Transmission Cable Construction in Korea: Structures to Earthing

Transmission cable construction in Korea covers underground structures, duct continuity tests, cable pulling, jointing and line earthing to install transmission cables in ducts and tunnels. The stages share names with distribution cable work, but 154 kV and 345 kV cables are heavy and large, making transport limits, pulling tension and joint sealing far more demanding. This guide sets out the overall flow in five stages and links each to a detailed guide.

Contents

• Common Pre-Work Review
• 1. Underground Structures
• 2. Duct Continuity Test
• 3. Cable Pulling
• 4. Cable Jointing
• 5. Line Earthing
• Distribution vs Transmission Cable Work
• FAQ
• Reference Standards
• Summary

Common Pre-Work Review

Before work, review the design documents, method statement, road occupancy permit and KEPCO standards, study the pulling concepts for ducts, tunnels and direct burial, and calculate pulling tension for each section. Walk the delivery route in advance to check overpass, footbridge and tunnel heights, and transport in line with road regulations. Prepare pulling equipment (pulling eyes, jacks, chain blocks, winches, caterpillar pullers, rollers, tension meters, cable guides), duct-test equipment (mandrels, swivels, wire brushes), measuring equipment (gas detector, earth and insulation testers), and notice boards, traffic signs, safety fencing and cones with reflective tape.

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 to the client before continuing.
4. Check each duct for debris or defects before joining.
5. Place protective concrete at manhole connections to prevent settlement and protect cables.
6. Fit spacers at specified intervals and install protection slabs and warning sheets.
7. Backfill and compact to restore the road and allow traffic.

Civil works for ducts, manholes and tunnels are detailed in Underground Transmission Civil Works.

2. Duct Continuity Test

1. Open the manhole and measure oxygen and toxic gases before entry.
2. Bring in equipment and assemble the mandrel and tools.
3. Remove sediment and carry out the continuity test.
4. If the test fails, carry out a 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.
3. Set up the drum and mark cable phases.
4. Fit tension meter, swivel, sheaves, pulling grip and mesh, and check the duct route between manholes.
5. Monitor tension so the limit is never exceeded, preventing drum-jack topple and tangling.
6. After winch pulling, cut and phase-mark the cable and waterproof the ends.
7. Record cable and accessory data, manhole layouts and line names.
8. With the supervisor present, carry out phase checks and a withstand test.

Secure caterpillar pullers firmly with ropes against the reaction force when cable enters, and provide snaking allowance in tunnels for thermal movement. Preparation and pulling details are in Laying Preparation and Cable Laying.

4. Cable Jointing

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

OF and XLPE jointing steps, cross bonding and test sequence are detailed in Underground Transmission Cable Jointing.

5. Line Earthing

1. Check soil and foundation conditions to choose electrode locations.
2. When excavating manholes, choose earthing locations considering duct and cable bending radii.
3. Measure soil resistivity first and install electrodes where resistivity is low.

Distribution vs Transmission Cable Work

	Underground distribution cable	Transmission cable
Voltage and cable	Distribution class, includes LV lines	154 kV / 345 kV, heavy large cables
Transport	Mainly standard trucks	Route height and weight limits surveyed in advance
Pulling	Winch and tension meter	Caterpillar reaction restraint, section tensions, snaking
Jointing	Distribution accessories	OF/XLPE joints, cross bonding, withstand and PD tests
NCS elements	6 (includes LV lines)	5 (no LV lines)

Compare with Underground Distribution Cable Construction.

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 Transmission Cable Construction (송전케이블 공사, 1901070232_22v4; NCS is Korea’s National Competency Standards) — ncs.go.kr

Summary

The most common mistake in transmission cable work is treating it like distribution cabling and underestimating transport limits, section tension calculations and thermal allowance in tunnels. Build the route with structures and continuity tests, pull under tension control, finish with jointing and earthing, and check the linked detailed guide at each stage. For pre-construction preparation, see Transmission Line Construction Planning. A Korean version of this guide is available here.

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This article restructures the Korean NCS competency unit ‘Transmission Cable Construction’ (송전케이블 공사, code 1901070232_22v4) 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