Introduction
As noted in previous articles, electrical engineering has been a cornerstone in the development of modern society, continuously exploring new technologies to advance the energy landscape. Discussions have covered GIS substations and the pros and cons of SF6 gas. However, despite the wide range of gas-insulated equipment, this field continues to grow due to the ongoing rise in population and industrial development, which daily demands more energy and environmental commitments.
In the context of evolution, expansion, and adaptation, there is a need for advanced solutions for energy transmission in environments where space is limited, atmospheric conditions are adverse, and where electrical capacitance conditions reduce the effectiveness of insulated conductors. This is where GIL (Gas-Insulated Line) and GIB (Gas-Insulated Busbar) ducts play a crucial role. GIL and GIB ducts are advanced technologies in the field of electrical transmission. They offer a reliable and efficient solution in situations where conventional overhead or underground lines are impractical, such as in densely populated urban areas, geographically challenging regions, and in substation-specific topological conditions, whether due to location or layout. This article provides a detailed explanation of what GIL/GIB ducts are, including their components, typical applications, as well as their advantages and disadvantages, drawing on the knowledge and experiences of ENERGISAR S.A.S and other valuable references.
What is a GIL and/or GIB Duct?
A GIL or GIB duct is a closed transmission line enclosed in a metallic casing and insulated with gas. These ducts are used for high-voltage electrical energy transmission. The most commonly used gas is sulfur hexafluoride (SF6), known for its exceptional insulating properties and its ability to maintain high stability under various operational conditions.
The design of GIL and GIB ducts allows for the efficient transmission of electricity in environments where conventional overhead or underground lines are impractical, such as in densely populated urban areas, geographically challenging regions, and in the topological conditions specific to electrical substations, whether due to location or layout. The metallic casing and insulating gas not only protect the conductor from external influences but also minimize electrical losses, reduce the possibility of failures, and provide solutions for expanding or interconnecting different transmission operators, allowing interaction and integration with different brands and conventional (air- AIS) substations.
A Brief History of GIL and GIB Ducts
As mentioned earlier, the development of GIL and GIB ducts is an example of continuous innovation in electrical engineering. In the 1960s, the development of ducts began with the first generation using SF6 as the sole insulator, as noted by Llorca in his thesis [2]. The need to reduce costs and mitigate environmental impact led to the evolution to a second generation, which employs a mixture of 20% SF6 and 80% N2. This innovation improved the efficiency and competitiveness of GILs, allowing their implementation in over 150 projects worldwide, noted for their performance and flexibility in various installations. However, as discussed in previous articles published by ENERGISAR S.A.S., new dielectric technologies with new gases and alloys are still being developed, a trend that promises to bring better environmental performance compared to the current technology still using SF6 as an insulating gas, while retaining its advantages. Although these ducts have been implemented in various parts of the world, one of the first significant applications was in Europe, where they were used for high-voltage underground connections in areas where overhead lines were not feasible.
In Colombia, there are several GIL and GIB ducts implemented to provide constructive solutions for high-voltage line adaptations. Notably, ENERGISAR S.A.S. installed the largest duct in Colombia, with nearly 1.1 km of GIB piping, expanding the main busbars of the Bolívar substation to a 220kV voltage level, under the supervision of the manufacturer Hitachi Energy, for the Termo Caribe S.A.S. E.S.P. plant.
As observed, over the years, this technology has evolved and refined, benefiting from advances in materials and manufacturing techniques that have improved its performance and reliability.
Description of GIL Duct Components
GIL ducts consist of several critical components, each playing an essential role in their operation [1]:
- Aluminum Alloy Casing: This casing provides the physical structure of the duct and protects the conductor and insulating gas from external factors. The aluminum alloy is an ideal material due to its light weight and corrosion resistance, which extends the duct’s lifespan.
- Aluminum Alloy Conductor: The conductor is responsible for carrying the electrical current. Made from aluminum alloy, this conductor is designed to offer high electrical conductivity while maintaining a low weight, facilitating installation and reducing mechanical wear.
- SF6 Gas: Sulfur hexafluoride (SF6) is an inert gas with excellent dielectric properties. Within the duct, SF6 acts as an insulator, preventing electrical arcs and reducing the need for space between the conductor and the casing. Additionally, its high chemical stability ensures consistent performance over time.
- Epoxy Supports: These supports keep the conductor centered within the duct, ensuring that the insulation provided by the SF6 is uniform and effective. Epoxy is chosen for its rigidity and durability, essential for maintaining the structural integrity of the duct under various operational conditions.
Applications of GIL Ducts in the Energy Industry
GIL ducts stand out in applications where other forms of electrical transmission are impractical or inefficient:
- Urban Environments: In urban areas where space is limited, GIL ducts allow for safe energy transmission with minimal visual impact. Their ability to be installed in underground tunnels or channels makes them an ideal option for large cities.
- River and Mountain Crossings: In complex geographical areas where overhead line installation would be costly or difficult, GIL ducts provide a viable solution, as they can be buried or installed in tunnels beneath rivers and mountains.
- Interconnections in GIS Substations: In GIS (Gas Insulated Substation) environments, GIL ducts are used to connect different sections, enhancing transmission efficiency and minimizing electrical losses. This integration allows for a compact substation design in areas where space is a critical factor, making it their primary application.
- Hybrid Systems: GIL ducts are also used to connect GIS substations with overhead lines.
Among other applications.
Comparison of GIL Ducts with Overhead Lines
GIL ducts offer several advantages over traditional overhead lines, but also present certain challenges:
Advantages:
- Increased Reliability: GIL ducts are less susceptible to damage from adverse weather conditions, such as storms or strong winds. This reduces electrical supply interruptions and increases transmission reliability.
- Lower Visual Impact: Unlike overhead lines, which can be a source of visual pollution, especially in urban or scenic areas, GIL ducts are discreet and do not alter the visual environment.
- Enhanced Safety: GIL ducts are fully enclosed, significantly reducing the risk of accidental contact or interference with other utilities. Additionally, the presence of SF6 gas as an insulator minimizes the risk of electrical arcs and short circuits.
- Reduced Electromagnetic Fields: Due to their compact, enclosed design and dielectric insulation, inductive currents are neutralized, resulting in a considerable reduction in electromagnetic fields, up to 20 times lower than in conventional lines.
- Durability: With a lifespan of over 50 years integrated into the system.
- Lower Losses: Losses compared to those in cables and transmission lines are much lower, translating into economic benefits.
- Space Savings: One of the main features of gas-insulated equipment and systems.
- Increased Transmission Capacity: GIL and GIB ducts can increase the transmitted power due to their high current carrying capacity.
Disadvantages:
- High Initial Cost: GIL or GIB ducts generally require a higher initial investment compared to overhead lines due to specialized materials and the need for highly skilled labor for installation.
- Installation Complexity: Installing ducts is a more complex process and requires rigorous quality control. Although most parts are assembled in the factory, on-site work must be precise to ensure correct assembly and operation of the system.
- Volume Fluctuations: These thermal variations refer to changes in the size of GIL duct components when subjected to temperature variations. For GIL ducts, this effect is crucial as it can affect system stability and operation. If not properly managed, temperature fluctuations can cause misalignment or deformation of duct components, compromising their integrity and long-term reliability. Therefore, controlling these factors is essential to ensure reliable system operation.
Conclusion
GIL and GIB ducts represent an advanced and efficient solution for energy transmission in situations where space and reliability are critical factors. Their use in conjunction with GIS substations improves the efficiency and safety of electrical networks, especially in urban and geographically complex environments. The company ENERGISAR S.A.S., with its experience in SF6 technology and ongoing research into new trends, is well-equipped to offer customized solutions using this innovative technology, contributing to the development of a safer and more efficient electrical infrastructure.
Call to Action
If you are interested in learning more about how GIL or GIB ducts can benefit your electrical transmission projects, contact EnerGISar S.A.S. and explore the specialized solutions the company can offer.
References:
[1] Huazheng Electric Manufacturing (Baoding) Co., Ltd., “¿Qué es GIL?,”2021. [En línea]. Disponible en: https://es.electric-test.com/info/what-is-gil-59347016.html. [Accedido: 03-ago-2024].
[2] J. R. Llorca Ortolá, “Technical-economic analysis of Gas Insulated Lines,” Trabajo de fin de grado, Escola Tècnica Superior d’Enginyeria Industrial de Barcelona, ETSEIB, 2018. [En línea]. Disponible en: https://upcommons.upc.edu/bitstream/handle/2117/167413/llorcajr-tfg.pdf?sequence=1&isAllowed=y#:~:text=As%20the%20area%20is%20inversely,due%20to%20high%20power%20rating. [Accedido: 09-ago-2024].