Guide for Design of Substation StructuresPrepared by Substation Structure Design Guide Subcommittee, of the Committee on Electrical Transmission Structures (CETS) DEFINITION INSIDE THE FENCE OUTSIDE THE FENCE Leon Kempner, Jr., Chair George T. Watson, Co-chair Wendelin H. Meuller, Secretary Reyes M. Barraza Martin L. de la Rosa Rulon Fronk Rodney N. Hutcherson Massoud Khavari Paul M. Legrand II William L. Magee Jean-Robert Pierre Wayne P. Schumm Albert J. Tharnish Terry G. Burley Harry V. Durden Jr. James M. Hogan Gary A. Johnston Steve M. Krohn Denis R. Lemelin Kenneth C. Malten Craig H. Riker David Tennent Chung J. Wong DOCUMENT HISTORY: Started in 1991 First Draft 1994 Projected Completion 2006 (Oct. 30 2006) The Committee Membership Represented • Utilities • Manufacturers • Consulting firms • Academic Institution • Research Institutions • General interest Individuals . P. Peabody Don Lott Elwood Treadwell Jake M. Clem Magdi F. E. Kramer Surrendar Menrai M. Calizar Lon C. Clayton Curt Hinkel Dan McIntyre Herman Kwan Carl Johnson . R. Peters Gino Stagliano Clayton L.PAST COMMITTEE MEMBERS AND OTHERS Richard X. Kazemi TS Spangenberg. King Mircea Iordanescu Tom Teevin M. R. Singh Alain Peyrot Brian C. Germann David Insinger Husein Hasan Peter Moskal Don Lott William J. Violette Alan J. Ishac Long Shan F. Jr David Ackermann Hank Page Subir Roy Brad Kemp Dale Beason OTHERS Rapheal O. Hamilton Joe Shepherd Jean-Bernard Dastous M.C. Koch Gary C. Shainauskas Brian Goplen Patrick A. Byrne Michael F. Kennedy M. Chan (Trudy) P. Spencer Jean-Robert Pierre Dick Standford J. Kozlowski Gary Engmann Alan B. Banat Steven Groom Don G. Heald Donald Laird Warren Crossman James T. Kescharvarzian Jerry Tang Bing C. BACKGROUND INFORMATION: 9 Comprehensive document for the design of outdoor Electrical Substation Structures 9 Specific guidelines for 4-kV and above 9 Reference Existing Design Codes and Standards . Rigid Bus Structures. z IEEE 605.” 1997 IEEE 693 addresses electrical equipment and its "first support” requirements. Latest Edition Draft 8 .Companion Documents: z IEEE 693 “Recommended Practice for Seismic Design of Substations. The Substation Structure Design Guide will reference IEEE 693 and provide seismic requirements for structures not covered by IEEE 693. First support could be a pedestal for a current transformer (CT) or a support beam for a capacitor bank. RUS/REA Bulletin 65-1.Existing Industry Design Guides: . 1984 .Western Area Power Admin. Rural Substations . Draft Doc. (Structures. Outdoor Substations.NEMA SG6.Company Design Guides . Pole-top Frames and Other Parameters) . Section 36.. Mills Jerry Tang.STATUS: Completed PEER Review Committee: Chair: Henry W. Ho Hanna Essa Abdallah. Level 1 comment: Represents a reviewer’s request to change the document per the reviewer’s submitted change (221/108) Level 2 is a reviewer’s general comment for the Substation Structure Design Guide subcommittee consideration (60/14) . Lynch William B. Alston Michael Brown Kamran Khan Otto J. Hay Yin Yu. Duane R. or sooner .STATUS: • Complete Editorial Review • Complete a companion Document Coordination Review (IEEE 693 and IEEE 605) • Ready for submittal to ASCE for publication • Should be available early next year. 2007. DEFLECTION CRITERIA 5. INTRODUCTION 2.CONTENTS: 1. ELECTRICAL EQUIPMENT & STRUCTURE TYPES 3. LOADING CRITERIA FOR SUBSTATION STRUCTURES 4. METHOD OF ANALYSIS . DESIGN (ASD and USD) STEEL WOOD CONCRETE ALUMINUM SEISMIC BASEPLATE RIGID BUS DESIGN SPECIAL DESIGN CONSIDERATIONS .6. 7. IEEE 691. the same as foundations designed for other structures. QUALITY CONTROL AND QUALITY ASSURANCE 9.” is one source of information regarding the design of utility type structure foundations. “Guide for Transmission Structure Foundation Design and Testing. TESTING 10. CONSTRUCTION AND MAINTENANCE . 8. CONNECTIONS TO FOUNDATIONS (NOT FOUNDATION DESIGN) Foundations in substations should be designed according to accepted practice. 9 (Testing). 7 (Connections to Foundations).WORKSHOP SCHEDULE: Three Sections with short breaks in between Session 1: Introduction.) and 2 (Structure/Equipment Types) Session 2: Chapters 3 (Loading). 8 (Quality Control/Assurance. and 10 (Construction and Maintenance) . Chapters 1 (Into. and 5 (Analysis) Session 3: Chapters 6 (Design). 4 (Deflections). INTRODUCTION .1. PARTS OF A SUBSTATION Parts of a substation can be grouped into several categories: (a) Site Related Facilities (b) Bus & Equipment “Outdoor” (c) Relay.) . metering. The control house contains protection. 125vdc. Metering. Control. and Communications (d) Control House In general. etc. in substations there is a site on which is located the major circuit bus and equipment as well as a control house. and communication equipment as well as equipment related to the ancillary power systems (station service. control. OUTDOOR The typical switchyard or substation contains the following components: (a) Bus (b) Outdoor Equipment Switching Power Transformers Instrument Transformers Reactive Power Compensation Lightning and Surge Protection (c) Grounding Grid (d) Conduit and/or Trench (e) Lighting. power distribution.BUS AND EQUIPMENT . and yard phone (f) Support Structures yard phone booth . Power Transformer .Communications Equipment . EHV/MV. A single substation may perform more than one of these functions: Types of Substations: .Substation Bus .Substations Attach to Power Stations .Step-down (EHV/HV.SUBSTATIONS The three functions of a transmission network are fulfilled through the different types of substations shown below.Control Protection and Monitoring Equipment .Interconnect substations .Switchgear . HV/MV) substations Basic Structure of a Substation: . circuit breakers.SUBSTATIONS IEEE DEFINITION (1) An area or group of equipment containing switches.) . and transformers for switching power circuits and to transform power from one voltage to another or to one system to another (ac/dc) (2) An assemblage of equipment for the purposes other than generation or utilization. and usually is either the sole receiving point of commonly for more than one supply circuit. buses. a multiplicity of circuit breakers. through which electric energy in bulk is passed for the purpose of switching or modifying its characteristics. or it sectionalizes the transmission circuits passing through it by means of circuit breakers. (A substation is of such size or complexity that it incorporates one or more buses. 2. ELECTRICAL EQUIPMENT & STRUCTURE TYPES PURPOSE DEFINITIONS ELECTRICAL EQUIPMENT AND SUPPORTS PHOTOGRAPHS . The foundations for the structures are included with the supports. Supports are also used to terminate outgoing transmission or distribution line conductors within the switchyard. and termination structures for overhead or underground transmission and distribution lines. surge arresters. bus support insulators.SUBSTATION DESIGN SUPPORT STRUCTURES Switchyard Support Structures: Switchyard supports provide support for the switchyard equipment and bus at the elevations needed to provide adequate electrical clearance from finish grade to the bus or equipment live parts. instrument transformers. The structures include the various stands for disconnect switches. . Typical Substation Structure Material Types LATTICE STEEL WOOD CONCRETE ALUMINUM STEEL TUBE BOX STRUCTURE TYPE OF CONSTRUCTION Box Structure: The box structure is generally applied at 138 kV and below. It requires the least amount of land area and utilizes layers of bus, disconnect switches and related equipment, one above the other, connected with vertical bus runs, and supported on a common structure. GAS INSULATED SUBSTATION CONSTRUCTION Gas Insulated: Gas insulated construction consists of completely enclosed buses and equipment insulated with SF6 gas. Because of the excellent insulating properties of this gas, very compact phase spacing. Gas insulated substations are generally installed for one or more of the following reasons: 1. Land area for the substation is extremely limited. 2. Environmental contamination is severe. 3. Site Environment, such as deep snow, etc. Since gas-insulated substations are shipped as factoryassembled units or modules, field erection time and cost are minimized. Live Tank PBC Rigid Bus Bushing Wave Trap Power Transf. PT . SUBSTATION Dead Tank PBC EQUIP. OUTDOOR EQUIPMENT Lightning Arrester Instrument Transf. Current Transf.Disconnect Sw. C ertain equ ip m e nt can sw itc h (co nnect o r disco n ne ct) norm a l le ve ls o f lo ad current w herea s other equ ip m e nt can o n ly be o perated if little o r no current is flo w ing. S o m e eq u ip m e nt used. such as the c ircu it breaker. are capable o f interru pting (d isco nne cting) the very large qu a nt it ies o f cu rrent asso c iated w ith fau lts. E q uip m e nt can be o perated electrica lly fro m a re m o te lo catio n o r can o nly be o perated m a nua lly at the equ ip m e nt lo catio n .SUBSTATION DESIGN OUTDOOR EQUIPMENT S w itch ing E qu ip m e nt-T he fu nct io n o f sw itc hing equ ip m e nt is to co nnect and d isco n nect e le m e nts o f the substatio n o r utilit y syste m fro m the rest o f the su bstatio n o r utilit y syste m . SUBSTATION DESIGN BUS Bus: The function of bus is to interconnect the high voltage portions of the various components of the switchyard to form the required bus configuration for the substation. The parts of a bus layout includes rigid or strain bus conductors. and the insulators that support the bus conductors. RIGID BUS FLEXIBLE BUS . the fittings used to connect the bus conductors to the switchyard equipment. Strain bus . SUBSTATION DESIGN OUTDOOR EQUIPMENT DISCONNECT SWITCH . SUBSTATION DESIGN OUTDOOR EQUIPMENT CIRCUIT BREAKER . SUBSTATION DESIGN OUTDOOR EQUIPMENT CIRCUIT SWITCHER . SUBSTATION DESIGN POWER TRANSFORMATION EQUIPMENT 500/230KV XFMR .SINGLE PHASE UNITS WITH SPARE . SUBSTATION DESIGN INSTRUMENT TRANSFORMERS CURRENT TRANSFORMER (CT) POTENTIAL TRANSFORMER (PT) . . coupling capacitor voltage transformers (CCVTs). The equipment can include potential transformers (PTs). and bushing current transformers (BCTs).SUBSTATION DESIGN INSTRUMENTATION TRANSFORMERS Instrument Transformers: The functions of instrument transformers is to provide low voltage or low current inputs that can be used with protective relays and metering equipment. These inputs are proportional to the voltage or current which exist in the substation buses or equipment. current transformers (CTs). SUBSTATION DESIGN POWER SYSTEM CONTROL: REACTIVE POWER EQUIPMENT SHUNT CAPACITOR BANK SHUNT REACTOR BANK . SUBSTATION DESIGN REACTIVE POWER EQUIPMENT Reactive Power Compensation Equipment: Large quantities of capacitive or reactive power are used for power factor improvement or voltage control. They limit fault current on buses or distribution lines, and supply low impedance tuned paths to ground for harmonic voltages (which are “nuisance” voltages occurring at frequencies above 60 hertz). The typical equipment used for reactive power compensation includes capacitor banks and reactors, installed individually or in combinations. Series Capacitors 9Used (typically at 230kV and above) to improve power transfer capability by compensating for voltage drop along a transmission line. 9If desired, load distribution between lines can be enhanced. 9Series capacitors can also force more power to flow over the line with larger conductors when parallel lines have different conductor sizes. SUBSTATION DESIGN LIGHTNING AND SURGE PROTECTION ROD GAPS LIGHTNING ARRESTOR and to protect the insulation system of the switchyard equipment from transient. . The equipment for lightning and surge protection include the shielding masts and wires installed within the switchyard. or from switching of the transmission system. These transient voltage waves can be caused by lightning strikes to the transmission or distribution lines. rod gaps. and the surge arresters installed within the switchyard.SUBSTATION DESIGN LIGHTNING AND SURGE PROTECTION Lightning and Surge Protection: The purpose of lightning and surge protection equipment is to protect the switchyard and control building from being struck by lightning. high voltages entering the substation from the transmission or distribution systems. TYPICAL SUBSTATION LAYOUT . SUBSTATION LAYOUT DIAGRAMS . SUBSTATION LAYOUT DIAGRAMS THREE PHASE ACTUAL ARRANGEMENT EQUIVALENT SINGLE LINE DIAGRAM . SUBSTATIONS TYPES OF SUBSTATIONS . SUBSTATIONS: Substation Types .Generating Station to transform generating voltage to network voltage . SUBSTATIONS: Substation Types .Transmission Switching Station to switch interconnect portions of the utility system . Transmission Substation which can step-down or step-up voltage to interconnect the network .SUBSTATIONS: Substation Types . SUBSTATIONS: Substation Types .Distribution Substation to step-down voltage to the distribution level . Isolate a faulted line or other component from the rest of the utility system .SUBSTATIONS: Substation Functions . SUBSTATIONS: Substation Functions .To step-up or step-down voltage levels . SUBSTATIONS: Substation Functions .To allow for maintenance of line or equipment . To allow for the addition of capacitors or reactors for electrical system control .SUBSTATIONS: Substation Functions . To allow for operational voltage. power and frequency measurements . current.SUBSTATIONS: Substation Functions . To allow control of power flows by switching lines in and out .SUBSTATIONS: Substation Functions . Analysis .SESSION 2: Chapter 3. Loading Chapter 4. Deflections Chapter 5. LOADING CRITERIA FOR SUBSTATION STRUCTURES • INTRODUCTION • BASIC LOADING CONDITIONS Dead Loads Equipment Operating Loads Wire Tension Loads Extreme Wind Loads Combined Ice and Wind Loads Earthquake Loads Short Circuit Loads Construction and Maintenance Loads Wind Induced Oscillations Deflection Loads NESC Loads State and Local Regulatory Loads • APPLICATION OF LOADS • LOAD FACTORS AND COMBINATIONS • ALTERNATE DESIGN LOADS AND LOAD FACTORS • SERVICEABILITY CONSIDERATIONS • EXAMPLES .3. Wind Wind Maps Maps ASCE 7-05 3 Second Gust . 5.5.2. Cf = Force Coefficient.2. defined in Section 3. GRF= Gust Response Factor (Structure and Wire). V = Basic Wind Speed.2. (0.3. (m/s) defined Section 3. 3-second gust wind speed. square feet (square meters). kz = Terrain Exposure Coefficient. defined in Section 3. defined in Section 3. pounds. IFW = Importance Factor.5. A = Projected wind surface area normal to the direction of wind.2.1.613 SI). default value = 0.2.4.5.5.6. (Newtons).5. defined in Section 3.F = Q kz V2 IFW GRF Cf A Where: F = Wind force in the direction of wind. . mph.2.5. defined in Section 3. Q = Air Density Factor.2.00256. 3-3) Where: ε = 0. Non-supporting Wire Structures. GSRF = 0. < 1 Hertz For Rigid.( G SRF = 1 + 3 .85 .00 Flexible Non-Wire Supporting Structures.5 )/ k v 2 (Eq.75 Wire Supporting Structures (Dead-end and Line Termination) ε = 1.6 (ε ) E S (B S ) 0 . GSRF.15 0.75 Height.0 Height.99 > 33 to 40 1.95 0.25 1.11 0.19 1.02 0.06 0. h (ft) Exposure B Exposure C Exposure D ≤ 15 1.Table 3-4a Structure Response Factor.12 0.80 Table 3-4b GSRF.84 > 40 to 50 1.83 > 60 to 70 1.48 1.03 0.20 1. ε = 0.00 0.96 > 40 to 50 1. Flexible Non-wire Supporting Structures.81 > 90 to 100 1.22 1.06 0.03 0.08 0.37 1. h (ft) Exposure B Exposure C Exposure D ≤ 33 1.15 0.94 0. ε = 1.94 > 60 to 70 1.91 > 90 to 100 1. Wire Supporting Structures.59 1.84 > 50 to 60 1.81 > 80 to 90 1.85 > 33 to 40 1.91 0.92 0.92 > 80 to 90 1.33 1.95 > 50 to 60 1.28 1.02 > 15 to 33 1.88 0.01 0.17 1.00 0. < 1Hertz.93 > 70 to 80 1.88 0.17 0.05 0.08 0.82 > 70 to 80 1.96 0.89 0.90 . Ice Ice Maps Maps ASCE 7-05 . Ice-sensitive structures are structures for which the load effects from atmospheric icing control the design of part or all of the structural system. in dead end structure design. Typically in a substation ice-sensitive structures include equipment. but the ice load on the structure is often neglected. For example. . ice loads may be applied to only selected components in ice-sensitive structures. Consideration should be given to only ice-sensitive structures.Ice-Sensitive Substation Structures Not all structures or structural components have to consider ice loads in design. the ice load on the conductor is included in design. In addition. and rigid bus. 2003 .Seismic Seismic Maps Maps Relative Seismic Hazard Map (USGS) NEHRP . 2 second period) and velocity-based Site Coefficient Fv (at 1.2 second map.0 second period) SDS = (2/3) (Fa) (Ss) SD1 = (2/3) (Fv) (S1) Sa = SDS For substation structure periods T > (SD1/SDS) use.0 second map S1 (2) Acceleration-based Site Coefficient Fa (at 0.Maximum Considered Earthquake Ground Motion (1) The spectral response acceleration obtained from the 0. Ss (short periods) and the 1. Sa = SD1/T . such as conductors. need not be included) = Design Spectral Response Acceleration . Earthquake Loads = Dead Load (Including all rigidly attached equipment or conductor Sa Flexible attachments. Lateral Force applied at the Center of Gravity of the structure/component = Structure Response Modification Factor W = Importance Factor.Structure Seismic Design Force: Sa FE = W IFE R Where: FE R IFE = Seismic Design Force. 7 .7 1.5 3. R Structure/Component Type Moment-Resisting Steel Frame Trussed Tower Cantilever Support Structures Tubular Pole Steel and Aluminum Bus Supports Station Post Insulators Rigid Bus (Aluminum and Copper) Structures with Natural Frequency Great Than 25Hz USD 4.Structure-Response Modification Factor.7 2.3 2.0 2.5 2.0 2.0 4.0 1.0 2.0 1.0 2.0 1.3 ASD 6.7 1. specified in this section are the recommended valves for Ip used in IEEE 693 for foundation analysis. IFE. The Importance Factors.The Importance Factors.0 All other structures (or equipment) 1. . IFE Structures and Equipment Essential to Operation 1.25 Anchorage for Structures and equipment Essential to operation 2.0 The selection of the appropriate Importance Factor (IFE) is the responsibility of the design engineer. TWO EXAMPLES IN THE DOCUMENT FOR DETERMINING STRUCTURE LOADS LINE TERMINATION STRUCTURE 69 KV DISCONNECT SWITCH SUPPORT . . . FIRST SUPPORT . EXAMPLES OF FIRST SUPPORT . Deflection Loads Where the structural designer has not developed specific loading conditions for deflection analysis. applied to the dead weight. A load factor of 1. Wind Load for Deflection Calculations Wind Deflection Load Conversion Factors 5-year mean recurrence Wind Deflection Load Conversion Factor 0. the following minimum load conditions may be used as a basis for deflection analysis.78 . is used with the deflection load cases.0. . Loads resulting from bus short circuit and earthquake events should not be considered in deflection analysis.Ice and Wind Combined Load for Deflection Calculations Ice Thickness Deflection Conversion Factors 5-year mean recurrence Ice Thickness Deflection Conversion Factor Wind Deflection Load Conversion Factor 0.50 Other Deflection Considerations If the electrical equipment is expected to operate during extreme winds. If the electrical equipment is expected to operate during extreme icing. then the unfactored extreme wind should be used for deflection calculations.50 0. then unfactored extreme icing loads should be used for deflection calculations. Horizontal Bus Forces Fault Force on a cylindrical surface:(IEEE 605 formula) The magnetic fields produced by fault currents cause forces on the bus conductor.RIGID BUS DESIGN Bus Loading . The bus conductor and its supports must be strong enough to withstand these forces.4 X 10-7 for English units Fsc = short circuit current unit force lbf/ft Isc = Symmetrical short circuit current D = conductor spacing center to center = constant based on type of short circuit and conductor location Df = decrement factor . Decrement Factor Formula: Fsc = C (Df 2Isc )2 (D) C = 5. Structure/Equipment Structure/Equipment Support Support Loads Loads Loading Conditions Wire Loaded Structures Switch and Other Interruption Rigid Bus Equipment Supports Supports Supports NESC* Y N N N Extreme Wind/Hurricane Y Y Y Y Extreme Ice and Wind Y Y Y Y Seismic Y Y Y Y Short Circuit N Y Y N ** Construction & Maintenance Y Y Y Y Operational N Y N Y Deflection Y Y Y Y * Other Codes ** Design Should Consider if significant (rigid bus connected equipment) . NESC (other State or Local Regulatory Codes). 2. Equipment Operational Loads. Section 3. Sections 3.2. 5.2 The following loading conditions should be considered for checking substation structure deflections: 1.8 6. Section 3.2 3.9 7. Section 3.11.2. Wind.1 2. Section 3.12 and 3.7 Short Circuit (combined with other load conditions when considered appropriate).2. 3.5 Combined Ice and Wind.2. Construction and Maintenance. 4.2.2.2 .2. Combined Ice and/or Wind (Operational).APPLICATION OF LOADS The following loading conditions should be considered for checking substation structure stresses: 1. Section 3.2. Section 3.13 Extreme Wind.2. Section 3.6 Earthquake.2. Section 3.2. Equipment Operation Loads.2. Section 3.11. 25 E (or EFS)IFE + 0.75 SC + 1.75 SC + 1. W = Extreme Wind Load. EFS = Reactions from First Support.1 D + 1. IFI.0)+ 0. and IFE).2 IWIFI+ 1.1 D + 1.1 TW Case 3 1. . SC = Short Circuit.Ultimate Strength Design Cases and Load Factors LOAD CASES LOAD FACTORS AND COMBINATIONS Case 1 1. IF = Importance Factors (IFW. Iw = Ice Load in combination with Wind. E = Earthquake. Tw = Horizontal Wire Tension for the appropriate load condition.1 D + 1.1 D + 1.1 TW Case 4 1.0 SC + 1.1 TW D = Structure and Wire Dead Load.75 SC + 1. WI = Wind Load in combination with Ice.2 WI(1.1 TW Case 2 1. IFWI.2 W IFW + 0. applicable to the Utilities service region.Allowable Stress Design 9Load Factors should be 1. etc.e. These load combinations do not imply that only these four loads cases are adequate for the design of a substation structure.0 Load Combinations A particular structure may not have all the individual load components listed in the load combination equations. wind direction. ice.. and earthquake) should be considered and the level of short circuit load used in combination with other loads determined by the owner. . Variations of these or other loads cases may be required to account for conditions.. It is the responsibility of the design engineer to determine whether a load case and/or load combination is appropriate. short circuit fault location. i. The combining of short circuit loads with other loads (wind. 4. vertical reach switches. DEFLECTION CRITERIA Class A structures: support equipment with mechanical mechanisms where structure deflection could impair or prevent proper operation. ground switches. and circuit interrupting devices. circuit breaker supports. Examples are group operated switches. . but where excessive deflection could result in compromised phase-to-phase or phase-to-ground clearances. fittings. . surge arresters.4. hot-stick switches/fuses. metering devices (such as CT’s. and CCVT’s). or bus. Examples are support structures for rigid bus. and wave traps. station power transformers. PT’s. DEFLECTION CRITERIA Class B structures: Support equipment without mechanical mechanisms. unpredicted stresses in equipment. wind-induced vibrations.4. masts for lightning shielding. DEFLECTION CRITERIA Class C structures: Support equipment relatively insensitive to deflection. and visual impact. Examples are support structures for flexible (stranded conductor) bus. . and dead-end structures for incoming transmission lines. Deflection limitations for these structures are intended to limit "P-delta" stresses. (Not in SG6). or are stand-alone structures that do not support any equipment. Deflection shall be the gross.2. or for cantilever members. the distance to the nearest vertical support. (3) Loading Criteria for deflection Limitations.SUMMARY OF STRUCTURE DEFLECTION LIMITATIONS Maximum Structure Deflection as a Ratio of Span Length. 2000 1/50 ** NEMA SG6. relative to the member support points. Section 3. horizontal displacement relative to the foundation support. (2) Spans for vertical members shall be the vertical distance from the foundation connection to the point of investigation.1 . NO CLASS C REQUIREMENT (1) Spans for horizontal members shall be the clear span between vertical supports. horizontal or vertical. L (3) Member Type Deflection Direction Structure Classes Class A Class B Class C** Horizontal (1) Vertical L/200 L/200 L/100 Horizontal (1) Horizontal L/200 L/100 L/100 Vertical (2) Horizontal L/100 L/100* L/50 * NEMA SG6. SECTION 36. Deflection shall be the net displacement. SECTION 36. SPAN LENGTH DEFINITIONS HORIZONTAL MEMBER SPAN VERTICAL MEMBER SPAN . CLASS A STRUCTURES 1/100 OF THE VERTICAL SPAN EXAMPLES • Group Operated Switches • Vertical Reach Switches • Ground Switches • Breaker Supports • Circuit Interrupting Devices. 1/200 OF THE HORIZONTAL SPAN (ANY DIRECTION) . CLASS B STRUCTURE EXAMPLES • Support structures for rigid bus • Lighting/surge arresters • Metering devices (such as CT’s. and CVT’s) • Station power transformers • Hookstick switches/fuses • Line/wave traps 1/100 OF THE VERTICAL SPAN (ANY DIRECTION) 1/200 OF THE HORIZONTAL SPAN (VERTICAL DIRECTION) 1/100 OF THE HORIZONTAL SPAN (HORIZONTAL DIRECTION) . PT’s. 1/100 OF THE HORIZONTAL SPAN (ANY DIRECTION) .CLASS C STRUCTURES 1/50 OF THE VERTICAL SPAN EXAMPLES • Support structures for flexible (stranded conductor) bus • Masts for lightning shielding • Dead-end structures for incoming transmission lines. MULIPLE CLASS STRUCTURE LIN E END CLASS DEFLEC TIO N C SW ITC H CLASS DEFLEC TIO N A . Such structures can be susceptible to fatigue cracking and failure. with dampers and no ice. it is recommended that the vertical deflection of rigid bus conductors (aluminum or copper tubing or shapes) be limited to L/200 of the span length. slender structures In certain cases the structure type. Rigid Bus Conductor Deflection Criteria In order to obtain an acceptable appearance. Lightning masts and other tall. This criterion should be applied with the dead weight of the rigid bus. design loads. These structures can be subject to potentially damaging wind-induced oscillations. and the lower deflection limits for Class C structures can result in a flexible (low stiffness) structure. .Rotational limitations Some equipment and rigid bus designs may be sensitive to rotation of supporting members in addition to the deflection of the member. Equipment manufacturers should be consulted as to any rotational limits which may be necessary to ensure reliable operation. RECOMMENDATION Static Analysis Earthquake Analysis Dynamic Analysis of Short Circuit Events .OVERVIEW Approximate Analysis First Order and Second Order Elastic Analysis First Order Inelastic Analysis DYNAMIC ANALYSIS METHOD .5.Natural Frequencies and Normal Modes Response Spectrum Analysis ANALYSIS METHOD . DEFLECTION CRITERION MODEL Truss and Frame Models Finite Element Model STATIC ANALYSIS METHOD . METHOD OF ANALYSIS STRESS CRITERION VS.OVERVIEW Steady State Analysis Eigenvalue Analysis . Session 3: Chapter 6. Design Chapter 7. Construction and Maintenance . Connections to Foundations Chapter 8. Testing Chapter 10. Quality Control and Quality Assurance Chapter 9. DESIGN • GENERAL • STEEL • CONCRETE • ALUMINUM • WOOD • SEISMIC • BASEPLATE • RIGID BUS DESIGN • SPECIAL DESIGN CONSIDERATIONS .6. 9 Ultimate Strength Design (USD) and Allowable Stress Design (ASD).6. is not recommended for substation structures. also referred to as LRFD. DESIGN: GENERAL 9 Specific guidelines for member design and fabrication are not included in this guide. 9 Allowable Stress Design (ASD): Unfactored design loads and limits stress levels to a value which is less than the yield strength of the material. such as wind and seismic events. The 1/3 increase in the allowable stress for short duration loads. 9 Ultimate Strength Design (USD): Factored design loads with stress levels up to yield strength or buckling capacity of the material and strength resistance factors. . Ultimate strength design is recommended. This guide refers to other documents for design guidelines and will note any exceptions. Design of Steel Transmission Pole Structures .6. 2005 Edition 9 The ASCE/SEI Standard 48 (2005) . DESIGN: STEEL 9 ANSI/ASCE (1997) Standard 10. Design Transmission Structures (ASCE Standard 10) of Latticed Steel 9 The American Institute of Steel Construction Load and Resistance Factor Design (LRFD) Manual . Precast and Prestressed Concrete by the Prestressed Concrete Institute 9 Prestressed Concrete Poles ASCE Guideline for the Design and Use of Prestressed Concrete Poles . DESIGN: CONCRETE 9 Reinforced Concrete Structures ACI 318 Building Code Requirements of Reinforced Concrete 9 Prestressed Concrete Structures PCI Design Handbook.6. ” using stresses for building type structures. DESIGN: WOOD Ultimate Strength Design 9 IEEE Standard 751. 2003 .6. 6.1 can be used for wood pole stresses with the NESC 0.65 reduction factor (Grade B Construction. DESIGN: ALUMINUM 9 Aluminum structures should be designed and fabricated in accordance with the Aluminum Association “Specifications for Aluminum Structures. Design Guide for Wood Transmission Structures 9 National Electric Safety Code (NESC) 9 National Standard ANSI O5. Table 253-1) Allowable Stress Design 9 International Building Code (IBC). The first support can be a steel pedestal supporting a cantilever type piece of equipment. DESIGN: SEISMIC A structure defined by IEEE 693 as a “first support” is the single structural element upon which the equipment is supported. The first support can also be a structural member (component) within a support structure. such as a surge arrester. .6. .6. DESIGN: BASE PLATE DESIGN 2 2 1 3 2 1 1 3 1 2 3 (a) 3 (b) 2 1 1 1 2 1 3 3 (c) (d) tmin ⎛ 6 = ⎜ ⎜ b F or F ⎝ eff y b ( ) ⎞ ⎟ (BL c + BL c +. Design of Steel Transmission Pole Structures .+BL c ) 1 1 2 2 k k ⎟ ⎠ ASCE Standard 48. 6. DESIGN: SEISMIC 9 Allowable Stress Design The 1/3 increase in allowable stress for seismic loads is not recommended for substation structures.. but with ASCE Substation Document Loading. 9 Short Circuit Load Obtained From IEEE 605 9 Design guidance per IEEE 605.6. DESIGN: RIGID BUS DESIGN 9 Rigid bus design should be approached as a system requiring both an electrical and design engineer 9 Ultimate Strength Design (LRFD) of rigid bus design systems. Load Factors. etc. 9 Seismic design per ASCE Substation Document . DESIGN: SPECIAL DESIGN CONSIDERATIONS • • Structures for Air Core Reactors Wind Induced Vortex Shedding • Galvanizing Steel Considerations • Painted or Metallized Steel Considerations • Member Connection Design • Bolted Connections in Steel • Welded Connections in Steel • Welded Connections In Aluminum • Concrete Structure Connections • Connections in Wood Structures • Weathering Steel Structures • Bolted Connections in Weathering Steel • Guyed Substation Structures .6. CONNECTIONS TO FOUNDATIONS • INTRODUCTION • ANCHOR MATERIALS • ANCHOR ARRANGEMENTS • ANCHORS CAST-IN PLACE • DRILLED CONCRETE ANCHORS INSTALLED IN EXISTING CONCRETE • EXAMPLES .7. 1983. “Design of Headed Anchor Bolts. ASCE 10 "Design of Latticed Steel Transmission Structures. J. Haninger.G. These types of anchorage are covered by ASCE 10 (Latticed Steel Structures) and ASCE 48 (Tubular Pole Structures) . 9 Cast-in-place headed bolts are the recommended anchor bolt type 9 Design Considerations – Concrete: ACI 318 Appendix D 9 Stub angle and direct embedded structures can also be used in substations.” Engineering Journal. Also references ACI 355. CONNECTIONS TO FOUNDATIONS 9 Anchor Bolt Design (Headed Anchors or Straight Length Deformed Reinforcing Bars) 9 Ultimate Strength Design approach to calculate the required cross sectional area of an anchor bolt is based on: ACI 349 “Code Requirements for Nuclear Safety” ." and Shipp. American Institute of Steel Construction.7. it is recommended that the allowable bolt stresses exceed the applied stresses by not less than a factor of two (2) . ASTM A615 or A706 • In seismically active regions recommend ductile bolts • Minimum bolt size is 0. and bolts manufactured from ASTM A36 Steel • Straight Deformed Reinforcing Bars. diameter • When smaller bolt sizes are used.ANCHOR MATERIALS • ASTM F1554.75 in. ANCHOR ARRANGEMENTS Base Plate Supported by Anchor Bolts with Leveling Nuts Anchor Bolts with Base Plate on Concrete or Grout Allows for adjustment of the base plate during erection Large Shear Transfer Applications . Design of Steel Transmission Pole Structures). then a bending stress analysis of the bolts is required (ASCE Standard 48.9 Base Plate Supported By Anchor Bolts With Leveling Nuts If the clearance between the base plate and concrete exceeds two times the bolt diameter. . ANCHORS CAST-IN PLACE Smooth bar hook bolts are not recommended because of less predictable behavior in tension tests . EXAMPLE OF A HOOK BOLT PULL-OUT FAILURE . DESIGN CONSIDERATIONS 9 Anchor Bolts With Base Plate on Concrete Or Grout TENSION AREA Pu Aa = fdt As = Aa + Av SHEAR AREA FOR COMPRESSION Av = Vu .( μ )(Pcm) [(φ )(fy )] SHEAR AREA FOR UPLIFT Vu Av = [(φ )(fy )] REQIURED DIAMETER d = ( 2) 1 ⎛ Αs ⎞ 2 ⎜ ⎟ + ⎝ π⎠ ⎛ 0.974 ⎞ ⎜ ⎟ ⎝ n ⎠ . DESIGN CONSIDERATIONS 9 Base Plate Supported By Anchor Bolts With Leveling Nuts As = Aa + Ab + Av Mu Ab ⎛ 5⎞ = ⎜ ⎟ ( h)(Vu ) ⎝ 8⎠ 1 ⎧ 2⎫ 3 ⎡ ⎤ ⎪ 5hVu ⎪ = ⎨π ⎢ ⎥ ⎬ 2 f φ y ⎦ ⎪ ⎪ ⎣ ⎩ ⎭ Av = Vu [(φ)( f )] y REQUIRED DIAMETER d = ( 2) ⎛ ⎜ ⎝ As ⎞ 1 2 ⎛ 0.974 ⎞ ⎟ + ⎜ ⎟ π⎠ ⎝ n ⎠ . CONCRETE 9 Tensile Capacity Of Concrete (ACI 318) 9 Design Of Side Cover Distance For Tension (ACI 318) 9 Design Of Side Cover Distance For Shear (ACI 318) 9 Anchor Bolt Embedment Length (ACI 318) .ANCHORAGE DESIGN CONSIDERATIONS . 11)⎜⎜ ⎝ f 'c ⎠ If the calculated value for Aplate is smaller than the area of the nut or bolt head. then a bearing plate is not required.CONCRETE 9 Localized Bearing Failure ASCE “Wind Loads and Anchor Bolt Design for Petrochemical Facilities” Bearing Plate Requirements ⎛ fy ⎞ ⎟⎟ Aplate = Abolt + As (0.ANCHORAGE DESIGN CONSIDERATIONS . . EXAMPLES 1. BASE PLATE ON CONCRETE 2. BASE PLATE ON LEVELING NUTS 3. BASE PLATE ON LEVELING NUTS IN A DRILLED PIER . 8. QUALITY CONTROL AND QUALITY ASSURANCE • GENERAL QC = Fabricator. QA = Purchaser • STEEL STRUCTURES • ALUMINUM STRUCTURES • CONCRETE STRUCTURES • WOOD STRUCTURES • SHIPPING • HANDLING AND STORAGE General Topics Materials Welding Fabrication Inspection Visual Inspection Specific Inspection Methods Of Welds Test Assembly Structure Coating Wood Treatment . Seismic response (dynamic loading) requires that the support structure and equipment be seismically tested/evaluated as a system. Component testing (a section of the tower. or if it is a unique structural system.) may be cost effective for substation structures. Full-scale testing should be considered when a standard and/or large quantities. ANSI/ASCE 10. connections. 2005. (3) ASCE "Guide for the Design and Use of Concrete Poles" (1987). "Design of Latticed Steel Transmission Structures" (1997). (2) ASCE Standard 48. TESTING • • • • • Full-scale structural proof tests are rarely performed on substation structures.9. "Design of Steel Transmission Pole Structures" (2005). Structural testing guidance can be found in the following documents: (1) ASCE Standard. Seismic tests are performed in accordance with IEEE 693. etc. . IEEE-1307.10.” is one source of information for worker safety during climbing of utility structures. should be considered for climbing with a fall protection device. • WORKER SAFETY All structures and equipment inaccessible with bucket trucks or small ladders. “Trial Use Guide for Fall Protection of the Utility Industry. . • MAINTENANCE Engineer(s) should consider accessibility of equipment for maintenance and/or operation. CONSTRUCTION AND MAINTENANCE • CONSTRUCTION Engineer(s) should anticipate construction loads imposed on the structure. THE END .