Electric Substation Planning and Engineering
From concept through commissioning — actively engaged at every phase
Every megawatt that flows from the transmission system to a distribution feeder passes through a substation that must be planned, engineered, procured, and built to industry and client standards. When major substation equipment is aging, at capacity, or transformer capacity is needed due to load growth, the reliability consequences could be severe. Getting it right requires an engineering team with technical depth and a local presence to manage the project programmatically.
Tangibl Group provides electric substation planning and engineering services for rural electric systems, public power utilities, investor-owned utilities including transmission owners and distribution utilities, and large-load customers such as hyperscale data centers. Our services span the full project lifecycle — from initial planning and front-end engineering through major equipment procurement, detailed design, construction oversight, and commissioning. Tangibl self-performs primary electrical engineering, civil and structural engineering, protection and control design, and major equipment procurement, managing subconsultants and contractors as an integrated project team with a single point of technical accountability.
“Every substation project is different — different site constraints, different load growth drivers, different transmission owner requirements. What does not change is the need for an engineering team that is technically deep across all the disciplines involved and present enough to manage the interfaces between them. That is exactly what Tangibl provides.”
138-25kV Substation Planning and Engineering
A new distribution substation is one of the most significant capital investments a public power or small distribution utility can make. Getting from a selected site to a commissioned, energized substation integrates electrical, civil, structural, and protection engineering disciplines, major equipment procurement, transmission owner interconnection coordination, and construction management into a multi-year program. And smaller systems require professional services that are both comprehensive and nimble.
Tangibl currently serves as Electric Engineer for a municipal electric system planning and executing a new 138-25kV distribution substation. The work encompasses a complete front-end engineering and design package for a facility whose ultimate layout includes four power transformers, a metal-clad integrated switchgear and control house assembly, automatic sectionalizing and backup provisions with the utility’s existing substation, and interconnection with the investor-owned transmission owner’s 138kV ring-bus substation. Tangibl self-performs primary electrical and civil/structural engineering, manages a civil subconsultant for site survey and geotechnical assessment, and manages the engineering services arm of a major protective relay and control system supplier.
Our 138-25kV substation planning and engineering services include:
- System planning studies to determine substation capacity, configuration, and load growth requirements
- Site evaluation, site plan development, and civil subconsultant coordination for survey and geotechnical assessment
- Single-line diagram development and general arrangement finalization
- Transmission owner interconnection feasibility coordination, including PJM transmission owner coordination where applicable
- Front-end engineering and design for protection and control systems, including relay selection, scheme design, and control house layout
- Major equipment specification and procurement management
- Substation packager and construction contractor selection and oversight
- Automatic sectionalizing scheme design with backup provisions to the existing substation
- Construction observation and as-built documentation
CASE STUDY
As Electric Engineer for a municipal electric system, Tangibl is planning and providing front-end engineering and design for a new 138-25kV distribution substation. The facility will provide capacity to serve existing and future load driven by commercial and residential development, with automatic sectionalizing and backup with feeders from the existing substation. The project encompasses site plan finalization, single-line diagram development, power transformer vendor selection after proposal evaluation, PJM Transmission Owner interconnection feasibility coordination, and front-end protection and control engineering. Read more: tangiblinc.com/blog/distribution-substation/
Major Equipment Procurement
Major substation equipment — power transformers, circuit breakers, metal-clad switchgear E-houses, and protective relay and control systems — represents the largest cost components of a substation project with transformers and high-voltage circuit breakers, the longest lead-time items in the construction schedule. A procurement process that is technically incomplete or poorly timed can delay a project by months or years and expose the owner to significant cost and schedule risk.
Tangibl manages major substation equipment procurement from specification development through factory acceptance testing and delivery. Our substation engineers write the technical specifications, evaluate vendor proposals, and witness factory acceptance testing for the same equipment they are incorporating into the design — eliminating the translation errors that occur when procurement is separated from engineering. Where project schedules require it, Tangibl pre-purchases major equipment on behalf of clients to protect against long lead times.
Our major equipment procurement services include:
- Power transformer specification — MVA rating, voltage ratio, impedance, cooling, tap changer, bushings, and auxiliary equipment
- Circuit breaker specification — interrupting rating, operating mechanism, SF6 or vacuum technology, and associated disconnect switches
- Walk-in metal-clad switchgear and E-house specification — bus configuration, breaker compartment layout, control house integration, and SCADA interfaces
- Protective relay and control system specification in coordination with major relay suppliers
- RFI development and distribution to prequalified vendors
- RFP development, weighted proposal evaluation, and award recommendation
- Factory acceptance test planning, witness testing coordination, and test report review
- Delivery schedule management and on-site receiving inspection coordination
CASE STUDY
New 25kV Feeder Position — Major Equipment Pre-Purchase and RFP Administration
As Electric Engineer for a municipal electric system, Tangibl provided preliminary and detailed protection and control engineering for activating an available 25kV feeder position at an existing 138-25kV substation. Tangibl prepared AC and DC schematics, wiring diagrams, panel views, cable schedules, and civil/structural foundation analysis, pre-purchased the 25kV gas circuit breaker on behalf of the client, assembled the issue-for-bid package, administered the RFP process for construction and commissioning, provided construction observation, and incorporated field changes into as-built drawings. Read more: tangiblinc.com/blog/new-25kv-feeder-position/
25kV Feeder Additions
Serving new load, improving reliability, and providing backup capacity between substations often requires adding feeder positions to an existing substation — activating a built-out but unused bay, adding a new circuit breaker to an existing bus, or extending a duct bank and cable to the outside-plant distribution system. These projects are smaller in scale than a new substation but no less demanding in their engineering requirements, and their impact on reliability and capacity is often immediate.
Tangibl provides complete engineering services for 25kV, 13kV, and 34.5kV feeder additions to existing distribution substations, from preliminary design through issue-for-bid construction packages, construction observation, and as-built documentation. A feeder addition is not simply a matter of adding a breaker to a bus. The new circuit must be integrated into the existing protection scheme, bus capacity confirmed, underground routing designed, and control house space coordinated for new protection and control equipment. Tangibl manages all of these engineering tasks as a self-performing team.
Our feeder addition engineering services include:
- Protection and control engineering — relay selection, scheme design, settings calculation, and coordination with existing protection
- AC and DC schematics, wiring diagrams, panel views, and cable schedules
- Circuit breaker and bay hardware specification and procurement, including pre-purchase where schedule requires
- Underground duct bank and conduit design for routing outgoing cable from the new line position
- Civil and structural analysis for new breaker bay foundations
- Secondary and control cable routing between the control house and breaker bay
- Issue-for-bid and RFP package preparation for construction, testing, and commissioning
- Construction observation, field change documentation, and as-built drawing preparation
REQUEST INFORMATION
If you have a project that you believe is a good fit for our capabilities, please contact us. We can schedule an exploratory conversation to better understand your needs and together determine how best to serve you.
Electric Substation Planning and Engineering — FREQUENTLY ASKED QUESTIONS
What does front-end engineering and design (FEED) for a new substation include?
Front-end engineering and design encompasses the preliminary engineering deliverables required to define project scope, establish the equipment list and budget, and support major equipment procurement before detailed design and construction begin. A FEED package typically includes the final site plan, single-line diagram and general arrangement, transformer and switchgear specifications, protection and control scheme definition, geotechnical assessment results, transmission owner interconnection feasibility coordination, and a preliminary project schedule and cost estimate. Tangibl self-performs electrical and civil/structural FEED and manages subconsultants for site survey, geotechnical investigation, and relay and control system engineering.
How does Tangibl manage the interface between engineering and major equipment procurement?
Tangibl manages equipment procurement as an integrated part of the engineering process. Under the direction of our Technical Program Managers, substation engineers write the technical specifications, evaluate vendor proposals, and witness factory acceptance testing for the same equipment they are incorporating into the design. Integrating engineering with procurement reduces translation errors that can occur when procurement is separated from engineering — ensuring that what is specified, what is purchased, and what arrives on site are the same thing. Where project schedules require it, Tangibl pre-purchases major equipment on behalf of clients to protect against long lead times.
What is the typical timeline from site selection to energization for a new 138-25kV substation?
The timeline typically ranges from three to five years, depending on site complexity, transmission interconnection availability, major equipment lead times — power transformers and high voltage circuit breakers currently carry lead times of two to three years in some cases — and permitting and right-of-way requirements. Engaging an Electric Engineer with utility experience early in the process to coordinate site, equipment, and interconnection in parallel is the most effective way to compress this timeline.
Can Tangibl serve as Electric Engineer for a municipal utility without in-house engineering staff?
Yes. Tangibl regularly serves as Electric Engineer of record for municipal and public power electric systems without in-house engineering departments. In this role Tangibl provides the full range of electrical engineering services — planning, design, procurement, construction oversight, and as-built documentation — and manages all subconsultants and contractors on the utility’s behalf. This model gives smaller utilities access to the same depth of engineering capability as investor-owned utilities with large internal engineering departments, at a cost and scale appropriate to their project needs.
How does adding a feeder position to an existing substation affect the protection scheme?
Adding a feeder position requires integrating the new circuit into the existing protection and control scheme — reviewing bus relay settings, bus differential protection coverage, breaker failure scheme logic, and coordination with upstream transmission protection. It is not simply a matter of connecting a new breaker to the bus. Tangibl’s protection engineers review the existing scheme documentation, identify any required modifications, and deliver a complete set of updated relay settings and scheme drawings as part of the feeder addition engineering package.