Transmission line maintenance in Korea means inspecting the operating condition of transmission lines to prevent unexpected faults, and repairing weak points and equipment that needs reinforcement in advance. A fault on one transmission circuit can affect supply across a wide area, so prevention-led management — finding deterioration through periodic inspection and replacing it on a plan — is the core. This guide covers two stages — inspection and maintenance.
Contents
- Common Pre-Work Review
- 1. Line Inspection
- 2. Maintenance
- Submarine Cable Protection Points
- FAQ
- Reference Standards
- Summary
Common Pre-Work Review
Reference values and normal conditions follow the client’s (for example KEPCO’s) transmission maintenance guidelines and manuals. Measurements use thermal cameras, insulation and earth resistance testers and gas detectors, and toxic gases must always be measured before entering manholes or tunnels. Safety equipment includes hard hats, safety vests, safety shoes, harnesses and lanterns.
1. Line Inspection
- Select inspection targets by interval and equipment type and carry out equipment and preventive inspections.
- Confirm inspection intervals and methods for the line, inspect and assess compliance.
- Inspect cable deterioration and joint condition and assess compliance.
- Inspect cable terminations and surge arresters on underground sections for deterioration.
- Check manual operation and batteries of automation and monitoring devices.
- Measure earth and insulation resistance for each piece of equipment and assess compliance.
- Measure toxic gases inside manholes and tunnels and plan work-environment and safety improvements.
- Check control boxes, batteries and breakers for defects.
- Measure contact resistance of switch or breaker contacts to detect defects.
The NCS performance criteria for this unit repeat the underground distribution maintenance wording (underground distribution lines, distribution automation), so they are adapted here to transmission lines. Overhead transmission lines also require checks on towers, insulators, conductors and vegetation clearance, so confirm the client’s inspection standards as well.
2. Maintenance
- Prepare a maintenance plan for transmission equipment.
- Replace lines and equipment according to the plan, based on inspection and assessment results.
- Operate replaced lines and equipment to confirm normal operation.
Submarine Cable Protection Points
| Item | Details |
|---|---|
| External damage | Burial, mechanical protection and warning markers against bottom trawling and anchors |
| Corrosion | If the metallic sheath corrodes, seawater enters and causes faults; use corrosion-protected lead sheaths and reinforcing tapes |
| Armor | Usually steel wire; copper or aluminum wire to reduce AC losses, FRP to prevent electrolytic corrosion |
| Route management | Clearance to existing cables and telecom lines; future reclamation and dredging plans |
The NCS considerations for this unit cover submarine cables, so they are summarized here as protection points for managing submarine (HVDC) sections of transmission lines. Submarine laying is covered in Underground Transmission Cable Laying.
FAQ
What is the core of transmission line maintenance?
Prevention-led management: finding deterioration and weak points through periodic inspection and replacing them on a plan before they fail.
Why does the NCS text use distribution terms?
The published performance criteria repeat the underground distribution maintenance wording. In practice, the client’s transmission maintenance guidelines should be the reference.
What matters most on submarine sections?
External damage from fishing gear and anchors, metallic sheath corrosion, and reclamation or dredging plans near the route.
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 Line Maintenance (송전선로 유지보수, 1901070245_22v1; NCS is Korea’s National Competency Standards) — ncs.go.kr
Summary
The most common mistakes in transmission line maintenance are accumulating inspection results without assessment and skipping the operating check after replacement. Inspection depends on interval-based targets, measurement and assessment; maintenance on planned replacement and operating checks; and submarine sections need extra attention to external damage and corrosion. 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 ‘Transmission Line Maintenance’ (송전선로 유지보수, code 1901070245_22v1) 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