Civil / Structural – Substation Design Calculations

Civil / Structural – Substation Design Calculations

Land survey and site grading analysis

Land topography - substation design calculations
Figure 18: Drawing created based on a land survey. The lines on the contour indicate areas of the same altitude. Picture credit: Landmarksurveyors
Power Substation Design Calculations - A Checklist of 18 Studies for Engineers to Consider 1
Figure 19: Substations where site grading played a significant role. Left image credit FE Penn power hoytdale substation. Right image credit: FE Lorain county substation.
Why conduct land survey and site grading analysis?
How much money is spent on building a new substation is largely influenced by the location. Cutting and filling the earth to create a flat property (in a mountainous area), creating the right slope to channel water away from substation, stormwater management, etc is an expensive affair.
Outcome of land survey and site grading analysis
Determine if the land is feasible for construction.

Create a grading plan. Design drainage facilities like culverts, ditches, detention ponds, lift-stations etc, to handle stormwater.

Create compensatory storage when building in a floodplain.

Results are incorporated in the following drawings:
– Site grading plan drawing
– Site grading detail drawing
– Property plan drawing

Geotechnical investigation and foundation calculations

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Figure 20: Soil sample collected for analysis. Portions of sample have been scooped out on the right. Picture credit: Nauman khan.
Power Substation Design Calculations - A Checklist of 18 Studies for Engineers to Consider 2
Figure 21: Transmission tower being lowered onto anchor-bolts. The design of this foundation factors-in soil condition (among others). Picture credit WAPA ED5 substation..
Why conduct geotechnical investigation and foundation calculations?
Soil conditions play a significant role in the design of foundations.
Outcome of geotechnical investigation and foundation calculations
Geotechnical investigation reveals information on soil conditions, underground obstructions or hazards, seismic conditions, topography, etc. Based on this information:
– Remediate contamination or other hazards in the soil.
– Design foundations to mount buildings, steel structures, and substation equipmentResults are incorporated in the following drawings:
– Foundation plan drawing
– Foundation details drawing

Structural steel calculations

Power Substation Design Calculations - A Checklist of 18 Studies for Engineers to Consider 3
Figure 22: Steel structure analysis in RISA 3D software. Picture credit: Nauman Khan.
Why conduct structural steel reaction calculations?
Structural steel is subjected to horizontal loads (line tensions, wind load, etc) and vertical loads (dead weight of equipment mounted on it, ice load, etc). Any inadequacy in design may lead to structural failure.
Outcome of structural steel reaction calculations
Specify steel structure capable of handling the horizontal and vertical loads. The legs of tall structures are also susceptible to aeolian vibration. Install adequate cross-bracing or vibration dampers to prevent this condition.

Results are incorporated in the following drawings:
– Steel framing plan drawing
– Steel framing section view drawing

Bus calculations

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Figure 23: Video of what 40,000amps of fault current for 300 milliseconds does to a piece of substation bus.
Why conduct bus calculations?
As seen in the video, a piece of substation bus is subjected to extreme forces generated by fault current. A setup without adequate bus support and under-rated bus support insulators – will collapse.

The study also analyses the effects of wind loading, snow loading, bus material, etc.

Outcome of bus calculations
The goal would be to insert enough bus supports to stabilize the bus (considering all the forces acting on it). Also, specify extra high strength insulators where necessary.

Results are incorporated in the following drawings:
– General arrangement plan drawing
– General arrangement section view drawing