Design guide for rural substations

764 Pages·9.971 MB·English

United States
Department of Design Guide for
Agriculture
Rural
Utilities Rural Substations
Service
RUS Bulletin
1724E-300
Issued
June 2001
(BLANK PAGE)
UNITED STATES DEPARTMENT OF AGRICULTURE
Rural Utilities Service
RUS BULLETIN 1724E-300
SUBJECT: Design Guide for Rural Substations
TO: All RUS Borrowers
RUS Electric Staff
EFFECTIVE DATE: Date of approval.
OFFICE OF PRIMARY INTEREST: Transmission Branch, Electric Staff Division.
INSTRUCTIONS: This bulletin is an update and revision of previous REA Bulletin 65-1, “Design
Guide for Rural Substations” (revised June 1978). Replace previous Bulletin 65-1 with this bulletin
and file with 7 CFR Part 1724.
AVAILABILITY: This bulletin is available on the Rural Utilities Service website at:
http://www.usda.gov/rus/electric
PURPOSE: This bulletin provides a basic design guide and a reference tool for designing rural
substations.
GENERAL: This Bulletin has been revised to bring the publication up to date with latest industry
standards, current RUS format, and technical requirements.
Our thanks to Cooperative Research Network of the National Rural Electric Cooperative Association,
(NRECA) which has supported this project, and it's consultant Burns & McDonnell Engineering
Company 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 in
preparing this document.
1. Bardwell, Jim, SGS Witter, Inc., Albuquerque, New Mexico
2. Chapman, George, Patterson & Dewar Engineers, Inc., Decatur, Georgia
3. Eskandary, Mike, USDA-RUS-ESD-TB, Washington, DC
4. Howard, Jerrod, Central Electric Power Co-op, Inc., Columbia, SC
5. Kahanek, Bil, Lower Colorado River Authority, Austin, TX
6. Myers, Tom, Berkeley Electric Co-op, Moncks Corner, SC
7. Malone, Ken, Middle Tennessee EMC, Murfreesboro, TN
8. Nicholson, Norris, USDA-RUS-ESD-TB, Washington, DC

Bulletin 1724E-300
Page 5
TABLE OF CONTENTS
ABBREVIATIONS AND ACRONYMS..........................................................................................31
CHAPTER 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.................................................................................................................40
CHAPTER 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.................................................................................................................52
CHAPTER 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
Bulletin 1724E-300
Page 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...........................................................................................117
CHAPTER 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
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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.........................................................................................188
CHAPTER 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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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
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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.......................................................................................................297
5.7 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.......................................................................................................323
5.8 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.......................................................................................................357
5.9 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.......................................................................................................376
5.10 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
Bulletin 1724E-300
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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.........................................................412
CHAPTER 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