Switchgear installation in Korean substations covers installing breakers, disconnectors and their accessories that open and close circuits, then testing them to confirm performance, including relay interlock tests and interlocks between devices. In GIS, every live part sits inside the tank, so a speck of dust or drop of moisture let in during installation can later become an insulation failure. Working conditions such as humidity and wind, and cleanliness, decide installation quality. This guide covers three stages: installation, SF6 filling and testing.
Contents
- Common Pre-Work Review
- 1. Installing Switchgear
- NCS Transport and Installation Limits
- 2. SF6 Filling
- 3. Testing and Measurement
- FAQ
- Reference Standards
- Summary
Common Pre-Work Review
Review the manufacturer’s manuals and installation procedure, the transmission and substation quality checklist, KEPCO’s GIS installation standard and the construction, quality, environmental and safety plans. Identify live and dead parts; keep safe clearance near live parts, and earth equipment and rope off the area on outage work. Check accessories against the packing list and prepare equipment, tools and people in advance. Prepare an SF6 recovery unit, vacuum pump and gauge, dry-air generator, SF6 filling manifold, timing analyzer, contact resistance meter, SF6 analyzer and leak detector, and a mobile crane. Set up a clean room if needed to protect quality from the outside environment.
1. Installing Switchgear
- Review switchgear ratings and shipping and packing units from the manufacturer drawings.
- Check the impact recorders and indicators, then unload and bring in with a crane of suitable capacity.
- Check anchor bolt length and position, earth conductors and control cable conduits on the foundation.
- Set the switchgear on the base channel, check level and plumb, and match tank and bus heights.
- Compare bellows dimensions before and after compression to measure contact depth, and place desiccant in inspection covers to protect dielectric strength from moisture.
- Set standalone breakers on their foundations and connect to disconnectors; for phase-segregated or compressor-fed breakers, install inter-phase control wiring and air piping between compressor and breaker.
- Mount disconnectors on stands or under beams and connect conductors to breakers and buses.
For equipment shipped in parts, replace transport covers with dust covers to keep debris out. Photograph any parts that will be concealed, and record measurements on the quality checklist.
NCS Transport and Installation Limits
| Item | Limit |
|---|---|
| Transport position | CB open (closed for some manufacturers), DS and ES closed |
| Transport gas pressure | 0.2–0.5 kg/cm² |
| Impact recorder | 3 G or less longitudinal, vertical and lateral |
| Impact indicator | Ball not released or dislodged; arrow aligned |
| Installation level | ±1° |
| Installation plumb | Aligned with foundation marks |
| Working conditions | Humidity 80% or less; wind 10 m/s or less |
These values come from the considerations in the NCS competency unit. Check the manufacturer’s installation procedure as well.
2. SF6 Filling
- Identify the GIS gas compartments.
- Connect the vacuum pump and high-pressure hoses and pull vacuum.
- During vacuum, check tank and joint tightness and inspect spacers for cracks.
- Fill each compartment with SF6 to rated pressure.
- Measure and record the SF6 used.
3. Testing and Measurement
- Test interlocking between GIS or GCB and related equipment.
- Measure main and auxiliary circuit insulation and main circuit contact resistance.
- Measure SO₂ and moisture in the SF6.
- Measure opening and closing times per phase and pole discrepancy.
- Function-test breaker, disconnector and earthing switch operators.
- Test trip-free, interlocks and the emergency opening device.
Use calibrated gas analyzers at 0–40 °C and humidity of 80% or less. If gas pressure is well below rated, do not measure — top up slowly at low pressure first.
FAQ
In what weather can GIS be installed?
Under the NCS, at 80% humidity or less and wind of 10 m/s or less. Otherwise postpone or control the environment with a clean room.
How is transport shock judged?
The impact recorder must read 3 G or less in all three directions, and the indicator ball must stay in place with the arrow aligned.
Why put desiccant in inspection covers?
Moisture left in the tank lowers dielectric strength. Desiccant absorbs it and protects insulation.
Why record SF6 usage?
SF6 is a potent greenhouse gas, so filled and recovered quantities must be measured and managed. Records support environmental compliance and settlement.
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 Substation Switchgear Installation (개폐장치 설치공사, 1901070327_22v2; NCS is Korea’s National Competency Standards) — ncs.go.kr
Summary
The most common mistakes are opening equipment regardless of humidity and wind, and covering concealed parts without records. Installation depends on transport shock checks, level and contact depth; gas filling on vacuum tightness and pressure and usage records per compartment; and testing on timing, interlocks and SF6 analysis. Related guides: Switchgear Routine Maintenance, Switchgear Overhaul Maintenance, Substation Switchgear Removal. A Korean version of this guide is available here.
This article restructures the Korean NCS competency unit ‘Substation Switchgear Installation’ (개폐장치 설치공사, code 1901070327_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