Electrical Substation Projects

Electrical substation projects involve many aspects of engineering, management, supply and construction. In general, they require electrical, substation, structural and foundation engineering, as well as project management. There is also the specification, purchase & supply of major equipment, substation equipment and structures. And finally the construction, testing and start-up.

PLAN VIEW - Low-Profile, two feeder, single sectionalized bus substation

Basic Design Requirements

The following outline lists the basic information required for the specification and/or design of an outdoor substation. The list includes substation drawing requirements, basic substation design parameters, basic structure design parameters, basic foundation design parameters, and basic grounding design parameters. This list does not include information relative to the power system design, site design & procurement, environmental requirements, safety requirements, relaying, control, low voltage, grading, drainage, conduits, cables and wiring, fences, etc.

Substation Drawings Requirements

  • Plot plans
  • One line diagrams (basic switching)
  • One line relaying diagrams
  • Substation bill of materials
  • Substation layout plan & elevation drawings
  • Substation grounding plans
  • Conduit layout and lists
  • Control house drawings
  • Station service diagrams, control panels, schematics, etc.
  • Structure design calculations
  • Structure design drawings
  • Structure shop and erection drawings
  • Anchor bolt plan drawings
  • Foundation design calculations
  • Foundation plan
  • Foundation details
  • Transformer oil containment drawings
  • Grading & sub-grade drainage drawings
Depending on the project scope, some of the above may not be required.

Basic Substation Design Parameters:

  • Type of substations: Transformer, Distribution, Transmission & Switching
  • Types of feeders: Single, Multiple, Feed-through, etc.
  • Types of bus arrangements:
    • Single bus
    • Sectionalized bus
    • Double bus, single or double breaker
    • Main & transfer bus
    • Ring bus
    • Breaker and a half
  • Design parameters:
    • Ultimate substation KVA capacity
    • Nominal voltages
    • BIL requirements
    • Continuous currents
    • Momentary currents
    • Short Circuit capacity
    • Electrical Spacings & Clearances
  • Equipment:
    • Transformer
    • Substation bus (rigid or strain bus)
    • Switches (Vertical, side, center, double, etc. break)
    • Switchgear
    • Bus Support Insulators
    • Suspension insulators
    • Arresters
    • Breakers
    • Reclosers
    • Voltage regulators
    • Current transformers
    • Potential Transformers
    • Coupling Capacitors
    • Line Traps
    • Other
Basic Structure Design Parameters:
  • Material:
    • Steel: Hot-dip galvanized, painted or weathering
    • Aluminum
    • Concrete
  • Types of construction:
    • Low profile
    • High bay
    • Latticed
    • Structural shapes - Wide flange, channel, angle, structural tubing, pipe, etc.
    • Tapered tubular - octagonal, multi-sided, round, etc.
  • Design Loads:
    • Dead loads, line tensions, ice loads, wind loads, seismic loads, equipment operation loads, short circuit, construction loads, etc.
    • Incoming Line Tension
    • Incoming OHGW Tension
    • Incoming Line Angles
    • Incoming Line Span
    • NESC Heavy, Medium or Light
    • High wind ASCE 7
    • Heavy ice + wind ASCE 7
    • Seismic UBC Zones
    • Design approach ASD or USD
  • Deflection requirements:
    • NEMA SG-6 (or special)
Basic Foundation Design Parameters:
  • Common types of foundations:
    • Spread Footings
    • Drilled Piers
    • Slab-on-grade
    • Pile foundations
  • Basic design parameters:
    • Allowable Soil Bearing Pressure
    • Allowable Passive Lateral Pressure
    • Allowable Skin Friction
    • Frost depth
    • Soil Layers for Drilled Piers
    • Soil Type
    • Cohesion
    • Angle of Internal Friction
    • Unit Weight
    • Modulus of Subgrade Reaction
    • Ultimate End Bearing Capacity
    • Ultimate Skin Resistance
    • Ultimate Pull-out Skin Resistance
    • Water Table Depth
Basic Grounding Design Parameters:
  • Electrical:
    • Ground fault current
    • Time duration
    • System growth factor
    • Current division factor
  • Resistivity:
    • Soil
    • Crushed rock
  • Ground Grid:
    • Grid Area
    • Grid conductor - size, spacing, depth
    • Ground rods - size, length, quantity


ACI 318, AISC (ASD & LRFD), The Aluminum Association, ANSI C37, ASCE 7, ASCE 10, ASCE Manual 52, ASCE Manual 72, ASCE Manual 74, ASTM, AWS, IEEE 80, IEEE 344, IEEE 605, IEEE 693,IEEE1267, NEMA SG6, NEMA TT1, NESC, REA 65-1 (RUS 1724E-300)