Substation Structure Installation in Korea: Foundations to Bus and Cable Trays

Substation structure installation in Korea covers the foundations, equipment stands, steel gantries, overhead bus and steelwork such as cable trays and ducts that carry and support substation equipment. A few millimeters of error in foundation level can stop an equipment install, and insufficient bus clearance can cause an insulation failure, so civil and electrical works have to fit together exactly. This guide covers five stages: foundations, equipment stands, steel structures, bus and steelwork.

Contents

• Common Pre-Work Review
• 1. Equipment Foundations
• 2. Equipment Stands
• 3. Steel Structures
• 4. Overhead Bus
• NCS Criteria for Structures and Bus
• 5. Steelwork: Cable Trays and Ducts
• FAQ
• Reference Standards
• Summary

Common Pre-Work Review

Prepare a method statement before work, brief everyone involved, and work to it. Review the design documents (drawings, specifications, bills of quantities), manufacturer drawings, the Korea Electro-technical Code (KEC), KEPCO substation design standards and pre-energization inspection criteria. Prepare a surveying instrument, level and concrete air-content meter; a torque wrench, angle drill, winch and concrete vibrator; and hire an excavator and mobile crane. Workers wear insulated helmets, flame-resistant clothing, insulated boots and harnesses, and carry proximity alarms and voltage detectors. Install safety ropes, fall protection, No Entry signs and fencing on site.

1. Equipment Foundations

1. Plan materials, equipment and labor, and check the scope against design and manufacturer drawings.
2. Excavate according to the design and site survey, matching depth and width to the drawings without over-excavating.
3. Plan to keep surface water out and to drain any inflow.
4. Compact crushed stone thoroughly and fill gaps with blinding concrete to a level surface.
5. Check and correct formwork flatness with a level; cut and fix rebar to the bar schedule with the required cover.
6. Compact concrete thoroughly during placement, observe the curing period and review compressive strength test records.
7. Set the positions of earthing conductors and cable entry conduits from the earthing terminal and control cable layouts.
8. Install anchor bolts and tower stubs, and fit earthing angles when forming cable ducts.
9. Finish with backfilling, compaction and site tidying.

Placing all concrete at once can deform formwork under concentrated load, so plan construction joints and pour in stages, checking that anchor bolts, earthing conduits and duct angles have not moved.

2. Equipment Stands

1. Review design and manufacturer drawings for each equipment stand.
2. Secure lifting and assembly equipment suited to the stand type.
3. Confirm that foundation bolt dimensions are within tolerance.
4. Check member quantities, galvanizing, damage and deformation, and manage materials so nothing runs short.
5. Assemble main and secondary members from the bottom up, setting the bolt and nut sequence and direction.

3. Steel Structures

1. Review design and manufacturer drawings for the steel structures.
2. Select erection equipment based on structure size, height and total weight.
3. Check working radius, ground bearing, slope and material storage on the work area.
4. Confirm tower stub dimensions are within tolerance, then position members and pre-assemble with bolts.
5. Check the pre-assembly against tolerances, adjust, then make the joints by bolting or welding as specified.
6. Erect main and secondary members from the bottom up.
7. Decide whether to lift beams whole or in sections, based on ground assembly location and lift weight.
8. Act early on any material shortages.

Tower stubs must be set to the manufacturer drawings for position, face direction, squareness and inclination.

4. Overhead Bus

1. Review bus layout drawings and fittings drawings.
2. Select fittings and insulator assemblies for the conductor type and size, and calculate insulator count from the nominal voltage.
3. Decide where suspension and tension insulator assemblies go.
4. Install insulator assemblies on the structure, then install the bus.
5. Check phase-to-phase and phase-to-earth clearances.
6. Connect main and branch buses, and buses to equipment, with the proper fittings.
7. Allow for expansion and contraction of aluminum tube, copper bar and copper rod.
8. Measure insulation resistance of the bus and insulator assemblies.
9. Install overhead shield wires to protect the substation from external surges.

Do not let insulator assemblies kink when connecting compression dead-end clamps, and avoid excessive tension on the bus or load on equipment bushings.

NCS Criteria for Structures and Bus

Item	Criterion
Base channel level	Within ±2 mm across the same H-beam
Bus expansion	Provide expansion terminals and sliding clamps
Aluminum tube joints	Apply conductive compound to contact faces
Aluminum tube drainage	Drill a drain hole at the bottom center of each length
Aluminum tube vibration	Insert scrap ACSR inside main and transfer bus tubes to damp vibration
Steelwork earthing	Earth cable trays, ducts, angles and racks with properly sized conductors

These values come from the considerations in the NCS competency unit. Apply the client’s design standards and manufacturer drawings first.

5. Steelwork: Cable Trays and Ducts

1. Review installation and fabrication drawings for cable trays and ducts.
2. Establish tray routes with adequate clearance from the bus.
3. Separate trays by voltage and purpose.
4. Run a correctly sized earthing conductor in the tray to guard against abnormal voltages.
5. Check duct angles, cable racks, supports and foundation bolts for quantity, galvanizing, damage and deformation.
6. Confirm rack anchor and hole spacing are within tolerance, and check expansion joints in duct angles.
7. Assemble trays and racks from the bottom up, and fit duct covers for safety.

FAQ

Reference Standards

• Electricity Business Act (전기사업법) — law.go.kr
• Electrical Safety Management Act (전기안전관리법) — law.go.kr
• Electric Technology Management Act (전력기술관리법) — law.go.kr
• Electrical Construction Business Act (전기공사업법) — law.go.kr
• Occupational Safety and Health Act (산업안전보건법) — law.go.kr
• Korea Electro-technical Code (KEC, 한국전기설비규정) — law.go.kr
• Technical Standards for Electrical Equipment (전기설비기술기준) — law.go.kr
• KEPCO design standards and substation construction practice; Korean Industrial Standards (KS)
• NCS competency unit Substation Structure Installation (구조물 설치공사, 1901070304_22v2; NCS is Korea’s National Competency Standards) — ncs.go.kr

Summary

The most common mistake is moving past the foundation stage with anchor bolt and stub positions and levels only roughly right. Foundations depend on level and embedded items; stands and structures on tolerance checks and assembly order; the bus on clearances and expansion allowance; and steelwork on earthing and expansion joints. Related guides: Substation Mesh Grounding, Substation Structural Grounding, Main Transformer Installation. A Korean version of this guide is available here.

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This article restructures the Korean NCS competency unit ‘Substation Structure Installation’ (구조물 설치공사, code 1901070304_22v2) as a practical reference. Actual work must follow applicable standards and the judgment of qualified professionals; always confirm specific values, deadlines and criteria against the latest regulations and client standards.

Written/reviewed by VOLT · Last updated 2026-10-26