minimum metal to metal separation during switching 1

[NAZ55]

Does anyone know of any chart, code or standard that describes minimum metal to metal spearation for different high voltages during switching to avoid and arc? I have read some references where it talks about accounting for 1 ft per 110kV, but am not sure where that number came from.

 

[jraef]

If you are switching, there will be an arc. There is no "avoiding" it.

So if you are asking about the distance that contact elements must separate in order for the dielectric value to increase to the point of quenching the arc, then that will depend on the medium in which your switching is taking place, because ionization (or actually lack thereof) is the key to the quench. Vacuum bottle contacts are only separated by a fraction of an inch, because there is no air, so no ionization. Air contacts are sometimes required to be separated by feet depending on the voltage. Check this out:

http://www.youtube.com/watch?v=Ntl5vgkGOjg

If on the other hand you are asking about the amount of required separation for exposed metal parts to current carrying conductors, that's different. this paper is actually a great brief on the subject.

http://www.powellind.com/main/Uploadpdf/01.4TB.059 Bus Spacings in Metal-Enclosed Switchgear.pdf

"Will work for (the memory of) salami"

 

[NAZ55]

jraef, thanks for your response. My question is in regards to a high voltage air-disconnect, where the quenching medium is air.
My concern is that the arc from the blade on the switch jumps over to the conductor (connected to the jaw side of the switch) during closing and stays on until the switch closes. I need to know how far that conductor needs to be for the arc to not jump over to the conductor and stays on the arcing horns.

 

[MKFPE]

ZAZM,

Search: "CURRENT INTERRUPTION USING HIGH VOLTAGE AIR-BREAK DISCONNECTORS."

Google turns up a thesis with excellent information regarding HV air break switch interruption.

"Pre-strike" is found in the document, considering an EHV switch.

You didn't mention your application voltage, so I'm not sure if anything in this document helps you.

Good luck,