Gas Insulated or Air Insulated Switchgear 

By on

Various arguments exist around SF6 Gas Insulated (GIS) and Air Insulated (AIS) switchgear. Recently we had to change a GIS design to AIS due to an instruction from one of  our clients.  His concern is the global warming potential of SF6.   While understanding the clients reasons, I'm not convinced on the argument.

General arguments in favour of GIS include:

  • GIS is more cost effective
  • requires less space (up to 70% less that Air Insulated)
  • is safer in operation
  • has overall lower system loses
  • has higher protection against ambient conditions
  • is more reliable

As far as I can see the main argument against SF6 is that it has a global warming potential.  From an environmental view, the potential of releasing gas which contributes to global warming is obviously bad.  However, to quantify the effect, Capiel (see link below) has carried out some research:

  • GIS switchgear emissions (Europe, 2002) contribute 0.05% to total greenhouse gas emissions
  • measures implemented in switchgear design since 1995 have reduced GIS gas emissions by 40%
  • there is continuing technological progress in further reducing GIS gas emissions

Key Question

I think the key question in all of this is:

  • do the benefits of a safe reliable, cost effective electrical supply networks outweigh the potential SF6 contribution to greenhouse gas emissions ?

My View

The direct contribution of SF6 to greenhouse gas emissions is relatively low and I tend to think the advantages of a reliable electrical system outweigh these negatives.  Lower system loses and less materials required during manufacture reduce the life cycle carbon emissions, potentially offsetting the negative effects of SF6. 

A life cycle analysis of the German distribution system by Capiel (see link below) which considers materials, manufacture, ohmic losses and SF6 emissions shows that overall GIS contributes 30% less to global warming than AIS. Currently the arguments given against GIS don't appear sufficiently thought out and consider only the SF6 emission issue.

Without closing the door on the debate, I don't see enough evidence to force move away from GIS to AIS. 

Related Links



Steven McFadyen's avatar Steven McFadyen

Steven has over twenty five years experience working on some of the largest construction projects. He has a deep technical understanding of electrical engineering and is keen to share this knowledge. About the author

myElectrical Engineering

comments powered by Disqus



Three Phase Current - Simple Calculation

The calculation of current in a three phase system has been brought up on our site feedback and is a discussion I seem to get involved in every now and...

Star-Delta Motor Starting - Performance

Many questions sent in to the site are in connection with motor starting and in particular star-delta.  For all but the simplest application, there is...

Laplace Transform

Laplace transforms and their inverse are a mathematical technique which allows us to solve differential equations, by primarily using algebraic methods...

Understanding LV Circuit Breaker Fault Ratings

I think this post is going to be helpful to several of our readers. While the IEC low voltage circuit breaker Standard [IEC 60947-2, Low voltage switchgear...

Voltage Levels – Confused?

I was having a conversation the other day about voltage levels.  While everyone was in agreement that low voltage was 1000 V and less, there was more confusion...

Variable Frequency Drive

Variable frequency drives are widely used to control the speed of ac motors.  This note looks at the mechanisms which enable drive units to control the...

Contribute to myElectrcial

Have an opinion or something to say, want to ask or answer questions, share your knowledge then use our site to do it . As a community of people interested...

How to Calculate Motor Starting Time

Request to look at induction motor starting time have come up a few times on the site. Hopefully in this post, I give you guys some idea on how to calculate...

Meeting room of the future

The IET site has a video of a visit showing of a high tech meeting room developed at Napier University in Edinburgh. It a good demonstration of innovative...

Understanding Circuit Breaker Markings

IEC 60947 is the circuit breaker standard and covers the marking of breakers in detail. Any manufacturer following this standard should comply with the...

Have some knowledge to share

If you have some expert knowledge or experience, why not consider sharing this with our community.  

By writing an electrical note, you will be educating our users and at the same time promoting your expertise within the engineering community.

To get started and understand our policy, you can read our How to Write an Electrical Note