MV switchgear spacing 1

[tem1234]

Hi,

I looking for a IEEE standard with recommended spacing between phase and ground in a switchgear (metal clad and metal enclosed), for MV voltage 125 kV bil.

I search but didn't find what i need. Do you have some idea?

Thanks

 

[dpc]

You checked ANSI C37.20.2?





David Castor

http://www.cvoes.com

 

[tem1234]

Yes I checked C37.20.2 for metal clad. It tell me what BIL is necessary, but not minimum spacing to achieve it.

Maybe i just didn't see it, but i tried to look very carefully.

 

[jghrist]

IEEE standards generally don't go into that kind of construction detail. Try NEMA standards.

 

[alehman]

For ANSI switchgear, I'm think it may have to be established by testing.

NEC table 490.24 provides clearances for field-fabricated installations. 125kV requires 7.5 inches indoors and 10 inches outdoors.

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[jraef]

There is a great paper at one time available from Powell Switchgear that addressed this, I'll see if I can find in. But the upshot was, there is no standard. How you get there is your own business. There are common practices, but no absolutes. I ran into this after being challenged by an inspector on the spacing of some 5kV equipment my company had supplied. He red-tagged it saying the spacing was inadequate, even though we had passed 35kV BIL per the design specs. I asked him to produce the ANSI spec or even an IEEE recommendation on spacing, he was unable. But I found that Powell white paper and spanked him with it.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[jraef]

Found it.[/LINK]


For everyone's info,[url=http://www.powellind.com/pub_page3.asp?MenuCategory=4&MenuPosition=2&MenuID=89] this [/LINK]is a great resource for many things Switchgear related. Powell used to publish a single Table of Contents that made it easy to scan titles, but apparently that has been "web optimized" which means it is harder to look for individual items now. Luckily, someone saved that old TOC [url=http://www.capitol-technologies.com/powell%20technilcal%20briefs.pdf]here. I used that to Google the actual PTB#.





"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[dpc]

Jeff,

Thanks for posting that link. After reading it, I realized I had read it before, years ago. The lack of specified minimum spacing does seem odd, but that's the way it is, I guess.

David Castor

http://www.cvoes.com

 

[tem1234]

Thank you Jraef, that's a very useful link and a good starting point.