Episode 33 ~2:10 MV Switchgear EN · العربية

MV switchgear, AIS vs GIS

Two ways to insulate medium-voltage switchgear: with air or with SF6 gas. AIS dominates Saudi commercial sites; GIS wins where space is at premium. And now both are facing pressure from SF6-free alternatives, clean air, fluoroketones, vacuum.

NLC Academy · Episode 33
MV Switchgear, AIS vs GIS
~2:10
Animated explainer, press play to watch the concepts now; the filmed cut publishes once production wraps.
How it works

The trade-off, in pictures

Five diagrams for the parts that words alone make heavy: why AIS is bigger, why GIS can shrink, what SF6 costs the climate, and how to choose.

Footprint, to scale
Same 12-panel lineup, three floor areas
= 1 m² of floor 1.7 m AIS ~12 m² SF6-free ~5 m² GIS ~4 m² Identical 12-panel lineup. GIS folds it into a third of the area.
The same electrical job, three room sizes. GIS needs roughly a third of the floor an AIS lineup does; SF6-free clean-air sits just above GIS.
Why the size differs
Dielectric strength sets the clearance, the clearance sets the cabinet
Same conductor, same voltage, different insulator wide air gap insulator: air AIS small gap sealed in SF6 GIS air-class gap clean air / vacuum SF6-free
SF6 holds off far more voltage per millimetre than air, so GIS can pull the live parts close together and seal them. Less clearance, smaller cabinet, less room.
The SF6 catch
A potent greenhouse gas, watched for every leak
Global warming potential (100-yr, CO₂-eq) SF6 23,500× CO₂ 1× Fluoroketone <1× Clean air ≈0 bar length not to scale SF6 density monitor (GIS) now alarm −10% trip −20% 100% sealed Per-compartment density transducers, not pressure: temperature-compensated, so a real leak is never masked by a cold night.
SF6 insulates beautifully but warms the planet 23,500× as hard as CO₂, so every GIS compartment is metered and alarms before it ever empties.
Cost crossover
Land price decides where GIS overtakes AIS
Total installed cost → Land price per m² → crossover AIS cheaper GIS cheaper AIS GIS
AIS panels cost less but eat floor area, so their total cost climbs with land price. Past the crossover, the room GIS saves is worth more than its panel premium, central Riyadh and downtown Jeddah usually sit on the right.
How to choose
Two questions pick the technology
MV switchgear to specify Floor area scarce / costly? No AIS cheapest · largest Yes Sustainability mandate or ≤24 kV? Yes SF6-free clean air No GIS smallest · SF6-sealed
Specify by the site, not the brochure: how scarce the floor is, then whether a sustainability score or a ≤24 kV rating opens the SF6-free door.
Key Takeaways

What you'll walk away with

Four ideas to carry into the next specification conversation you have.

01

AIS = Air-Insulated Switchgear.

Insulation by air gap. Larger footprint, cheaper, easier to maintain. Saudi default for 13.8 kV indoor distribution rooms.

02

GIS = Gas-Insulated Switchgear.

Insulation by SF6 in sealed compartments. ~30% the footprint of AIS, higher cost, 30+ year sealed life.

03

SF6 is a potent greenhouse gas.

23,500× CO2 over 100 years. F-Gas regulations push the industry toward SF6-free designs, clean air for ≤ 24 kV, fluoroketones for higher.

04

Pick by site, not by brochure.

AIS for big indoor rooms. GIS for substations near a NEOM ridge where every m² costs money. SF6-free on any project with sustainability scoring.

Reference

AIS · GIS · SF6-free, compared

Typical values for 13.8 kV / 24 kV MV switchgear. Premium SF6-free options ship now from ABB, Siemens, GE.

Attribute Typical value Notes
AIS footprint (12-panel lineup)~ 12 m²Lower cost / m²
GIS footprint (same lineup)~ 4 m²SF6 sealed
SF6-free clean-air footprint~ 5 m²ABB AirPlus, Siemens 8VN1
AIS service life30+ yearsAir gaps re-set
GIS service life sealed30+ yearsNo SF6 top-up if leak-tight
SF6 GWP (100 yr CO2 equiv)23,500F-Gas regulated
Internal arc class (premium)AFLR 80 kA / 1 sIEC 62271-200
KSA NEOM / RSG mandateSF6-free preferredProject RFP language
Deep Dive

AIS vs GIS in practice

Five points that decide the right choice on a Saudi project.

Footprint drives the cost crossover.

GIS is 2–3× the panel cost of AIS but reduces room area by 60–70%. At Saudi land prices in central Riyadh or downtown Jeddah, the GIS premium pays back in saved built-up area. In suburban industrial zones with cheap land, AIS wins.

Maintenance posture is different.

AIS allows visual inspection of every busbar, contact, and connection through transparent panels or cover removal. GIS is sealed, partial discharge monitoring + SF6 gas density alarms are your eyes. Plan operator training accordingly.

SF6 leak detection is non-negotiable.

Modern GIS includes online gas density transducers per compartment. Saudi MEP specs now demand alarm at 10% loss, trip at 20% loss. Manual top-ups with SF6 are increasingly tracked under F-Gas chain-of-custody rules even where not legally required.

SF6-free is no longer experimental.

ABB's AirPlus, Siemens' Clean Air, GE's g3, all type-tested, all IEC-compliant, all delivered on real projects in 2024–2026. For new Saudi MV designs at ≤ 24 kV, clean air is now a credible alternative without a price penalty above ~10%.

Internal arc classification is the spec line that matters.

AFLR (Accessible from Front, Lateral, Rear) at 50 kA / 1 s is mid-range. Premium projects (hospitals, government, NEOM) spec AFLR 80 kA / 1 s. The arc-vent design and pressure-relief flap have to be tested at this level, not just calculated.

From the Academy to the Field

NLC Switchgear, type-tested AIS, GIS, and SF6-free.

Our factory in Dammam assembles Schneider-licensed AIS for 24 kV down, partners on GIS for higher voltages, and ships ABB AirPlus SF6-free for NEOM-grade tenders.

See the solution
Next Episode

Type-Tested Assembly (TTA)

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