How to Commission SF₆-Free High-Voltage Systems Safely and Successfully

The energy sector is moving quickly toward SF₆-free gas-insulated switchgear (GIS). New systems using clean air, g³, fluoroketones, and CO₂/N₂ blends offer a drastically lower environmental footprint — but they also introduce new requirements for installation, testing, and commissioning.

While the core principles of high-voltage engineering remain the same, SF₆-free systems behave differently. Gas pressures, handling procedures, leak testing, and documentation all require updated methods. And the safe execution of these methods depends heavily on the competence of the people on site.

And as always, safety depends on the competence of the people on site.

This is where Sirius Energy’s approach becomes meaningful.

All our consultants are maskinmestre — a Danish engineering profession combining mechanical, electrical, operational, and safety-based training. Some have additional HSE qualifications. This makes them uniquely suited for commissioning tasks that require both technical precision and safe, controlled execution.

In this blog, we look at what SF₆-free commissioning really requires — and how project owners can ensure safe-to-energise, compliant results.

1. Commissioning SF₆-Free GIS: A New Set of Practical Requirements

Commissioning SF₆-free equipment is not simply “old tasks with a new gas.”
Several critical steps change:

Gas quality and purity must be verified differently

Alternative gases have different:

moisture tolerances
density curves
leak detection sensitivities
decomposition signatures

Tools and test methods must match the specific gas type.

Gas-handling equipment must be compatible

Recovery units, hoses, fittings, filters, and sensors all need to be designed for the new gas mixture. Using traditional SF₆ equipment is often not allowed.

Pressurisation and monitoring follow updated limits

SF₆-free gases often require higher nominal pressures to achieve equal dielectric strength.
This means:

new pressure thresholds,
updated monitoring settings,
revised alarm levels.

Technicians must understand new behaviour curves

Gas temperature, density, and humidity influence performance differently in SF₆-free systems.

In other words, the world is moving in the same direction:
Commissioning SF₆-free systems requires updated knowledge, updated tools, and updated discipline.

2. Planning and Pre-Commissioning: Getting It Right Before Work Begins

A successful SF₆-free project often succeeds—or fails—before installation even starts.

At Sirius Energy, pre-commissioning typically includes:

Reviewing manufacturer documentation

Each alternative gas has its own handling requirements. We align with the latest IEC 62271-4 and manufacturer guidelines before work begins.

Identifying gas-specific risks

Including:

pressurisation hazards,
oxygen displacement,
storage temperature limits,
ventilation requirements.

Ensuring certified gas-handling equipment is available

Including:

calibrated leak detectors,
approved filling/recovery units,
correct fittings and hoses,
gas purity test instruments.

Preparing site-specific risk assessments

Especially important when:

multiple contractors operate simultaneously,
gas storage areas are limited,
hot works or confined spaces are involved.

This groundwork ensures that installation teams can work safely and efficiently from day one.

3. Installation, Gas Handling, and Testing on Site

Once installation begins, the commissioning workflow becomes extremely hands-on.

Gas filling under controlled conditions

Alternative gases often require slow filling at controlled temperatures and pressures.
Maskinmestre excel here because they understand:

thermodynamic behaviour,
pressure system safety,
leak path risks,
equipment tolerances.

Leak testing using approved detectors

Some gases require trace gas methods or higher-sensitivity detectors.
Testing must match IEC 62271-203/304 requirements.

Monitoring moisture, temperature, and density

Dielectric strength depends heavily on moisture content. Values must remain within manufacturer-approved limits before energisation is allowed.

Integrated QA

Every test result — pressure, purity, temperature, leak rate — must be:

recorded,
verified,
signed off,
stored traceably.

This documentation is often required by the utility, regulator, and manufacturer — and becomes part of the asset’s lifetime record.

4. HSE in the SF₆-Free Era: New Gases, New Safety Considerations

One of the misconceptions in the industry is that SF₆-free automatically means “lower risk.”
Environmentally, yes.
Operationally? Not always.

Some gases operate at higher pressures.
Some mixtures require ventilation planning.
Others involve different by-products or handling rules.

This makes HSE involvement absolutely essential.

What Sirius typically coordinates on site:

pressure system risk assessments (PED alignment)
ATEX considerations where applicable
emergency response procedures for leaks
safe work coordination when several contractors share a GIS hall
gas recovery, storage, and disposal plans

With maskinmestre who already think operationally and safely — and some with formal HSE Coordinator certification — Sirius ensures that HSE is integrated into commissioning rather than added as a late-stage “check.”

Not replacing HSE.
Not doing their job.
But collaborating — with real technical understanding behind every decision.

5. The Safe-to-Energise Process: Final Step Before Switching On

Sirius Energy uses a structured Safe-to-Energise workflow developed over multiple high-voltage projects.
It includes:

✔ Full validation of all test results
✔ Final physical inspections
✔ Confirmation of access control and barriers
✔ HSE sign-offs
✔ QA documentation assembled and submitted
✔ Approval from the client’s responsible engineer

This creates a transparent, traceable chain between:

- installation,
- Testing,
- HSE,
- and operation.

6. Retrofits: Replacing SF₆ Without Replacing the Entire System

Many utilities cannot replace entire GIS systems right away
Fortunately, retrofit solutionssolutions like Hitachi Energy's EconiQ Retrofill and GE's g³ Retrofit, where existing equipment can be reused with new gas.

Sirius Energy supports these projects with:

site readiness and eligibility assessments
on-site supervision during evacuation and refilling
commissioning and verification
QA and HSE documentation

Retrofits often reduce environmental impact by over 90%, making them an attractive transitional strategy.

7. Why Maskinmestre Are the Right Fit for SF₆-Free Commissioning

Sirius Energy’s strength lies in its people.
All our consultants are maskinmestre — a profession built on:

electrical and mechanical engineering
operational awareness
practical problem-solving
safety mindset
the ability to adapt across systems

Some of them also hold formal HSE qualifications.

This gives project owners confidence that onsite commissioning is handled by professionals who:

understand the equipment,
understand the risks,
understand the procedures,
and understand how to bring technical and safety requirements together.

In SF₆-free projects, that combination is invaluable.

A New Technology Needs a New Level of Execution

The transition to SF₆-free GIS isn’t just a regulatory milestone.
It’s a fundamental change in how high-voltage systems are built, tested, and energised.

Success requires:

updated technical knowledge,
disciplined gas-handling procedures,
strong HSE coordination,
and rigorous documentation.
and rigorous documentation.

But most of all, it requires people who can bridge engineering, operations, and safety.

That’s exactly what Sirius Energy delivers.

About Sirius Energy Infrastructure

Sirius Energy supports utilities, EPC contractors, and OEMs across Europe with commissioning, site management, retrofit support, and owner’s representation. All our consultants are maskinmestre, combining technical sharpness with operational and safety awareness — ensuring that SF₆-free systems are installed, tested, and energised safely and correctly.