900kcmil cable impedance? 1

[budhiman]

Hello,

Does anyone have specification sheet for 900kcmil (600V). I need impedance data at 60HZ.

 

[7anoter4]

Copper or aluminum conductor, concentric stranded, compressed or compacted, single-core or 3-4 cores, XLPE, pvc or EPR insulated, armored or not [and what other specific data- if there are].And what kind of reactance: X1 or Xo?

 

[budhiman]

"Copper or aluminum conductor, concentric stranded, compressed or compacted, single-core or 3-4 cores, XLPE, pvc or EPR insulated, armored or not [and what other specific data- if there are].And what kind of reactance: X1 or Xo?"

Aluminum, XHHW Resitance, X1, X0, Xc. All the generic information. Since the information on the 900 kcmil is not available on NEC.

 

[7anoter4]

In my opinion, you may take the maximum D.C.conductor resistance at 20oC from UL 1581 standard[=0.01966 ohm/1000 ft.]
From the above mentioned standard Table 20.2 Diameter of round compact-stranded conductors nominal conductor diameter for 900 kmls is 0.999 [minimum 0.979 maximum 1.009 inches].
The overall diameter of XHH cable will be 0.999 inches conductor diameter +2*80 mls insulation thickness[See UL44 Standard].
If you intend to purchase the cable this will be enough.
However, if you want to use it to calculate voltage drop, for instance, you need to employ other factor as temperature factor.
For 90oC insulation[XLPE or EPR, for instance] you have to multiply by:
kT=(228+90)/(228+20)=1.282
Now you have to calculate the skin effect[ycs].
See for instance EPRI 5036-V4 Table 4.14 ycs=0.02 for aluminum from 750 to 1000 kmls.
You need to calculate also proximity effect[ycp].
But at first you have to state what will be the distance between phase conductors.
If the distance is only one cable diameter[1.16 inhes] then ycp=0.02
If the distance is one feet laying symmetrical flat the ycp is negligible.
The a.c. resistance will be 0.01966*1.28225*(1+0.02+0.02)=0.026217 ohm/1000 ft.
From EPRI 5036-V4 (Eq.4-10):
X1=2*PI()*frq*(0.1404*log10(S'/rc)+0.0153) /1000 ohm/1000 ft
S'=1.26*Dist ; rc=0.999/2 inches
If Dist=overall dia[1.16 inches] X1 = 0.02513608 ohm/1000 ft.
To evaluate the zero sequence impedance, it is necessary to know the return path of the current:
Return through the neutral wire (phase-to-neutral fault):
Zo=Zc+j.3.Znc=(Rc+3*Rnc)+j(Xc+3.Xnc)
Return through PE (phase-to-PE conductor fault ):
Zo=Zc+j.3.ZPEC=(Rc+3*RPEC)+j(Xc+3.XPEC)
Return through ground (phase-to-ground fault ):
Zo=Zc+j.3.ZEC=(Rc+3*REC)+j(Xc+3.XEC)
where:
ZC, RC and XC refer to the line conductor
ZnC, RnC and XnC refer to the neutral conductor
ZPEC, RPEC and XPEC refer to the protection conductor PE
ZEC, REC and XEC refer to the ground.