Overhead Distribution Line Construction in Korea: Conductors to Service Drops

Overhead distribution line construction in Korea covers everything from stringing conductors to grounding, lightning protection and service drops that supply customers. A single kink or a skipped compression sequence on a sleeve can lead to a broken conductor or a fault, so each stage has clear criteria. This guide covers four stages — conductors, grounding, lightning protection and service drops.

Contents

• Common Pre-Work Review
• 1. Conductor Stringing
• 2. Grounding
• 3. Lightning Protection
• 4. Service Drops
• NCS Criteria for Lines, Grounding and Service Drops
• FAQ
• Reference Standards
• Summary

Common Pre-Work Review

Before work, review the design documents, method statement, road occupancy permit and KEPCO design standards and field manuals. Prepare an aerial bucket truck, compressor, dies, insulation stripper, come-along, stringing rollers and conductor reel stand, plus a laser distance meter, staff, pressure gauge and earth resistance tester. Workers wear hard hats, safety vests, safety shoes, insulating gloves and harnesses; materials include sleeves, compression lugs and insulating tapes.

1. Conductor Stringing

1. Review conductor size and length, pole-top configuration, pole type and size and local traffic in advance, and prepare traffic safety measures and tools.
2. String conductors while taking care to avoid damage to insulation and twisting.
3. Set the conductor sag, then fix the conductor to the insulators.
4. Keep crossing heights and clearances to other facilities for each conductor size.
5. Obtain sleeves and dies that match the conductor size and fit the dies to the compressor head.
6. Follow the compression sequence and number of compressions for each size.
7. Fit a sleeve cover after compression to insulate live parts.

Paying out conductor faster than it is laid causes slack and kinks, and a kinked conductor loses roughly 20–50% of its tensile strength. For branch sleeves, strip insulation so that about 10 mm of margin remains on each side after compression, allowing for the sleeve’s elongation.

2. Grounding

1. Check soil and foundation conditions and choose an electrode location with good earth contact.
2. To achieve a good earth resistance, select locations with low soil resistivity before installing.
3. Understand the characteristics of each electrode type and install according to location.
4. Confirm the required earth resistance for each point and carry out the grounding work.
5. Measure earth resistance with an earth resistance tester.

3. Lightning Protection

1. Design effective lightning protection considering lightning activity, terrain and weather.
2. Install overhead ground wires and surge arresters to protect the line from induced and direct strikes.
3. Know where arresters are required and install them correctly.
4. Identify line sections with frequent lightning faults.
5. Know the required earth resistance for ground wires and arresters and install accordingly.

4. Service Drops

1. Select the service drop type suited to the location.
2. Select conductor sizes for single-phase lighting and three-phase power service drops.
3. Choose the service entrance point and route considering the meter location.
4. Make the connection between the service drop and entrance wiring at the drop’s end slack (jumper) so the joint is easy to insulate.
5. Install a protective device on service drops branching from the low-voltage line.

NCS Criteria for Lines, Grounding and Service Drops

Item	Criterion
Electrode burial depth	At least 0.75 m below ground
Electrode clearance from supports	Keep clear of concrete poles; at least 1 m from towers, steel and tubular steel poles
Ground conductor	Run on the inside of the pole as a rule
Arrester leads	Connect outside the equipment lead connection so surges are absorbed by the arrester
Arrester earth resistance	10 Ω for incoming cable protection; 25 Ω for line and equipment protection
Overhead span of service drop	No joints except where unavoidable
Branch protection	Install near the branch point (may be omitted for three-phase motor loads where phase loss is a concern)

These values come from the considerations in the NCS competency unit. On site, confirm the current values in the KEC and KEPCO distribution design standards first.

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 Overhead Distribution Line Construction (가공배전선로공사, 1901070212_22v4; NCS is Korea’s National Competency Standards) — ncs.go.kr

Summary

The most common mistakes in overhead distribution line construction are creating kinks by ignoring pay-out speed and skipping the sleeve compression sequence. Conductors depend on sag and clearances; grounding on soil resistivity and required values; lightning protection on arrester lead connection; and service drops on protection devices and joint location. 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 ‘Overhead Distribution Line Construction’ (가공배전선로공사, code 1901070212_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