Underground Transmission Cable Laying in Korea: Ducts, Tunnels, Subsea

Underground transmission cable laying in Korea covers installing ducts, testing their continuity and pulling underground transmission cables into ducts and tunnels; on HVDC projects it also includes laying submarine cables. Missing the bending radius, entry speed or tension limit during pulling damages insulation, and inadequate allowance for thermal movement in tunnels causes problems in service. This guide covers four stages.

Contents

• Common Pre-Work Review
• 1. Duct Installation
• 2. Duct Continuity Test
• 3. Cable Pulling
• Key Points by Laying Method
• 4. HVDC Submarine Cable Laying
• FAQ
• Reference Standards
• Summary

Common Pre-Work Review

Before work, review the design documents, method statement, road occupancy permit and KEPCO standards, and study the pulling concept drawings for ducts, tunnels and direct burial. Prepare pulling equipment — pulling eyes, jacks, chain blocks, winches, caterpillar pullers, rollers, cable drums, tension meters, take-up winders, wire rope, cranes, cable guides (rollers, guide pipes, flexible tubes) and communications — and duct-test equipment such as wire rope, swivels, wire brushes and test mandrels. Measuring equipment includes a gas detector, earth resistance tester, insulation tester, multimeter and discharge device. On roads, set out notice boards, traffic signs (beacons, work-in-progress and slow signs), danger signs, safety fencing and cones with reflective tape for night visibility.

1. Duct Installation

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.
5. Place protective concrete at manhole connections to prevent settlement and protect cables.
6. Fit spacers at the specified intervals and install protection slabs and warning sheets.
7. Backfill and compact to restore the road and allow traffic.

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 as designed.
3. Remove debris and carry out the continuity test.
4. If the test fails, carry out a piece test.

3. Cable Pulling

1. Position cable drums on site and pull using pulling equipment.
2. Check bending radius and maintain entry speed to avoid damaging the cable inside ducts.
3. In tunnels, review snaking allowance for thermal expansion before laying.
4. Carry out a dielectric test on the anti-corrosion jacket as specified.
5. Install hangers and cleats to support the cable as drawn.
6. Remove drums and pulling equipment after pulling.

Caterpillar pullers take a strong reaction force when cable enters, so secure them firmly with ropes, and monitor tension continuously so the pulling limit is never exceeded. Keep vehicle and pedestrian safety measures in place during pulling.

Key Points by Laying Method

Method	Key points
Duct	Bending radius and entry speed; tension monitoring; prior continuity test
Tunnel	Snaking allowance for thermal movement; hangers and cleats
Direct burial	Burial depth; protection slabs and warning sheets
Submarine (HVDC)	Pre-clearance of obstacles; burial depth control; sheath protection

Snaking allowance is slack set in advance for thermal expansion. The laying method follows the installation type — direct burial, duct or tunnel. For preparation, see Underground Transmission Cable Laying Preparation.

4. HVDC Submarine Cable Laying

1. Survey the submarine route and select the armor construction.
2. Clear ropes, wires, abandoned nets and fishing gear in advance to protect the burial equipment and the cable.
3. Transport the submarine cable to the laying position by vessel.
4. Lay cable along coastal, aquaculture, shipping-lane and strait sections using the cable-laying vessel’s equipment.
5. Measure and control burial depth from the vessel’s central control room to keep it constant.
6. Plan protection measures against damage to the cable sheath.

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 Transmission Cable Laying (지중송전케이블 깔기공사, 1901070234_22v4; NCS is Korea’s National Competency Standards) — ncs.go.kr

Summary

The most common mistakes in cable laying are rushing the pull so bending radius and tension limits are exceeded, and fixing cables in tunnels without thermal allowance. Ducts depend on installation and continuity tests; pulling on radius, speed, tension and jacket testing; and submarine laying on obstacle clearance and burial depth control. For pre-construction preparation, see Transmission Line Construction Planning. A Korean version of this guide is available here.

---

This article restructures the Korean NCS competency unit ‘Underground Transmission Cable Laying’ (지중송전케이블 깔기공사, code 1901070234_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