WIRE BENDING SPACE

[dhiggins]

I have 3-1550 MCM cables per lug terminating in an enclosure. The '99 NEC Table 373-6b list cables in this situation up to 900 only. Cables 1000 and larger have no figures in the colum. How do I determine space required?

 

[mpparent]

In my copy of the '99 code(handbook), the list goes up to 2000 kcmil. However, the clearance is 24" for ONE WIRE PER TERMINAL. It shows no values for two or more wires per terminal. I was thinking about it more, how are you terminating?? I'm sure there is no mechanical lug that can terminate three 1500 kcmil conductors?

 

[dhiggins]

Each cable will have a 2 hole press on lug. Then 3 cables will be bolted to each buss.

 

[dpc]

If you bolting each lug directly to the bus, then I think you use the 1 wire per terminal column.

I believe the intent of the Code is dealing with situations where you are physically putting multiple conductors under one lug since this will require additional bending space.

For 1550 kcmil, you probably don't want to make any bends inside the enclosure, if you can avoid it.

Good luck.

 

[resqcapt19]

dhiggens
Just curious as to why you would be using such large conductors? Conductors over 750kcmill are rarely cost effective.
Don(resqcapt19)

 

[dhiggins]

The cables are being used for excitation of a 200 MW Generator. There are 6-1550s. Each has an individual press on two hole lug. Then 3 cables will be bolted to a terminal buss and three to the other terminal buss. There are a total of 2 terminal busses in the enclosure. The enclosure presently has only 11 in. clearance between the terminal ends and enclosure wall.

 

[busbar]

Engineers that design insufficient wiring spaces have serious fluorescent-light burns--they never get out of the office to see the finished version of they have designed.

DLO/RHW/RHH cable is a bit more flexible than building wire, but looks like 1111kcmil (2745-stand 2kV) is the upper limit.