Underground distribution equipment installation in Korea covers the structures, auxiliary facilities and pad-mounted transformers and switches that connect to underground distribution lines, so the equipment can be built and operated safely. If manhole and handhole positions do not match the equipment layout, or drainage is missing, flooding and faults recur in service. This guide covers three stages — underground structures, auxiliary facilities and pad-mounted equipment.
Contents
- Common Pre-Work Review
- 1. Underground Structures
- 2. Auxiliary Facilities
- Auxiliary Facility Checklist
- 3. Pad-Mounted Equipment
- FAQ
- Reference Standards
- Summary
Common Pre-Work Review
Before work, review the design documents, specifications and bill, single-line diagram and construction drawings, the construction plan report and the road occupancy permit. The site construction manager must confirm that staffing meets the engineer placement rules of the Electrical Construction Business Act for the project size. Prepare cable pulling equipment (winch, cargo crane, truck, tension meter), jointing tools (electric compression pump, compressor, stripper), a cable cutter and drum jack; materials include sleeves, lugs, insulating tapes, cable accessories (straight, termination, switch elbows, transformer elbows), connection plugs, insulating plugs and caps. On roads, set out traffic signs, cones, beacons and barrier ropes.
1. Underground Structures
- Apply for road excavation and occupancy permits under the Road Act.
- Excavate along the route and restore by backfilling.
- Check foundation level and build the structural foundations.
- Confirm that manhole and handhole positions match the pad-mounted equipment layout.
- When installing low-voltage structures, confirm they match the equipment layout and can operate safely despite traffic or natural hazards.
- Build the duct connections between the underground structures and pad-mounted equipment.
After trenching, lay sand under the ducts to prevent settlement and set the level, then cover the ducts with sand after laying to protect them.
2. Auxiliary Facilities
- Install branch openings, vents and access openings.
- Install sumps and control boxes for drainage pumps.
- Install ladders or handrails.
- Connect corrugated ducts and install cable joint supports.
- Install disaster-prevention equipment, lighting, power and ventilation.
- Install earthing, measure earth resistance and record the results.
- Confirm that the facilities are set up safely for test operation and service.
Auxiliary Facility Checklist
| Facility | What to check |
|---|---|
| Branch openings, vents, access | Location, opening condition, ventilation path |
| Sump and drainage pump | Sump location; pump control box operation |
| Ladders and handrails | Fixing and safe access |
| Corrugated ducts and joint supports | Duct connections; support locations |
| Disaster prevention, lighting, power, ventilation | Operation confirmed by test run |
| Earthing | Earth resistance recorded |
3. Pad-Mounted Equipment
- Review the installation drawings, prepare the method statement and material list, evaluate them, and visit the site if needed.
- Install riser pipes for underground service entry and underground low-voltage distribution boxes.
- Install pad-mounted switches on the ground structures (base, equipment mounting, terminations).
- Install pad-mounted transformers on the ground structures (base, equipment mounting, terminations).
- Inspect accessory installation, backfill compaction, waterproofing and earthing, and prepare an inspection report.
FAQ
What should be checked before installing pad-mounted equipment?
Whether manhole and handhole positions match the equipment layout, and whether low-voltage structures can operate safely despite traffic and natural hazards.
Why are sumps and drainage pumps needed?
Water in underground structures degrades cable and joint insulation, so sumps and pumps allow it to be removed.
What is inspected after installing a pad-mounted transformer?
Accessory installation, backfill compaction, waterproofing and earthing, recorded in an inspection report.
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
- KEPCO design standards; field practice manuals for transmission and distribution work; Korean Industrial Standards (KS)
- NCS competency unit Underground Distribution Equipment Installation (지중배전기기 설치공사, 1901070230_22v3; NCS is Korea’s National Competency Standards) — ncs.go.kr
Summary
The most common mistakes in underground distribution equipment installation are building structures without matching them to the equipment layout, and leaving drainage, pumping and waterproofing until the end. Structures depend on permits, level and layout match; auxiliary facilities on drainage and earthing; and pad-mounted equipment on terminations and inspection reports. Cable work continues in Underground Distribution Cable Construction. For pre-construction preparation, see Distribution Line Construction Planning. A Korean version of this guide is available here.
This article restructures the Korean NCS competency unit ‘Underground Distribution Equipment Installation’ (지중배전기기 설치공사, code 1901070230_22v3) 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 2026-10-25