Other Substation Equipment Works in Korea: VTs, Arresters, Disconnectors, Compressors

Other substation equipment works in Korea cover voltage transformers (VT), surge arresters (LA), disconnectors (DS) and air compressors that support stable operation of the main plant, including their inspection. Each item looks minor, but a wrong VT skews metering and protection, an arrester placed too far away gives no protection, and a misaligned disconnector–earthing switch interlock can cause a serious accident. This guide covers four stages: VTs, arresters, disconnectors and compressors.

Contents

• Common Pre-Work Review
• 1. Voltage Transformers
• 2. Surge Arresters
• 3. Disconnectors
• 4. Air Compressors
• NCS Criteria for Other Substation Equipment
• FAQ
• Reference Standards
• Summary

Common Pre-Work Review

Review the regulations, manufacturer drawings, design, general and particular specifications and the substation construction standard, and set the work procedure by checking the interface with other trades. First measure that foundation dimensions, anchor bolt positions and surfaces match the design. For equipment shipped with an impact recorder, check the chart on arrival and after installation, plus fixings, seals, structure and appearance. Stabilize the crane, then earth its chassis before operating. Prepare a multimeter, insulation tester, leakage current meter, oil dielectric tester and torque wrench.

1. Voltage Transformers

1. Check that foundation anchor bolt lengths, earth leads and drainage grooves are within the drawing tolerances.
2. Assemble and install the VT to the manufacturer drawings once its condition is confirmed, and check earthing.
3. Check terminal box position, conduit size and bend radius, earth bar and the fuse-failure alarm circuit.
4. After installation, measure insulation resistance and power factor, and confirm phase rotation matches the remote substation and parallel equipment.
5. During work, confirm the VT is out of service and its source side is securely earthed.

2. Surge Arresters

1. Check anchor bolt lengths, earth leads and drainage grooves on the foundation.
2. Unpack, check every part and assemble to the manufacturer drawings.
3. Connect the earth terminal to the leakage current meter with rated HV insulated wire so leakage current does not flow through the stand.
4. Measure insulation resistance and power factor to confirm condition.
5. After energizing, measure leakage current to confirm normal operation.
6. Check terminal connections, leads and the surge counter reading.

Install the arrester as close as possible to the protected equipment, within the protective distance set by insulation coordination.

3. Disconnectors

1. Check every part for damage or deformation against the packing list.
2. Confirm foundations, anchor bolts and earth leads are where the design shows.
3. Assemble and install the stand to the assembly drawing.
4. Confirm the functions of the main current path, insulators, base and motor operator.
5. Fit the inter-phase operating rods while checking fixing and rotation of each part.
6. Install the motor drive after checking level and anchor bolts, assemble the rods and fine-tune operation.
7. Adjust the mechanism so contacts close fully under motor operation.
8. Check the earthing switch (EDS) mechanism and adjust its mechanical interlock with the DS.
9. Confirm interlock, local and remote control work as designed.

4. Air Compressors

1. Inspect the exterior and components on receipt for damage.
2. Check foundation dimensions, level, anchor bolt positions and earth leads.
3. Install the compressor level and tighten anchor bolts firmly against vibration.
4. Connect compressor and breakers with rated copper pipe, sealed and insulated.
5. Check the air dryer stop valve is open and the auto drain valve works on start and stop.
6. Inspect every part and dismantle for inspection if anything is abnormal.

Position the compressor so it is easy to observe from the patrol route.

NCS Criteria for Other Substation Equipment

Item	Criterion
Control cable conduit bend radius	At least 6D
Terminal box height	1.5 m ± 0.2 m above ground line
Arrester location	Within protective distance after insulation coordination review
Arrester earth lead	HV insulated wire so no leakage flows through the stand
Disconnector and earthing switch	Mechanical interlock confirmed
Crane	Earth the chassis after stabilizing, then operate

These values come from the considerations in the NCS competency unit. Apply the client’s design standards and manufacturer drawings 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
• Technical Standards for Electrical Equipment (전기설비기술기준) — law.go.kr
• KEPCO design standards and substation construction practice; Korean Industrial Standards (KS)
• NCS competency unit Other Substation Equipment Works (기타 변전설비공사, 1901070317_22v2; NCS is Korea’s National Competency Standards) — ncs.go.kr

Summary

The most common mistakes are placing arresters wherever is convenient on the drawing and rushing disconnector–earthing switch interlock adjustment. VTs depend on terminal boxes and phase rotation; arresters on protective distance and leakage wiring; disconnectors on full contact closure and interlocks; and compressors on sealed, insulated piping and auto drains. Related guides: Substation Switchgear Installation, Substation Structure Installation, Substation Equipment Grounding. A Korean version of this guide is available here.

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This article restructures the Korean NCS competency unit ‘Other Substation Equipment Works’ (기타 변전설비공사, code 1901070317_22v2) 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 2026-10-26