Detailed Guide to GIS Gas-Insulated Switchgear: Structure, Features, Components, and Maintenance

In modern power systems, Gas Insulated Switchgear (GIS) plays a vital role. Thanks to its compact design, high reliability, and excellent environmental adaptability, GIS switchgear has become a core equipment for medium- and high-voltage power distribution and protection. Whether in urban power grids, large power stations, or industrial electricity consumption sites, GIS provides strong support for the safety and stable operation of power systems with its unique technical advantages. Understanding the structural principles, technical features, and maintenance requirements of GIS is essential for power industry professionals and related users.
I. Role and Necessity of Understanding GIS Switchgear

GIS is a high-voltage switchgear that uses SF₆ (sulfur hexafluoride) gas as the insulation and arc-quenching medium. Compared to traditional air-insulated switchgear (AIS), GIS has a more compact structure and significantly reduces the footprint, making it particularly suitable for urban substations with limited space, underground distribution rooms, and harsh environmental conditions. GIS can effectively cut off fault currents, control and protect the power system, and also boasts high operational safety and environmental tolerance. A deep understanding of GIS helps improve system design, equipment selection, and operational maintenance management, reducing outage risks and extending equipment lifespan.

II. Structure and Components of GIS Switchgear

A complete set of GIS typically includes the following core modules, with all high-voltage live parts sealed in a metal enclosure filled with SF₆ gas:

Circuit Breaker (CB)
Responsible for switching circuits under normal and fault conditions; it is the most critical switching device in GIS.

Disconnector (DS) & Earthing Switch (ES)
The disconnector is used for electrical isolation, while the earthing switch is used for safe discharge during equipment maintenance.

Current Transformer (CT) & Voltage Transformer (VT)
Used for system monitoring, measurement, and protection signal acquisition.

Busbar & Connection Components
All gas chambers are connected via busbars to form a complete electrical path.

SF₆ Gas Chamber & Density Monitoring System
Each gas chamber is filled with SF₆ gas at a specific pressure and equipped with a density relay to monitor the gas status in real time.

Operating Mechanism and Control System
Includes spring, hydraulic, or electric operating mechanisms, as well as local/remote control cabinets.

Enclosure and Insulators
The grounded metal enclosure ensures personnel safety, and basin-type insulators provide gas chamber isolation and mechanical support.

III. Key Features of GIS Switchgear

Compact Structure: Saves over 70% of space compared to AIS, making it suitable for space-constrained applications.

High Reliability: The fully enclosed structure is unaffected by environmental factors (e.g., pollution, humidity, salt spray).

Enhanced Safety: All live parts are enclosed and grounded, eliminating the risk of electric shock and ensuring safer operation.

Low Maintenance: SF₆ gas is highly stable with strong arc-quenching capabilities, resulting in a long equipment lifespan.

Environmental Adaptability and Smart Compatibility: New-generation GIS is adopting eco-friendly gases and integrating smart monitoring features.

IV. Typical Application Scenarios

GIS is widely used in the following fields:

Urban central substations;

Switchyards of hydropower, thermal power, and nuclear power stations;

Rail transit power supply systems;

Large industrial and mining enterprise power distribution systems;

Special environments such as offshore wind power platforms.
V. Future Development Trends

Application of Eco-Friendly Alternative Gases
To reduce the greenhouse effect of SF₆ gas, mixed gases (e.g., SF₆/N₂) or pure green gases (e.g., g₃, C₄-PFN) will be gradually promoted.

Intelligent and Digital Transformation
Integration of various sensors and IEDs (Intelligent Electronic Devices) enables real-time status monitoring, fault prediction, and health management (PHM).

Modular and Miniaturized Design
Further reduction in equipment volume improves deployment flexibility.

High Voltage and Large Capacity
With the expansion of power grids, ultra-high-voltage GIS at 1100kV and above will become key equipment in future backbone power grids.

VI. Usage Precautions and Maintenance Guidelines

Usage Precautions:

SF₆ Gas Management: Leakage is strictly prohibited; protective equipment must be worn when handling gas chambers.

Anti-Misoperation: Strictly implement the "five preventions" requirements to prevent misoperations such as disconnecting under load.

Environmental Control: Installation sites should be well-ventilated to prevent SF₆ accumulation.

Reliable Grounding: All enclosure grounding must be secure and reliable.

Maintenance Recommendations:

Regular Inspections: Check pressure gauges, mechanism status, abnormal sounds, or discharge traces.

Gas Monitoring: Regularly perform SF₆ gas leakage detection and purity analysis.

Mechanical Characteristic Tests: Conduct mechanical operation tests and loop resistance measurements for circuit breakers and disconnectors.

Insulation Performance Evaluation: Assess insulation status through withstand voltage tests and partial discharge detection.

Component Maintenance: Keep mechanism components lubricated and check terminal connections for tightness.

Maintenance Records: Establish a complete equipment file to record all maintenance and test data.

Conclusion

As a critical equipment in modern power systems, GIS combines high-voltage technology, gas insulation technology, and intelligent control technology. Its reliable operation is directly related to the overall performance of the power grid. By deeply understanding its structural features, mastering correct usage and maintenance methods, and keeping abreast of technological trends, users can significantly enhance the operational reliability and lifespan of GIS, providing a solid guarantee for the efficient and stable operation of power systems.

If you have any needs regarding GIS equipment selection, technical upgrades, or operational maintenance services, please feel free to contact us. We are committed to providing you with professional support.