Substation design: primary engineering

What it is and when you need it

Substation primary engineering is the design of the power system itself: the bus configuration, the bays, power transformers, circuit breakers, disconnect switches and instrument transformers, how they are arranged in the yard or in the switchgear room, and how people and equipment are protected by grounding and lightning shielding. It is the foundation of any substation design: everything designed afterward, from protection to communications, depends on it.

Most jurisdictions require a documented electrical design before a substation can be built or energized. We adapt the design and the calculation reports to the local code and to the utility requirements that you give us, so the package can go straight into your approval process.

We do it for medium, high and extra-high voltage (EHV) substations and for industrial facilities, typically for:

• New substations, from the configuration through construction drawings.
• Expansions: a new line or transformer bay, a transfer bus or a change of bus configuration.
• Generation interconnections, solar or thermal, or the connection of a large industrial load to the utility or transmission grid.
• Equipment replacement, when a new breaker or transformer has to be specified to fit what is already there.

This design is part of our engineering design and studies service.

What is included

• Single-line diagram and bus configuration. We choose the configuration with you, based on the reliability you need and what the interconnecting utility asks for: single bus, double bus, breaker-and-a-half, ring bus or others. The single-line diagram uses IEC 60617 symbols, or IEEE 315 symbols if your project calls for them.
• Physical layout. Plan and section views of the yard or room, with safety clearances, cable routes, access roads and space for maintenance and future bays.
• Equipment selection and specification. Data sheets for breakers, disconnects, CTs and VTs, surge arresters and power transformers, with ratings checked against the short-circuit study.
• Insulation coordination. Equipment insulation levels and surge arrester locations, using the IEC 60071-1 method (IEEE 1313.1 for US-based projects).
• Grounding grid. Grid design with tolerable step and touch voltages per IEEE 80, based on soil resistivity and ground fault current.
• Lightning shielding. Protection of the yard against direct strokes with shield wires and masts, following the IEEE 998 methods, plus the lightning risk assessment your local code may require.
• Calculation reports, organized to match the items your local code asks for, with a justification for those that do not apply.

How we work

Primary design is desk work. What we need from the substation arrives as drawings, data and photos; what you receive is documents. You do not pay for travel or wait for an engineer to be available on site, and the project moves the same way wherever the substation is. Our team works from Bogotá (UTC−5).

1. Scope and requirements. We review the scope with you, the utility’s feasibility or interconnection response, and the technical standard of whoever will receive the drawings.
2. Information review. We read what exists and tell you what is missing. If something can only be obtained in the field, such as soil resistivity or the real condition of a yard without current drawings, we schedule a site visit (in Colombia, or elsewhere on request) or your local contractor collects it following our instructions.
3. Basic engineering. Single-line diagram, configuration and general arrangement, so you can make the big decisions before we go into detail.
4. Detailed engineering. Calculations, construction drawings, specifications and reports.
5. Review with you and the utility. We address comments from the utility or transmission owner until the design is accepted.

What we need from you

• Existing drawings of the substation or the property, and the topographic survey for a new project.
• Nameplate data of the equipment that stays in service.
• Short-circuit level at the point of interconnection, provided by the utility or transmission owner.
• Rated system frequency (50 Hz or 60 Hz) and nominal voltages.
• Soil resistivity, if it has already been measured.
• Photos of the yard, the switchgear and the nameplates.
• The technical standard or specifications of whoever approves the design, and the local code that applies.

Standards and criteria

• IEC 61936-1 sets the design and erection requirements for AC power installations above 1 kV.
• IEEE 80 is the guide for safety in AC substation grounding; IEEE 998 covers direct-stroke lightning shielding of substations.
• IEC 60071-1 and IEEE 1313.1 define insulation coordination: standard insulation levels and the procedure to select them.
• Interrupting ratings and short-circuit mechanical forces are verified with a short-circuit study per IEC 60909-0, or IEEE 551 practices when the project follows US standards.
• Local code and utility requirements. We adapt clearances, documentation and the list of calculation items to the code and interconnection requirements you tell us apply.

What you receive

• Single-line diagram and physical layout drawings, plans and sections.
• Grounding grid and lightning shielding drawings.
• Technical specifications and data sheets for the power equipment.
• Calculation reports, organized to the local code you indicate.
• Bills of quantities for procurement and construction.
• A complete engineering package for your review, with revision control.

Why Tiza Group

• Engineering that can be built and tested: our team also tests and commissions substations, and designs with energization in mind.
• Medium to extra-high voltage, in utility substations and in industry.
• The whole design under one team: primary engineering is coordinated with secondary engineering, communications engineering and the protection coordination study.
• Truly remote: you send the information and receive drawings and reports, wherever the project is. Contact us to scope your substation.