CT secondary lugs 3

[wwyyca]

Hi all, could anyone tell me which kind of lugs used for CT secondary if the installation is to be to UL requirements or CSA? I know should be use ring lugs , but where is the UL or CSA standard? Could you send to me the link address?

 

[dpc]

Not aware of a specific UL requirement, but might be covered in UL 508 or the newer UL 60947. But regardless, ring lugs are highly preferred.

 

[davidbeach]

Uninsulated ring lugs... We've encountered too many cases where insulated lugs were used and the insulation hid an incomplete crimp that should have been more obvious without the insulation.

 

[DTR2011]

Uninsulated lugs also make it much easier for the folks in the field for testing.

 

[wwyyca]

Just highly preferred, no standard ( UL.CSA, NEMA, IEC.....) force you to use ring lugs, is it right? So I can use ring or fork lugs?

 

[ScottyUK]

When everyone is recommending rings, why would you want to use something else?

 

[wwyyca]

Because I buy somebody's switchgear, they used folk lugs for CT and ABB test switch. I want to them to change to ring lugs. But they said it not UL.CSA, NEMA, IEC..... forced.
That is why I looking for the standard.

 

[roydm]

It's not a good idea to open the secondary of a CT, ring type lugs are less likely to fall off, even if the nut was loose they should still keep the secondary Volts to a safe level.

 

[ScottyUK]

I don't think you will find it in any of the IEC standards. It's more often written into the customer specification issued to the manufacturer. The standards set the acceptable minimum performance requirements, the specification defines what you want. So often I see gear ordered with no specification and passing reference to a few standards, and customers who don't understand why the board they end up with isn't what they wanted.

As a slight aside, the CEGB and Weidmuller developed the RSF series of terminals many years ago. These are a regular rising cage type terminal which incorporates a powerful spring which is sufficient in its own right to clamp a conductor even if the screw works loose. They're used with a special lug which is pretty much impossible to work loose from the RSF terminal. Excellent for CT circuits, accommodate up to two conductors per entry.

 

[marks1080]

We use ring lugs everywhere, except on the back of protection racks where we use DOUBLE clamp terminal blocks (with springs like in the picture above - just two clamps per termination instead of one).

As far as I know none of this is specifically covered by any standards. I think the idea of an open CT for most folks is enough to make them ultra conservative with these circuits.

 

[waross]

Further to David's post:
On the sizes of terminals and conductors used for CT secondary connections:
Typically a bare terminal is installed with a "U" shaped staked crimp.
Typically an insulated terminal is installed with a diamond shaped squeeze crimp.
Almost all of the failed terminal crimps that I have encountered have been the insulated squeeze type of crimp.
I almost never encounter a failed staked type of crimp. The staked type of crimp is much more robust than the squeeze type of crimp.


Bill
--------------------
"Why not the best?"
Jimmy Carter