ACI CODE-318-19106, 135, 144ACI PRC-201.2-23135A-frame dead-end structures10, 252Air core reactors. See current-limiting inductorsAir density factor (Q)34Air-insulated substations7, 252AISC. See American Institute of Steel ConstructionAISC 341-1650Allowable strength design (ASD)2, 76, 103Alloy 6061-T6106Alloy 6063-T5106Alloy 7075-T54106Aluminum Design Manual106, 108American Institute of Steel Construction (AISC)169AnalysisANSI/AISC 360-22, requirements in93–94approximate92ASCE 10-15, requirements in95ASCE 48-19, requirements in94definition89eigenvalue95–96first-order elastic92first-order inelastic93recommendation fordynamic analysis96–97seismic analysis96–97static analysis96response spectrum96second-order elastic92–93of short-circuit events97–102A-frames/jumper transitions, arrangements with100–102dynamic time-history model99–100joint fixity100rigid bus analysis methods98–100simplified static analysis99steady-state95stress criterion vs. deflection criterion89structure model89–91finite-element model91frame model90–91individual members and connections90loads and support conditions91truss model90Anchor materials147–149Anchor rod on leveling nuts design (example)216–217Anchor steel, design considerations for153–160anchor rods with base plate on concrete/grout154–155base plate supported by anchor rods with leveling nuts155–160ANSI/AISC 360-2292, 93–94, 104–105ANSI/AWC NDS-2015108ANSI O5.1-2017108, 185Application of loads73Approximate analysis92Arresters. See surge arrestersASCE 7-2233–34, 44, 52ASCE 7 Hazard Tools website44–45, 52ASCE 10-1595, 104ASCE 48-1994, 104–105ASCE 7433–34ASCE 123-12106ASCE MOP 141172ASD. See allowable strength designAspect ratio42, 266ASTM A123/A123M120Autotransformers13Ballistic walls195–196Barrier walls194–196ballistic walls195–196blast walls195–196firewalls194–195general194sound walls195Base plate design109–113anchor rod holes in112–113anchor rod loads, determination of111deflection-sensitive structures, base and flange plate design for113example217–218thickness, determination of111–112Biot–Savart law238 Blast walls195–196Box-type structures10Bus ducts25Bus-work system8, 252Cable bus system8, 252Cable terminators24, 26CC. See coupling capacitorCCVT. See coupling capacitor voltage transformerCIGRE Brochure 105: The Mechanical Effects of Short-Circuit Currents in Open Air Substations68Circuit breakers19–20Circuit breaker tank19–20Circuit switcher (load interrupter switch)18–19Class A structures82–84deflection limits of horizontal members in82–83deflection limits of vertical members in82–83Class B structures84deflection limits of horizontal members in84deflection limits of vertical members in83–84Class C structures85deflection limits of horizontal members in83, 85deflection limits of vertical members in84–85Combined footing foundation126Concrete, design considerations for160–162anchor rod embedment length160–161anchor spacing160capacity160concrete punch out from anchor rods161–162edge distance160localized bearing failure162Connections to foundations143–164Constructability137Construction175Construction loads70–71, 136Control enclosures27Corrosion132Coupling capacitor (CC)15Coupling capacitor voltage transformer (CCVT)15–17CTs. See current transformersCurrent-limiting inductors13–15Current transformers (CTs)21–22Dead-end structures9, 252A-frame10, 252H-frame10, 252load development for (example)211–216combined ice and wind213–214extreme wind212–213NESC district loading—heavy loading215–216Dead loads29Dead tank circuit breaker19–20Deep foundations127–128drilled shafts127–128pile foundations128Deflection analysis and criteria81–82horizontal members81–85special considerations for85–87anchorage and member connection restraints85–86gross vs. net deflections86–87multiple-use structures85rigid bus vertical deflection criteria87rotational limitation85shielding masts and other tall, slender structures86–87vertical members82–85Deflection (example)218–224three-phase bus support stand—class “B” structure218–220three-phase switch support stand, double column—class “A” structure222–224three-phase switch support stand, single column—class “A” structure220–222Deflection limitations, loading criteria for71–72ice with concurrent wind load for deflection calculations72other considerations72wind load for deflection calculations71–72Design103–123aluminum structures106–108allowable strength design according to IEEE 693,108applications to substation structures107bolted connections107limitation with aluminum substation structures107substation alloys and tempers106ultimate strength design108weldments107aluminum with dissimilar materials122–123concrete in contact with aluminum123steel in contact with aluminum122–123wood in contact with aluminum123base plate109–113anchor rod holes in112–113anchor rod loads, determination of111deflection-sensitive structures, base and flange plate design for113thickness, determination of111–112concrete structures105–106prestressed106prestressed concrete poles106reinforced106galvanizing steel considerations120general principles103guyed substation structures122magnetic fields of air core reactors, precautions regarding117–119member connection design120–122aluminum, welded connections in121bolted connections in steel120concrete structure connections121steel, welded connections in120–121wood structures, connections in122methods103painted/metallized steel considerations120rigid bus113–117aluminum in114aluminum shapes in114bolted-type fittings115bus layout configuration113composite116copper in114couplers115expansion fittings115fixed fittings115porcelain insulators115–116seismic considerations116–117slip fittings115system design116seismic design guidelines108–109structures not included in IEEE 693109structures support electrical equipment qualified for IEEE 693109spectral accelerations52steel structures104–105hollow tubular member shapes104–105lattice angle structures104local buckling of irregular polygonal shapes105standard structural shapes other than angles104vortex-induced oscillation and vibration119weathering steel structures122wood structures108allowable strength design108ultimate strength design108Design-level qualification63Direct embedded foundations128Disconnect switches16–18Distribution lines6Downdrag forces132Drilled pier foundations146Drilled shafts127–128DTHM. See dynamic time-history modelDynamic time-history model (DTHM)99–100Earthquakes48, 74Eigenvalue analysis95–96Electrical clearances8, 252Electromagnetic force variation with time238–243Embedded structural shapes147Equipment operating loads29–30Equivalent lateral force (ELF) procedure57–59horizontal distribution of seismic forces59rigid substation structures59vertical distribution of seismic forces59Excavations136–137Expansive/collapsible soils131–132Fabrication inspection168–169AISC169reports169test assembly169visual inspection168of welds168–169Fabricators28Finite-element analysis91Fire barriers27, 194–195Firewall. See fire barriersFirst-order elastic analysis92First-order inelastic analysis93Force coefficient (Cf)42–44lattice structure42–44Foundations125–141anchor arrangements and general design considerations149–152anchor rods with base plates on concrete or grout152base plates supported by anchor rods with leveling nuts151–152anchor materials147–149anchor rods installed without grout beneath base plates147anchors cast in place152–162anchor steel, design considerations for153–160concrete, design considerations for160–162deformed reinforcing bars153headed rods153hooked rods153combined footing126concrete for135connections to143–164deep127–128design considerations131–133corrosion132dynamic loads132–133expansive/collapsible soils131–132frost action131seismic loads132–133soil–structure interaction133direct embedded128drilled pier146drilled shafts127–128embedded structural shapes147geotechnical subsurface exploration129–131existing subsurface and geotechnical data129general129geotechnical report130other considerations131seismic considerations130site-specific subsurface exploration129–131soil borings130grade beams127helical screw anchor piles128loading considerations133–134load application133load combinations134mat126overview125pile128post-installed anchors in concrete162–164design163installation163–164types and application162–163shallow126–127special considerations135–141constructability137construction loads136deflection137–138grounding of substation equipment and structures138–139group effects136National Electrical Safety Council District Loading and Foundation Design140–141operational loads135rotation137–138seismic base isolation138–139settlement137–138slopes and excavations136–137uplift loads138spread footing126, 144–145Foundations and Earth Structures, NAVFAC DM 7.02125Frame model90–91Frost action131Full-scale structural proof tests176Gas-insulated substations (GISs)7–8, 252General cable theorem31–32Geotechnical subsurface exploration129–131existing subsurface and geotechnical data129general129geotechnical report130other considerations131seismic considerations130site-specific subsurface exploration129–131soil borings130GISs. See gas-insulated substationsGlaze ice44–48Grade beams127Group effects136Gust response factors (GSRF and GWRF)37–42Heavy Timber Construction (HTC)185Helical screw anchor piles128H-frame dead-end structures10, 252Horizontal members81–82Ice loads with concurrent wind44–48effects of icing event on structures47–48ice thickness variation with height48Ice with concurrent wind load for deflection calculations72IEC 60865-1: Short-Circuit Current – Calculation of Effects68IEEE 605: IEEE Guide for Bus Design in Air Insulated Substations68IEEE 6932, 30, 49–50, 52, 63–65, 109IEEE 980-2013193IEEE 1527-201830IEEE C37.0430IEEE C37.30.130IEEE C57.19.0130IEEE C57.19.10030Insulators24–26Joint fixity100Lightning mast12–13Line trap15–16Live tank breaker19–20Load and Resistance Factor Design (LRFD). See ultimate strength design (USD)Loadsallowable strength design (ASD) load combinations76alternate design78application of73basic loading conditions74construction and maintenance70–71dead29deflection limitations71–72equipment operating29–30factors and combinations73–78ice loads with concurrent wind44–48seismic48–67serviceability considerations78–79short-circuit (fault)9state and local regulatory72ultimate strength design (USD) load combinations75wind32–44wire tension30–32Maintenance136, 175–176Manual of Practice (MOP)1–3, 6, 8, 28–30, 35–44, 47, 49–50, 53–55, 57, 62Mat foundations126Maximum considered earthquake (MCE)49MCE. See maximum considered earthquake Mean recurrence interval (MRI) wind speed37Metalclad switchgear. See unit substationsMOP. See Manual of PracticeNational Electrical Safety Code Loads72, 103National Electrical Safety Council District Loading and Foundation Design140–141Natural Resources Conservation Service (NRCS)129Negative skin friction. See downdrag forcesNeutral grounding resistors23–24Ohm's law233Oil containment191–194berms and dikes193design considerations193–194general191–192oil absorbents193oil retention drainage193oil retention pit192oil solidifiers193self-extinguishing193substation mat192systems192Oil retention drainage193Operational loads135Owners28Pack out122PCI MNL-120 Design Handbook—Precast and Prestressed Concrete106P-delta amplification92Peak ground acceleration (PGA)49Peak ground velocity (PGV)49Performance-level qualification63PGA. See peak ground accelerationPGV. See peak ground velocityPhase-to-ground fault68Phase-to-phase fault68Pile foundations128Post-installed anchors in concrete162–164design163installation163–164types and application162–163Potential transformers (PTs)21Pothead. See cable terminatorsPower transformers13Pre-Standard for Substation Structure Design (draft)249–318applicable documents249–251barrier structure requirements301–313construction and maintenance317–318design of members294–301foundations313–316load cases and combinations for strength design252–256loads256–294purpose249quality assurance and control316–317scope249Prestressed concrete poles106Prestressed concrete structures106Prestressed Concrete Transmission Pole Structures: Recommended Practice for Design and Installation106PTs. See potential transformersQuality assurance/quality control (QA/QC) programs167–173aluminum structures170–171fabrication171inspection171material170structure coating171welding170–171concrete structures171–172inspection172prestressed concrete poles172reinforced concrete171handling and storage173shipping172–173steel structures168–170fabrication inspection168–169material168structure coating170welding168wood structures172fabrication172inspection172manufacturing172material and treatment172Recommended Practice for the Design and Use of Wood Pole Structures for Electrical Transmission Lines108Reinforced concrete structures106Response spectra (RS)49Response spectrum analysis96Retrofit of existing substation infrastructures179–190of anchorage183design considerations187–189environmental concerns185–186asbestos in existing substations185–186demolition activities186renovation activities186soil contamination in existing substations186galvanized structures184–185general179–180installation190methods for181–183painted structures184security and resilience of electrical substations186–187steel structures, considerations for183–184timber structures185types of structures for180–181weathering structures185Rigid bus analysis methods98–100Rigid bus system8, 252Rime ice48RS. See response spectraSecond-order elastic analysis92–93Seismic base isolation138–139Seismic design guidelines108–109structures not included in IEEE 693109structures support electrical equipment qualified for IEEE 693109Seismic design parameters245–248Seismic loads48–67anchorage design forces63–65equipment to structure64–65IEEE 69363–65basic effect61–62design response spectra52importance factors for55with overstrength factor62purpose and scope49–50seismic analysis55–60dynamic analysis procedure60equivalent lateral force procedure57–59selection of method55–57seismic deflection considerations63seismic demand on other components65seismic design coefficients/factors52–54seismic ground motion acceleration parameters50–52design spectral accelerations52site-specific ground motion procedures51–52vertical seismic load effect60–61on wire bus66–67Self-extinguishing oil containment193Series capacitors22, 24Serviceability78–79Shallow foundations126–127combined footing foundation126grade beams127mat foundations126spread footing foundation126Shielding mast11–12, 252Short-circuit current233–238Short-circuit events analysis97–102A-frames/jumper transitions, arrangements with100–102dynamic time-history model99–100joint fixity in100rigid bus analysis methods98–100simplified static analysis99Short-circuit (fault) loads9, 67–70, 252additional information70on equipment70on rigid conductors69–70on strain bus70to structures243Shunt capacitors21–23Shunt reactors13–14Slab foundation. See mat foundationsSlack-span tension30Slopes136–137Soil–structure interaction49Solidity ratio (Φ)43–44Sound walls195Spread footing foundations126, 144–145Square root of sum of squares (SRSS)60State and local regulatory loads72Steady-state analysis95Steel lattice rack-type structure, dynamic analysis of (example)224–231modal properties229–231overview224–228Strain bus conductor31Strain bus system8, 252Stress criterion vs. deflection criterion89Structure designer28Substation dead-end structures30Substations5–6, 252Sub-transmission6Suppliers28Surge arresters23, 25Switchyard/switching station5–6, 252Taps31Terminal connection loads for electrical equipment30Terminal connectors30Terrain exposure coefficient (Kz)34–37effective height (z37exposure categories35–36Three-phase bus support structure, load development for (example)199–211combined ice and wind loads202–203deflection case wind loads210–211extreme wind loads201–202insulator and bus fitting data201rigid bus data200–201seismic loads203–209short-circuit loads209–210structure data and geometry199–200 Three-phase fault68Transformers27Transmission lines6–7, 252Truss model90Ultimate strength design (USD)2, 75, 103United States Geological Survey (USGS)48Unit substations6, 252Uplift loads138USD. See ultimate strength designUS Geological Survey (USGS)129USGS. See United States Geological SurveyUSGS Relative Seismic Hazard map50Vertical members82Vertical seismic load effect60–61VIO. See vortex-induced oscillationVIV. See vortex-induced vibrationsVortex-induced oscillation (VIO)71Vortex-induced vibrations (VIV)86Wave trap. See line trapWind equation32–33Wind-induced oscillations71Wind loads (extreme)32–44air density factor (Q)34application of wind forces to structures44basic wind speed (VMRI)37for deflection calculations71–72equation32–33force coefficient (Cf)42–44lattice structure42–44gust response factors (GSRF and GWRF)37–42mean recurrence interval wind speed37terrain exposure coefficient (Kz)34–37effective height (z)37exposure categories35–36Wind shading/shielding44Wire tension loads30–32Worker safety176Working stress design. See allowable strength design (ASD)Yawed wind42Zero-tension condition105
