arc proof vs arc resistance 1

[cmelguet]

Hi,

I would like to know if there is any difference in the definition of Arc Proof and Arc Resistance switchgear. To me it sounds the same. I always have understand an arc resistance switchgear as an equipment tested to C37.20.7 or IEC 62271-200. But according to some of my collegues there are diference between an arc proof switchgear and an arc resistance one. I dont know according to what standard they classify a switchgear as an arc proof. Please provided an standard which define arc proof.

Regards and thanks,
Cristian

 

[ScottyUK]

IEC TR 61641 allows equipment to be classed as "arc-proof" by virtue of it being "impossible" to place an ignition wire in a location where it can initiate an arc. These designs typically use a lot of plastic and are fairly lightweight as switchgear goes. In the "impossible" event of an arc occuring within the board, the whole assembly will likely disintegrate. Arc-resistant gear is designed to direct the energy of the arc and its byproducts in a reasonably controlled manner to a defined vent point in order to minimise the hazard to personnel. This type of gear is relatively heavily built.

A very famous ocean liner was claimed to be "impossible" to sink, yet 100 years ago it went to the bottom of the North Atlantic. Draw your own conclusions about "arc-proof".


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If we learn from our mistakes I'm getting a great education!

 

[jraef]

I don't believe there is an IEEE definition that uses the term "Arc Proof". I wasn't aware this was a valid term in IEC world until just now reading ScottyUK's post. It appears to be yet another Siemens manipulation of specifications.

But get this, from a Siemens website:
"This test is a voluntary test, either at the discretion of the manufacturer or subject to an agreement between the manufacturer and the user. This test is still considered a special test outside the IEC 60439-1".

That's aboput as toothless of an engineering test specification as one can attain.

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— Kilgore Trout (via Kurt Vonnegut)
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[ScottyUK]

jraef,

Actually I'm not sure it is entirely Siemens' doing - a large French manufacturer and Another Big Bill both have presence on the standards committee too. Is it any surprise that the the wording allows the manufacturers to claim "arc proof" on their products?

The IEC Technical report can be made fairly onerous, but equally it can be made fairly easy to pass. The client needs to be very specific about what the test requirements are: simply requiring that equipment comply with IEC TR61641 is virtually meaningless.


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If we learn from our mistakes I'm getting a great education!