SF6 Leakage in a 225kV Substation

[Elecme]

Could anyone advise about the different methods of repair for the leakage of the SF6 Gas in a GIS 225kV susbtations.
Also i will appreciate if anyone can recommend specific web sites for this concern.
Elecme

 

[purplepete]

Are you looking for epairs or initially how to find the leaks?
In a previous life we used a SF6 leak detector from GasVue with great success.

http://www.sunline.net/lis/gasvue.htm

Sorry I can't help with much more. Cheers

 

[dpc]

If you are in the U.S., you must follow EPA procedures for capture and handling of any SF6 gas since it is an ozone depleter. Most utilities sub-contract this work out to outfits specializing in handling of SF6 gas. Special equipment is required.

I'd call any of the major circuit breaker manufacturers - they will be able to do the necessary maintenance.

I'm sure you know that a HV breaker that is low on SF6 may fail catastrophically trying to interrupt a fault.

 

[cuky2000]

Gas Insulated Substation (GIS) are designed to acept small leak. If large leak is happening there is indication of major problems that need to be inmediatelly addressed.

Since all GIS design varies for each manufacturer and voltage levels. The spare parts are can not be interchanged or found outside the GIS factory.

Using unqualified personel could be dangerous and enviromental questionable since the SF6 is classified as a green house gas.

In my oppinion, the potential savings do not justify the risk. Therefore, It is strongelly suggested to contact the equipment manufacturer (after sale/service department) specially if the installation are still are under guaranty.

If you are looking for ben educated in handling, storage and SF6 reclaiming technology I suggest to log in the following sites:

http://www.epa.gov/highgwp1/sf6/pdf/loppt.pdf

http://www.epa.gov/highgwp1/sf6/pdf/dililloppt.pdf

http://www.tde.alstom.com/p-c/ftp/docs/papers/PS909RJE.pdf

 

[Robert789]

I thought SF6 was chemically stable, and doesn't like to combine with anything. Furthermore, it is several times heavier than air. How would it have any affect on ozone in the upper atmosphere?

 

[cuky2000]

Dear RGMaxwell:

You have a valid questionan. How the Sf6 travell to the atsmosphere? This is a mistery for me. Perhaps the enclose publication could help us.

Science Magazine, 28 July 2000.
_{".....How do we know the atmospheric increase of this gas? The Max Planck Institute for Chemistry in Mainz has participated in expeditions in Antarctica to extract air samples from the thick firn layers (snow).
These layers can be up to 100 meter thick and contain old air, sometimes reaching to the beginning of the last century. This air has been extensively analyzed in our institute and in Norwich, England. The new gas was discovered at extremely low concentrations.
At the surface the concentration is the same as in the air at the moment, and amounts to about 0.1 ppt (parts per trillion; one ppt is one part in 1012). At 100 meter depth in the snow its concentration was close to the detection level of 0.01 ppt.
This shows the grown of the gas during the second half of the last century. Because the increase of the new gas is very much like that of SF6, we suspect a link between the two gases."}

 

[dpc]

I'm not sure of the chemistry or the breakdown process, but there is no doubt that intentional release of SF6 to the atmosphere is not allowed in the US and there are special requirements for handling SF6 gas.

Now that it has entered the regulatory world, the physical reality of the situation is no longer relevant.

 

[Elecme]

Guys, what about my question?
What do you recomend for the repair of this leakage? Elecme

 

[hy]

About your repair question, my experience is more in SF6 circuit breakers (from 30 to 500kV)

1.- SF6 gas leakages are very nasty, as one hair beneath a joint or o-ring can cause leakage, you have to use very sensitive detectors as recommended.

2.- leakages as I experienced are normaly in flanges area, so problems in joints and rings due many times of ageaing of bad compounds, installation defects, moisture, etc.
So first take out the gas of that section (service car or SF6 pump), taking account safety regulations (EPA, OSHA, or own countrie`s).
Clean the flange surfaces and polish if necessary, and use silicone grease so as to seal from moisture to enter.
Some makers use special grease (Fomblim, BarrierTA) in the SF6 side and for the rings.

3.- Vacumm must be applied and maintened so as to evacuate any moisture, and finally remplish with gas (from service car or bottles).

4.- Check for leakage (detectors such as used for industrial Freon refrigeration systems, or soapy water).

This may vary, so will be better to ask your GIS maker for the complete procedure.

I hope will serve you