P37.108: Gas Insulated Substations and Lines
Objective
Gas insulated substations (GIS) and gas insulated lines (GIL) offer many benefits, including compact size, modularity, physical security, and protection from pollution and harsh environments. They also present unique challenges in how to reduce SF6 emissions and effectively detect and locate defects. EPRI research is addressing this need through laboratory tests on representative defects. The value provided will be practical and well-informed guidance on GIS and GIL application, use, and management. The GIS and GIL research is focused on two key areas: SF6 alternatives and condition monitoring of GIS/GIL systems.
Because GIS and GIL use large volumes of SF6, it is important to understand the upcoming technologies and dielectrics that offer reductions in that usage. EPRI has a GIS laboratory that is being used to answer key open issues. The research will also report on the latest field applications and trends in the industry.
The second important focus is on GIS condition monitoring and leak detection. There are various existing and emerging techniques, including ultra-high frequency (UHF), acoustic emission, and SF6 gas analysis. Each has unique merits in defect detection. To better assess each approach, EPRI has built and commissioned a full-scale GIS laboratory. The facility allows EPRI to introduce a range of defects into GIS components and explore the performance of each approach. The effectiveness of each technology to reject external noise will also be quantified. The results will guide the industry in the specification, interpretation, and adoption of technologies.
Research Value
The research aims to provide value in the following key areas:
- Guidance on SF6 alternatives
- Reduced SF6 emissions through improved leak detection
- Lowered maintenance cost of GIS and GIL through improved diagnostics
- Improved reliability of electric service through better reliability and availability
Planned 2025 Research
The approach in 2025 will be to conduct laboratory testing on GIS and to research field applications and industry trends. Results each year add to the EPRI GIS/GIL Guidebook. The following activities will be conducted to support the objectives:
Emerging issues with new GIS and GIL technologies: The first goal of the 2025 research is to provide further valuable and practical insights into the continually growing topic of using C4-fluoronitrile mixtures or clean air as insulation gases instead of SF6. The focus of this portion of the research is to explore the new technologies/equipment that use alternative insulating gases to SF6 and to probe issues and considerations for gas handling, analysis, safety, and reclaiming/recycling.
A second goal of this research is to further explore the use of vacuum technologies for arc interruption. Elucidating issues such as understanding high-frequency transients that can occur at elevated voltages is a primary objective of this research portion.
The third aim of this research stream spans all three alternative SF6 technologies. With the implementation of new insulating technologies, independent of the composition, the ability to detect wear of internal components noninvasively is of high importance to users. Evaluating new detection technologies, detection techniques previously used for SF6-based systems, and/or mechanical wear detection techniques used for other gas systems to determine physical system condition is planned.
The findings of this work are intended to guide the industry on how to best respond to the ever-increasing pressures to reduce SF6 emissions and usage.
EPRI Guidebook on GIS and GIL – 2025 update: Under this task in 2025, EPRI plans to use its GIS laboratory to introduce classically observed SF6 (and C4-fluoronitrile) leaks and defects in components and reproduce abnormalities observed by users on equipment in the field. Systematically standardizing an assessment of the technologies, to observe detriments accurately and precisely in live GIS, is planned to be the focus. The findings from this work will help the industry with specification and interpretation of deficiencies and irregularities.
Anticipated Deliverables
| Deliverable | Description | Date |
|---|---|---|
| Emerging issues with new GIS and GIL technologies | EPRI research results and industry trends and lessons learned | December 31, 2025 |
| EPRI Guidebook on GIS and GIL – 2025 Update | Practical and well-informed guidance on GIS and GIL leak detection and condition monitoring | December 31, 2025 |
Past EPRI Research on Topic
| Product ID | Title | Description | Published Date |
|---|---|---|---|
| 3002027117 | GIS and GIL EPRI Guidebook – 2023 Edition | This guidebook is updated each year to include the latest research. In 2022, chapters were added on SF6 leak detection. | December 2023 |
| 3002027120 | SF6 Alternatives: Industry Status Update for 2023 | A status update of the current state of the industry when it comes to progression and availability of SF6 alternatives. | December 2023 |