Adnan Hasan
Member
- Location
- baghdad, Iraq
How do I arrange 120 cables (1*300 mm2), 400 Vac in parallel ventilated trough cable trays to mitigate the effects of magnetic and electric fields? Please notice that my grounding system is TN-S type.
Cables Grouping
- Thread starter Adnan Hasan
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Julius Right
Senior Member
- Occupation
- Electrical Engineer Power Station Physical Design Retired
The simplest way is to bond all the cables in groups of 2*4- as follows: first group, upper layer C-N, down A-B; second group upper N-C down B-C. In addition, is to keep a two*cable diameter clearance between two adjacent groups.
Phil Corso
Senior Member
- Location
- Boca Raton, Fl, USA
Adnan...
1) Are you contemplating the installation of 40 sets of 3-ph, 3 x 1/c wire systems, or 30 sets of 3-ph, 4 x 1/c wire systems?
2) Are you concerned only about how physical arrangement impacts EMI, without economic consideration?
Regards, Phil Corso
1) Are you contemplating the installation of 40 sets of 3-ph, 3 x 1/c wire systems, or 30 sets of 3-ph, 4 x 1/c wire systems?
2) Are you concerned only about how physical arrangement impacts EMI, without economic consideration?
Regards, Phil Corso
Phil Corso
Senior Member
- Location
- Boca Raton, Fl, USA
Andnan...
Clarifying my "economic" comment... are N and PE conductors also 300 mmq in size?
Phil
Clarifying my "economic" comment... are N and PE conductors also 300 mmq in size?
Phil
Julius Right
Senior Member
- Occupation
- Electrical Engineer Power Station Physical Design Retired
As Phil Corso said, if you know the triplen harmonic percent of the main current you may reduce the neutral cable accordingly. However, the size does not change the required position in space.
If the cable tray is steel or aluminum made it could be a PE conductor.
The earthing cable does not depend on main conductor cross section but on short-circuit current and the protection fault clearing time.
If the cable tray is steel or aluminum made it could be a PE conductor.The earthing cable does not depend on main conductor cross section but on short-circuit current and the protection fault clearing time.
Adnan Hasan
Member
- Location
- baghdad, Iraq
1) they are 30 sets of 3-ph, 4 x 1/c. (EGC shall be considered as well)
2) my concern is the physical arrangement that impacts EMI without economic consideration.
Note: my cable tray is Made of Galvanized STEEL. width is 500 mm. Layout of cable tray as shown in the attached picture.
Adnan Hasan
Member
- Location
- baghdad, Iraq
N is also 300 mm2. PE shall be calculated
I think you meant B-A for the last pairing...
Is this based on empirical data, authoritative reference, or speculation?
I would think it better...
CN AB CN AB CN AB (top)
AB CN AB CN AB CN (bottom)
AB CN AB CN AB CN (bottom)
Adnan Hasan
Member
- Location
- baghdad, Iraq
are you leaving spaces between groups?
example:
CN AB CN
AB space CN space AB
If I dont want to leave space, shall I multiply by grouping factor (derating)?
Single conductors are required to be distributed evenly across the width of the cable tray [392.22(B) general statement]. Does not apply to a "cabled" group.
If you don't leave space, you will have to derate [392.80(A)(2)]... but IIRC, 300mm? is in between 500 and 600kcmil, so we have a problem determining whether 75% or 65% derating applies.
If you space, it'll have to be 2.15 times the O.D. of a single conductor, with ampacity to Table 310.15(B)(20)... but there we run into problem as NEC doesn't recognize metric sized conductors.
Julius Right
Senior Member
- Occupation
- Electrical Engineer Power Station Physical Design Retired
First 300 mm^2=600 MCM:weeping: .Second the grouping has to be as follows:
CN NC CN NC
AB BA AB BA
in order to mitigate current unbalance.
If your cable is XLPE insulated and the maximum air temperature is 40dgr.C and you cannot keep 2.15 times the cable diameter clearance you have to calculate according to:
ICEA/NEMA STANDARDS PUBLICATION NO.P-54-44/WC5
"Ampacities of Cables in Open-top Cable Trays"
The cable tray width in inches=500/25.4=20
Cable overall diameter 31.5 mm=1.24 inches
depth=21[no.of loaded cables]*1.24^2/20=1.61 inches
From Table 3-1 you have for 500 mcm[250 mm^2] and 2 depth 320 A for 750mcm- same depth 467A. Then for 600 mcm will be (320+467)/2=393 A.
For 1.6 inches, depth is approx.400 A
Calculated following "Ampacity for Cables in Randomly Filled Trays" by J.Stolpe it results the same 400 A.
CN NC CN NC
AB BA AB BA
in order to mitigate current unbalance.
If your cable is XLPE insulated and the maximum air temperature is 40dgr.C and you cannot keep 2.15 times the cable diameter clearance you have to calculate according to:
ICEA/NEMA STANDARDS PUBLICATION NO.P-54-44/WC5
"Ampacities of Cables in Open-top Cable Trays"
The cable tray width in inches=500/25.4=20
Cable overall diameter 31.5 mm=1.24 inches
depth=21[no.of loaded cables]*1.24^2/20=1.61 inches
From Table 3-1 you have for 500 mcm[250 mm^2] and 2 depth 320 A for 750mcm- same depth 467A. Then for 600 mcm will be (320+467)/2=393 A.
For 1.6 inches, depth is approx.400 A
Calculated following "Ampacity for Cables in Randomly Filled Trays" by J.Stolpe it results the same 400 A.
300mm? = 592,058cmil
Please cite reference. This is not an NEC requirement.
Not an NEC compliant method.
Julius Right
Senior Member
- Occupation
- Electrical Engineer Power Station Physical Design Retired
1)The conductor diameter is the same for both 300 sqr.mm and 600 MCM [depends on how it is built-concentric stranded, compressed or compacted].
The insulation [and jacket if any] is different following different standards-UL 1581/UL 1277 or IEC 60502.
2)You are right ICEA/NEMA WC5 it is not NEC recommended procedure.
If the cable is built according to IEC 60228/60502 then NEC it is for information only [also ICEA/NEMA]. Since IEC 60287 does not include cable in cable tray ampacity calculation way, one has to employ all other way to get close to the actual ampacity.
3)There is a lot of publication how to group the single-core cables to reduce the unbalance.
I am sorry, I did not find the English version:
http://www.ingeborda.com.ar/bibliot...potencia/Errores en el trabajo con cables.pdf
Of course, the Alt. no.1 [Cables with neutral] it is better than mine but it is wider [3 cables instead of 2 per group].
The insulation [and jacket if any] is different following different standards-UL 1581/UL 1277 or IEC 60502.
2)You are right ICEA/NEMA WC5 it is not NEC recommended procedure.
If the cable is built according to IEC 60228/60502 then NEC it is for information only [also ICEA/NEMA]. Since IEC 60287 does not include cable in cable tray ampacity calculation way, one has to employ all other way to get close to the actual ampacity.
3)There is a lot of publication how to group the single-core cables to reduce the unbalance.
I am sorry, I did not find the English version:
http://www.ingeborda.com.ar/bibliot...potencia/Errores en el trabajo con cables.pdf
Of course, the Alt. no.1 [Cables with neutral] it is better than mine but it is wider [3 cables instead of 2 per group].
Julius Right
Senior Member
- Occupation
- Electrical Engineer Power Station Physical Design Retired
I checked the currents unbalance according to F.H.Buller method and according to:
EPRI-Power Plant Electrical ref. series" "VOL.4-WIRE AND CABLES"
EQ.A-1 FROM APPENDIX A " and the configuration presented by me [see post#11] is perfect balanced.
EPRI-Power Plant Electrical ref. series" "VOL.4-WIRE AND CABLES"
EQ.A-1 FROM APPENDIX A " and the configuration presented by me [see post#11] is perfect balanced.
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Conductor diameter is not what is being measured, especially when stranded, or the conductor has any other gaps within the periphery of its cross section. 600kcmil refers to the kcmil sum of all strands' cross-sectional area. I believe it is the same for metric-sized conductors. I got the cmil equivalent of 300mm? from a General Cable equivalents chart.
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