The NCS testing unit for overhead and underground line work in Korea covers testing and measurement for project completion, followed by charging and energizing the line. Tests are split between construction-stage tests and those carried out during the pre-use inspection, and a wrong circuit or missed phase check at energization leads straight to outages or accidents. This guide covers two stages — testing and energization.
Contents
- Common Pre-Work Review
- 1. Testing and Measurement
- 2. Charging and Energization
- Pre-Use and Completion Inspection Documents
- FAQ
- Reference Standards
- Summary
Common Pre-Work Review
First confirm KEPCO quality regulations, the approved quality test plan and the construction specifications. Prepare a compression tester, dielectric strength tester and protective relay tester, plus a gas analyzer, earth resistance tester, insulation tester, multimeter, discharge device and phase meter, along with pulling-tension software, camera, radios and a voltage detector. Workers wear hard hats, safety vests, safety shoes and harnesses and carry lanterns.
1. Testing and Measurement
- Carry out stage tests on transmission and distribution lines with the supervisor present, following KEPCO quality regulations and the approved quality test plan.
- For foundations, carry out concrete, soil and material tests at mandatory hold points.
- For superstructure work, carry out quality tests by measurement for every trade.
- During each trade’s work, test visually or with instruments.
- Inspect spacers and conductor joints (sleeves) with reference to the compression joint measurement records.
When the pre-use inspection is requested from the Korea Electrical Safety Corporation (한국전기안전공사), visual inspection comes first — tower foundations, site restoration, tower assembly, stringing and sagging, fittings and attachments, painting, phase rotation and loop tests.
2. Charging and Energization
- After passing the pre-use inspection, establish communication with the distribution center before energizing.
- After inspecting overhead and underground lines, carry out no-load and on-load charging, then energize.
- To prevent wrong-circuit errors, re-check the line between switch terminals before energizing underground lines.
- Confirm phases before closing the switch, then connect to other lines.
Pre-Use and Completion Inspection Documents
| Stage | Key documents |
|---|---|
| Pre-use inspection request | Inspection application, copy of construction plan approval, copy of electrical safety manager appointment, supervisor deployment confirmation |
| Completion inspection | Construction confirmations (electrical and fire), supervisor deployment confirmation, power supply contract, construction plan report and approval, safety manager appointment, pre-use inspection certificate, fire inspection certificate, KS materials summary, supervision report, CCTV and aviation obstruction light confirmations, defect liability bond |
| Facility handover | Project overview; operating guide (specifications and functional checks, procedures, test equipment and calibration, manuals, drawings); commissioning report; pre-completion inspection results; special notes |
This list summarizes the NCS considerations; actual submissions follow the client and inspection body. The completion inspection is carried out by the non-resident supervisor with KEPCO present.
FAQ
What is checked first in the pre-use inspection?
Visual inspection — tower foundations, site restoration, assembly, stringing and sagging, fittings and painting — together with phase rotation and loop tests.
Why check phases before energization?
Connecting to another line with mismatched phases causes a short circuit, so phases are always confirmed before closing the switch.
What needs special care when energizing underground lines?
Re-check the line between switch terminals before energizing to avoid wrong-circuit errors.
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 Line Testing and Energization (시험, 1901070223_22v3; NCS is Korea’s National Competency Standards) — ncs.go.kr
Summary
The most common mistakes in line testing are failing to keep construction-stage test records by trade — so evidence must be rebuilt for the pre-use inspection — and skipping the phase check just before energization. Testing depends on supervisor witness and hold points; energization on communication, circuit re-checks and phase confirmation. For pre-construction preparation, see Distribution Line Construction Planning. A Korean version of this guide is available here.
This article restructures the Korean NCS competency unit ‘Line Testing and Energization’ (시험, code 1901070223_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