15kV Unshielded Cable Separation 5

[DanDel]

Does anyone have a reference (IEEE, ANSI, etc) for conductor air separation and creepage distances for unshielded 15kV cable, as installed as jumpers in a switch or transformer?
I found a listing of 4.5" separation and 7" creepage between cables, and between cables and grounded parts, but no actual reference of where this data came from.
Thanks.

 

[ougrad1999]

unshielded cable above 2000V is no longer allowed per NEC 2005, article 310.6.

 

[davidbeach]

ougrad1999, unshielded jumpers are still used in switchgear. I'd check the relevant ANSI standard for the class of gear being considered.

 

[arcflash99]

I have seen some recent installations at 15kV being only a few inches from Phase to ground supported by a piece of glastic/ fiberglass channel.

Be very careful of using any glastic/ fiberglass supports for unshielded cables as the supports need to be sealed on any cut ends to prevent the absorbtion of moisture. Also, make sure the space heaters work in the cubicle for these types of installations (keeping things dry help reduce the chance of failure). We recently had a phase to phase cable fault on a glastic/ fiberglass support because the support had absorbed moisture allowing the unshielded cables laying on the support to conduct to each other and then to ground.

I know this is was bit off subject, but, this was the first thing I thought of when I read the title of this thread. I just hate to see the same mistake made twice.

 

[cuky2000]

I believe there not standard to cover this issue. My guess is that partially insulated conductor (unshielded cable) may behave somewhere between bare conductor and fully insulated conductor.

See the enclose publication and articles related with this topic.

http://engstandards.lanl.gov/engrman/7elec/pdf/Ch7_G4010-R1.pdf

http://www.powellind.com/main/Uploadpdf/ptb 59 bus spacings in metal-enclosed switchgear.pdf

http://www.southwire.com/processGetArticle.do?commonId=0d8df24ceca6a010VgnVCM1000002702a8c0____

 

[DanDel]

Thanks, guys, I did find some references to the subject as cuky2000 did, but I haven't found any actual specification. We have a customer with 15kV unshielded cable installations between switches and transformers where the cables are touching, and there are corona problems.

 

[alehman]

I swgr. manufacturer's engineer told me once that the spacing should be the same as for uninsulated conductors. In any case, I would not want them touching!