Unsa ang GIS (Gas-Insulated Switchgear)? Kalihukan, Mga Tipo, ug Paggamit
Unsa ang GIS Equipment?
Ang GIS mao ang English abbreviation sa Gas Insulated Switchgear, nga gipasabot sa Chinese isip Gas-Insulated Metal-Enclosed Switchgear. Kasagaran kini nagamit og sulfur hexafluoride (SF6) gas isip insulating ug arc-quenching medium. Ang GIS giintegro, pinaagi sa optimized design, ang primary equipment sa substation—wala na ang transformer— sama sa circuit breakers (CB), disconnectors (DS), earthing switches (ES/FES), busbars (BUS), current transformers (CT), voltage transformers (VT), surge arresters (LA), cable terminations, ug incoming/outgoing line bushings—isip usa ka sealed metallic enclosure, nahimong usa ka integrated unit.
Karon, ang range sa voltage rating sa GIS equipment maoy extensive, gikan sa 72.5 kV hangtod sa 1200 kV.
Characteristics of GIS Equipment
Ang SF6 gas adunay excellent dielectric strength, arc-quenching capability, ug chemical stability. Taliwala niini, ang GIS equipment adunay compact size, minimal footprint, high operational reliability, long maintenance intervals, ug strong electromagnetic interference resistance. Bisan pa, tungod sa iyang fully enclosed structure, ang mga internal components protektado gikan sa external environmental factors ( sama sa dust, moisture, ug salt fog), sigurado ang stable operation, low electromagnetic noise, ug reduced maintenance workload.
Pero, ang dielectric performance sa SF6 gas dako kaayo ang sensitiveness sa electric field uniformity. Ang mga internal defects sama sa conductor burrs, metallic particles, o assembly flaws mahimo kasagaran mog resulta og partial discharge o even insulation breakdown. Giyahan, ang sealed structure sa GIS komplikado ang internal fault diagnosis ug maintenance, limitado ang diagnostic tools. Ang poor sealing mahimo usab mag resulta og water ingress o gas leakage, kompromiso ang equipment safety.
Types of Electrical Contacts in GIS Conduction Circuits
Ang conduction circuit sa GIS gisangpot sa daghang components ug makaklasiha ngadto sa tulo ka types batasan sa contact method:
Fixed Contact: Electrical connections secured by bolts or other fasteners, with no relative movement during operation, such as the connection between a busbar and a basin-type insulator.
Separable Contact: Electrical contacts that can be opened or closed during operation, such as the contacts in circuit breakers and disconnectors.
Sliding or Rolling Contact: Contacts that allow relative sliding or rolling between contact surfaces but cannot be separated, such as intermediate contacts in switchgear.
Introduction to HGIS
Aside from GIS, there is another type called HGIS (Hybrid Gas-Insulated Switchgear), a hybrid gas-insulated switchgear. HGIS does not include components such as busbars, busbar voltage transformers, or busbar surge arresters, resulting in a simpler structure. It is suitable for harsh environments or locations with space constraints and offers greater flexibility in layout.
Classification of GIS Equipment
By Installation Location: Indoor and outdoor types.
By Structure: Single-phase single-enclosure and three-phase common-enclosure. Generally, busbars at voltage levels of 110 kV and below can adopt the three-phase common-enclosure design, while voltage levels of 220 kV and above typically use the single-phase single-enclosure design to reduce the risk of phase-to-phase faults.
Basic Operating Principles
Under normal conditions, GIS circuit breakers and disconnectors are primarily operated remotely. The "Remote/Local" selector switch should be set to the "Remote" position.
Earthing switches can only be operated locally. During operation, the "Disconnector/Earthing Switch" selector switch must be switched to the "Local" position.
All operations must follow programmed procedures. The "Interlock Release Switch" on the control cabinet must remain in the "Interlock" position. The unlocking key, along with the microcomputer anti-misoperation unlocking key, must be sealed and managed strictly according to regulations.
Basic Operational Requirements
For indoor SF6 equipment rooms frequently accessed by personnel, ventilation should be performed at least once per shift for no less than 15 minutes, with air exchange volume exceeding 3–5 times the room volume. Air exhaust outlets should be located at the lower part of the room. For areas not frequently entered, ventilation for 15 minutes is required before entry.
During operation, the induced voltage on accessible parts of the GIS enclosure and structure should not exceed 36 V under normal conditions.
Temperature Rise Limits:
Easily accessible parts: no more than 30 K;
Parts easily touched but not contacted during operation: no more than 40 K;
Rarely accessible individual parts: no more than 65 K.
SF6 switchgear should be inspected at least once daily. For unattended substations, inspections should be conducted according to established procedures. Inspections should focus on visual checks for abnormalities such as unusual sounds, leaks, or abnormal indications, with records maintained accordingly.
