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Room Ventilation for SF6 gear

Room Ventilation for SF6 gear

Room Ventilation for SF6 gear

(OP)
We are installing 5kV SF6 gear. Anyone know if there is a standard document for room ventilation requirements for SF6 gear?

The gear is defined as "sealed for life" but also states the leakage % per year. Anyone have experience with maintenance and leakage issues on with similar SF6 gear?

Thanks.
b

RE: Room Ventilation for SF6 gear

I don't have a quantitative answer to your question, but as I understand the electrical and physiological risks, you'll be getting the low-low SF6 alarm long before the personnel are at risk.

RE: Room Ventilation for SF6 gear

Perhaps one of the few exceptions to David's advice is where you have large gas zones such as a gas-insulated busbar entering the substation. The plant I worked at until fairly recently had about 3/4 of a tonne of SF6 per phase in the gas insulated bus, and that's likely enough to get you in trouble as an asphyxiant. The zones on the switchgear are much smaller.

Bear in mind that it is a very dense gas and will accumulate in cable trenches regardless of room ventilation. Treat tranches as a confined space and wear a gas monitor. SF6 will show up as depleted oxygen even if you can't indentify the gas itself.

RE: Room Ventilation for SF6 gear

It is benefecial to have the medium voltage installations such as 34.5KV GIS installed in a room with Ventilation fans.The leak can be either a small leak or due to any fault inside switchgear. There are in each cubicle flappers which are places from where high pressure gas will be released. Also annunciation panels are installed where "SF6 Gas leak" alarm appears & ideal location of annunciation panel is outside this GIS room.

RE: Room Ventilation for SF6 gear

(OP)
I checked ANSI, IEEE, and NEMA for a standard when using SF6 or any other GiS gear but did not find anything. Is there a standard or design guideline availability?

RE: Room Ventilation for SF6 gear

French standard NFC 13-200

712.3.5 Ventilation des locaux contenant des matériels isolés au SF6
Dans les locaux situés au-dessus du sol naturel où se trouvent des matériels isolés au SF6, une ventilation naturelle est suffisante selon les conditions du sous-paragraphe 712.3.2. En cas d’impossibilité une ventilation mécanique doit être prévue.
Dans les locaux situés entièrement au-dessous du sol naturel où se trouvent des matériels isolés au SF6 une ventilation mécanique doit être prévue si le volume de gaz susceptible de se répandre présente un danger pour la santé et la sécurité du personnel.
La ventilation mécanique n’est pas nécessaire lorsque le gaz contenu dans le plus grand compartiment des matériels considérés et susceptible de se répandre à la pression atmosphérique ne constitue pas sur la surface du local une couche de plus de 10 cm.
C’est notamment le cas pour tous les matériels HTA dans lesquels le volume de SF6 est très faible.
La mise en oeuvre de la ventilation mécanique doit prendre en compte le fait que le gaz SF6 se concentre au niveau du sol et dans les parties basses des locaux et bâtiments.
En l’absence de ventilations mécanique et naturelle, les locaux doivent pouvoir être ventilés lors d’une intervention.
Les conduits, fosses, puits, vides techniques, faux planchers, etc. situés sous les locaux contenant des installations SF6 et qui communiquent avec ces derniers doivent pouvoir être ventilés lors d’une intervention.

712.3.2 Ventilation naturelle
Tout local doit comporter :
• à la partie inférieure, une ou plusieurs prises d'air extérieures au local dont le bord inférieur est situé à 10 cm au-dessus du sol du local ;
• à la partie supérieure, des grilles de ventilation voire des cheminées ou lanterneaux, voire des baies ouvrant de préférence à l'air libre. Il y a lieu de s'assurer que la circulation de l'air contribue effectivement au refroidissement désiré dans toutes les conditions.
Les dimensions des orifices sont généralement déterminées par le calcul. On peut prévoir, en première approximation pour un facteur de charge égal à 1 et un sur-échauffement de l’air de 20°C entre l’entrée et la sortie, une section à donner aux ouvertures de ventilation de 0,7 m² de surface nette pour 10 kW de pertes. Pour un transformateur de 1000 kVA, la section nette correspondante est de 1 m².

RE: Room Ventilation for SF6 gear

I have worked on various MV and HV GIS, and while there is almost always detection and ventilation for HV gears, I don't remember seeing any of that for MV installations. For example, some GE wind turbines are supplied with a Schneider SF6 gear inside, up to 38kV, it is located inside a small round room in the turbine base where there may not be more then few cubic meters of air to breath but there was still nothing to detect SF6. I suppose the rational behind this is small quantity. Even though that 5kV GIS is probably of the same size as those up to 20kV, the cells are still very small, qty of gas is small and since it is not poisoning, I would think that danger of depleted oxygen in a larger electrical room is practically non-existent. If there is a leak, it will only be from one gear compartment, not all of them, and the releases amount of gas will be small to cause a serious harm. Unless the whole gear explodes, but that will be sort of obvious.

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