Switchgear routine maintenance in Korea means inspecting out-of-service circuit breakers, disconnectors and gas-insulated switchgear (GIS) from the outside without dismantling them. You check appearance and structure, run operating and characteristic tests, measure insulation and confirm that pressure devices and indicators work, so the equipment stays in its best operating condition. Routine results decide whether a full overhaul is needed, so record every measurement. This guide covers two stages: inspection and routine testing.
Contents
- Common Pre-Work Review
- 1. Switchgear Inspection
- 2. Routine Tests
- NCS Rules for SF6 Analysis and Measurement
- FAQ
- Reference Standards
- Summary
Common Pre-Work Review
Routine inspection timing weighs joint outage schedules, equipment age, fault history, overload periods and ease of outage. Identify live and dead parts at the work location and keep at least the safe clearance from anything live. Work to the manufacturer’s manuals, the client’s maintenance checklists and KEPCO’s GIS installation standard. Prepare a breaker timing analyzer, contact resistance meter, SF6 gas analyzer, insulation resistance tester, SF6 leak detector and SF6 filling kit, plus grease, O-rings and desiccant.
1. Switchgear Inspection
- Confirm the outage and earthing, and install barrier ropes, Do Not Operate and No Entry signs.
- Switch off breaker and disconnector control power and close pressure system valves to prevent operation during work.
- Check whether GIS buses are live or dead and mark off the work zone.
- Inspect exterior and structure to the checklist for each switchgear type.
- Check VT, CT and control circuits to confirm breaker protection.
- Check valves and joints for air or gas leaks and measure leak rates.
- Inspect breaker and disconnector mechanisms for deformation, wear and burning.
- Clean off and re-apply grease on rotating parts, and top up oil dashpots if low.
- Use the manual to judge whether any defect calls for an overhaul.
2. Routine Tests
- Test interlocking between GIS or GCB and related equipment.
- Measure breaker CT saturation and ratio.
- Measure main circuit insulation and contact resistance.
- Measure gas and air tightness and air valve leakage.
- Measure SO₂ and moisture in the SF6 gas.
- Measure opening and closing times per phase and pole discrepancy.
- Measure pressure gauge and auxiliary relay characteristics and the operating pressure of hydraulic and pneumatic drives.
- Test interlocks between devices, trip-free operation and the emergency opening device.
- Measure auxiliary circuit insulation and resistor values.
- Operate breakers, disconnectors and earthing switches, and judge whether an overhaul is needed if defects appear.
If gas pressure is well below rated, stop measuring and top up SF6 immediately. Filling a pressurized compartment can cause a secondary fault, so fill slowly at the lowest practical pressure while watching the gauge.
NCS Rules for SF6 Analysis and Measurement
| Item | Rule |
|---|---|
| Instruments | Calibrated and within validity |
| Conditions | Ambient 0–40 °C, humidity 80% or less |
| Hose connection | Check each manufacturer’s gas port design and use the right adapter |
| Equipment storage | Store dry; never leave hoses open to air |
| Contaminated sensor | Replace if accurate measurement is not possible |
| Stopping | Stop and restore immediately if a cascading fault is possible, and record the reason |
These rules come from the considerations in the NCS competency unit. Pass/fail values follow the client’s diagnostic criteria and manufacturer guidance.
FAQ
How does routine maintenance differ from an overhaul?
Routine maintenance checks operation, characteristics and insulation from the outside. An overhaul dismantles the interrupter and mechanism to inspect and replace contacts and parts.
Under what conditions is SF6 analyzed?
With calibrated instruments, at 0–40 °C and humidity of 80% or less. Keep hoses sealed from air.
Can I measure when gas pressure is low?
Not if it is well below rated. Top up SF6 first, slowly and at low pressure.
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 Switchgear Routine Maintenance (개폐장치 보통유지보수공사, 1901070310_22v2; NCS is Korea’s National Competency Standards) — ncs.go.kr
Summary
The most common mistakes are working with control power and pressure valves still live, causing unwanted operation, and measuring with low gas pressure. Inspection depends on outage, earthing and preventing operation; testing on timing, interlocks and protection; and SF6 analysis on calibrated instruments and proper conditions. Related guides: Switchgear Overhaul Maintenance, Substation Switchgear Installation, Condition Monitoring System Installation. A Korean version of this guide is available here.
This article restructures the Korean NCS competency unit ‘Switchgear Routine Maintenance’ (개폐장치 보통유지보수공사, code 1901070310_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