Internal arc containment for GIS?

[AusLee]

Hi,

I just want to understand the terminology if possible.

When you have an 11kV vacuum based HV metal clad switchgear, i am being told that in case there is an arc inside the cubicle, it comes out from the back, then by the time it is out it is no longer hot to be dangerous. However, if you have an SF6 insulated switchgear, then there is no need for venting, because the arc is quenched inside the sealed switchgear.

Can someone please clarify/confirm the above? I'm particularly thinking:
1. IEC 62271.200 defines IAC internal arc containment for any case, even if the fault happens at the cables terminals, before the GIS chamber. Consequently GIS by itself is not a guarantee for internal arc containment or is it?

2. Small scale switchgear say 11 to 33kV usually do not have the busbars enclosed in GIS compartment, what if the fault happens on the busbars at the interconnection between two adjacent cubicles, say due to an overvoltage condition with deteriorated insulation over time?

Any clarification much appreicated.

Thanks.