Single Conductor Lug Voltage Rating 1

[tulum]

I posted the following under the thread "Cable Crimp Types for HV or LV posted by stu1 on 1/7/05. I am reposting it because I want to make sure I get it out there because I know someone knows the answer...


tulum (Industrial) Jan 7, 2005
This will probably sound stupid but...

I have always wondered why single conductor lugs come with a voltage rating? I realize there is a reason, however, what is it? How can one piece of copper (lug) have a voltage rating on its own? Excuse my ignorance.

Regards,
TULUM

 

[busbar]

 
A guess is that the “rating” has been established by a UL standard {like 486A} and anything higher may be beyond their purview. For instance, 138kV shielded polymeric cable is routinely furnished by outfits like Kerite, and I know they also furnish built-up termination and splice instructions for their products.

The voltage rating for compression terminals may stop at 35kV because no one has paid for standards development and requisite testing above 35kV. You might call some majors like Burndy and Anderson and get their take on the matter.

I don’t think standards like IEEE C37 typically have such limitations, and utilities rarely rely on the UL/NEC ‘blanket’ in their work. Industrials and related facilities more extensively adopt UL/NEC methods, so sometimes blindly insist on such de facto boilerplate for all electrical projects, which in some cases may be unnecessarily myopic.

 

[tulum]

Busbar thanks for the response.

I guess my question is more to do with how do you get any voltage rating at all? It is just a piece of copper...

Thanks
TULUM

 

[TMD]

I think it's more a matter of semantics than engineering.

 

[jraef]

tulum,
I agree with you that a piece of copper knows not what passes through it. However I believe that voltage ratings of lugs have more to do with convention than physics. If someone were to claim that a lug is rated for any voltage, but something in the lug design interferes with other unrelated but proximal 15kV termination requirements for instance, then technically that lug is not really suitable for 15kV terminations.

"Venditori de oleum-vipera non vigere excordis populi"

 

[mc5w]

At a high enough voltage lug design would affect corona discharge and voltage stress of adjacent insulation. This has more to do with avoiding sharp corners than anything else.

 

[rbulsara]

This is my guess...

UL (or other such agency) only lists/stamps the products for which they test, meaning if they tested the lugs at a given system voltage then they may require the manufacturers to stamp that on their prodcuts to qualify for UL lableing. As someone said it has little to to with engineering, but more to do with legal things.