Introduction to Substation Design TADP 542

Transcription

1 Introduction to Substation Design TADP 542 Substation Structures- Introduction Instructor: Dr. Yenumula Prasad Transmission & Distribution Program

2 Substation Structures Reference Substation Structure Design Guide (2008), ASCE Manuals and Reports on Engineering Practice No. 113, American Society of Civil Engineers

3 Based on Function Based on Materials Based on Profile Configurations

4 - Based on Function Based on Function Equipment support structures Line support structures Box structures

5 - Based on Function Equipment support structures Bus support structures Switch stands Line Trap stands CT and PT stands Lightning arrestor stands

6 - Based on Function Equipment support structures Single column stands vertical cantilevers Eg. Single phase bus support Multiple column stands Two legged stands Four legged stands Frame action Eg. Three phase bus stand supported by two columns

7 - Based on Function Line support structures Line deadend or takeoff structures Carry forces from tensions of conductors and overhead shield wires on one side Highly stressed structures

8 - Based on Function Line support structures - Slack span deadends - Full tension deadends Configurations Single pole deadends H-frame deadends Lattice frame deadends A-frame deadends

9 - Based on Function Box structures Similar to building frames Uses beam and columns structures Used for low voltage substations/distribution substations (normally 69 kv & below)

10 - Based on Materials Based on Materials Steel Concrete Aluminum Wood

11 - Based on Materials Steel Structures Most common material Economical due to structural properties & availability Finishes Galvanizing Painting

12 - Based on Materials Steel Structures Steel Grades for Equipment support structures ASTM A36 steel Rolled shape members Yield strength=36 ksi ASTM A500-GrB Hollow square tube and round sections Yield strength=42 & 46 ksi Low grade steel used Member stresses usually low Provide stiffer members, helps in reduction of structure deflections

13 - Based on Materials Concrete Structures May be economical if fabricators plant in close vicinity Precast and Prestressed concrete structures Useful in Coastal areas due to corrosion resistance Handling and construction costs high due to heavy weight Aluminum Structures Limited application Good corrosion resistance Less weight Less rigid as compared to steel due to the low modulus of elasticity deflections are higher Alloy 6061-T6 grade

14 - Based on Materials Wood Structures Available in different species such as Douglas Fir Southern Yellow Pine Western Red Cedar etc. Rupture bending strength for different species 8000 psi for Douglas Fir & Southern Yellow Pine 6000 psi for Western Red Cedar ANSI (American National Standards Institute) classifies poles based on minimum circumference of pole 6 feet from the butt

15 - Based on Materials Wood Structures The fungi, insects and other low forms of plant life cause decay of wood poles Maintenance costs and life-cycle costs higher Life of wood pole less as compared to steel Deflections of wood pole structures due to low modulus of elasticity

16 - Based on Profile Configurations Based on Profile Configurations Lattice Profile Solid Profile Semi-Solid Profile

17 - Based on Profile Configurations Lattice Profile Widely used in the past for substation structures Open structures and occupy bigger footprint Erection costs higher Made of steel angle members

18 - Based on Profile Configurations ASCE (2000) ASCE Standard, Design of lattice steel transmission structures Each of the elements of structure is a truss member, pin connected at joints Analyzed as a space truss constructed with straight members and pin-connected at joints Forces in members are either compression or tension These forces are then compared to allowable values as per ASCE-10 design specifications (in US)

19 - Based on Profile Configurations Solid Profile Rigid frame Made of Wide flange shapes Tapered polygonal or round, rectangular sections More popular choice for equipment supports Erection time less Aesthetically pleasing Less maintenance costs

20 - Based on Profile Configurations Semi-Solid Profile Made of wide flanges, pipes, tubes and braced with angle members Very stable and rigid due to bracing