Minimum Clearances for Switchgear
Minimum Clearances for Switchgear
(OP)
I work for a switchgear manufacturer and we have been using the attached chart as a guideline for clearances for around 30-35 years. I have been told that the chart came from an old NEMA standard but several engineers as well as myself have been unable to find the original. We have checked IEEE, ANSI, & NEMA. The problem with the chart is when you go from 15KV @ 110 BIL to 25KV @ 125 BIL, the minimum clearance drops... Is there any way that some of you may be able to shed some light on this situation? On the bright side, this is the first time to my knowledge that we have designed switchgear over the 15KV class. Any help will be greatly appreciated!! Thanks in advance!!






RE: Minimum Clearances for Switchgear
Being somewhat conservative, I'd use the 15/110 values for a 25/125 system as well. If someone chose to derate the 25 kV gear for a 15 kV system, found the same table and got nit-picky, they could reject it.
RE: Minimum Clearances for Switchgear
RE: Minimum Clearances for Switchgear
The original NEMA standards were superceded when AIEE came into being in the 50's (so I'm told, because I'm not THAT old...), which became IEEE. So if yours were from NEMA, they are likely long outdated.
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RE: Minimum Clearances for Switchgear
RE: Minimum Clearances for Switchgear
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies