Siemens 245kV GIS maintainance 3

[kushanCEB]

Siemens 8DN9 245kV GIS need to be cleaned after a bus bar fault at bus VT. After opening the bus bar chamber there is a white dust in busbar chamber. What is this white dust and how it can be cleaned?

 

[ScottyUK]

Yes, you should clean the GIS.

The white powder is probably a fluorine compound resulting from the breakdown of the SF₆ due to the arc. Be very careful: some arcing by-products mix with water to form hydrofluoric acid. You don't need that stuff inside your lungs. Take advice from Siemens, or possibly from your SF₆ supplier, on how to proceed safely with the cleanup.

 

[low1]

The metal fluorides are also pretty toxic themselves. We have full body suits with full face respirators for cleaning and restoration following a fault.

 

[kushanCEB]

Hi "low1"
Do you have any experience in this kind of GIS maintenance??

 

[obborbb]

Hi kushanCEB,

Please check your Operating Manual for further information on handling SF6, including the appropriate PPE required. You certainly do not want to expose yourself to SF6 decomposition byproducts. Please contact Siemens for further information.

 

[low1]

kushanCEB, I was a maintenance technician, and later an engineering technician at a hydroelectric station in Northern Manitoba that contained a Siemens 8D.4 GIS installation in a breaker and a half arrangement. Operating voltage was 230kv, I'm sure it was rated at 245kv. I've been involved with 20 year overhauls, and general maintenance and troubleshooting, but I've never been involved in a fault cleanup. I am aware of our safety procedures in the event of a cleanup, though.

From one of our manuals:

d) Arcing causes decomposition products to form in the gas.
Even a small amount of gaseous decomposition products
warns anyone, e.g. very strong, unpleasant smell, similar to
rotten eggs (hydrogen sulphide), before there is any risk of
suffocation.
e) Sulfur-hexafluoride (SFe) particularly when subjected to
arcing, should be evacuated into a gas-maintenance equipment
but not into the open air.
f) Switching dust is a solid decomposition product caused by
arcing. It may have a corrosive effect or act as an irritant
when combined with moisture.
g) Personnel opening a gas chamber after having reduced to
atmospheric pressure savely, gives cause to come in touch
with switching dust.

The following should therefore be noted:
- Thoroughly ventilate the room when carrYing out maintenance.
Do not inhale the dust (use dust protection mask), do not let
it come into contact with your eyes (use gas proof protective
glasses) and do not let it come into contact with your
skin (wear protective clothes).
Any dust on the skin should be washed off with plenty of
water.
Do not stir up the dust. Remove it with a vacuum cleaner
with paper filter (let-through < 0,5%) or wipe it off with dry
cleaning rag.
Treat filters, cleaning rags and other material so that the
trapped dust is not set free again. Do not open filter bags.
Before being discarded they should be neutralized by being
immersed in a 3% soda solution for 24 hours, then disposed
off as waste.
Do not eat, drink and smoke in rooms, particular where
switching dust is likely to be present.
Before taking a break and after work, thoroughly clean your
face, neck and arms using soap and plenty of water.
In particular cases of SFe-waste disposal contact the next
Siemens office.