value fo conductors

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Derick

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Point to point Method of short circuit calculation: how the value of conductors is calculated from?
Note p.8 says:1/z (per 1 foot) which is found based on R an X in IEEE 241-1990.

I don't get it.

Ex.500 mcm in steel conduit :
Table 9 NEC for 500 mcm
X=0.048 and R=0.029

So according to note p.8
1/(0.029+0.048)=0.077


What am I doing wrong here?
 
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Derick said:
Point to point Method of short circuit calculation: how the value of conductors is calculated from?
Note p.8 says:1/z (per 1 foot) which is found based on R an X in IEEE 241-1990.

I don't get it.

Ex.500 mcm in steel conduit :
Table 9 NEC for 500 mcm
X=0.048 and R=0.029

So according to note p.8
1/(0.029+0.048)=0.077

What am I doing wrong here?
Click to expand...

Well that number come up in the Grey book:

IEEE recommended practice for electric power systems in commercial buildings. (Color Book Series - Gray Book)

I don't have access but will study what they do allow :)

Could you put the second equation in or reference the complete one to us, Lay men and women

As the math sits you used both R and x for a Z... where's the 1000 ft pluging in.

I'm sure Im missing something as well here, Clue me in... other's can play along at there will. :)
 
Your right I just asked the teacher!

Sorry I missed table 9 reference, plug it in.
 
zog said:
1/(0.029+0.048)= 12.98
Click to expand...

Yes I made typo mistake in calc.
But what I am trying to find out is :
How to calculate "C" values for conductors by using NEC only.
Also IEEE 241-1990 table 2 shows 3 single conductors.On 3ph 4w
system neutral is CCC so there are 4 conductors in the raceway.
(unbalanced load)
 
cadpoint said:
Well that number come up in the Grey book:

IEEE recommended practice for electric power systems in commercial buildings. (Color Book Series - Gray Book)

I don't have access but will study what they do allow :)

Could you put the second equation in or reference the complete one to us, Lay men and women

As the math sits you used both R and x for a Z... where's the 1000 ft pluging in.

I'm sure Im missing something as well here, Clue me in... other's can play along at there will. :)
Click to expand...


Well if I used Table 9 to obtain conductor impedance the values are shown per 1000 LF,so to obtain per 1 LF it would be: Z= X+R/ 1000 per linear foot
Am i on the right track with finding Z?

Thanks
 
Derick said:
Point to point Method of short circuit calculation: how the value of conductors is calculated from?
Note p.8 says:1/z (per 1 foot) which is found based on R an X in IEEE 241-1990.

I don't get it.

Ex.500 mcm in steel conduit :
Table 9 NEC for 500 mcm
X=0.048 and R=0.029

So according to note p.8
1/(0.029+0.048)=0.077


What am I doing wrong here?
Click to expand...
Z=sqrt(R^2+X^2)
 
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