Underground Distribution Cable Construction in Korea: 6 Field Stages

Underground distribution cable construction in Korea covers structures, duct continuity testing, cable pulling, jointing, line earthing and underground low-voltage lines so cables can be installed in ducts and tunnels. The work splits into six strands with much of it inside manholes, so safety steps such as oxygen and gas measurement and pulling-tension control matter as much as quality. This guide covers all six stages.

Contents

• Common Pre-Work Review
• 1. Underground Structures
• 2. Duct Continuity Test
• 3. Cable Pulling
• Cable Pulling Checklist
• 4. Cable Jointing
• 5. Line Earthing
• 6. Underground Low-Voltage Lines
• FAQ
• Reference Standards
• Summary

Common Pre-Work Review

Before work, review the design documents, method statement, road occupancy permit and KEPCO standards and field manuals. For pulling, prepare a winch, tension meter, swivel, sheaves, pulling grip, protective mesh and drum jack; for duct testing, a mandrel and tools; and before any manhole entry, an oxygen and toxic gas meter. Place cones, progress boards and notice boards and assign flaggers; workers wear hard hats, safety vests, safety shoes and harnesses.

1. Underground Structures

1. Review the design documents and survey the site.
2. Use a locator to find electricity, gas, telecom, foul and storm water, water and sewer lines.
3. If rock is encountered, report the condition to the client before continuing.
4. Check the inside of each duct for debris or defects before joining with couplers.
5. After connecting ducts, place protective concrete at manhole connections to prevent settlement and protect future cables.
6. Fit spacers at the specified intervals to keep separation until backfilling, and install protection slabs and warning sheets.
7. Backfill and compact to restore the road and allow traffic.

2. Duct Continuity Test

1. Before work, open the manhole and measure oxygen and toxic gas levels.
2. Bring in equipment and assemble the test mandrel and tools as designed.
3. Remove sediment and debris from the duct and carry out the continuity test for cable entry.
4. If the test fails, carry out an additional piece test.

3. Cable Pulling

1. Survey the ducts and confirm the cable system diagram to prepare the cable method statement.
2. Place cones, progress boards, notice boards and flaggers for worker and traffic safety.
3. Set up the cable drum for pulling and mark the cable phases.
4. Fit the tension meter, swivel, sheaves, pulling grip and protective mesh, and check the duct route between manholes.
5. Monitor tension so it never exceeds the limit, preventing drum-jack topple and cable tangling.
6. After pulling with the winch, cut the cable, mark phases and waterproof the ends with sealing tape.
7. Record cable and accessory data, manhole layouts and feeder names for the database.
8. With the supervisor present, carry out phase checks and a withstand test to confirm quality.

Cable Pulling Checklist

Stage	What to check
Before manhole entry	Open access; measure oxygen and toxic gases
Preparation	Duct test passed (piece test if not); phases marked; tension meter, swivel, grip and mesh fitted
During pulling	Tension within limit; no drum-jack topple or tangling; traffic control
After pulling	Cable cut and phase-marked; ends waterproofed
Records and tests	Cable and accessory data, manhole layouts; phase check and withstand test with supervisor

4. Cable Jointing

1. Review the design documents to identify problems in advance.
2. Understand and prepare the cable accessories and tools.
3. When pulling in tunnels, utility tunnels or manholes, attach the cable position drawing and agree the work sequence and method.
4. Understand the characteristics of each cable and accessory type, and install the accessories.

5. Line Earthing

1. Check soil and foundation conditions to choose electrode locations with good earth contact.
2. When excavating manholes, choose earthing locations considering duct and cable bending radii.
3. Measure soil resistivity before installation and choose low-resistivity locations for good earth resistance.

6. Underground Low-Voltage Lines

1. Build underground low-voltage lines using ducts and manholes.
2. Use joint boxes, distribution boxes and accessories on low-voltage lines.
3. Separate low-voltage lines into mains and branches.

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
• KEPCO design standards; field practice manuals for transmission and distribution work; Korean Industrial Standards (KS)
• NCS competency unit Underground Distribution Cable Construction (지중배전케이블 공사, 1901070231_22v3; NCS is Korea’s National Competency Standards) — ncs.go.kr

Summary

The most common mistakes in underground distribution cable work are pulling without a duct continuity test and skipping manhole gas measurement. Structures depend on duct inspection and protection; testing on continuity and piece tests; pulling on tension and phase marking; and jointing, earthing and LV work on accessory characteristics and soil resistivity. For equipment connections, see Underground Distribution Equipment Installation. For pre-construction preparation, see Distribution Line Construction Planning. A Korean version of this guide is available here.

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This article restructures the Korean NCS competency unit ‘Underground Distribution Cable Construction’ (지중배전케이블 공사, code 1901070231_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