356 5.8.10 References....................................................................................................... 3575.9 AUTOMATIC CIRCUIT RECLOSERS.......................................................................... 357 5.9.1 General............................................................................................................ 357 5.9.2 Recloser Classifying Features............................................................................ 361 5.9.3 Recloser Ratings............................................................................................... 363 5.9.4 Construction ..................................................................................................... 371 5.9.5 Recloser Operation ........................................................................................... 373 5.9.6 Maintenance and Inspection .............................................................................. 375 5.9.7 Mounting.......................................................................................................... 376 5.9.8 References....................................................................................................... 3765.10 INSTRUMENT TRANSFORMERS................................................................................ 377 5.10.1 General............................................................................................................ 377 5.10.2 Service Conditions ............................................................................................ 377 5.10.3 Accuracy......................................................................................................... 379 5.10.4 Secondary Burdens ........................................................................................... 381 5.10.5 Construction ..................................................................................................... 381 5.10.6 Current Transformers ....................................................................................... 382 5.10.7 Voltage Transformers ....................................................................................... 389 5.10.8 Combination Units............................................................................................. 398 5.10.9 Tests................................................................................................................ 399 5.10.10 References....................................................................................................... 399
  9. 9. Bulletin 1724E-300Page 10 5.11 COUPLING CAPACITORS AND COUPLING CAPACITOR VOLTAGE TRANSFORMERS......................................................................................................... 400 5.11.1 General............................................................................................................ 400 5.11.2 Coupling Capacitors .......................................................................................... 400 5.11.3 Coupling Capacitor Voltage Transformers .......................................................... 401 5.11.4 Service Conditions ............................................................................................ 404 5.11.5 Ratings............................................................................................................. 404 5.11.6 Tests................................................................................................................ 408 5.11.7 References....................................................................................................... 408 5.12 MOBILE UNITS............................................................................................................ 409 5.12.1 Feasibility ......................................................................................................... 409 5.12.2 Mobile Transformers......................................................................................... 409 5.12.3 Mobile Substations ............................................................................................ 410 5.12.4 Phase Rotation Indicators.................................................................................. 410 5.12.5 Other Considerations......................................................................................... 410 5.12.6 Accessories Included with the Mobile Unit ......................................................... 412CHAPTER 6 - SITE DESIGN ........................................................................................................ 413 6.1 GENERAL..................................................................................................................... 413 6.2 TYPES OF GRADED YARDS....................................................................................... 413 6.2.1 Flat Yards ........................................................................................................ 414 6.2.2 Sloped Yards .................................................................................................... 414 6.2.3 Stepped Yards (Two or More Levels)................................................................ 414 6.3 PRELIMINARY REQUIREMENTS............................................................................... 414 6.4 DRAINAGE CONSIDERATIONS................................................................................. 415 6.4.1 Stormwater Management .................................................................................. 415 6.4.2 Surface Drainage System.................................................................................. 415 6.4.3 Closed Drainage System ................................................................................... 415 6.4.4 Planning ........................................................................................................... 415 6.4.5 Design ............................................................................................................. 415 6.5 EARTHWORK CONSIDERATIONS AND DESIGN ..................................................... 419 6.5.1 Borrow ............................................................................................................ 419 6.5.2 Topsoil............................................................................................................. 419 6.5.3 Cut and Fill....................................................................................................... 421 6.5.4 Compaction ...................................................................................................... 421 6.5.5 Cleanup............................................................................................................ 422 6.6 ROADS AND OTHER ACCESS.................................................................................... 422 6.6.1 General Access Roads ...................................................................................... 422 6.6.2 Grade............................................................................................................... 422 6.6.3 Curvature......................................................................................................... 422 6.6.4 Design ............................................................................................................. 422 6.6.5 Railroad Spur.................................................................................................... 422 6.6.6 Roadways in the Substation Yard....................................................................... 423 6.7 EROSION PROTECTION ............................................................................................. 423 6.7.1 General............................................................................................................ 423 6.7.2 Legal Requirements .......................................................................................... 423 6.8 YARD SURFACING MATERIAL ................................................................................. 423
  10. 10. Bulletin 1724E-300 Page 11 6.9 SECURITY FENCE ....................................................................................................... 424 6.10 REFERENCES .............................................................................................................. 424 APPENDIX C—SAMPLE SUBSTATION SECURITY FENCE SPECIFICATION.................. 426CHAPTER 7 - STRUCTURES....................................................................................................... 431 7.1 MATERIALS................................................................................................................. 431 7.1.1 Steel................................................................................................................ 431 7.1.2 Aluminum......................................................................................................... 431 7.1.3 Concrete .......................................................................................................... 432 7.1.4 Wood............................................................................................................... 432 7.2 FUNCTIONAL STRUCTURE TYPES........................................................................... 432 7.2.1 Line Support Structures..................................................................................... 432 7.2.2 Equipment Support Structures............................................................................ 432 7.2.3 Distribution Substation Structure ........................................................................ 433 7.3 STRUCTURE MEMBER TYPES................................................................................... 433 7.3.1 Lattice ............................................................................................................. 433 7.3.2 Solid Profile ...................................................................................................... 433 7.3.3 Semi-Solid Profile ............................................................................................. 434 7.3.4 Summary.......................................................................................................... 434 7.4 DESIGN ........................................................................................................................ 434 7.4.1 Design Loads ................................................................................................... 434 7.4.2 Line Support Structures..................................................................................... 434 7.4.3 Deflection Consideration ................................................................................... 435 7.4.4 Lightning Masts ................................................................................................ 436 7.4.5 Equipment Support Structures............................................................................ 436 7.4.6 Base Condition ................................................................................................. 436 7.4.7 Seismic Loads .................................................................................................. 437 7.4.8 Wind Loads ...................................................................................................... 439 7.4.9 Construction Loading ........................................................................................ 440 7.4.10 Loading Combination for Design ........................................................................ 441 7.4.11 Typical Design Approach.................................................................................. 441 7.5 FASTENERS ................................................................................................................. 450 7.5.1 ASTM A394 .................................................................................................... 450 7.5.2 ASTM A307 .................................................................................................... 450 7.5.3 ASTM A325 .................................................................................................... 450 7.6 WELDING..................................................................................................................... 452 7.7 FINISHES...................................................................................................................... 452 7.7.1 Galvanizing....................................................................................................... 452 7.7.2 Painting............................................................................................................ 452 7.7.3 Wood Preservatives.......................................................................................... 453 7.8 COMPUTER PROGRAMS ............................................................................................ 453 7.8.1 Model Geometry............................................................................................... 453 7.8.2 Load Input........................................................................................................ 454 7.8.3 Computer Output .............................................................................................. 454 7.9 REFERENCES ................................................................................................................ 455 APPENDIX D—RISA-3D INPUT AND OUTPUT FOR A SIMPLE “T” STRUCTURE.......... 458
  11. 11. Bulletin 1724E-300Page 12CHAPTER 8 - FOUNDATIONS.................................................................................................... 465 8.1 GENERAL..................................................................................................................... 465 8.2 SOIL INFORMATION................................................................................................... 465 8.2.1 General............................................................................................................ 465 8.2.2 Soil Classification.............................................................................................. 466 8.2.3 Bearing Values................................................................................................. 466 8.2.4 Groundwater Level........................................................................................... 467 8.2.5 Differential Settlement ...................................................................................... 467 8.2.6 Chemical Tests................................................................................................. 468 8.2.7 Seismic Evaluation ............................................................................................ 468 8.3 FOUNDATION TYPES................................................................................................. 468 8.3.1 Drilled Shafts (Piers)......................................................................................... 468 8.3.2 Drilled Shaft Design.......................................................................................... 469 8.3.3 Drilled Shaft Design (Line Support Structure) ..................................................... 475 8.3.4 Compression and Uplift Capacity (Drilled Shafts)................................................ 478 8.3.5 Spread Footings ................................................................................................ 482 8.3.6 Slabs on Grade ................................................................................................. 489 8.4 OIL POLLUTION.......................................................................................................... 492 8.4.1 Basic Retention System..................................................................................... 493 8.4.2 Oil Separator Tank............................................................................................ 493 8.4.3 Summary.......................................................................................................... 494 8.5 REFERENCES ............................................................................................................... 494 APPENDIX E—SPECIFICATION FOR PROCURING GEOTECHNICAL SUBSURFACE INVESTIGATION.......................................................................................... 497CHAPTER 9 - GROUNDING........................................................................................................ 501 9.1 GENERAL..................................................................................................................... 501 9.2 DEFINITIONS............................................................................................................... 503 9.2.1 DC Offset........................................................................................................ 503 9.2.2 Earth Current ................................................................................................... 503 9.2.3 Ground Fault Current ........................................................................................ 503 9.2.4 Ground Potential Rise (GPR)............................................................................. 503 9.2.5 Mesh Voltage ................................................................................................... 503 9.2.6 Soil Resistivity .................................................................................................. 503 9.2.7 Step Voltage..................................................................................................... 503 9.2.8 Touch Voltage .................................................................................................. 503 9.2.9 Transferred Voltage.......................................................................................... 503 9.3 SOIL RESISTIVITY MEASUREMENTS ....................................................................... 504 9.3.1 Analyzing Soil Resistivity Measurements ............................................................ 505 9.3.2 Uniform Soil Assumption................................................................................... 506 9.4 AREA OF THE GROUND GRID................................................................................... 506 9.5 GROUND FAULT CURRENTS..................................................................................... 506 9.5.1 Symmetrical Grid Current.................................................................................. 510 9.5.2 Determine the Split Factor, Sf............................................................................. 510 9.5.3 The Decrement Factor, Df................................................................................. 533 9.5.4 Maximum Grid Current ..................................................................................... 534 9.5.5 Asymmetrical Fault ........................................................................................... 534
  12. 12. Bulletin 1724E-300 Page 13 9.6 GROUND CONDUCTOR.............................................................................................. 535 9.6.1 Conductor Material........................................................................................... 535 9.6.2 Ground Conductor Sizing ................................................................................... 535 9.6.3 Sizing Equipment Ground Conductor................................................................... 536 9.6.4 Sizing Ground Grid Conductors .......................................................................... 537 9.6.5 Additional Conductor Sizing Factors ................................................................... 537 9.6.6 Connections from Equipment and Structures to Ground Grid ................................ 537 9.7 SAFETY CONSIDERATIONS....................................................................................... 538 9.7.1 Tolerable Limits of Body Current....................................................................... 539 9.7.2 Typical Shock Situations.................................................................................... 540 9.8 TOLERABLE TOUCH AND STEP VOLTAGES........................................................... 540 9.9 PROTECTIVE SURFACE MATERIAL AND REDUCTION FACTOR CS .................... 545 9.9.1 Reduction Factor Cs .......................................................................................... 546 9.10 DESIGN OF A SUBSTATION GROUNDING SYSTEM................................................ 548 9.10.1 General Concepts ............................................................................................. 548 9.10.2 Design Procedures............................................................................................ 548 9.10.3 Preliminary Design............................................................................................ 550 9.10.4 Calculate Design Mesh Voltage ......................................................................... 551 9.10.5 Step Voltage (Es).............................................................................................. 553 9.10.6 Ground Potential Rise (GPR)............................................................................. 554 9.10.7 Design Modifications......................................................................................... 555 9.10.8 Application of Equations for Em and Es ............................................................... 557 9.10.9 Use of Computer Analysis in Grid Design........................................................... 557 9.10.10 Special Danger Points ....................................................................................... 557 9.10.11 Investigation of Transferred Voltage .................................................................. 561 9.10.12 Effect of Sustained Ground Currents.................................................................. 562 9.11 REFERENCES............................................................................................................... 562CHAPTER 10 - INSULATED CABLES AND RACEWAYS......................................................... 563 10.1 GENERAL..................................................................................................................... 563 10.2 600-VOLT CABLE ........................................................................................................ 563 10.2.1 Circuit Requirements......................................................................................... 563 10.2.2 Conductors....................................................................................................... 564 10.2.3 Conductor Configurations .................................................................................. 564 10.2.4 Conductor Insulation and Jackets ....................................................................... 566 10.2.5 Cable Sizing...................................................................................................... 567 10.2.6 Segregation of Control Cables............................................................................ 567 10.2.7 Installation Considerations ................................................................................. 569 10.3 POWER CABLE OVER 600 VOLTS ............................................................................. 570 10.3.1 Medium-Voltage Shielded Power Cable (2 kV up to 35 kV) ................................ 570 10.3.2 Conductors....................................................................................................... 570 10.3.3 Conductor Shield............................................................................................... 570 10.3.4 Insulation.......................................................................................................... 571 10.3.5 Insulation Shield................................................................................................ 571 10.3.6 Jackets............................................................................................................. 571 10.3.7 Cable Voltage Rating ........................................................................................ 572 10.3.8 Conductor Sizing............................................................................................... 572
  13. 13. Bulletin 1724E-300Page 14 10.3.9 Terminations and Splices ................................................................................... 573 10.3.10 Cable Segregation............................................................................................. 573 10.3.11 Installation Considerations ................................................................................. 573 10.3.12 High-Voltage Power Cable (69 kV up to 230 kV) ............................................... 574 10.4 SPECIALIZED CABLE ................................................................................................. 574 10.5 RACEWAYS................................................................................................................. 575 10.5.1 Function ........................................................................................................... 575 10.5.2 Economics........................................................................................................ 575 10.6 UNDERGROUND RACEWAYS................................................................................... 576 10.6.1 Direct-Buried Cable .......................................................................................... 576 10.6.2 Direct-Buried Conduit ....................................................................................... 577 10.6.3 Concrete-Encased Conduit (Duct Bank)............................................................. 578 10.6.4 Cable Trenches ................................................................................................ 582 10.6.5 Manholes ......................................................................................................... 584 10.6.6 Handholes ........................................................................................................ 584 10.7 RACEWAY COMBINATION ....................................................................................... 585 10.8 SUMMARY—UNDERGROUND RACEWAYS............................................................ 586 10.9 OVERHEAD RACEWAYS ........................................................................................... 586 10.9.1 Cable Trays...................................................................................................... 587 10.9.2 Cable Duct....................................................................................................... 587 10.9.3 Plastic Conduit.................................................................................................. 587 10.9.4 Metal Conduit ................................................................................................... 587 10.9.5 Above-Grade Cable Trench............................................................................... 588 10.10 SUMMARY—OVERHEAD RACEWAYS .................................................................... 588 10.11 RACEWAY MATERIALS............................................................................................. 588 10.11.1 Plastic .............................................................................................................. 588 10.11.2 Fiber ................................................................................................................ 588 10.12 RACEWAY SIZING...................................................................................................... 588 10.13 REFERENCES............................................................................................................... 589CHAPTER 11 - CORROSION....................................................................................................... 591 11.1 GENERAL..................................................................................................................... 591 11.1.1 Characteristics of Corrosion .............................................................................. 591 11.1.2 Dissimilar Metals .............................................................................................. 591 11.1.3 Dissimilar Environments .................................................................................... 592 11.2 PRELIMINARY PREVENTIVE MEASURES ............................................................... 593 11.2.1 Surveys ............................................................................................................ 593 11.2.2 Selection of Materials........................................................................................ 594 11.3 TESTING AND INSTALLATION ................................................................................. 595 11.3.1 Earth Resistivity Measurements......................................................................... 595 11.3.2 Soil Samples ..................................................................................................... 595 11.3.3 Anode Locations............................................................................................... 595 11.3.4 Underground Connections ................................................................................. 595 11.3.5 Estimating Corrosion Conditions from DC Potential Measurements ...................... 595 11.4 REFERENCES............................................................................................................... 598
  14. 14. Bulletin 1724E-300 Page 15CHAPTER 12 - PROTECTIVE RELAYING.................................................................................. 601 12.1 GENERAL..................................................................................................................... 601 12.1.1 Purpose of Protective Relays............................................................................. 601 12.1.2 Design Objectives............................................................................................. 601 12.1.3 Indications of Defective Equipment or Abnormal Conditions ................................ 601 12.2 FUNDAMENTAL CONSIDERATIONS........................................................................ 603 12.2.1 Phasors............................................................................................................ 603 12.2.2 Polarity ............................................................................................................ 603 12.2.3 Faults............................................................................................................... 603 12.2.4 Symmetrical Components .................................................................................. 604 12.2.5 Relay Input Sources.......................................................................................... 604 12.3 BASIC RELAY TYPES ................................................................................................. 604 12.3.1 General............................................................................................................ 604 12.3.2 Relay Selection................................................................................................. 607 12.3.3 Overcurrent Relay............................................................................................ 609 12.3.4 Distance Relay................................................................................................. 609 12.3.5 Differential Relay ............................................................................................. 611 12.3.6 Overvoltage Relay............................................................................................ 612 12.3.7 Undervoltage Relay .......................................................................................... 612 12.3.8 Power Relay .................................................................................................... 612 12.3.9 Directional Overcurrent Relay........................................................................... 612 12.3.10 Frequency Relay............................................................................................... 612 12.3.11 Thermal Relay.................................................................................................. 613 12.3.12 Pressure Relay................................................................................................. 613 12.3.13 Auxiliary Relay................................................................................................. 613 12.4 RELAY SCHEMES........................................................................................................ 613 12.4.1 General............................................................................................................ 613 12.4.2 Transmission Line Protection............................................................................. 614 12.4.3 Distribution Feeder............................................................................................ 624 12.4.4 Major Equipment .............................................................................................. 626 12.4.5 Reclosing ......................................................................................................... 631 12.4.6 Coordination ..................................................................................................... 633 12.5 REFERENCES.............................................................................................................. 635 APPENDIX F—STANDARD DEVICE FUNCTION NUMBERS............................................ 637 APPENDIX G—SUGGESTED SUFFIX LETTERS .................................................................. 646CHAPTER 13 - INSTRUMENTS, TRANSDUCERS, AND METERS ............................................ 651 13.1 INTRODUCTION.......................................................................................................... 651 13.2 INSTRUMENTS AND TRANSDUCERS....................................................................... 651 13.2.1 Definitions........................................................................................................ 651 13.2.2 Types of Instruments and Transducers............................................................... 651 13.2.3 Classification of Instruments.............................................................................. 651 13.2.4 Components of Instruments and Transducers...................................................... 651 13.2.5 Analog Instrument Scales.................................................................................. 652 13.2.6 Operating Procedures ....................................................................................... 653 13.3 METERS........................................................................................................................ 654 13.3.1 Definition ......................................................................................................... 654
  15. 15. Bulletin 1724E-300Page 16 13.3.2 Types of Electric Meters................................................................................... 654 13.3.3 Demand Meter ................................................................................................. 654 13.3.4 Combination Watt-Hour and Demand Meters ..................................................... 655 13.3.5 Types of Meter Indicating and Recording Devices .............................................. 655 13.3.6 Connection of Watt-Hour and VAR-Hour Meters............................................... 656 13.4 MULTI-FUNCTION METERS....................................................................................... 657 13.4.1 Definition ......................................................................................................... 657 13.4.2 Input Quantities ................................................................................................ 658 13.4.3 Measured and Calculated Values....................................................................... 658 13.4.4 Communications ............................................................................................... 658 13.5 REFERENCES............................................................................................................... 658CHAPTER 14 - SUBSTATION AUTOMATION........................................................................... 659 14.1 INTRODUCTION.......................................................................................................... 659 14.2 OPEN VS. PROPRIETARY SYSTEMS......................................................................... 659 14.3 SUBSTATION AUTOMATION ARCHITECTURE....................................................... 660 14.4 DATA ACQUISITION AND CONTROL ELEMENTS .................................................. 660 14.4.1 Substation Host Processor ................................................................................. 661 14.4.2 Intelligent Electronic Devices............................................................................. 663 14.4.3 Programmable Logic Controllers........................................................................ 664 14.4.4 Data Concentrator ............................................................................................ 665 14.4.5 Substation Local Area Network......................................................................... 665 14.4.6 Communication Protocols .................................................................................. 666 14.5 REFERENCES............................................................................................................... 669 APPENDIX H—GLOSSARY OF TERMS............................................................................... 671CHAPTER 15 - AC AND DC AUXILIARY SYSTEMS................................................................. 673 15.1 AC AUXILIARY SYSTEM............................................................................................ 673 15.1.1 Typical Loads Supplied...................................................................................... 673 15.1.2 Design Requirements ........................................................................................ 673 15.1.3 Equipment ........................................................................................................ 678 15.1.4 Summary.......................................................................................................... 680 15.2 DC AUXILIARY SYSTEM............................................................................................ 680 15.2.1 Typical Loads Supplied...................................................................................... 680 15.2.2 Design Requirements ........................................................................................ 681 15.2.3 Types of Cells .................................................................................................. 681 15.2.4 Typical Loads and Duty Cycle ........................................................................... 682 15.2.5 Equipment ........................................................................................................ 683 15.3 REFERENCES............................................................................................................... 686CHAPTER 16 - CONTROL HOUSES ........................................................................................... 689 16.1 INTRODUCTION.......................................................................................................... 689 16.2 CONTROL HOUSE CONSTRUCTION......................................................................... 689 16.2.1 Foundation........................................................................................................ 689 16.2.2 Floor ................................................................................................................ 689 16.2.3 Superstructure .................................................................................................. 690 16.3 CONTROL HOUSE LAYOUT ...................................................................................... 692
  16. 16. Bulletin 1724E-300 Page 17 16.3.1 Control and Relay Panels .................................................................................. 692 16.3.2 DC Equipment.................................................................................................. 695 16.3.3 AC Equipment.................................................................................................. 695 16.3.4 Cableways ....................................................................................................... 695 16.3.5 Cable Entrance................................................................................................. 696 16.3.6 Lighting............................................................................................................ 697 16.3.7 Control House HVAC Systems ......................................................................... 697 16.3.8 Control House Plumbing.................................................................................... 698 16.3.9 Communications ............................................................................................... 698 16.4 REFERENCES............................................................................................................... 698CHAPTER 17 - COMMUNICATIONS.......................................................................................... 699 17.1 INTRODUCTION.......................................................................................................... 699 17.2 APPLICATIONS........................................................................................................... 699 17.2.1 Relaying........................................................................................................... 699 17.2.2 SCADA........................................................................................................... 699 17.2.3 Telemetering .................................................................................................... 700 17.2.4 Voice............................................................................................................... 700 17.3 METHODS.................................................................................................................... 700 17.3.1 Power Line Carrier........................................................................................... 700 17.3.2 Audio Tone ...................................................................................................... 705 17.3.3 Carrier or Audio Tone on Shield Wire ................................................................ 706 17.3.4 Microwave ....................................................................................................... 706 17.3.5 Optical Fiber..................................................................................................... 709 17.3.6 Wire Lines ....................................................................................................... 711 17.3.7 Satellite Communications ................................................................................... 712 17.4 REFERENCES............................................................................................................... 714 APPENDIX I—GLOSSARY OF TERMS ................................................................................ 715CHAPTER 18 - INSPECTION....................................................................................................... 717 18.1 PURPOSE ..................................................................................................................... 717 18.2 GENERAL..................................................................................................................... 717 18.2.1 Records ........................................................................................................... 717 18.2.2 Safety .............................................................................................................. 717 18.3 PERIODIC INSPECTIONS............................................................................................ 718 18.3.1 Visual Inspections ............................................................................................. 719 18.3.2 Inspection with Diagnostic Online Test Equipment .............................................. 723 18.3.3 Detailed Inspection of Major Equipment ............................................................. 726 18.3.4 Internal Inspection of Transformers and Regulators ............................................ 728 18.4 NON-PERIODIC INSPECTIONS.................................................................................. 729 18.4.1 Inspection of Porcelain ...................................................................................... 729 18.4.2 Fuses, Disconnects, and Other Switches............................................................. 730 18.4.3 Buses............................................................................................................... 730 18.4.4 Transformers.................................................................................................... 730 18.4.5 Transformer On-Load Tap Changers ................................................................. 730 18.4.6 Regulators........................................................................................................ 730 18.4.7 Oil Circuit Reclosers ......................................................................................... 730
  17. 17. Bulletin 1724E-300Page 18 18.4.8 Circuit Breakers ............................................................................................... 730 18.4.9 Grounding System............................................................................................. 730 18.4.10 Structures......................................................................................................... 730 18.5 REFERENCES............................................................................................................... 731CHAPTER 19 - TESTS.................................................................................................................. 733 19.1 GENERAL..................................................................................................................... 733 19.1.1 Records ........................................................................................................... 733 19.1.2 Safety .............................................................................................................. 733 19.2 DETAILED REQUIREMENTS...................................................................................... 734 19.2.1 Acceptance Tests............................................................................................. 734 19.2.2 Periodic Tests................................................................................................... 734 19.2.3 Tests After Failure............................................................................................ 734 19.3 DESCRIPTION OF TESTS ............................................................................................ 734 19.3.1 Insulation Resistance Test ................................................................................. 734 19.3.2 Power Factor Test............................................................................................ 737 19.3.3 DC High Potential Test ..................................................................................... 737 19.3.4 Dielectric Absorption Test................................................................................. 739 19.3.5 AC Over-Potential Test .................................................................................... 740 19.3.6 Contact Resistance Test.................................................................................... 740 19.3.7 Winding Resistance Test ................................................................................... 740 19.3.8 Insulating Oil Tests ........................................................................................... 741 19.3.9 Combustible Gas Analysis ................................................................................. 742 19.3.10 SF6 Gas Analyses ............................................................................................. 742 19.3.11 Timing Test ...................................................................................................... 742 19.3.12 Motion Analyzer Test........................................................................................ 743 19.3.13 Series Overcurrent Test .................................................................................... 743 19.3.14 Turns Ratio Test............................................................................................... 743 19.3.15 Polarity Test..................................................................................................... 743 19.3.16 Protective Relay System Tests .......................................................................... 743 19.3.17 Meter Calibration Tests..................................................................................... 744 19.3.18 Capacitance Test.............................................................................................. 744 19.3.19 Pressure Test ................................................................................................... 744 19.3.20 Ground Grid Resistance Measurement ............................................................... 745 19.4 REFERENCES............................................................................................................... 745CHAPTER 20 - MAINTENANCE ................................................................................................. 747 20.1 GENERAL..................................................................................................................... 747 20.1.1 Records ........................................................................................................... 747 20.1.2 Safety .............................................................................................................. 747 20.2 PERIODIC MAINTENANCE ........................................................................................ 747 20.2.1 Specific Requirements....................................................................................... 748 20.2.2 Painting............................................................................................................ 749 20.3 UNSCHEDULED MAINTENANCE.............................................................................. 750 20.4 RELIABILITY-CENTERED MAINTENANCE.............................................................. 751 20.4.1 Methods ........................................................................................................... 751 20.4.2 Application ....................................................................................................... 752
  18. 18. Bulletin 1724E-300 Page 19 20.4.3 Conclusion........................................................................................................ 754 20.5 REFERENCES............................................................................................................... 754CHAPTER 21 - UPRATING AND EXPANDING EXISTING SUBSTATIONS.............................. 755 21.1 APPLICABILITY.......................................................................................................... 755 21.2 FEASIBILITY................................................................................................................ 755 21.3 SUBSTATION UPRATING........................................................................................... 755 21.3.1 Major Equipment Uprating................................................................................. 756 21.4 SUBSTATION EXPANSION......................................................................................... 758 21.4.1 General............................................................................................................ 758 21.4.2 Site Work......................................................................................................... 760 21.4.3 Grounding......................................................................................................... 760 21.4.4 Raceway System.............................................................................................. 760 21.4.5 Control House .................................................................................................. 761 21.4.6 Equipment ........................................................................................................ 761 21.5 PLANNING FOR UPRATING OR EXPANSION .......................................................... 762 21.6 COMPARISONS—NEW VS. UPRATING OR EXPANSION........................................ 763 21.7 SUBSTATION UPGRADING........................................................................................ 763 21.8 REFERENCES............................................................................................................... 764
  19. 19. Bulletin 1724E-300Page 20 LIST OF FIGURESThese exhibits are available electronically as well as in hard copy.FIGURE TITLE2-1 Basic Wind Speed..................................................................................................... 482-2 Seismic Zone Map of the United States...................................................................... 503-1 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............................................................ 704-1 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 Bus—Low Profile ......................................................................................... 1304-10 Single Bus—High Profile ......................................................................................... 1314-11 Sectionalized Bus .................................................................................................... 1324-12 Main and Transfer Bus—Low Profile ...................................................................... 1344-13 Main and Transfer Bus—High Profile ...................................................................... 1354-14 Ring Bus ................................................................................................................ 1374-15 Breaker-and-a-Half ................................................................................................ 138
  20. 20. Bulletin 1724E-300 Page 21FIGURE TITLE4-16 Double Breaker–Double 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.............................................................................. 1805-1 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 Bank—Two 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 Connected.......................................................... 2755-18 A Complete Typical Capacitor Equipment Connected Grd Wye with Two Series Sections/Phase in a Single Stack.................................................................... 2765-19 Typical Internally and Externally Fused Capacitor Units ............................................ 2815-20 Capacitors Vertically Mounted................................................................................. 2865-21 Capacitors Horizontally Mounted ............................................................................. 2875-22 Horizontally Mounted Double-Break Switch with Grounding Switch........................... 3005-23 Horizontally Mounted Double-Break Switch ............................................................. 3005-24 Horizontally Mounted Vertical-Break Interrupter Switch ........................................... 3015-25 Vertically Mounted Vertical-Break Switch ............................................................... 3045-26 Tilting Insulator Switch............................................................................................ 3055-27 Single Side-Break Switch ........................................................................................ 3065-28 Underhung Center-Break V-Switch......................................................................... 3065-29 Hook Stick Switches on Structure at Termination of Bus from Transformer................ 3075-30 Vertical Reach Switch ............................................................................................ 307

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