How SF6 Leak Detection Is Performed in Live Substations
SF6 leak detection in live substations is primarily performed using Optical Gas Imaging (OGI) cameras and handheld electronic detectors. OGI allows technicians to scan energized equipment from a safe distance and visualize gas plumes without taking equipment offline. Once a leak is identified, handheld detectors are used to pinpoint the exact source, enabling EPA-compliant documentation while maintaining grid stability.
Why live SF6 leak detection matters
In a substation environment, the most expensive leak is often the one that forces an unplanned outage. De-energizing equipment for inspection can cost utilities tens of thousands of dollars per hour in lost service, labor, and risk exposure.
In our field experience, many SF6 leaks can be identified and documented while the power remains on, provided the right tools, safety protocols, and detection sequence are used. This shift—from outage-based inspections to live detection—is now a defining feature of modern LDAR (Leak Detection and Repair) programs.
The “safe-distance” scan: optical gas imaging (OGI)
The first step in live SF6 leak detection is typically an Optical Gas Imaging (OGI) survey. OGI cameras are designed to detect SF6 because the gas absorbs infrared energy at a specific wavelength, making leaks visible as a dark plume on the camera display.
Why OGI is used first:
Large areas of energized equipment can be scanned in minutes
Entire GIS bays, breakers, and bus sections can be evaluated without contact
No de-energization is required for the initial sweep
In live substations, this matters because technicians can remain outside the flash protection boundary, reducing arc-flash exposure while maintaining operational continuity.
Pinpointing the source with handheld electronic detectors
Once OGI identifies a general leak location, technicians switch to handheld electronic detectors, often referred to as “sniffers.” These instruments use technologies such as negative ion capture or corona discharge sensing to detect minute concentrations of SF6.
In practice, the probe is moved slowly—approximately one to two inches per second—along:
Flanges and bolted connections
Valves and service ports
Bushings and sealed interfaces
OGI shows the gas cloud. Handheld detectors find the exact fitting or seal responsible for the leak.
Quantifying SF6 leaks for EPA reporting
Detection alone is not sufficient for compliance. In 2026, utilities are increasingly expected to quantify SF6 leaks to support greenhouse gas reporting and internal audits.
Common quantification methods include:
Comparing real-time gas density or pressure readings against nameplate data
Using laser absorption spectroscopy to measure SF6 concentrations in parts per million (ppm)
These measurements can be converted into estimated annual gas loss, supporting documentation aligned with EPA Subpart DD and proactive LDAR programs.
Safety protocols in live high-voltage environments
Performing SF6 leak detection in live substations requires strict safety controls.
Key considerations include:
Asphyxiation risk: SF6 is significantly heavier than air. In indoor GIS rooms, detectors are often positioned close to floor level to identify oxygen displacement.
Atmospheric monitoring: Technicians commonly use multi-gas monitors that track SF6 and oxygen levels, ensuring oxygen concentrations remain above 19.5 percent.
Access control and PPE: Live work zones require controlled access, appropriate personal protective equipment, and continuous situational awareness.
Safety procedures are not optional—they are what make live detection possible without increasing operational risk.
Why a multi-method approach reduces compliance risk
Relying on a single detection method introduces blind spots. Environmental factors such as wind speeds above 10 miles per hour can disperse gas plumes, making OGI alone less effective in outdoor switchyards.
For this reason, Substation Solutions uses a multi-method approach, combining:
Optical gas imaging for rapid visualization
Handheld electronic detectors for precise leak location
Acoustic detection for high-pressure leaks
Soap-bubble testing to verify repairs
This layered process ensures that leaks are not only found, but fully verified and documented before technicians leave the site.
How live detection supports long-term reliability
As discussed in our guide on Where SF6 Gas Is Used in Substations, the most common leak points are mechanical joints and aging seals. Identifying these issues early—without shutting equipment down—helps operators reduce chronic emissions, avoid emergency outages, and prepare for tighter regulatory oversight.
In our upcoming SF6 pillar article, we’ll examine the cost difference between reactive repairs and proactive leak management, and how live detection plays a central role in both compliance and reliability.
How this article was researched
This article was developed using EPA greenhouse gas reporting guidance, infrared spectroscopy principles, and observed practices in live substation environments, combined with current LDAR and SF6 handling standards.
Last fact-checked: January 5, 2026