132 kV Outdoor Gas Insulated Substations (GIS) & Ancillary Equipment
Gas Insulated Substations (GIS) are a type of substation in which the major electrical equipment is contained within a sealed, gas-insulated environment. For outdoor substations operating at 132 kV, GIS technology provides several advantages, including compact design, reduced space requirements, enhanced reliability, and minimized maintenance needs. Here is an in-depth look at 132 kV outdoor GIS and its associated ancillary equipment.
1. Overview of 132 kV GIS
A 132 kV Gas Insulated Substation typically uses sulfur hexafluoride (SF₆) gas as the insulating medium. SF₆ is a highly effective dielectric gas, which allows for smaller physical dimensions of the equipment while maintaining high voltage handling capabilities. This is crucial for outdoor installations where space is often a limiting factor.
Key features of 132 kV GIS:
- Compact Size: The use of SF₆ gas insulation enables a significant reduction in the size of the substation.
- Safety and Reliability: GIS provides high reliability due to the sealed environment, which reduces exposure to external contaminants such as dust, moisture, and wildlife.
- Low Maintenance: SF₆ gas-insulated equipment typically requires less maintenance compared to conventional air-insulated substations.
- Environmental Impact: Despite its benefits, SF₆ is a potent greenhouse gas, so its use is regulated, and proper handling is essential to minimize environmental impact.
2. Main Components of 132 kV Outdoor GIS
a. Gas-Insulated Switchgear (GIS)
- Circuit Breakers: 132 kV GIS circuit breakers are crucial for interrupting fault currents. They are enclosed in a metal chamber filled with SF₆ gas, ensuring insulation and arc extinction during switching operations.
- Disconnectors and Earthing Switches: Disconnectors provide isolation of electrical circuits for maintenance, while earthing switches ground the isolated section to ensure safety.
- Current and Voltage Transformers: These transformers provide accurate current and voltage measurements for metering, protection, and control.
- Busbars: The busbars are enclosed in SF₆-filled metal tubes, interconnecting various substation components. They facilitate power distribution while maintaining high dielectric strength.
b. Surge Arresters
Surge arresters protect the substation equipment from transient overvoltages caused by lightning strikes or switching operations. They are strategically placed near the entry and exit points of the substation to absorb high-energy surges.
c. Control and Relay Panels
The control and relay panels are responsible for monitoring, controlling, and protecting the substation. They include microprocessor-based protection relays that detect faults and issue commands to circuit breakers to isolate faulty sections.
d. Gas Monitoring and Alarm Systems
These systems continuously monitor the pressure and quality of the SF₆ gas. They detect any gas leaks or abnormalities, triggering alarms to alert maintenance personnel. Maintaining optimal gas pressure is crucial for the safe operation of the GIS.
e. Auxiliary Power Supply
The auxiliary power supply system provides power to substation equipment such as lighting, heating, cooling, and control systems. It typically includes a combination of AC and DC systems, with backup power sources like batteries or diesel generators.
f. Cooling Systems
For high-capacity 132 kV GIS installations, cooling systems may be necessary to manage the heat generated by the electrical equipment, ensuring optimal performance and preventing overheating.
3. Ancillary Equipment
Ancillary equipment supports the main GIS components and contributes to the overall functionality and safety of the substation. Key ancillary equipment includes:
a. Earthing Systems
Earthing or grounding systems provide a safe path for fault currents, protecting both equipment and personnel. They include ground conductors, rods, and mats that ensure the substation maintains a low resistance path to earth.
b. Cable Terminations and Connections
Specialized cable terminations are used to connect the GIS to overhead transmission lines or underground cables. These terminations are designed to handle high voltages while maintaining gas-tight seals.
c. HVAC Systems
Heating, Ventilation, and Air Conditioning (HVAC) systems control the temperature and humidity inside control rooms and other enclosed areas. Maintaining a stable environment is critical for the reliable operation of sensitive electronic equipment.
d. Communication Systems
Modern 132 kV GIS installations often include advanced communication systems for data exchange between the substation and control centers. These systems use protocols like IEC 61850 for efficient and secure communication.
e. Fire Protection Systems
Due to the high energy levels present, GIS substations require robust fire protection systems. These may include gas-based fire suppression systems (like CO₂ or inert gases) to extinguish fires without damaging the equipment.
4. Advantages of 132 kV Outdoor GIS
- Space Efficiency: GIS requires up to 90% less space compared to conventional Air-Insulated Substations (AIS), making it ideal for urban and industrial areas where space is limited.
- Enhanced Reliability: The sealed SF₆ environment protects the equipment from environmental factors, reducing the risk of faults and extending the lifespan of the components.
- Reduced Maintenance Costs: The enclosed design minimizes the need for frequent inspections and maintenance activities, lowering the overall operational costs.
5. Disadvantages and Environmental Considerations
- High Initial Cost: The construction and installation costs of GIS are typically higher than those of AIS due to the specialized equipment and technology involved.
- SF₆ Gas Concerns: Although SF₆ is an excellent insulating medium, it is a potent greenhouse gas. Special handling and recycling measures are required to prevent its release into the atmosphere.
- Complex Repair Processes: In the rare event of a fault within the GIS, repairs can be more challenging and time-consuming compared to traditional air-insulated systems.
6. Applications of 132 kV Outdoor GIS
132 kV outdoor GIS installations are commonly used in:
- Urban Substations: Where space constraints make AIS impractical.
- Industrial Plants: Where reliability and reduced maintenance are crucial.
- Renewable Energy Integration: For connecting wind, solar, and hydroelectric power to the grid, especially in challenging environments.
- Utility Grid Enhancements: For upgrading existing substations to increase capacity without expanding the physical footprint.
Conclusion
132 kV Outdoor Gas Insulated Substations provide a reliable and space-efficient solution for high-voltage power transmission. The integration of advanced control systems, monitoring equipment, and reliable insulation technology makes GIS a preferred choice for modern power networks. However, environmental considerations related to SF₆ gas usage require ongoing innovations in gas handling and potential alternatives to ensure a sustainable future.
By combining high performance with reduced spatial requirements, 132 kV GIS substations are instrumental in meeting the growing demand for reliable power transmission in both urban and industrial settings.
