P37.108: Gas Insulated Substations and Lines
Objective
Gas insulated substations (GIS) and gas insulated lines (GIL) provide significant advantages for modern electrical infrastructure, including compact footprints, modular construction, enhanced physical security for indoor installations, and strong resistance to pollution and harsh environmental conditions. These features make GIS and GIL attractive solutions for many applications. However, they also introduce specific challenges—most notably the need to reduce SF₆ emissions and to reliably detect and locate internal defects.
Quantum sensing technologies offer potential to significantly improve diagnostics and EPRI is evaluating these opportunities in laboratory testing with realistic defects. In addition to quantum sensing, research will continue to advance the capabilities of techniques such as ultra high frequency (UHF) detection, acoustic emission monitoring, and SF₆ gas analysis. Each method offers distinct strengths in defect detection. To objectively assess these approaches, EPRI has designed and commissioned a full scale GIS laboratory that allows controlled introduction of representative defects into GIS components. This capability enables direct comparison and quantification of each monitoring technology’s effectiveness.
Because GIS and GIL installations rely on large volumes of SF₆, exploring emerging dielectric gases and technologies that can reduce or replace SF₆ is critical. EPRI’s GIS laboratory is dedicated to resolving key open questions in this area, including the identification and testing of alternative gases and materials that offer comparable performance with lower environmental impact.
The results of this work will support the industry in specifying, selecting, and interpreting GIS condition monitoring technologies. By improving approaches to SF₆ management and defect detection, EPRI is helping advance more sustainable, reliable, and environmentally responsible GIS and GIL systems.
Research Value
The results of the R&D will impact both the members and the public in three key areas:
- Guidance on SF6 Alternatives – lowers the risk of adoption of these new technologies
- Improved diagnostics of GIS/GIL assets, addressing the challenges posed by fully enclosed designs and the high consequence of in-service of failures
- Application of cutting-edge technology such as quantum sensing – for enhanced insights into the location and intensity of internal discharges in the GIS/GIL
Approach
The GIS and GIL of the future: Compared to the past two decades, there is an exponential increase in the new technologies for GIS and GIL. It is challenging to remain abreast of the deep technical advances and effectively include the appropriate solutions into future specifications. The 2027 research goal is to research, evaluate and share these advances and thus lower the risk of adoption for the industry. Topics in 2027 include the continually growing topic of new dielectrics, including C4-fluoronitrile mixtures, clean air, and CO2+O2 as insulation gases instead of SF6. In addition to the laboratory, EPRI learns from the field implementations on new GIS and GIL concepts. The collaborative nature of EPRI allows for sharing of utility experiences with new technologies. The sharing of these experiences will help the industry reduce risks when selecting and applying these new technologies.
Quantum sensing for GIS: 2027 update to the EPRI Guidebook on GIS and GIL: Quantum sensing holds the promise for detecting partial discharges at much lower levels than before - and being able to locate them more accurately. The most promising technology is Diamond NV (Nitrogen-Vacancy) Centers. This quantum technology measures minute magnetic field perturbations by monitoring the fluorescence of intentional flaws in a diamond lattice. EPRI research in 2027 will introduce a partial discharge within a GIS in the EPRI laboratories and evaluate this new technology - whilst keeping an eye on further emerging technologies for improved diagnostics of GIS/GIL. Quantifying the value brought by these new technologies will help the industry to rapidly apply the appropriate solutions at much lower risk.
Anticipated Deliverables
| Deliverable | Type | Date |
|---|---|---|
| The GIS and GIL of the future | Technical Update | 12/31/2027 |
| Quantum sensing for GIS: 2027 update to the EPRI Guidebook on GIS and GIL | Technical Update | 12/31/2027 |
Past EPRI Work on Topic
| Product ID | Title | Description | Published Date |
|---|---|---|---|
| 3002032930 | EPRI Guidebook on GIS and GIL - 2025 Edition | EPRI research results and industry trends and lessons learned. | December 2025 |
| 3002032932 | Applying new GIS/GIL Technologies | Practical and well-informed guidance on new GIS and GIL technologies – including SF6 Alternatives. | December 2025 |
| 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 |