The temporary switch method in Korea applies when there is no load within the work section and an outage of that section is acceptable: a temporary switch is installed on the load side so only the work section is made dead, and the work proceeds without a wider outage. Switching and jumper cutting and reconnection must follow a fixed order, and confusing live and dead sections leads straight to accidents. This guide covers two stages — preparation and execution.
Contents
- Common Pre-Work Review
- 1. Preparation
- 2. Execution
- Switching and Restoration Sequence
- FAQ
- Reference Standards
- Summary
Common Pre-Work Review
This method applies to 22.9 kV-Y and below overhead distribution lines when work is done without de-energizing the line. Prepare an insulation resistance tester, HV ammeter, HV and LV phase meters and HV voltage detector, plus an insulated aerial device; and a temporary switch as no-outage equipment. Workers wear hard hats, safety vests, safety shoes, insulating gloves and harnesses, with line and insulator covers ready. Materials include sleeves, lugs and insulating tapes.
1. Preparation
- Prepare the site: pedestrian route, traffic marshals, earthing of equipment and vehicles, wheel chocks and load current measurement.
- Hold a safety meeting covering task assignment, PPE, equipment and line checks and risk assessment.
- Confirm substation breaker and source-side recloser (R/C) reclosing status, notify the distribution center, cover live parts and send site monitoring data.
On arrival, review traffic, pole-top configuration and buried services and carry out hazard prediction training; control traffic and pedestrians with barrier ropes, signs and marshals. Before no-outage work, notify the distribution center and confirm auto-reclosing is blocked; notify completion afterwards.
2. Execution
- Measure load current, cover the neutral and prepare to install the temporary switch.
- Install the temporary switch as the procedure requires and, following the supervisor’s instructions and watching live and dead sections, carry out dead work such as new or relocated poles, conductors and transformers.
- After the main dead work, remove the temporary switch in reverse order to restore normal service.
- Notify the distribution center of completion and tidy the site to avoid complaints.
Switching and Restoration Sequence
| Stage | Sequence |
|---|---|
| Convert to dead | Install temporary switch → riser clamps and HV riser cables → connect risers at switch pole → phase check and close temporary switch → cut jumper at switch pole → close normally-open switch → open temporary switch → cut source-side jumper of work section |
| Restore | Remove short-circuit earths → phase-check and reconnect source-side jumper → close temporary switch → open normally-open switch → reconnect jumper at switch pole → open temporary switch → disconnect, discharge and remove risers → remove covers |
This sequence summarizes the NCS considerations; actual work follows KEPCO standard procedures and the site supervisor.
FAQ
What is dead-section work?
Work done after converting only the work section to a de-energized (dead) state, while the surrounding line and customers stay supplied, so the job needs no outage.
When is the temporary switch method used?
When the work section has no customers and can be de-energized, by installing a temporary switch on the load side so only that section is dead.
What is checked before closing the temporary switch?
Riser cable connections, followed by a phase check every time.
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 Temporary Switch Method for No-Outage Work (개폐기공법 공사, 1901070239_22v3; NCS is Korea’s National Competency Standards) — ncs.go.kr
Summary
The most common mistakes with this method are confusing the conversion and restoration sequences or skipping the phase check. Preparation depends on reclosing checks and covering; execution on correct switching order and clear live/dead boundaries; and restoration on reverse-order removal. Compare with the bypass cable method and the mobile transformer method. 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 ‘Temporary Switch Method for No-Outage Work’ (개폐기공법 공사, code 1901070239_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