Maximum number of parallel runs allowed

[fazeel]

The load on SMDB is 540kVA, (780 A) the distance between SMDB and MDB(utility building) is 370meters, what set of cable would be suitable?

I have taken 8 runs of 4C 300sq mm copper cable. is that okay? (Voltage Drop < 3%)
What alternative would be right?

 

[iwire]

Almost 800 amps about 1,200 feet?

Look into using higher voltage.

 

[infinity]

You can use as many runs as necessary as long as you can keep the parallel runs the same length and have enough room on each end for all of the terminations.

 

[don_resqcapt19]

What is the system voltage?

 

[electrofelon]

Seems like a perfect application for aluminum conductors...just sayin'

 

[Ingenieur]

Assuming 3 phase
I = 780
kva = 540 load
v = 400 x 1.2 if sized at 80% or 480 ???
if kva is not sizing load but actual power then 400 v

so vdrop <0.03 x 480 = <14 v

 

[wsbeih]

Assuming 3 phase
I = 780
kva = 540 load
v = 400 x 1.2 if sized at 80% or 480 ???
if kva is not sizing load but actual power then 400 v

so vdrop <0.03 x 480 = <14 v

Seems your application falls under IEC. If my understanding is correct, you can use this, http://www.cablesizer.com/iec/, to verify as there are some factor to consider like grouping, etc...
Your FLA seems correct for 400V 3PH:
FLA= KVA / (V x sqrt3).

 

[Ingenieur]

Seems your application falls under IEC. If my understanding is correct, you can use this, http://www.cablesizer.com/iec/, to verify as there are some factor to consider like grouping, etc...
Your FLA seems correct for 400V 3PH:
FLA= KVA / (V x sqrt3).

Using
Cu
pvc
multicore
3 phase
400 v
780 A
type B
pf 0.9
490 kw
eff 1
temp 30 C
1 cable run per group (8 parallel seperate runs)

8 runs together derates by 48% !

can't get a cable size

 

[Smart $]

Seems your application falls under IEC. ...

I agree. However, every once and a while there are queries on this forum which fall under IEC per government regulation, but compliance with the NEC is required per project specifications. One major problem is the NEC does not recognize metric size conductors. You can convert sizes and go slightly larger, but ampacities are based on insulation ratings per listing standards. IEC conductors and cables are not manufactured or tested to these standards. It amounts to compliance being an educated guess rather than a certainty.

 

[petersonra]

I agree. However, every once and a while there are queries on this forum which fall under IEC per government regulation, but compliance with the NEC is required per project specifications. One major problem is the NEC does not recognize metric size conductors. You can convert sizes and go slightly larger, but ampacities are based on insulation ratings per listing standards. IEC conductors and cables are not manufactured or tested to these standards. It amounts to compliance being an educated guess rather than a certainty.

yep.

we have a control panel sitting in our shop built to IEC standards that the customer wants to make UL listed. After taking a quick look at it, my guess is it has to be gutted and completely rewired and many of the components need to be replaced. The cabinet itself does have a UL label though.

 

[Julius Right]

In my opinion, according to International Standard IEC 60364-5-52
[See Table A.52-17, Table A.52-13, Table A.52-14]:
For 3*300 mm^2 copper XLPE insulated [0.6/1 kV] 8 circuits touching 40oC ambient[air] on cable tray current carrying capacity I=571*0.91*0.52=270 A/conductor and for 8 parallel cables =8*270 =2161 A >780A.
Also according BS 7671 Table 4E2B resistance at 90oC of 3*300 mm^2 copper is 0.14 ohm/km and reactance 0.12 ohm/km. So, the voltage drop at 371 m[ 8 parallel circuits] long cable and 0.8 p.f.
DV=SQRT(3)*780/8*(0.14*0.8+0.12*0.6)*371/1000=11.52 V[2.88%]

 

[fazeel]

line voltage is 400V and phase is 230V

 

[topgone]

line voltage is 400V and phase is 230V

How do you run those cables in the tray/s? Does the tray have covers? Is the tray perforated? Are the conductors touching each other or spaced?

 

[fazeel]

How do you run those cables in the tray/s? Does the tray have covers? Is the tray perforated? Are the conductors touching each other or spaced?

they run underground.

 

[topgone]

they run underground.

Please consider correction factors (per IEC) regarding the type of soil then.

Nature of soil, k3
Very wet soil (saturated)  1.21
Wet soil	           1.13
Damp soil                  1.05
Dry soil	           1
Very dry soil (sunbaked)   0.86

That is aside from the soil resistivity correction factor:

Resistivity = correction
1.0 m/W    = 	1.18
1.5 m/W = 	1.1
2.0 m/W =       1.05
2.5 m/W  =      1.0
3.0 m/W  = 	0.96

 

[Julius Right]

Please consider correction factors (per IEC) regarding the type of soil then.

Nature of soil, k3
Very wet soil (saturated)  1.21
Wet soil	           1.13
Damp soil                  1.05
Dry soil	           1
Very dry soil (sunbaked)   0.86

That is aside from the soil resistivity correction factor:

Resistivity = correction
1.0 m/W    = 	1.18
1.5 m/W = 	1.1
2.0 m/W =       1.05
2.5 m/W  =      1.0
3.0 m/W  = 	0.96

[/QUO
I agree with it. However in this case for xlpe ins,.90oC copper as per IEC 60364-5-52 Table A.52-5 Method D 20oC earth [and RHO 250 -2.5 K.m/W] the current carrying capacity will be only 396 A.