Engineer’s Checklist for the Design of Substations

| Increased electrical demand in areas served by RUS    borrowers indicates more need for the construction of substation facilities now and in the    future. Therefore, it’s important that the engineer take a closer look at the    construction techniques available in RUS publications and other resources to utilize in    the construction of substation facilities. We recommend that engineers use the following    construction drawings list and the checklists as a quick aid in helping in the substation    design process.

Drawings to be submitted by the engineer for RUS review: - One line diagram (relaying systems; ratings for breakers, transformers, switches, etc.)
- Three line diagram (PT’s, CT’s, phasing, etc.)
- Plot plan (Plan View)
- Grading plan (Site Plan, fence layout and details)
- Foundation plan and details
- Elevation plan and details
- Grounding plan and details
- Control house plan, elevations and details
- Material lists

One & Three Line Diagrams Checklist: - All spare CT’s are shorted and properly grounded at the cabinets
- Station service transformers are internally or externally fused
- Surge arresters are used on all high and low sides
- Voltage and current ratings included for all equipment
- All existing and future equipment properly identified
- Underground cables are clearly identified at the termination points
- Reflects plan view of equipment arrangement
- All conductors are identified as to size, material and number per phase
- Legend, revision notes with date, and reference drawings and equipment notes are added

Plan View - Drawing Checklist: - Access roads, culverts and other drainage surfacing provided
- Fence and gate locations selected properly and shown on scale
- Allowance for maintenance crew accesses for removal and installation of equipment
- Allowance for future expansion and mobile substation connections
- Electrical clearances (phase to phase and phase to ground) are clearly shown
- North arrow properly positioned
- Landscaping is architect to meet local requirements

Grading - Drawings Checklist: - Elevation of the finished subgrade and existing contours
- Cross-sectional views indicating slopes for cut and fill areas

Foundations - Drawings Checklist: - Steel reinforcement bar size, spacing, and location
- Thickness of concrete pads between 8" (20 cm) and 24" (61 cm)
- Top of concrete elevations
- Construction notes including reinforcing bar chart, footings, anchor bolts with        tolerance tables, and all foundation details

Grounding Plan and Details Checklist: - Ground grid buried a minimum of 1 foot 6 inches (0.5 m) below grade
- Adequate grounding conductor buried to allow for expansion due to temperature changes        and future construction additions
- Below ground connections by exothermic weld process
- Ground grid extended minimum of 2 feet (0.6 m) (3 feet [.9 m] is recommended)        outside of the fence and gate bypass extending a minimum of 1 foot 6 inches (0.5 m)        beyond open gates
- Above ground connections by compression or bolted
- All structures connected to ground grid
- Two or more ground paths for surge arresters, transformers and all other electrical        equipment
- Disconnect switch handles grounded adequately to the ground grid and to the grounding        mats according to the grounding detail drawings
- Chain link fence and gate grounded
- Reinforcing bars not used for grounding electrodes
- Adjoining metal fence (farm fence, etc.) not connected directly to substation fence
- Grounding conductors including grounding rods
- Shall meet the applicable standards and RUS acceptable materials
- The entire area inside the fence and including a minimum of 3.3 feet (1 m)        (4.9 feet [1.5 m] recommended) outside the fence shall be covered with minimum        of 4 inches (10 cm) of crushed rock possessing a minimum resistivity of        3,000 ohm-meters wet or dry

Elevation Plan and Details Checklist: - Material Size and Shape
- Expansion Provisions
- Weep Holes
- Precautions for aluminum-to-copper connections
- Welding procedures notes (inert gas shielding for aluminum bus)
- Corona Bells (above 161 kV)
- Bus adequately supported, with provisions for mounting surge arresters
- Use of damping cable to minimize vibration
- Lightning protection shield angle less than 45 degrees, or use of "Rolling Sphere        Methods" (refer to the "Lightning Protection for Substations" article in        the 1998 Items of Engineering Interest)
- Surge arresters lead length short as possible, surge arresters not used as bus supports
- Proper length and BIL of suspension and post insulators
- Adequate construction details to construct
- Provisions for construction notes, legend, future expansion, and mobile substation        connection

If you would like more information or have any questions, please call    Ted V. Pejman, Electrical Engineer, Transmission Branch, at (202) 720-0999.
 

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