John,
It is true that people used to worry about GDTs
venting. In venting the GDT sparkover voltage greatly
increased. In fact, there was a US trend to include a
Back-Up (air) Gap (BUG) across the GDT component in case
this happens. In fact, due to contamination, these BUGs were
more unreliable than the GDTs they "protected".
UL came to the rescue and came up with a standard and
expensive testing so that a BUG was unnecessary. Although
the term is not much used today, these qualified components
were known as Bugless GDTs.
I've worked with many major GDT manufacturers and the
main life concern these days is voltage degradation with
surging. The so-called fast GDTs do degrade in sparkover
voltage a lot faster than (well made) standard GDTs. One
service provider was replacing SPDs using fast GDTs every
two years because of this problem.
Surge Protective Devices (SPDs) are complete assemblies
made up from terminals, bases, housings and surge protective
components (SPCs - GDTs, MOVs, ABDs etc.). I've notice that
people wrongly use SPD when they are really talking about a
surge protective component, SPC.
Regards
Mick
On 12/05/2013 20:39, John Woodgate wrote:
In message <518feba9.7000...@ieee.org>, dated Sun, 12 May
2013, Richard Nute <ri...@ieee.org> writes:
As for the requirement for the GDT to pass the hi-pot
test...
??? I don't have any rationale for this.
If its seal was broken, letting the magic gas out, would
it arc over at a lower voltage?
-
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