SF6 Vs Vacuum

i suggest you attend the National Seminar on Recent Developments in Switchgear . . . . at Mumbai on 9th and 10th October 2009 - organized by the Academy of Resources Management

kindly give further detail of event. web address and prereq of seminar as mentioned by Fatehi

All India Seminar " SWITCHGEAR – RECENT DEVELOPMENTS "

( 09th & 10th October, 2009 )

Prof. R. Chatterjee (Chairman)

Academy of Resource Management

11, Maya Apartments, Plot No. 467, TPS - III, 14th Road, Khar (W), Mumbai - 400 052.

Phone : - +91 9820656206 / +9122 2600 2966

academyresource@yahoo.com academyresource@gmail.com

http://cr4.globalspec.com/thread/1686/SF6-or-Vacuum-Circuit-Breaker

Dear Manimaran,

Hope you are in ABB. We are using the ABB SF6 breakers in 400kV switch yards. You can very well look into the specs. In my opinion, the SF6 are best suited for EHV. We use it for 33kV, 66kV, 230kV & 400kV S/S. We widely use the VCBs in 11kV panels indoor & as field VCBs. Bye.

best would be to call ABB and enjoy the fun if they respond to your call.

crm

This is 200% correct . No response , no call from ABB ,

Dear Sh.Manimaran,

1)At the outset it is to be noted that in the case of VCB -breaker the making and breaking action takes in Vacuum medium, while in the case of SF-6 breaker the same takes place in SF-6 medium.Accordingly these are named as VCB or SF-6 Breaker.

2)The insulating strength of SF-6 gas in the case of SF-6 breaker is much higher than that of vacuum used in VCB.

3)It is due to this high dielectric strength of SF-6, Sf-6 breakers are used above 66KV system ie 66Kv,132KV,220KV and 400Kv systems as breaker applications.

4)VCB breakers are normally used and economical upto 33KV system.

5)SF-6 breaker also used for 11Kv and 33Kv system

6)VCB breakers are economical compared to SF-6 breakers.in lower range upto 33kv

7)In SF-6 breaker there is no maintnance except occassional gas leakage filling whereas in VCB the no of operations of breaker are limited and VCB bottle has to be replaced.

Finally SF-6 breaker scores over to VCB in all voltage ranges due to NIL maintenance ,excellent insulating properties and economy.

Regards

V.Ambarani

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Sh.Manimaran,

1)At the outset it is to be noted that in the case of VCB -breaker the making and breaking action takes in Vacuum medium, while in the case of SF-6 breaker the same takes place in SF-6 medium.Accordingly these are named as VCB or SF-6 Breaker.

2)The insulating strength of SF-6 gas in the case of SF-6 breaker is much higher than that of vacuum used in VCB.

3)It is due to this high dielectric strength of SF-6, Sf-6 breakers are used above 66KV system ie 66Kv,132KV,220KV and 400Kv systems as breaker applications.

4)VCB breakers are normally used and economical upto 33KV system.

5)SF-6 breaker also used for 11Kv and 33Kv system

6)VCB breakers are economical compared to SF-6 breakers.in lower range upto 33kv

7)In SF-6 breaker there is no maintnance except occassional gas leakage filling whereas in VCB the no of operations of breaker are limited and VCB bottle has to be replaced.

Finally SF-6 breaker scores over to VCB in all voltage ranges due to NIL maintenance ,excellent insulating properties and economy.

Regards

V.Ambarani

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how green are SF6 breakers compared to vac breakers?

What Ambarani wrote were mostly correct and I have something to add in answering your simple question.

1.In my opinion,at the time when the manufacturing of oil circuit breakers started to decline,European MV (11,22 KV) manufacturers mostly went into the developement SF6 CB while the Japanese and some US manufacturers went into VCB technology.Westinghouse,Toshiba,Meidensha,Mitshubishi,Aichi,Toyo Denki who make their own vacuum interruptors were the early ones.European manufacturers such as Siemens Germany,Brush UK were much later in manufacturing 11/22/33kv VCB.

ABB started using BBC's Carlo Emag 11kv VCB when ASEA and BBC merged in Europe.The ABB vacuum interruptor (where the normal or fault currents are broken/interrupted ) was manufactured in Ratingen(I forgot the spelling) near Duseldoff,Germany.ABB have been buying so many other switchgear and transformer companies all over the world that ABB's Engineers have a lot to study and learn on/about ABB's own products if they want to be competent and confident in giving the right technical imformation/answers.Otherwise,they just do not response.

2.The sucess and survival of any MV switchgears depends mainly on 2 major primary reasons,(A) Engineering/Technical Functionality,reliability,safety etc (B) Costs.

For example,11kv VCB panel is between 600 to 700 mm wide for almost any manufacturer in the world because almost everyone is dependent on the dielectric strength of (atmospheric,humid)air as the insulating medium for the conductor parts(main busbars,dropper bars,CT,PT,cable terminations etc) outside the vacuum bottles.800 to 900mm W for 22kv and 1200 W for 33kv. This is also true for SF6 CB panels.The distance needed by the copper-chromium alloy main contacts in the 11kv vacuum interruptors for the arc to be extinguished is a travel of about 12 mm.The time to interrup or break is about 50 milli seconds.This distance and time are much longer in SF6 interruptors.

To assist in the quick extinguishing of the electric arc,different manufacturers uses different designs and arrangements.A simple and effective design in vacuum interruptors of VCB is "flat main round centre with spiral star fingers" Cu-Cr contacts.The lines of arcs which are actually HV currents in electron/plasma state travel from one surface to the other and repelling each other with the self generated concetric magnetic fields.These lines of arcs diminishes as it rotate and move away from the circular contact center.All these happen in 50 mSec in a gap of 12mm.The ionised plasma,vapour of copper will stick onto the stainless steel cylindrical sheet as solids while cooled,which is placed a little away from this contacts.The hermatically sealed vacuum bottle thus maintains its degree of vacuum.For normal current switching,most Japanese VCB interruptor are garanteed for 10,000 times of switchings and 10 to 20 times of switching at fault current levels before you need to change any vcb bottle which should not happen in 30 to 40 years of usage.

In SF6 interruptors,"puffer" arrangement is used to pump SF6 gas and blow across/along the path of the arc to quench and "draw/lengthen"the arc so as to extinguish it while the main contacts are moving away from each other.The SF6 gas is about 6 times heavier than air and its molecules can break and recombine and help to dissipate the arcing heat in the process.However, I have not seen any SF6 manufacturer matching the VCB'garantee of 10K In and 20K no current switching life.

For 11/22kv SF6 CB ( and RMU),the tendency is for a manufacturer to put the complete 3 pole switching/breaking contacts in a single common SF6 gas tank as all the live parts can be place closely together and minimise gas leakage by using one common actuating sharft instead of 3 individual sharfts for each pole.This arrangement contradict phase to phase segregation of some specification.Extremely minute gas leakage is happening all the time,mainly through the "o"ring gas seal on the actuating shaft,gas filling valve,gas pressure meters/sensors and through the wall of the steel tank plate! to minimise this, stainless steel tank(where costly welding in inert gas enviroment is required) and lower gas pressure (1.1 atmosphere ) designs are employed thus limiting the miniturisation effort.SF6 is Sulphur hexa floride where florine is a helogen gas which is not good for the ozone layer.This is a small quantity compared to hair spray and tyre/furniture polish sprays for example.

3.SF6 switchgears using vacuum interuptors are the interesting designs taking advantage of the characteristics of the two.

In 33kv level indoor/outdoor switchgears where in ABB's design,3 single vacuum interruptors are placed in a common SF6 tank and the main bus bars chamber,dropper bars and Primary sides of CT PT are in another chamber,the cable termination requires single core cable which has expensive and elobrate epoxy molded parts and copper and rubber seals to make it air tight.For circuit and busbar isolation one has to operate the 2 isolating switches,one above one below vcb, in side the main gas tank via a seperate shaft as the CB is non withdrawable physically.The one advantage for this design is that it is less than 700mm wide as compared to 1200 or 1300 mm W VCB panels and it is sealed off from its enviroment.The disavantage is high costs.In most commercial,public and industrial projects,one can place the bigger and cheaper 33KV VCB in the less expensive floors/levels.Siemen has individual phase gas insulated,vacuum interruptor CB design.

4. Eventhough SF6 can easily cover the whole range of CB from 11kv to EHV. The original strong believer of SF6 gas only CB manufacturers had no choice but to eventually involved in the design and manufacturing of VCB for 11KV to 33KV range.In this range,VCB has the distinct advantages of simplicity,reliability,low maintenance,lower costs in itself and cable/termination.The ease of extension and coupling to alternative make but similar designs,thus cheaper future extension thus it needs no spare panels at the on set of the project.

As a consulting or consummer engineer considering the economic and technical advantages,I choose VCB in MV.

Best regards,

Khor

Excellent chap ,you are too educative on SF6 and VCB.I concur with you,VCB is the way economically,financially,environmentally and technically.

Thanks

Eng.ole Khabi

Dear Guest,

Your jumping to conclusion to VCB as better over SF6 is a hasty and decision based on without proper technical understanding.

You seemed to have some negative mktg skills and are groomed too do the same.

ABB has been targetted by few competitors and they go to very negative limits.

Even I was also working in such company earlier where whole orgainsation used to work on proving VCB better against SF6. Whereas the true VCB technology promoter - Siemens never worked on negative mktg and they enjoy high level of customer preferences and have their own market share.

Don't work for company , work for yourself and think as an engineer. You shall earn your reputation based on the same wherever you go in the world.

Dear Guest,

I wrote this article based on many years of direct working experience under varied applications,as a manufacturer,end user,electrical consulting engineer,project and maintenance engineer and trading of varous makes of VCB and SF6 switchgears.I did not give more points or details / type test reports as I was/am not in my home country and do not intend to do that.I am not with any big company at the moment.

I sincerely hope and will be very grateful that you or any kind engineer/technician can provide all of us with more unbiased in-depth technical and economical comparisions on this topic so that others and I may share this knowledge in CR4 forum.Economical in terms of the use of material,space,insulations,interchangeability,safety,cost,and time.I value engineer who can understand and evaluate based on engineering data and imformation and can form his/her own opinion/stand.Some do not and cannot.

Both ABB and Siemens have VCB and SF6 switchgears.

Best regards,

Khor.